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SECTION IV
RESULTS AND DISCUSSION
Results and Discussion
Page 85
CHAPTER– 1
PHY SIC O-CHE MICAL PROPERTIES, ANTINUTRIENT AND PROTEIN
PROFILE OF PEARL MILLET AS INFLUENC ED BY PROCESSING
Pearl millet has significant potential as food and feed in addition to its current
usage as forage. It is a drought-tolerant crop and can be grown under difficult
ecological conditions. For this reason it is widely grown in tropical regions of world
including Africa and Asia. It is comparable and even superior in some of the
nutritional characteristics to major cereals, with respect to its energy value, protein,
fat and minerals content (Abdalla et al. 1998). The use of pearl millet for human
consumption is limited due to non-availability in convenience form. The millet is
mostly used as whole flour for traditional food preparation and hence confined to
traditional consumers and to people of lower economic strata. Pearl millet can be
consumed raw after soaking and sprouting in form of salads but most of them require
cooking to improve digestibility, palatability and keeping quality. Two commercially
available pearl millet varieties such as Kalukombu (K) & Maharashtra Rabi Bajra
(MRB) were subjected to various processing methods [milling, wet and dry heat
treatments (Pressure cooking, boiling and roasting) and germination] commonly
adopted practices in Indian households and was studied for its influence on the
physico-chemical properties, nutrient composition, antinutrient profile as well as
influence of cooking medium which is a potential source of iron/calcium
contamination on total iron and calcium was explored. Total sugar and total soluble
protein of the raw and processed flours were also analyzed. Buffer-soluble proteins
were extracted from the raw and processed flours and separated by sodium dodecyl
sulfate – poly acrylamide gel electrophoresis (SDS-PAGE).
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Table 4.1. Proximate Composition of the Two Pearl Millet Varieties (per 100g)
Proximate composition Reported values* Analyzed values
Kalukombu MRB
Moisture (g) 12.4 10.1 9.6
Proteins (Nx6.25) (g) 11.6 9.3 10.2
Fat (g) 5.0 4.8 5.4
Ash (g) 2.3 2.0 1.5
Iron (mg) 8.0 5.0 6.4
Calcium (mg) 42.0 41.3 40.0
Phosphorus (mg) 296.0 327.8 255.7
Zinc (mg) 3.10 4.40 4.2
Copper (mg) 1.06 0.99 0.90
Manganese (mg) 1.15 1.61 1.78
Magnesium (mg) 137 99.34 105.08
Sodium (mg) 10.9 7.8 7.2
Potassium (mg) 307 200 180
* National Institute of Nutrition (NIN), Hyderabad, MRB – Maharashtra Rabi Bajra.
The proximate compositions of the two pearl millet varieties (K and MRB)
were determined and compared with the reported values (Table 4.1). K variety
contained 9.3% protein, 4.8% fat and 2.0% ash. Comparatively, MRB contained
higher protein (10.2%), fat (5.4%) and lower ash (1.5%) content. However, these
Results and Discussion
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values were similar to the reported values. The highest content of iron (6.4%) was
found in MRB while K had high phosphorus content (327.8%). Values for minerals
like calcium, zinc, copper and manganese were found to be similar for both varieties.
However, values for iron, zinc, manganese, magnesium, sodium and potassium
content were lower than the reported values.
Table 4.2. Bulk Density, Water and Oil Holding Capacity of Pearl Millet as
Influenced by Processing
Processing
Bulk Density
(ml/g)
Oil Holding Capacity
(g/g)
Water Holding Capacity
(g/g)
K MRB K MRB K MRB
WF (Raw) 1.68 a ± 0.1 1.65
a ± 0.2 1.38
a ± 0.1 1.18
a ± 0.0 0.88
a ± 0.11 0.95
a ± 0.05
SRF 1.84 ab
± 0.1 1.88 ab
± 0.1 1.43 a ± 0.1 1.35
a ± 0.1 1.13
a ± 0.08 1.08
a ± 0.08
BRF 1.93 b ± 0.0 2.03 c ± 0.0 2.87 b ± 0.0 3.00 b ± 0.0 3.13 d ± 0.09 2.97 d ± 0.05
Boiling 1.75 a ± 0.1 1.83
a ± 0.0 1.43
a ± 0.1 1.40
a ± 0.1 2.25
b ± 0.30 1.70
b ± 0.17
PC 1.75 a ± 0.0 1.80
a ± 0.1 1.25
a ± 0.2 1.50
a ± 0.1 2.38
c ± 0.04 2.23
c ± 0.30
Roasting 1.98 bc ± 0.0 2.00 bc ± 0.0 1.30 a ± 0.1 1.38 a ± 0.1 1.13 a ± 0.13 1.15 a ± 0.17
G 2.08 c ± 0.1 2.08
c ± 0.0 1.50
a ± 0.2 1.43
a ± 0.1 1.00
a ± 0.07 0.98
a ± 0.11
Values are mean ± SD (n = 4), Means with different superscripts (a, b, c, d) along the column are
significantly (P ≤ 0.05) different based on Tukey’s test. K – Kalukombu, MRB – Maharashtra Rabi
Bajra, WF – whole flour, SRF – semi refined flour, BRF – bran rich fraction, PC – pressure cooking, G
- germination
Results and Discussion
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Knowledge of physical/functional properties and their dependence on the
moisture content are useful for design and development of any processing methods
and equipment. Functional properties such as bulk density, water and oil holding
capacities of raw and processed pearl millet are presented in Table – 4.2. Bulk density
is an important parameter that determines the packaging requirement of a product
(Chandi et al 2007). The bulk densities of processed pearl millet flours (WF < Boiling
< PC < SRF < BRF < Roasting < Germination) were significantly (P ≤ 0:05) different
from each other, with whole flour (WF) having the lowest density (about 1.66 ml/g).
Germinated grains produced finer flours which led to its higher bulking capacity
(2.08ml/g). Interactions of water and oil with proteins are very important in the food
systems because of their effects on the flavor and texture of foods (Chandi et al 2007).
The oil holding capacity (OHC) ranged from 1.18 – 3.0 g/g for K and MRB. OHC of
the flours were not significantly (P ≤ 0.05) affected by different heat treatments and
germination respectively. However, bran rich fraction, a byproduct of milling, showed
highest OHC (3.00 and 2.87g/g for K and MRB respectively). Water absorption
capacities are related to the starch and protein contents and the particle size
distribution of the ingredient. The water holding capacity (WHC) of a sample is an
important determinant of stool-bulking effect, which is more related to the manner in
which water is held, rather than to the absolute amount held. These properties are also
important for stating the usefulness of the sample obtained as bulking, swelling and/or
thickening agents in formulations or foods of relatively high water activity
(Raghavendra et al 2004; De Escalada et al 2007). The water holding capacity (WHC)
ranged from 0.88 to 3.13 g/g for both varieties. BRF (3.13 and 2.97 g/g for K and
MRB respectively) and wet heat treatments such as boiling (2.25 and 1.70g/g for K
Results and Discussion
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and MRB respectively) and pressure cooking (2.38 and 2.23 g/g for K and MRB
respectively) presented highest WHC, whilst no significant (P ≤ 0:05) differences
were found between whole flour; semi refined flour, roasted or germinated flour. The
highest WHC of wet heat treated millet (boiling and pressure cooking respectively)
might be attributed to its lowest density among the processed samples. Flours with
lower bulk densities have larger surface area, polar groups, and uronic acid groups to
the surrounding water, leading to an increase in water absorption or swelling volume
(Bao et al 1994). However, this trend was not followed in case of BRF, which
exhibited highest bulk density, WHC and OHC. In this study, variations in the
functional properties (bulk density, WHC and OHC) amongst the processed millet
flours indicated that all these properties were affected by different preparation
methods.
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Table 4.3a. Swelling Power of Pearl Millet as Influenced by Processing (g/g)
Processing 55
oC 65
oC 75
oC 85
oC 95
oC
K MRB K MRB K MRB K MRB K MRB
WF (Raw) 2.77
a3 ±
0.02
2.94 b2
±
0.05
3.95 b2
±
0.05
3.31 c3
±
0.00
4.71 d4
±
0.05
4.91e4
±0.03
5.67 f3
±
0.01
6.05 g4
±
0.01
8.01 h5
± 0.02
10.01 i7
± 0.01
SRF 3.03 b4 ±
0.02
2.95 a2 ±
0.05
3.37 d4 ±
0.01
3.14 c2 ±
0.00
4.47 e2 ±
0.01
4.93 f4 ±
0.02
5.54 d2 ±
0.04
6.69 g3 ±
0.01
8.76 i7
± 0.03
8.80 i6
± 0.00
BRF 3.85 b5 ±
0.02
3.90 bc3 ±
0.00
3.72 a5 ±
0.01
3.94 c5 ±
0.02
4.63 d3 ±
0.04
4.80 e3 ±
0.00
6.06 f6 ±
0.00
6.32 g5 ±
0.02
8.57 i6
± 0.06
8.32 h4
± 0.01
Boling 4.87
b6 ±
0.03
4.56 a4
±
0.01
5.31 d6
±
0.03
5.24 c6
± 0.01
5.43 e5
±
0.02
5.86 fg6
±
0.02
5.83 g4
±
0.02
6.06 h4
±
0.04
6.48 i2
± 0.00
7.69 j3
± 0.00
PC 4.80 a6 ±
0.00
5.14 b5 ±
0.01
5.54 d7 ±
0.00
5.61 e7 ±
0.01
5.70 f6 ±
0.01
5.11 b5 ±
0.01
5.95 g5 ±
0.04
5.19 c2 ±
0.01
6.70 h3
± 0.00
6.67 h2
± 0.01
Roasting 2.61
a2 ±
0.00
2.88 b2
±
0.06
3.17 c3
±
0.05
2.62 a1
± 0.02
4.47 d2
±
0.00
4.72 e2
±
0.01
6.02 g6
±
0.02
5.73 f3
±
0.03
7.73 h4
± 0.00
8.41 i5
± 0.01
G 2.45
b1 ±
0.04
2.55 c1
± 0.04
2.35 a1
± 0.01
3.49 f4
±
0.04
3.39 e1
±
0.00
3.28 d1
±
0.02
3.29 d1
±
0.02
3.53 f1
±
0.01
3.63 g1
± 0.02
3.50 f1
± 0.00
Values are mean ± SD (n = 4), Means with different superscripts (a, b, c, d) along the row and means with different superscripts
(1, 2, 3, 4, 5, 6,7) along the column are significantly different (P ≤ 0.05), K –Kalukombu, MRB – Maharashtra Rabi Bajra, WF
– whole flour, SRF – Semi refined flour, BRF – bran rich fraction, PC – pressure cooking, G - germination
Results and Discussion
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Table 4.3b. Solubility of Pearl Millet as Influenced by Processing (g/g)
Processing 55 oC 65 oC 75 oC 85 oC 95 oC
K MRB K MRB K MRB K MRB K MRB
WF (Raw) 0.085
b12 ±
0.00
0.112b2
±
0.00
0.068b2
±
0.01
0.090b1
±
0.00
0.008a1
±
0.00
0.012a1
±
0.00
0.006a1
±
0.00
0.117b2
±
0.02
0.012a1
±
0.00
0.079b1
±
0.05
SRF 0.123
d23 ±
0.00
0.108cd2
±
0.00
0.112d5
±
0.00
0.105cd1
±
0.00
0.078bcd2
±
0.05
0.094cd34
±
0.00
0.002a1
±
0.00
0.075bcd1
±
0.00
0.067bc3
±
0.00
0.045b1
±
0.00
BRF 0.098
ab123 ±
0.00
0.150c34
±
0.01
0.095ab4
±
0.00
0.093b1
±
0.00
0.084a2
±
0.00
0.082a3
±
0.00
0.117ab4
±
0.02
0.117b2
±
0.00
0.093a4
±
0.00
0.075a1
±
0.00
Boiling 0.135d3 ±
0.00
0.164e4 ±
0.00
0.082b3 ±
0.00
0.113c1 ±
0.00
0.045a12 ±
0.00
0.117c5 ±
0.01
0.045a2 ±
0.00
0.106c2 ±
0.00
0.049a2 ±
0.00
0.090b1 ±
0.00
PC 0.109
c123 ±
0.01 0.130
d23
±0.01 0.060
a12 ±
0.00 0.082
b1 ±
0.00 0.081
b2 ±
0.00 0.104
c45 ±
0.00 0.070
ab3 ±
0.00
0.113c2
± 0.00
0.060a3
± 0.00
0.071ab1
± 0.00
Roasting 0.068
bc12 ±
0.00
0.060bc1
±0.00
0.055ab1
±
0.00
0.119f1
±
0.01
0.084de2
±
0.00
0.061bc2
±
0.00
0.074cde3
± 0.00
0.071bcd1
±
0.00
0.042a2
±
0.00
0.088e1
±
0.00
G 0.342
bc4 ±
0.04
0.426c5
±
0.02
0.248ab6
±
0.01
0.179a1
±
0.08
0.531d3
±
0.00
0.545d6
±
0.00
0.543d5
±
0.04
0.592d3
±
0.00
0.342bc5
±
0.03
0.408c2
±
0.01
Values are mean ± SD (n = 4), Means with different superscripts (a, b, c, d) along the row and means with different superscripts (1, 2, 3, 4, 5, 6,7) along the
column are significantly different (P ≤ 0.05), K –Kalukombu, MRB – Maharashtra Rabi Bajra, WF – whole flour, SRF – semi refined flour, BRF – bran rich
fraction, PC – pressure cooking, G - germination.
Results and Discussion
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Swelling is a desirable physicochemical property making it useful in a range of
foods. The effect of temperature on swelling power and solubility of raw and processed
pearl millet is presented in table 4.3a&b. The swelling index is the measure of the ability
of the flour to absorb water and swell. Swelling power of raw and processed flours
increased with increase in temperature (55°C – 95°C). Swelling power of all the flours
significantly increased with increase in temperature. Whole flour had the highest value
(about 9g/g), while germinated flour had the lowest (3.5g/g) at 95oC.
Whole flour of K and MRB showed 8.5% and 11.2% solubility at 55oC. The
solubility of the millet after germination profoundly increased to 34.2 and 42.6% in K
and MRB respectively. Contrasting to swelling property, solubility of all the
processed flours decreased with the increasing temperature. For example, solubility of
processed flours was highest at 55oC and 65
oC, as the temperature increased from
75oC onwards the solubility of the flours decreased. For example, solubility of WF of
K and MRB was 0.085 and 0.112 g/g at 55oC which dipped to 0.012 and 0.079g/g at
95oC. Similar decreases were found in all processed flours except for germinated
flour. Germination altered the swelling and solubility of pearl millet. In germinated
flours, the decrease was not consistent, for instance, its solubility decreased at 65 o
C,
increased at temperatures 75oC – 85
oC and again decreased at 95
oC. The
solubilization of the flours progressively deceased with increasing in swelling power.
This result is different from that reported for corn (Yung et al 2006).
Results and Discussion
Page 93
Table 4. 4. Proximate Composition of Pearl Millet as Influenced by Processing
(Dry basis g/100g)
Processing
treatments Moisture Protein Fat Ash
Kalukombu
WF (Raw) 10.1 b
± 1.80
10.3 ab
± 1.08
5.3 bc
± 0.60
2.2 a ± 0.35
SRF 10.8 b ± 0.31 9.6
ab ± 0.75
5.0
bc ± 0.46
1.5
a ± 0.15
BRF 10.2 b ± 0.34 9.6
ab ± 0.70 7.8
d ± 0.77
3.6
c ± 0.36
Boiling 7.2 a± 0.30 7.9
a ± 0.26 5.2
c ± 0.26
1.3
a ± 0.29
PC 7.5 a ± 1.80 7.9
a ± 0.49 4.3
b ± 0.21
1.6
a ± 0.11
Roasting 6.6 a ± 0.40 8.1 a ± 1.64 4.4 b ± 0.19 1.9 b ± 0.08
Germination 7.4 a ± 0.10 10.4 b ± 1.27 3.4 a ± 0.12 2.0 b ± 0.04
Maharashtra Rabi Bajra
WF (Raw) 9.6 c ± 0.82 11.3 d ± 0.33 6.0 c ± 0.19 1.6 a ± 0.06
SRF 9.5 c ± 0.72 11.3 d ± 0.47 5.6 bc ± 0.14 1.4 a ± 0.17
BRF 9.5 c ± 0.30 9.4 bc ± 0.40 5.4 bc ± 0.24 3.9 b ± 0.09
Boiling 8.4 b ± 0.10
10.5
cd ± 0.20
3.9
a ± 0.32
1.5
a ± 0.08
PC 7.0 a ± 0.40
7.3
a ± 0.53
5.9
c ± 0.49
1.5
a ± 0.41
Roasting 6.4 a ± 0.20
7.9
ab ± 1.66
4.3
a ± 0.05
1.6
a ± 0.09
Germination 9.4 c ± 0.70
8.6
ab ± 1.53
5.1
b ± 0.81
1.5
a ± 0.02
Values are mean ± SD (n = 4), Means with different superscripts (a, b, c, d) along the column
are significantly different (P ≤ 0.05), WF – Whole flour, SRF – Semi refined flour, BRF –
Bran rich fraction.
Results and Discussion
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The proximate composition of processed pearl millet is presented in Table –
4.4. The moisture content of the flours were not altered by the process of milling or
germination however, heat treatments significantly (P ≤ 0.05) reduced the moisture
content in both varieties. The drying effect due to roasting caused a significant (P ≤
0.05) moisture loss in the millet. Reduction in moisture is favorable as high moisture
could possibly affect the storability of the product. The decrease in moisture content
upon roasting was in accordance with the earlier report (Komeine et al 2008).
Nonetheless the moisture content of all the flours, both raw and processed was below
the maximum moisture content limit (13%) for pearl millet flour recommended by
FAO/WHO (1995). This is the maximum allowable moisture content acceptable for
pearl millet flour meant for human consumption. The mean protein content of K and
MRB was 10.3% & 11.3% respectively. Processing did not affect the protein content
of K variety grains however; significant (P ≤ 0.05) reduction due to processing (heat
treatments, germination and bran rich fraction) was noticed in MRB. Reduction in wet
heat treatmented (boiling/pressure cooking) or germinated millet could be attributed
to leaching of water soluble and low molecular weight proteins into cooking/soaking
water (Alka et al 1997; Habiba 2002) while, decrease during roasting could be due to
destruction of amino acids as result of high temperature (Mauron 1982). The fat
content of K & MRB was 5.3% & 6.0% respectively. The BRF of K variety (7.8%)
retained significant (P ≤ 0.05) amount of fat content. The fat content of the heat
treated millet reduced significantly (P ≤ 0.05), could be attributed to its diffusion into
the cooking water or due to conversion of fat to fatty acid and glycerol which was
further hydrolyzed to acetate at high temperature (King et al 1987). Ash represents the
non-combustible fraction of the sample, i.e. minerals. The % ash content of K and
Results and Discussion
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MRB was 2.2% and 1.6% respectively. A significant (P ≤ 0.05) amount of ash content
was found in the bran rich fraction (3.6% in K & 3.9% in MRB). Roasting and
germination significantly (P ≤ 0.05) reduced ash content in K variety grains.The fat
and ash content reduced upon germination which could be due to losses of total
soluble solids during soaking prior to germination (Wang et al 1997).
Table 4.5. Mineral Content of Pearl Millet as Influenced by Processing
(Dry Basis, mg/100g)
Processing
treatments Iron Calcium Phosphorus
Kalukombu
WF (Raw) 5.9 c ± 0.35 45.7
a ± 4.54 364.0
b ± 33.67
SRF 4.6 b ± 0.52 51.0 abc ± 2.21 348.1 b ± 7.75
BRF 3.6 ab ± 0.01 61.5 d ± 1.52 307.9 b ± 71.53
Boiling 3.2 a ± 0.59 54.0
bc ± 1.41 225.2
a ± 27.5
PC 3.3 a ± 0.14 47.2
ab ± 2.37 241.8
a ± 17.0
Roasting 3.2 a ± 0.01 44.6
a ± 7.13 337.9
b ± 6.0
Germination 6.7 d ± 1.14 53.7 cd ± 4.50 239.0 a ± 11.4
MRB
WF (Raw) 7.1 c ± 1.50 44.2
ab ± 4.59 283.1
bc ± 36.9
SRF 6.5 bc
± 0.53 52.8 b ± 5.76 298.3
c ± 18.8
BRF 5.2 ab
± 0.80 85.9 c ± 8.30 392.0
d ± 31.4
Boiling 6.6 bc
± 1.77 53.3 b ± 2.21 257.6
abc ± 10.1
PC 7.3 c ± 0.42 52.4 b ± 2.27 247.7 ab ± 14.2
Roasting 4.0 a ± 0.26 39.6 a ± 9.46 262.4 abc ± 7.7
Germination 4.5a ± 0.49 53.7
b ± 3.25 221.5
a ± 21.1
Values are mean ± SD (n = 4), Means with different superscripts (a, b, c, d) along the column
are significantly different (P ≤ 0.05), MRB – Maharashtra Rabi Bajra, WF – Whole flour,
SRF – Semi refined flour, BRF – Bran rich fraction, PC – Pressure cooking.
Results and Discussion
Page 96
Table 4.5 depicts the mineral content of raw and processed pearl millet. The
total iron content was 5.6 & 7.1 mg/100g for K & MRB respectively. Pearl millet
subjected to milling and heat treatments significantly (P ≤ 0.05) lowered the iron
content whilst, a significant (P ≤ 0.05) increase in the germinated K variety was noted
which was in accordance with an earlier report on pearl millet (Sushma et al 2008).
This increase could be attributed to the mineral contamination in the water used for
soaking prior to germination. The total calcium content was 45.7 and 44.2 mg/100g in
K and MRB respectively. The bran rich fraction contained significant (P ≤ 0.05)
calcium levels. Pearl millet that was subjected to wet heat treatments or germination
had high calcium content. The total phosphorus content was significantly (P ≤ 0.05)
higher in K (364.0 mg %) compared to MRB (283.1 mg %). BRF of MRB contained
significantly (P ≤ 0.05) higher phosphorus whilst, wet heat treated K variety had low
phosphorus content. Similarly upon germination, the phosphorus content of the millet
reduced significantly (P ≤ 0.05).
Results and Discussion
Page 97
Table 4.6. Mineral Content of Processed Pearl Millet as Influence by Water
Type (dry basis, mg/100g)
Processing Iron Calcium Phosphorus
TW DMW TW DMW TW DMW
Kalukombu
Boiling 3.8 a ± 0.35 3.2
a ±0.59 53.3
a ±2.07 54.0
a ± 1.41 268.4
a ± 46.4 225.2
a ± 27.5
PC 4.6 b ± 0.49 3.3 a ±0.14 46.7 a± 3.76 47.2 a± 2.37 290.2 b± 42.7 241.8 a± 17.0
Germination 7.5 a ± 0.18 6.7 a ±1.14 54.7 a ± 1.82 53.7 a± 4.50 253.3 a± 26.2 239.0 a ±11.4
MRB
Boiling 6.6 a ± 1.43 6.6 a ± 1.77 54.0 a ± 3.1 53.3 a ± 2.2 256.9 a ± 12.3 257.6 a ± 10.1
PC 8.5 b ± 0.59 7.3 a ± 0.42 53.6 a ± 2.6 52.4 a ± 2.2 293.4 b ± 22.8 247.7 a ± 14.2
Germination 5.8 b ± 0.52 4.5
a ± 0.49 55.8
a ± 5.4 53.8
a ± 3.2 250.7
a ± 3.7 221.5
a ± 21.1
Values are mean ± SD (n = 4), means with different superscripts (a, b,) along the row are
significantly (P ≤ 0.05) different, MRB – Maharashtra rabi bajra, TW – tap water, DMW – de-
mineralized water, PC – Pressure cooking.
Results and Discussion
Page 98
Mineral contamination has been reported during the postharvest treatments of
cereals under uncontrolled conditions. Studies on the influence of iron pots and
utensils on iron content in a variety of foods have consistently shown that foods
cooked in iron pots and ⁄ or with iron utensils have significantly higher total iron
content than foods cooked with non-iron equipment (Prinsen et al 2003; Valerie et al
2011). Various food and water samples prepared in pots with and without an iron
ingot revealed low bioavailability of contaminant iron, while, approximately 75% of
the daily iron requirement was met by consuming 1L of lemon water prepared with an
iron ingot. Its use may be a cheap and sustainable means of improving iron intake for
those with iron-deficient diets (Christopher et al 2011). The introduction of iron pots
for the preparation of food may be a promising innovative intervention for reducing
iron deficiency and iron deficiency anemia (Prinsen et al 2003). Since this study was
an approach towards household practice, it was interesting to find out the extent of
contamination with extrinsic iron, calcium or potassium. Table 4.6 showed that
pressure cooked or germinated K variety millet, prepared using tap water had 1.3 and
48.4 mg/100g more iron and phosphorus than those prepared using de-mineralized
water. Similarly, pressure cooked MRB contained 1.2 and 45.7mg/100g more iron
and phosphorus. However, germinated MRB contained 1.3 mg/100g of more iron.
Millet cooked in tap water had around 1.3 mg/100 of iron and 47mg/100 of
phosphorus; however calcium contamination due to use of tap water for processes like
cooking or germination was not seen and also mineral transfer during the process of
boiling the millet was not seen.
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Table 4.7. Antinutrient Content of Pearl Millet as Influenced by Processing
Processing
treatments
Phytin
Phosphorus
(mg/100g)
Phytate
(g/100g)
Oxalate
(mg/100g)
Tannin
(g/100g)
Total Dietary
fiber (g/100g)
Kalukombu
WF (Raw) 219.1 c ± 5.50
0.78
c ± 0.02 36.0
b ± 4.90 0.23
c ± 0.01 13.3
a ± 1.80
SRF 186.6 b ± 18.30 0.66 b ± 0.06 45.2 c ± 1.94 0.21 b ± 0.01 9.20 a ± 0.20
BRF 277.7 d ± 17.30
0.99
d ± 0.06 65.8
d ± 10.4 0.31
d ± 0.01 28.0
b ± 5.00
Boiling 159.9 b ± 34.70 0.57 b ± 0.11 26.0 a ± 3.30 0.18 a ± 0.01 12.5 a ± 0.30
PC 164.5 b ± 12.60
0.58
b ± 0.04 35.3
b ± 2.10 0.18
a ± 0.01 12.6
a ± 0.70
Roasting 121.7 a ± 14.30 0.43 a ± 0.06 33.8 b ± 1.50 0.20 b ± 0.00 12.2 a ± 0.30
Germination 104.1 a
± 22.90
0.37 a
± 0.07 27.5 a ± 2.69 0.36
e ± 0.01 13.4
a ± 0.40
MRB
WF (Raw) 160.6 d ± 18.30 0.57 cd ± 0.07 31.6 b ± 1.10 0.21 a ± 0.02 11.9 a ± 1.80
SRF 93.2 ab
± 24.60
0.33 ab
± 0.09 41.8 c ± 0.97 0.19
a ± 0.01 10.6
a ± 0.40
BRF 326.5 d ± 13.60 0.61 d ± 0.10 58.4 d ± 8.27 0.32 b ± 0.01 29.1 b ± 7.80
Boiling 109.9 bc
± 12.50
0.39 ab
± 0.04
22.5 a ± 2.30 0.19
a ± 0.01 9.8
a ± 0.80
PC 167.8 d ± 16.20
0.60
d ± 0.06 30.7
b ± 3.20 0.22
a ± 0.02 11.1
a ± 0.20
Roasting 245.6 c ± 6.90
0.45
bc ± 0.11
22.6
b ± 3.70 0.23
a ± 0.03 11.7
a ± 1.00
Germination 75.60 a
± 3.20
0.26 a ± 0.01 16.4
a ± 1.77 0.28
a ± 0.01 9.7
a ± 0.10
Values are mean ± SD (n = 4), Means with different superscripts (a, b, c, d) along the column
are significantly different (P ≤ 0.05), MRB – Maharashtra rabi bajra, WF – Whole flour, SRF
– Semi refined flour, BRF – Bran rich fraction, PC – Pressure cooking.
Results and Discussion
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The antinutrient content of raw and processed pearl milled is presented in Table
4.7. The phytin P content of K variety was 219.1 and 160.6 mg/100g in MRB. The
phytin P values were used to derive phytic acid content by assuming 28.20% of
phosphorus is present in the molecule. Bran rich fraction (BRF) retained significant (P
≤ 0.05) phytin P and phytate content. As a result, semi refined flour contained lower
values for phytin P and phytic acid. This result correlate well with an earlier report on
pearl millet as well as wheat, stating that debranning to get refined flours considerably
reduced the phytate content, signifying the distribution of phytate in the outer layers
(Guansheng et al. 2005; Pawar et al. 2006). Pearl millet subjected to heat treatments
and germination respectively decreased Phytin P and phytate content (P ≤ 0.05).
The oxalate content was relatively low in pearl millet (31.6 and 36.0mg/g for K
and MRB). Heat treatments (boiling) and germination respectively further reduced
oxalate content to about 26% and 19% for K and MRB. Milling fractions such as SRF
and BRF retained significant (P ≤ 0.05) amounts of oxalate (ranging from 41.8 to
65.8mg/100g). Nevertheless, the values for the processed millet (except for BRF)
were below 50mg/100g, falling in the range of low oxalate foods. Similar amounts of
oxalates were found to occur widely in many vegetables and fruits which do not pose
a nutritional problem (Fasset, 1973; Ruth et al 2002).
Tannins are polyphenolic compounds which bind to proteins, carbohydrates
and minerals thereby reducing digestibility of these nutrients (Linda et al 2006). The
tannin content of pearl millet varied between the two varieties (K-0.23% and MRB-
0.21% tannic acid equivalents). However, these values were within the range reported
for millets (Pawar et al 1990; Ahmed et al 1996). The bran rich fraction of both
varieties retained most of the tannin content (about 0.32%). This increase can be
Results and Discussion
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attributed to concentration of tannins in the seed coat of the grain (Shivani et al 2004).
Tannin content significantly (P ≤ 0.05) reduced upon heat treatments but results
varied between the two varieties studied. Germination has been reported to reduce the
tannin content and improve in vitro digestibility of proteins in legumes (Maeda et al,
1991). In contrast, germination of pearl millet significantly (P ≤ 0.05) increased the
level of tannin in both varieties (from 0.21 to 0.28g/100 in MRB and 0.23 to
0.36g/100g in K).
The total dietary fiber content of the whole flour was higher in K variety
(13.3%) than MRB (11.91%). BRF had high total dietary fiber content (about
28.5g/100g). Heat treatments and germination did not did not bring about any
significant changes in the total dietary fiber content of pearl millet.
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Table – 4.8. Total and Soluble Amylose Content of Pearl Millet as Influenced by
Processing (g/100g)
Processing Soluble Amylose Total Amylose
K MRB K MRB
WF (raw) 1.06 b ± 0.07 1.72 c ± 0.03 3.47 d ± 0.05 2.89 a ± 0.07
SRF 2.15 e ± 0.05 1.60 c ± 0.10 4.29 f ± 0.10 4.81 f ± 0.08
BRF 1.60 c ± 0.12 1.15
b ± 0.07 2.47
a ± 0.02 3.83
d ± 0.03
Boiling 0.86 b ± 0.07 0.85
a ± 0.02 2.99
b ±
0.06 4.52
e ± 0.02
PC 0.53 a ± 0.02 0.85
a ± 0.04 2.51
a ± 0.03 4.93
f ± 0.14
Roasting 1.46 c ± 0.10 1.91
d ± 0.01 3.30
c ± 0.08 3.63
c ± 0.05
Germination 1.92 d ± 0.08 1.55 c ± 0.08 4.12 e ± 0.02 3.30 b ± 0.06
Values are mean ± SD (n = 4), Means with different superscripts (a, b, c, d, f) along the column
are significantly different (P ≤ 0.05), K – Kalukombu, MRB – Maharashtra Rabi Bajra, WF –
Whole flour, SRF – Semi refined flour, BRF – Bran rich fraction, PC – Pressure cooking.
Starch consists of two polydispersed α -D-glucan components, amylose and
amylopectin. Amylose is linear (α-D-[1 - 4]) or slightly branched and when dispersed
in water forms gels. The formation of a gel or paste, which is a determinant of food
texture, depends not only on the starch concentration but also the amount of amylose
and amylopectin leached from the granule and the heating conditions such as
temperature, time, heating velocity and shear stress (Miles et al 1985). Starch is
further classified based on the amylose content, as nonwaxy (17.0 to 31.9%), low
amylose (7.8 to 16.0%) and waxy type (0 to 3.5%) (Nakamura et al 1995). The total
Results and Discussion
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amylose content of defatted K (3.47g/100g) was higher than MRB (2.89g/100g)
(Table 4.8). Of this, 1.72% amylose was soluble in MRB while only 1.02% was
soluble in K. Based on the classification of starch as reported by Nakamura et al. the
starch in pearl millet can be classified as waxy. All the processing treatments
increased total amylose content in K variety with highest increase seen in pressure
cooked (4.93%) millet followed by boiled (4.52%) millet. However, in MRB, only
semi refined flour (4.29%) had the highest total amylose content followed by
germination (4.12%). All the processing treatments, except for wet heat treatment,
increased solubility of amylose content. Highest soluble amylose content was seen in
SRF (2.15%) of K variety followed by roasted MRB (1.91%).
Table 4.9. The Total Dietary Fiber Content and its Fractions of Pearl Millet as
Influenced by Processing (g/100g)
Processing Insoluble Dietary Fiber Soluble Dietary Fiber Total Dietary Fiber
K MRB K MRB K MRB
WF (raw) 12.6 a ± 1.6 10.9
a ± 1.7 0.70
a ± 0.0 1.05
a ± 0.1 13.3
a ± 1.8 11.9
a ± 1.8
SRF 8.6 a ± 0.2 9.2
a ± 0.2 0.65
a ± 0.2 1.5
a ± 0.3 9.2
a ± 0.2 10.6
a ± 0.4
BRF 27.1 b ± 4.9 27.0 b ± 7.8 0.90 a ± 0.1 2.1 b ± 0.5 28.0 b ± 5.0 29.1 b ± 7.8
Boiling 11.9 a ± 0.2 8.2 a ± 0.9 0.65 a ± 0.3 1.6 a ± 0.4 12.5 a ± 0.3 9.8 a ± 0.8
PC 12.0 a ± 0.6 9.9 a ± 0.3 0.63 a ± 0.2 1.2 a ± 0.2 12.6 a ± 0.7 11.1 a ± 0.2
Roasting 11.6 a ± 0.3 10.0 a ± 0.9 0.58 a ± 0.1 1.6 a ± 0.2 12.2 a ± 0.3 11.7 a ± 1.0
Germination 12.2 a ± 0.4 9.0 a ± 0.1 1.2 a ± 0.1 0.68 a ± 0.1 13.4 a ± 0.4 9.7 a ± 0.1
Means followed by different letters (a, b, c) in the same column differ significantly (P ≤ 0.05), K
– Kalukombu, MRB – Maharashtra Rabi Bajra, WF – Whole flour, SRF – Semi refined flour,
BRF – Bran rich fraction, PC – Pressure cooking.
Results and Discussion
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The influence of common household processing methods on the dietary fiber
composition of pearl millet is depicted in Table 4.9. The total dietary fiber content of
the whole flour was higher in K variety (13.3%) than MRB (11.91%). The process of
partial removal of bran by sieving to obtain semi refined flour resulted in a significant
amount of dietary fiber (10.6% - MRB & 9.2% - K). Dehusking has been reported to
decrease dietary fiber content in pulses (Ramulu et al 1997). The bran rich fraction, a
byproduct of flour milling contained around 29% of total dietary fiber of which
around 1.5% was soluble and 27% was insoluble fraction. By virtue of its high fiber
content, the bran rich fraction can be used as a novel source of dietary fiber. Semi
refined flour of pearl millet can also be used in bakery products as it will contribute to
both the texture and fiber content of the products.
From the nutritional point of view, data on dietary fiber content of processed
millet is of importance, because millets are never eaten raw. In this study, wet and dry
heat treatment of the millets did not considerably change the insoluble and soluble
dietary fiber content. Although, boiling, pressure cooking and roasting increased the
SDF in MRB, it was statistically not significant. Changes in dietary fiber composition
of processed cereal and pulses have been reported where increase in TDF content
could be due to formation of resistant starch (Ramulu et al 1997).
Germination is an inexpensive technique for improving the nutritional quality of
millet seeds. The total dietary fiber content of germinated millet was 9.68% in MRB
and 13.4% in K variety. The results indicate that germination did not alter the total
dietary fiber and its fractions. Studies have indicated that germination has a
significant impact on the dietary fiber content. In legumes, germination increased the
dietary fiber content, while another study reported a decrease in dietary fiber content
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due to germination, which could be partly attributed to the conversion of complex
carbohydrates into simpler molecules by the action of hydrolyzing enzymes
(Mahadevamma et al 2003; Mathers 1989).
Table 4.10. Total Sugar Content of Pearl Millet as Influenced by Processing
Processing Total sugars (g/100g)
Kalukombu MRB
WF (Raw) 0.10 ab
± 0.00 0.06 a ± 0.00
Semi Refined Flour 0.11 abc
± 0.00 0.15 c ± 0.01
Bran Rich Fraction 0.19 d ± 0.00 0.21
d ± 0.02
Boiling 0.09 a ± 0.00 0.12 b ± 0.01
Pressure Cooking 0.14 c ± 0.02 0.12 b ± 0.00
Roasting 0.12 bc ± 0.00 0.13 bc ± 0.00
Germination 0.35 e ± 0.02 0.39 e ± 0.01
Means followed by different letters (a, b, c) in the same column differ significantly (P ≤ 0.05);
MRB – Maharashtra Rabi Bajra,
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The total sugar content in the whole flour of K and MRB was 0.10% and
0.06% (Table 4.10). Overall, the milling fractions showed an increase in the total
sugar content for both varieties. Semi refining of MRB (0.15%) showed a substantial
increase in the total sugar content while; the same did not alter the sugar content of K
variety (0.11%). A three-fold increase in the total sugar content was noticed in the
germinated sample (about 0.37%) followed by 0.20% in BRF of both varieties.
Degradation of starch in grains during germination led to the increase in small dextrin
and fermentable sugar (Wijngaard et al 2005). Wet and heat treatments such as
boiling, pressure cooking and roasting respectively caused a marginal increase in the
total sugar content of both varieties compared to whole flour (raw).
Table 4.11. Total Soluble Protein Content of Pearl Millet as Influenced by
Processing
Processing Total soluble proteins (g/100g)
K MRB
WF (Raw) 2.63 b ± 0.18 3.63 c ± 0.30
Semi Refined Flour 2.48 b ± 0.22 3.75 c ± 0.41
Bran Rich Fraction 2.83 b ± 0.68 2.72
b ± 0.41
Boiling 0.92 a ± 0.10 2.04
a ± 0.35
Pressure Cooking 1.03 a ± 0.19 1.48
a ± 0.10
Roasting 1.29 a ± 0.12 1.51
a ± 0.39
Germination 2.76 b ± 0.46 3.68 c ± 0.34
Means followed by different letters (a, b, c) in the same column differ significantly (P
≤ 0.05); K – Kalukombu, MRB – Maharashtra Rabi Bajra.
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Soluble protein content of raw and processed pearl millet ranged from 0.92 to
2.83% in K variety and 1.48 to 3.75% in MRB (Table 4.11). Overall, both varieties
showed similar response to milling, heat treatments and germination. All the heat
treated samples (boiled, pressure cooked and roasted respectively) showed a
significant and sharp decline in the total soluble protein content however, semi
refining or germination did not alter the total soluble protein content in both varieties.
MWM – Molecular weight marker, WF – Whole flour, SRF – Semi refined flour, BRF – Bran
rich fraction.
Figure 4.1. Effect of Milling on Protein Profile of Pearl Millet
Results and Discussion
Page 108
MWM – Molecular weight marker, PC – Pressure cooking
Figure 4.2: Effect of Heat Treatment on Protein Profile of Pearl Millet
MWM – Molecular weight marker.
Figure 4.3: Effect of Germination on Protein Profile of Pearl Millet
Results and Discussion
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The SDS – PAGE was performed on the soluble protein extracts of two pearl
millet varieties (K and MRB) that were subjected to various processing treatments.
Both varieties showed similar electrophoretic patterns. The milling fractions were
classified as whole flour (WF), semi refined flour (SRF) and bran rich fraction (BRF).
The main protein bands at 38, 30 and 23 kDa along with some minor sub units of 66.2
and 45.0 kDa were found in the milling fractions of K and MRB (Fig. 4.1).
Protein bands of 66.2 and 45.0 kDa were prominent in all the heat treated millet
samples and low molecular weight protein bands were sparse in these samples.
Further wet heat treatment resulted in an enhanced appearance of 45, 42 and 36 kDa
in K and 35 to 38 kDa in MRB that was subjected to boiling (Fig. 4.2). Pearl millet
subjected to pressure cooking showed three characteristic bands of 40, 27 and 19kDa,
While, expression of only low molecular weight bands were found in MRB grains. In
roasted grains, the most prominent band was seen at 36 kDa. Further, expression of
low molecular weight bands was more prominent in K grains compared to MRB. In
general heat treatments caused shearing of protein, identified as a streak in the gel.
Upon germination a number of minor bands were concentrated between 34 –
14.4 and 45 – 35 kDa (Fig. 4.3). Biochemical as well as physical changes occur in
millets during germination. Functional proteins are synthesized in millet under a stress
circumstance, such as disease, physical or chemical stress. The stress plays an
important role in germination in the course of physiological response and functional
protein synthesis (Jingjun et al 2008).
Summing up, the results of the present investigation demonstrated a wide
variation in the nutrient composition of raw and processed pearl millet. MRB
contained higher protein and fat, while K variety exhibited higher ash reflecting its
Results and Discussion
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high mineral content. The bran rich fraction (BRF), a by product of milling, retained
significant amounts of fat, ash as well as antinutrients. Semi refining of pearl millet
flour displayed desirable nutritional qualities of both whole and refined flour. Heat
treatments and germination respectively reduced proteins, fat and ash content.
Functional properties varied with the processing methods with germination showing
higher bulk density. Variations in the total mineral content due to processing were
seen. For example, milling and heat treatment lowered iron, while the same was high
in the germinated millet. Calcium increased with the processing methods applied
while phosphorus reduced due to heat treatments and germination respectively.
Results and Discussion
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CHAPTER – 2
STUDIES ON ISOLATED STARCH FROM PEARL MILLET
Starch is the chief dietary source of carbohydrates and is the most abundant
storage polysaccharide in plants. It is present in high amounts in roots, tubers, cereal
grains and legumes (Eerlingen et al 1995). Starches have been used in the food
industry for variety of applications. The range of food products utilizing starch in one
form or another are soup, stew, gravy, pie filling, sauce or custard. Starch contributes
greatly to the textural properties of various foods and has many industrial applications
as a thickener, colloidal, stabilizer, gelling agent, bulking agent, water retention agent
and adhesive (Singh et al 2003).
Starch is a major component of pearl millet. In different pearl millet
genotypes the starch content of the grain varied from 62.8 to 70.5 % (Taylor 2004).
Attempts to isolate starch from pearl millet have been previously reported (Hadimani
et al 2001; Adelaide et al 1980; Hoover et al 1996). Most of the researchers used
random – mating bulk populations of pearl millet or cultivars grown in crop research
institutes for their research work. However, reports on isolated starch from local or
commercial varieties are scanty. Starch from the two commercially available pearl
millet varieties were isolated (K and MRB) and evaluate for its functional properties,
proximate composition, pasting and X-ray diffraction. The gelatinized pearl millet
starch was analyzed for nutritionally important starch fractions [rapidly digestible
starch (RDS), slowly digestible starch (SDS), and resistant starch (RS)] as described
by Englyst et al (1992).
Results and Discussion
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Table – 4.12. Chemical Composition of Corn and Pearl Millet Starches (g/100g)
Corn Kalukombu MRB
Yield† – 24.50
a ± 0.50 29.40
b ± 0.45
Moisture 9.62 a ± 0.14 12.81
b ± 0.20 12.47
b ± 0.20
Proteins£ 0.19 a ± 0.01 0.55
b ± 0.01 0.53
b ± 0.01
Fat 0.00 a ± 0.00 0.37 b ± 0.05 0.38 b ± 0.02
Ash 0.096 a ± 0.00 0.103 a ± 0.00 0.103 a ± 0.00
Total Amylose 16.8 c ± 0.06 14.0
a ± 0.10 15.0
b ± 0.16
† – The value represents the mean of three determinations, on whole flour basis
£ – Nitrogen x 6.25
Means followed by different letters (a, b, c) in the same column differ significantly
(P ≤ 0.05), MRB – Maharashtra rabi bajra.
Corn starch (control) K starch MRB starch
Figure 4.4. Pictures of Corn and Pearl Millet Starches
Results and Discussion
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The chemical composition of isolated starch from pearl millet is presented in
Table – 4. 12. The results revealed that MRB variety contained 29.4% starch which
was higher than K variety (24.5%) on the whole flour basis. However these values
were low when compared with the reported value (Wankhede et al 1990; Hoover et al
1996). The variations in the yield of starch from pearl millet may be due to isolation
and purification methods adopted by the researcher. The moisture content of pearl
millet starch was approximately 12% which was higher than corn starch (9.62%). The
amount and distribution of water within starch granules is important in relation to the
physical properties and chemical reaction of starch (Kokini et al 1992). The reported
moisture content of pearl millet starch was 10.18% while for cocoyam Starch; it
ranged from 9.4 to 17.3% which was considered to be within the acceptable range
(Wankhede et al 1990; Horsfall et al 2009). The protein content of pearl millet
starches (0.55 and 0.53% in K and MRB) was higher than corn starch (0.19%) and
were in the range reported by researchers (Wankhede et al 1990; Adelaide et al 1980).
The fat content of pearl millet starches was 0.37 and 0.38% for K and MRB. These
values were less than that reported (0.45 – 0.51%) (Hoover et al 1996). The amylose
content of the starch was approximately 14.5%. According to reported values (Badi
et al 1976) pearl millet starch contains 17% amylose.
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Table – 4.13a. Water Holding Capacity, Oil Holding Capacity and Bulk Density
of Pearl Millet and Corn Starches.
Isolated Starch WHC (g/g) OHC (g/g) Bulk Density (ml/g)
Corn (C) 0.41 a ± 0.01 1.90 c ± 0.08 1.85 a ± 0.05
Kalukombu 0.48 b ± 0.01 0.73
a ± 0.08 1.90
a ± 0.05
MRB 0.44 ab ± 0.03 1.27 b ± 0.09 1.90 a ± 0.05
Means followed by different letters (a, b, c) in the same column differ significantly (P ≤ 0.05),
MRB – Maharashtra Rabi Bajra.
4.13b. Swelling Power and Solubility of Pearl Millet and Corn Starches (g/g).
Starch 55 oC 65 oC 75 oC 85 oC 95 oC
Corn
(Control)
SP 1.80 a ± 0.00 2.10
b ± 0.05 7.40
c ± 0.01 8.50
d ± 0.01 8.54
d ± 0.04
Solubility 0.001 a ± 0.0 0.029
e ± 0.0 0.009
b ± 0.0 0.018
c ± 0.0 0.024
d ± 0.0
K
SP 2.02 a ± 0.01 5.43 b ± 0.05 7.62 c ± 0.05 8.76 d ± 0.05 12.13 e ± 0.03
Solubility 0.001 a ± 0.0 0.035 c± 0.0 0.027 b± 0.0 0.015 b± 0.0 0.024 b± 0.0
MRB
SP 2.77 a ± 0.05 4.60
b ± 0.01 7.19
c ± 0.02 10.75
d ± 0.04 12.06
e ± 0.04
Solubility 0.001 a ± 0.0 0.053
d ± 0.0 0.048
e ± 0.0 0.018
b ± 0.0 0.025
c ± 0.0
Means followed by different letters (a, b, c) in the same column differ significantly
(P ≤ 0.05), K – Kalukombu, MRB – Maharashtra rabi bajra, SP – Swelling power.
Results and Discussion
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K-Kalukombu, MRB- Maharashtra rabi bajra
Figure 4.5. Swelling Power and Solubility of Pearl Millet and Corn Starches
The ability to hold water is an important functional attribute of all flours and
starches used in food preparations such as custard, dough etc. The observed water
holding capacity (WHC) of the starches was lower than that reported for pearl millet
starch (Adelaide et al 1980). The ability of food materials to absorb water is
sometimes attributed to its proteins content (Kinsella 1976). The observed WHC of
starches studied cannot, however, be attributed to the protein content since pearl
millet starch in particular has low protein. Oil holding capacity (OHC) is useful in
structure interaction in food especially in flavor retention, improvement of palatability
and extension of shelf life particularly in bakery or meat products (Adebewale et al
2004). The range of OHC of the starch samples (0.73 – 1.90ml/g) showed that corn
Results and Discussion
Page 116
starch (1.90ml/g) had highest OHC followed by MRB (1.27ml/g) and K (0.73ml/g)
(Table 4.13a). The higher OHC of the millet flour could be due to its higher fat
contents, which can entrap more oil. Basically, the mechanism of OAC is mainly due
to the physical entrapment of oil by capillary attraction (Kinsella 1976).
Swelling and solubility of starches provides indication of noncovalent bonding
between molecules within starch molecule (Horsfall et al 2009). Swelling and
solubility of pearl millet and corn starches were determined over a range of
temperatures (55 – 95oC). Swelling power of pearl millet and corn starches (Table
4.13b & Fig 4.5) showed the amount of water absorbed significantly (P ≤ 0.05)
increased with increase in temperature (55 – 95oC). Swelling behavior of starch is
mainly due to swelling of amylopectin (Tsai et al 1997). Starch from K and MRB had
significantly (P ≤ 0.05) higher swelling power than corn starch. The swelling power
has been shown to be influenced by the amylose/amylopectin ratio and by the
characteristics of amylose and amylopectin in terms of molecular weight distribution,
degree of branching, length of branches and conformation of the molecules (Hoover
et al 2002).
The solubility pattern was determined in conjunction with swelling power (Table
4.13b & Fig 4.5). Solubility patterns did not basically follow swelling patterns. Pearl
millet and corn starches had higher solubility at 65oC. From 65 to 95
oC, all the starch
samples were less soluble in water. As the swelling of starch increased with increase
in temperature, its solubility decreased. Similar trend was also seen in pearl millet raw
and processed flours.
Results and Discussion
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Results and Discussion
Page 118
Figure 4.6. X – Ray Deffractograms of Pearl Millet and Corn Starches and Pearl
Millet Flours
Starch is a semi crystalline polymer with low and imperfect crystallinity. The
crystal structures in native starches are formed by packing of hexagonal arrays of
amylopectin in helical coils. The amylopectin side chains, organized in double helices
and constituting the crystalline fraction of starch, are considered as mesogens,
attached to the backbone through amorphous and flexible spacer units. The length of
these amylopectin double helices are related to the crystalline morphology of starch
(short double helices related to A – type and long double helices to B – type) (Zobel
et al 1988; Amparo et al 2007). Native starch granules display quite a complex
structure with several levels of organization. Starch constituting two main polymers
(essentially linear amylose and branched amylopectin) is distributed in amorphous
Results and Discussion
Page 119
and semi crystalline concentric shells. (Amparo et al 2007). Heat and humidity
involved in many processing conditions results in the disruption of starch’s structure,
a phenomenon known as gelatinization. Gelatinization involves loss of granular and
crystalline structures by heating with water and often including other plasticizers or
modifying polymers (Vermeylen et al 2006). Information regarding starch granule’s
crystalline properties can be acquired by X – ray diffraction studies by exposing the
starch samples to X – ray beam. Starch can be classified as A, B and C forms. In the
native granular forms, the A pattern is associated mainly with cereal starches, while
the B form is usually obtained from tuber starches. The C pattern is a mixture of both
A and B types, but also occurs naturally, e.g. smooth-seeded pea starch and various
bean starches (Norman et al 1998). The X – ray diffraction patterns of corn and
isolated pearl millet starches as well as whole flour of pearl millet are presented in
Fig. 4.6. The results revealed that pearl millet starches showed X – ray patterns
similar to corn starch (control). Corn starch exhibited sharper peaks at 2θ values of
14.69, 18.08 and 22.86 with an unresolved doublet at 2θ of 17.02. Similarly, K variety
showed peaks at 2θ values 14.92, 17.8 and 23.26 while MRB showed peaks at 15.3,
18.44 and 23.2. The diffraction pattern of corn and pearl millet starches was similar
to any other unprocessed cereal starch indicating its semi crystalline nature. The
whole flour of K exhibited diffraction patterns similar to its isolated starch but for a
slight shift in the 2θ values (from 15.36 to 14.92, 17.48 to 16.94 and 18.2 to 17.8
respectively). Whole flour and isolated starch from MRB exhibited similar diffraction
patters. However, the intensity of the peaks for the starch was comparatively higher
than that of the respective whole flour samples. The X – ray diffractograms mainly
represent the type of the starch present in the sample. Apart from starch which is the
Results and Discussion
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major component of the whole flour, it also contains other components such as
proteins, dietary fiber, fat etc. The presence of these components may slightly
interfere with the diffraction pattern of the samples. Hence, slightly sharper peaks for
the starch samples may be expected. It was observed from the diffractograms that
these samples exhibited ‘A’ type diffraction pattern similar to any other cereal
starches (Norman et al 1998). The sharp peaks in an X – ray diffractogram are
directly correlated to crystalline region and the diffused peaks to amorphous region of
the samples (Usha et al 2011). In the present study, all the three starches exhibited
semi – crystalline type.
Table – 4.14. Nutritionally Important Starch Fractions of Corn and Pearl Millet
Starches (g/100g).
Means followed by different letters (a, b, c) in the same column differ significantly (P ≤ 0.05).
K – Kalukombu, MRB – Maharashtra rabi bajra, TS – total starch, RDS – rapidly digestible
starch, SDS – slowly digestible starch, RS – resistant starch, RAG – readily available glucose.
Starch TS RDS SDS RS SDI RAG
Corn (C) 20.2 a ± 0.25 10.2
a ± 0.27 7.2
a ± 0.35 2.8
b ± 0.52 50
a ± 1.00 11.3
a ± 0.30
K 22.5 b ± 0.80 11.3
b ± 0.31 9.0
b ± 0.29 2.2
ab ± 0.23 50
a ± 0.45 12.5
b ± 0.34
MRB 21.5 ab
± 0.00 12.2 c ± 0.18 7.9
a ± 0.34 1.4
a ± 0.19 57
b ± 0.84 13.6
c ± 0.20
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Nutritionally important starch fractions of starch from two pearl millet
varieties and corn (control) is presented in table 4.14. Gelatinization is an important
step in starch processing; hence all the starch samples were gelatinized prior to
analysis (sample to water ratio of 1:4) and expressed on an as eaten basis. Starch is
the main carbohydrate in human nutrition and is chiefly divided into rapidly digestible
starch (RDS), slowly digestible starch (SDS), and resistant starch (RS). RDS and SDS
in pearl millet starches were higher than corn starch (control). However RS content
was higher in corn (2.8) and K (2.2) while lower in MRB (1.4). The lower RS content
of these gelatinized starches was apparently due to the elimination of structural
obstruction to amylase hydrolysis during the process of starch isolation (Perera et al
2010). Also during the process of gelatinization which involves uptake of water and
heat by starch granules lead to the disruption of the crystalline structure and
consequently increased accessibility of glucose chains to amylolytic enzymes
(Sadequr et al 2007). The pearl millet starches had similar total starch (TS) content
which was higher than corn starch.
A measure of the relative rate of starch digestion is given by starch digestion
index (SDI). In the present investigation, SDI ranged from 50 (K and corn) to 57
(MRB). Similar values were reported for freshly cooked spaghetti (52), millet (55)
and lentils (44). The rate of starch digestion was comparatively low in the starch
isolated from pearl millet and corn (control) may be due to the fact that the physical
form of these starches which are millet based possibly render starch partly
inaccessible to the digestive enzymes (Englyst et al, 1992). The simple in vitro
measurement of RAG and SAG is of physiologic relevance and could serve as a tool
for investigating the importance of the amount, type, and form of dietary
Results and Discussion
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carbohydrates for health (Klaus et al, 1999). RAG values are those which represent
the amount of glucose that can be expected to be rapidly available for absorption after
a meal. It is a better indicator of blood glucose and insulin response as it includes
RDS and FG (Free glucose). RAG ranged from 11.3 (Corn) to 13.6 (MRB). Similar
RAG values were reported for instant potatoes, millet and spaghetti (approx. 13%)
(Englyst et al 1992). Low RAG values could be attributed to the fact that time for
gelatinization was too short for complete gelatinization of starch molecules and due to
the dense matrix which hindered enzymatic hydrolysis of starch.
In conclusion, the yield of starch from pearl millet was lower (about 26.5%)
than that reported (Wankhede et al 1997; Hoover et al 1996). Water and oil holding
capacity of pearl millet starched were higher that corn starch. Swelling power of corn
and pearl millet starches increased with increase in the temperature (55 to 95 oC).
However solubility patterns did not follow the trend set by swelling power. As the
swelling power increased with temperature, its solubility decreased. X – Ray
diffraction of corn and pearl millet starches exhibited semi crystalline structure.
Relatively sharper peaks exhibited in the starch compared to respective whole flour
suggested the interference of other components such as proteins, fat etc. An invitro
method for measuring nutritionally important starch fraction provided a means for
predicting the rate and extent of digestion in the human digestion. Although RDS and
SDS were lower than corn starch, RS and TS were relatively higher.
Results and Discussion
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CHAPTER – 3
ANTIOXIDANT COMPONENTS AND ACTIVITY OF PEARL MILLET AS
INFLUENC ED BY PROCESSING
The term “phytochemicals” or “plant chemicals” refers to every naturally
occurring chemical substance present in plants, which also has a potential for
antioxidant activity. Antioxidants play an important role in the body defense system
against reactive oxygen species (ROS), which are the harmful byproducts generated
during normal cell aerobic respiration (Boxin et al 2002). In foods, antioxidants
prevent undesirable changes in flavor and nutritional quality of a product (Zielinski et
al 2000). Several methods have been developed to measure “Antioxidant activity”.
Commonly used assays are reducing power assay (RPA), ferric reducing antioxidant
power (FRAP) and DPPH free radical scavenging activity. There are two basic
categories of antioxidants, namely, natural and synthetic. Examples of nature
antioxidants are phenolic compounds (tocopherols, flavonoids, and phenolic acids),
nitrogen compounds (alkaloids, chlorophyll derivatives, amino acids, and amines),
carotenoids and ascorbic acid. Butylated hydroxyanisole (BHA) and butylated
hydroxytoluene (BHT) are examples of commonly used synthetic antioxidants that
have been in use since the beginning of this century. Restrictions on the use of these
compounds, however, are being imposed because of their carcinogenicity (Velioglu et
al 1998; Hudson 1990). Thus, natural antioxidants have gained considerable interest
in recent years.
Cereals and millets are the most commonly consumed food items in India.
They contain wide range of phenolics which are good sources of natural antioxidants.
Studies report that methanolic extracts from red sorghum showed higher antioxidant
Results and Discussion
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activity and contain higher polyphenolic levels compared to rice, foxtail millet,
prosomillet and barley (Youngmin et al 2007). Bran, a byproduct of milling has
antioxidant potential due to phenolic acids such as p- coumaric acid and vanillic acids
that are concentrated in the bran portion of cereal kernels. Antioxidant activity of five
bran extracts exhibited appreciable levels of total phenolics, flavonoids and DPPH
radical scavenging activities (Shahid et al 2007). Processing such as soaking and
roasting have been shown to influence total phenolic, flavonoid and antioxidant
contents in selected dry beans. Raw kodo millet and finger millet have higher DPPH
radical scavenging activities. However cooking of these millets by roasting or boiling
reduced their antioxidant activity (Prashant et al 2005).
Millets contain phytic acid, tannins, phenols which can contribute to
antioxidant activity important in health, ageing and metabolic diseases. Pearl millet
(Pennisetum typhoideum) is the most widely grown type of millet. Nutritionally, pearl
millet is superior to major cereals with reference to energy value, high quality
proteins, fat and minerals such as calcium, iron, zinc. Besides, it is also a rich source
of dietary fiber and micro nutrients (Anu Sehgal et al 2006; Malik et al 2002). While,
extensive information is available on proximate composition and mineral
accessibility, information on antioxidant activity and its influence on processing in
pearl millet are scanty. Research on the effect of processing on retention of bioactive
components with potential antioxidant activity is very important.
The objective of this investigation was to evaluate the effect of various
processing methods (milling, heat treatments and germination respectively) on
antioxidant components as well as antioxidant activities of pearl millet extracts. The
methanolic extracts of raw and processed pearl millet were analyzed for DPPH free
Results and Discussion
Page 125
radical scavenging activity; reducing power assay (RPA) and ferric reducing
antioxidant power (FRAP) assays respectively. The samples were also evaluated for
tannin, phytic acid and flavonoid content and were correlated with the antioxidant
activity assayed using three methods.
Table 4.15. Yield of Methanolic Extracts from Pearl Millet as Influenced by
Processing (g/100g)
Processing Kalukombu MRB
Whole flour (Raw) 5.8 cd ± 1.20 4.4 bc ± 0.87
Semi refined flour 4.8 bc ± 0.30 3.7 abc ± 0.26
Bran rich fraction 2.1 a ± 0.05 3.2
ab ± 0.15
Boiling 2.4 ab
± 0.38 2.2 ab
± 0.14
Pressure cooking 2.2 a ± 0.10 1.8
a ± 0.04
Roasting 3.0 ab
± 0.03 2.3 ab
± 0.04
Germination 7.7 d ± 0.12 6.1 c ± 0.34
Values are mean ± SD (n = 4), Means with different superscripts (a, b, c, d) along the column
are significantly different (P ≤ 0.05), MRB - Maharashtra Rabi Bajra.
Results and Discussion
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Antioxidants are difficult to extract due to differences in the active
compounds. A wide variation is seen in detecting antioxidant components due to
differences in the polarity of the extracting solvents. Methanol is a relatively polar
organic solvent and appears to be efficient in extracting compounds such as phenolics,
flavonoids, and other polar material from millets (Florence et al 2010; Singh et al
2002). Methanol was therefore selected as an extracting solvent in the present
investigation. Table 4.15 exhibits the yield of methanolic extracts obtained from the
raw and processed two pearl millet varieties. The K variety (5.8g/100g) had higher
yield than MRB (4.4g/100g). Wide variations in the yield as a result of processing
were seen. Lower yields were seen in the millet subjected to heat treatments (boiling,
pressure cooking, roasting) as well as in the bran rich fraction while, the processes of
germination facilitated maximum extraction in both varieties; however this increase
was not statistically significant.
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Table 4.16. Effect of Processing on Antioxidant Components of Pearl millet.
Processing
treatments
Tannins (g/100g)† Phytic acid (g/100g) Flavonoids (mg/g)
£
K MRB K MRB K MRB
WF (Raw) 0.23 c ± 0.01 0.21
a ± 0.02 0.78
c ± 0.02 0.57
cd ± 0.07
0.27
ab ± 0.04 0.21
a ± 0.02
SRF 0.21 b ± 0.01 0.19 a ± 0.01 0.66 b ± 0.06 0.33 ab ± 0.09 0.20 a ± 0.07 0.18 a ± 0.02
BRF 0.31 d ± 0.01 0.32
b ± 0.01 0.99
d ± 0.06 0.61
d ± 0.10 0.19
a ± 0.01 0.18
a ± 0.00
Bo 0.18 a ± 0.01 0.19
a ± 0.01 0.57
b ± 0.11 0.39
ab ± 0.04
0.32
abc ± 0.1 0.13
a ± 0.00
PC 0.18 a ± 0.01 0.22 a ± 0.02 0.58 b ± 0.04 0.60 d ± 0.06 0.36 bc ± 0.06 0.13 a ± 0.01
Ro 0.20 b ± 0.00 0.23
a ± 0.03 0.43
a ± 0.06 0.45
bc ± 0.11
0.44
c ± 0.10 0.27
a ± 0.07
G 0.36 e ± 0.01 0.28
a ± 0.01 0.37
a ± 0.07 0.26
a ± 0.01 0.17
a ± 0.02 0.10
a ± 0.02
† - g tannic acid equivalents/100 of dry flour
£ - mg rutin equivalents/g of extract.
Values are mean ± SD (n = 4), Means with different superscripts (a, b, c, d) along the column
are significantly different (P ≤ 0.05), K – Kalukombu, MRB – Maharashtra Rabi Bajra, WF –
Whole flour, SRF – Semi refined flour, BRF – Bran rich fraction, Bo – boiling, PC – Pressure
cooking, Ro – roasting, G – germination.
Results and Discussion
Page 128
Millets contain phytates, phenols, tannins, trypsin inhibitors and dietary fiber
which act as ‘antinutrients’ by chelating minerals. Tannins are naturally occurring
polyphenolic compounds linked to reduce protein digestibility by forming complexes
with proteins and inhibiting enzymes (Aganga et al 2001). It is now established that
phytates, phenols and tannins present in cereals are also good sources of natural
antioxidants important in health, aging and metabolic diseases (Krings et al 2000).
Phytic acid occurring in the grains acts as an antioxidant by the formation of chelates
with prooxidant transition metals. Although, phytic acid is generally regarded as an
antinutrient due to its mineral binding activity it is known to reduce the risk for colon
and breast cancer in animals (Graf et al 1990). Table 4.16 exhibits tannin, phytic acid
and flavonoid content of raw and processed pearl millet. The tannin content of K and
MRB expressed as tannic acid equivalents was 23 and 21g/100g of dry flour. Semi
refining reduced the level of tannins in the SRF thus increasing its levels in BRF
suggesting its localization in the outer hulls of the grain. Millet subjected to various
heat treatments lead to considerable reduction in tannin levels only in the K variety.
On the other hand, the increase in the tannin content of the germinated flour extract in
both varieties was pronounced, however, statistically not significant for MRB variety.
The phytic acid content was highest in K (78g/100g) compared to MRB
(57g/100g). Semi refining significantly reduced the corresponding values to 66 and
33g/100g for K and MRB respectively. They were mainly found concentrated in the
bran rich fraction (99 and 61g/100g K and MRB respectively). Phytic acid content
significantly (P ≤ 0.05) decreased due to heat treatments though maximum reduction
was seen in the germinated millet.
Results and Discussion
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The flavonoid content of raw and processed millet extract were expressed as
mg rutin equivalents per gram of the extract (10mg/ml). The flavonoid content was
high in K (27mg/g) than MRB (21mg/g). The milling fractions (SRF and BRF)
irrespective of varietal differences, showed a reduction in the flavonoid content,
nonetheless, the decrease was not statistically significant. Unlike tannins and phytic
acid, the flavonoid levels considerably increased due to heat treatments (boiling,
pressure cooking, roasting) while, germination did not alter the flavonoid content of
pearl millet.
Results and Discussion
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Table 4.17. Effect of Processing on the Radical Scavenging Activity of Pearl
Millet Extracts by DPPH Method
Processing 200µg 400µg 600µg
K MRB K MRB K MRB
WF (Raw) 22 a12
± 7.2 31 ab1
± 5.7 37 b12
± 7.3 42 b1
± 7.9 42 b1
± 9.3 40 b1
± 7.7
SRF 16 a1
± 3.9 30 bc1
± 8.3 29 b1
± 9.3 41 de1
± 8.8 42 cd1
± 10.5 53 e2
± 3.6
BRF 19 a12
± 7.9 21 a1
± 2.5 31 c12
± 11.5 31 b1
± 1.3 38 d1
± 14.0 40 c1
± 2.9
Boiling 26 a2
± 7.9 26 a1
± 8.3 42 b2
± 11.8 41 b1
± 7.9 57 c23
± 8.6 45 b1
± 6.0
PC 24 a12
± 4.0 23 a1
± 6.7 41 b2
± 7.3 34 b1
± 9.9 57 c23
± 4.5 40 b1
± 0.6
Roasting 23 a12
± 4.3 29 a1
± 9.9 46 b2
± 4.1 45 b1
± 11.3 56 c3
± 3.8 61 c2
± 4.3
Germination 16 a12 ± 2.4 22 a1 ± 5.3 24 a1 ± 5.7 33 b1 ± 8.7 35 b1 ± 4.8 41 b1 ± 3.8
Concentration of the extracts – 10mg/ml, Values are mean ± SD (n = 4), Means with different
superscripts (a, b, c, d) along the row are significantly different (P ≤ 0.05), Values are mean ±
SD (n = 4), Means with different superscripts (1, 2, 3) along the column are significantly
different(P ≤ 0.05) , K - Kalukombu, MRB - Maharashtra Rabi Bajra, WF – Whole flour, SRF
– Semi refined flour, BRF – Bran rich fraction, PC – Pressure cooking.
Results and Discussion
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Bars with different superscripts (a, b, c, d) are significantly different (P ≤ 0.05), WF – whole
flour, SRF – semi refined flour, BRF – Bran rich fraction, Bo – boiling, PC – pressure
cooking, Ro – roasting, G – germination.
Figure – 4.7: Effect of Processing on the Radical Scavenging Activity of Pearl
Millet Extracts by DPPH Method
Table 4.17 and Figure 4.7 summarize data on DPPH radical scavenging
activity of raw and processed pearl millet. In DPPH assay, the color stable DPPH
radical is reduced in the presence of an antioxidant which donates hydrogen to non –
radical DPPH – H (Sanna et al 2006). DPPH free radical scavenging activity was
studied at three concentrations (200 µg, 400 µg and 600 µg). Radical scavenging
activity varied with the processing methods used and was concentration dependent.
Results and Discussion
Page 132
The greatest activity was obtained at a higher concentration of 600µg in the raw and
processed flour extracts. For example, the antioxidant activity of K and MRB which
was 22% and 31% at 200µg considerably increased to 42% and 40% respectively at
600µg. Heat treatments such as boiling; roasting and pressure cooking exhibited
significantly higher antioxidant activity as compared to the raw flour. Similar findings
were reported for little millet where roasting of the millet enhanced its radical
scavenging activity (95.5%), compared to germinated (91.7%) and steamed (93.4%)
millet (Pradeep et al 2011). In contrast, cooked peppers showed a marked reduction
in the radical scavenging activity when cooked for 30 minutes in boiling water. This
may be due to leaching of antioxidant compound from the pepper into cooking was
during the prolonged exposure to water and heat (Ai Mey Chuah et al 2008). It was
noteworthy that significantly high radical scavenging activity in heat treated millet
had the lowest yield, whilst, germinated millet extracts which showed lowest activity
had highest yield.
Results and Discussion
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Table 4.18. Effect of Processing on the Ferric Reducing Power of Pearl Millet
Extracts at Various Concentrations
Processing 200µg 400µg 600µg
K MRB K MRB K MRB
WF (Raw) 0.07 a12
± 0.01 0.06 a1
± 0.01 0.20 c23
± 0.01 0.15 b12
± 0.01 0.31 d1
± 0.03 0.32 d3
± 0.03
SRF 0.06 a1
± 0.02 0.06 a1
± 0.00 0.11 b1
± 0.03 0.13 b1
± 0.01 0.29 c1
± 0.07 0.27 c123
± 0.02
BRF 0.10 b2± 0.03 0.05 a1± 0.02 0.23 e3 ± 0.09 0.14 c12 ± 0.06 0.34 f2 ± 0.11 0.20 d1 ± 0.05
Boiling 0.10 a2
± 0.03 0.08 a1
± 0.01 0.19 b23
± 0.04 0.17 b2
± 0.01 0.47 d2
± 0.04 0.29 c23
± 0.03
PC 0.08 a12
± 0.00 0.06 a1
± 0.01 0.17 b2
± 0.02 0.14 b12
± 0.01 0.29 d1
± 0.03 0.23 c12
± 0.03
Roasting 0.09 a2± 0.01 0.07 a1± 0.01 0.21 c23 ± 0.00 0.16 b12 ± 0.02 0.39 e12 ± 0.09 0.28 d23 ± 0.01
G 0.07 a12
± 0.01 0.07 a1
± 0.02 0.16 b2
± 0.01 0.17 b2
± 0.03 0.29 c1
± 0.02 0. 30
c23 ± 0.02
Concentration of the extracts – 10mg/ml, Values are mean ± SD (n = 4), Means with different
superscripts (a, b, c, d) along the row are significantly different (P ≤ 0.05), Means with different
superscripts (1, 2, 3) along the column are significantly different (P ≤ 0.05), K – Kalukombu, MRB –
Maharashtra Rabi Bajra, WF – Whole flour, SRF – Semi refined flour, BRF – Bran rich fraction, PC –
Pressure cooking, G – germination.
Results and Discussion
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Different superscripts (a, b, c) on each bars are significantly (P ≤ 0.05) different (n = 6), WF
– whole flour, SRF – semi refined flour, BRF – bran rich fraction, Bo – boiling, PC – pressure
cooking, Ro – roasting, G – germination.
Figure – 4.8: Effect of Processing on the Ferric Reducing Power of Pearl Millet
Extracts at Various Concentrations
The ferric reducing power of raw and processed millet is presented in Table
4.18 and Fig 4.8. It was observed that the results followed a similar trend of DPPH
free radical scavenging activity. The reducing power assay of methanolic extracts of
the two pearl millet varieties differed between the processing treatments employed.
Raw and processed millet extracts exhibited lower reducing power at 200 µg,
nevertheless, it increased with the concentration (600µg). The reducing power of K
and MRB flour extracts at 200µg concentration were A700 = 0.07 and 0.06 respectively.
The corresponding values increased to A700 = 0.31 and 0.32 respectively at 600 µg. The
Results and Discussion
Page 135
respective bran rich fraction, roasted and boiled millet extracts of K variety exhibited
an increase in the absorbance (A700 = 0.34, 0.39 and 0.47, respectively) compared to
the raw millet extract (A700 = 0.31) while, processing did not alter the antioxidant
activity (reducing power) of MRB.
Table . 4.19. Effect of Processing on FRAP of Two Pearl Millet Varieties
Processing Kalukombu MRB
Whole flour (Raw) 2.24 ab ± 0.57 1.85 ab ± 0.21
Semi refined flour 2.89 b
± 0.54 1.63 a ± 0.20
Bran rich fraction 2.08 ab
± 0.05 1.72 ab
± 0.09
Boiling 2.18 ab ± 0.03 1.99 ab ± 0.07
Pressure cooking 1.54 a ± 0.11 1.80
ab ± 0.00
Roasting 2.58 b
± 0.33 2.17 b
± 0.12
Germination 2.69 b ± 0.07 1.66 a ± 0.23
Values are mean ± SD (n = 6), Means with different superscripts (a, b, c, d) along the column
are significantly different (P ≤ 0.05), MRB - Maharashtra Rabi Bajra.
Results and Discussion
Page 136
Ferric reducing antioxidant power (FRAP) assay is a novel method for
assessing antioxidant power where the ferric reducing ability of sample extract is
tested. Ferric to ferrous ion reduction at low pH causes a colored ferrous-
tripyridyltriazine complex to form. FRAP values are obtained by comparing the
absorbance change at 593 nm in test reaction mixtures with those containing ferrous
ions in known concentration (Iris et al 1996). In this study, FRAP was calculated
using the equation Y = 0.2453x, where x is the OD of the sample. The ferric reducing
ability of the extracts was higher in K (2.24) followed by MRB (1.85) (Table 4.19).
Pressure cooked K variety and germinated MRB exhibited lowest activity, although
the decrease was not statistically significant. Overall, the processing methods
employed in this study did not cause any significant changes in the activity (FRAP) of
the millet.
Table 4.20. Correlations of Yield and Antioxidant Components with Antioxidant
Activity of Two Pearl Millet Varieties
Pearl millet Yield Phytic acid Tannins Flavonoids
Kalukombu
DPPH – 0.629** – 0.130 – 0.557** 0.712**
Reducing power – 0.361 0.222 – 0.100 0.456*
FRAP 0.478* – 0.148 0.165 – 0.078
MRB
DPPH – 0.317 – 0.279 – 0.121 – 0. 282
Reducing power – 0.317 – 0.273 – 0.110 – 0.282
FRAP – 0.322 0.276 – 0.141 0.181
* – correlation is significant at the 0.05 level (2 tailed); **– correlation is significant at the
0.01 level (2 tailed), MRB – Maharashtra rabi bajra, FRAP – Ferric reducing antioxidant
power.
Results and Discussion
Page 137
The relationship of antioxidant activity with antioxidant components as well as
the yield of methanolic extracts of raw and processed pearl millet is presented in
Table 4.20. There was variation in the antioxidant activity analyzed by different
assays and antioxidant components in K and MRB varieties. The results indicated
significant negative correlations between methanolic extract (r = – 0.629, P ≤ 0.01) as
well as tannin content (r = - 0.557, P ≤ 0.01) while, a positive relationship between
flavonoid content (r = 0.712, P ≤ 0.01) with DPPH free radical scavenging activity.
There was a strong positive relationship between reducing power and flavonoid
content (r = 0.456, P ≤ 0.05) and FRAP with methanolic extracts (r = 0.478, P ≤
0.05). These results suggest that the DPPH radical scavenging activity and reducing
power assay in K variety was largely due to the presence of flavonoids. However, in
MRB, antioxidant components such as phytic acid, tannin and flavonoids were poorly
correlated with antioxidant activity as determined by three methods suggesting that
these components did not contribute to the antioxidant activity of MRB variety.
In conclusion the antioxidant activity of pearl millet varied with the processing
methods and between the two varieties (K and MRB) studied. K variety had higher
content of antioxidant components reflecting its higher antioxidant capacity,
compared to MRB. BRF showed high antioxidant activity in terms of RPA which was
due to tannin, phytic acid and flavonoid levels. The millet subjected to various heat
treatments exhibited higher antioxidant activity (DPPH scavenging activity and RPA)
mainly due to flavonoid content. It was worthy of notice that significantly high radical
scavenging activity in heat treated millet had the lowest yield, whilst germinated
millet which showed lowest activity had highest yield.
Results and Discussion
Page 138
CHAPTE R– 4
STUDIES ON NUTRIENT DIGESTIBILITY (IN-VITRO) OF
PEARL MIL LET
Pearl millet, a lesser known and underutilized crop can be grown at low
maintenance cost, is relatively a cheaper source of nutrients and staple for population
below poverty line for economic reasons. It has the distinct advantage of being a
drought-resistant crop and hence acts as a principle source of energy, protein, fat and
minerals for poor people living in these regions. However, it has some limitations, due
to the presence of antinutritional factors such as phytate, tannins or dietary fiber.
These compounds are known to interfere with mineral bioavailability, carbohydrate
and protein digestibility (Fasasi, 2009; Anu Sehgal et al 2006; Malik et al 2002).
The bioavailability of minerals from foods is defined as the proportion of the
minerals that can be absorbed and utilized within the body (Lestienne et al 2005).
Poor absorption of minerals leads to mineral deficiency resulting in conditions like
anemia. The high prevalence of iron deficiencies in developing countries has several
adverse effects on the population particularly on women and children (Zimmermann
et al 2007).
Carbohydrate digestibility in small intestine is influenced by the food form
(physical form, particle size), type of preparation (cooking method and processing),
type of starch (amylose or amylopectin) and presence of antinutrients, transit time,
and amount of fiber, fat, and proteins (Julia et al 2007). For nutritional purposes,
Englyst and Cummings (1993) classified the starch in foods as rapidly-digestible
starch (RDS), slowly-digestible starch (SDS) and resistant starch (RS). RDS causes a
rapid increase in blood glucose level after ingestion; SDS is digested slowly but
Results and Discussion
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completely in the human small intestine and RS is a portion of starch that cannot be
digested in the small intestine, but may be fermented in the large intestine (Englyst et
al 1992).
Protein digestibility is essentially a measure of the susceptibility of protein to
proteolysis. A protein with high digestibility is potentially of better nutritional value
than one with low digestibility because it provides more amino acids for absorption
on proteolysis. Exogenous (interaction of proteins with non-protein components like
polyphenols, non-starch polysaccharides, starch, tannins, dietary fiber, phytates and
lipids.) and endogenous factors (changes within the proteins themselves) contribute to
poor digestibility of proteins. During the process of milling and cooking, proteins
interact with non-protein components and the proteins themselves thereby affecting
their digestibility (Duodu et al 2003). Studies indicate that dietary fiber and tannins
contribute to lower nutritional value of dietary proteins with soluble dietary fiber
playing a major role in reducing its in vitro digestibility. In beans, soluble dietary
fiber plays a more important role than insoluble dietary fiber in reducing protein
digestibility (Joe Hughes, 1996). The purpose of the present study was to analyze
mineral bioaccessibility, nutritionally important starch fractions and invitro protein
digestibility of two pearl millet varieties as influenced by processing.
Results and Discussion
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Table – 4. 21. In-Vitro Bioaccessible Iron Content of Pearl Millet as Influenced
by Processing
Processing Kalukombu MRB
Mg/100g % Mg/100g %
Whole Flour 0.16 a ± 0.03 3 0.44 c ± 0.07 6
SRF 0.20 ab
± 0.05 4 0.48
c ± 0.05 7
BRF 0.16 a ± 0.01 4 0.20 a ±0.01 4
Boiling 0.24 b ± 0.02 8 0.36 b ± 0.03 5
PC 0.33 c ± 0.03 10 0.33
b ± 0.02 5
Roasting 0.33 c ± 0.02 10 0.30
b ± 0.05 7
Germination 0.21 b ± 0.03 3 0.46 c ± 0.05 10
Values are mean ± SD (n = 6), Means with different superscripts (a, b, c, d) along the column
are significantly different (P ≤ 0.05), MRB – Maharashtra Rabi Bajra, SRF – semi refined
flour, BRF – bran rich fraction, PC – pressure cooking.
Table 4.21 represents data on bioaccessible iron content of pearl millet and its
impact on processing. The bioaccessible iron content of K was 0.16 mg/100g while
that of MRB was 0.44 mg/100g. Milling (SRF and BRF) did not alter the
bioaccessible iron content of pearl millet, except for bran rich fraction (BRF) of
MRB, where a two fold decrease was observed. On the other hand, heat treatments
enhanced iron bioaccessibility which was evident only in K variety. The bioaccessible
Results and Discussion
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iron content of K (0.16mg/100g) was increased to 0.24, 0.33 and 0.33 due to boiling,
pressure cooking and roasting respectively, while germination caused a minimal
increase of 0.21mg/100g. Although, bioaccessible iron content in MRB
(0.44mg/100g) was the highest, it subsequently decreased as a result of processing
with lowest decrease in the bran rich fraction followed by those subjected to heat
treatments.
Table – 4.22. In Vitro Bioaccessible Calcium Content of Processed Pearl Millet
Processing Kalukombu MRB
Mg/100g % Mg/100g %
Whole Flour 30.1 b ± 0.37 67 34.6
c ± 2.41 78
SRF 22.4 a ± 3.64 44 26.1
b ± 2.47 49
BRF 20.8 a ± 1.12 34 15.7 a ± 1.11 18
Boiling 34.5 c ± 2.99 66 34.5
c ± 1.56 65
PC 30. 0
b ± 1.61 64 39.5
c ± 4.89 75
Roasting 35.9 c ± 2.99 72 24.8 b ± 3.22 63
Germination 35.7 c ± 2.51 66 38.0 c ± 3.37 71
Values are mean ± SD (n = 6), Means with different superscripts (a, b, c, d) along the column
are significantly different (P ≤ 0.05), MRB – Maharashtra Rabi Bajra, SRF – semi refined
flour, BRF – bran rich fraction, PC – pressure cooking
Results and Discussion
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The bioaccessible calcium content of K and MRB was 30.1 and 34.5mg/100g
respectively (Table 4.22). K variety subjected to heat treatments such as boiling or
roasting increased the bioaccessible calcium content to 34.5 and 35.9 mg/100g
respectively. Germination also brought about a similar increase in the calcium
bioaccessibility (35.7mg/100g) of K variety. However, in case of MRB, neither of the
processing treatments caused any improvement in the calcium bioaccessibility.
Further, significant (P ≤ 0.05) decrease in the bioaccessible calcium of BRF and
roasted millet was observed. Similar to iron bioaccessibility, processing did not
enhance bioaccessible calcium content of MRB. Cooking is reported to modify seed
composition and lowering of antinutritional factors in turn influencing dialysability of
iron and calcium. (Sreeramaiah et al 2007). This was evident in case of calcium
bioaccessibility studied in both varieties. Calcium in foods exists mainly as complexes
with other factors (phytates, oxalates, fibre, lactate, fatty acids) from which the
calcium must be released to be absorbed and heat treatments aided this process.
Cooking effectively improved bioaccessible calcium while the same was less effective
in improving bioaccessible iron content suggesting that calcium and iron combined in
a meal may decrease iron bioaccessibility.
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Table 4.23. Effect of Processing on Bioaccessible Iron and Calcium as Influenced
by Tap / De – Mineralized Water (mg/100g)
Processing Bioaccessible Iron Bioaccessible Calcium
TW DMW TW DMW
Kalukombu
Boiling 0.25 a ± 0.01 (7) 0.24
a ± 0.02 (8) 35.5
a ± 2.61 (67) 35.9
a ± 2.99 (66)
PC 0.35 a ± 0.02 (8) 0.33
a ± 0.03 (10) 32.7
a ± 2.41 (70) 30.0
a ± 1.61 (64)
G 0.25 a ± 0.03 (3) 0.21
a ± 0.03 (3) 35.9
a ± 13.68 (66) 35.7
a ± 2.51 (66)
MRB
Boiling 0.36 a ± 0.03 (6) 0.37 a ± 0.01 (5) 36.7 a ± 2.63 (69) 34.5 a ± 1.56 (65)
PC 0.33 a ± 0.02 (4) 0.35 a ± 0.04 (5) 36.6 a ± 4.02 (70) 39.5 a ± 4.89 (75)
G 0.46 a ± 0.05 (8) 0.47 a ± 0.01 (10) 40.8 a ± 4.93 (76) 38.0 a ± 3.37 (71)
Values are mean ± SD (n = 4), means with different superscripts (a, b,) along the row are
significantly (P ≤ 0.05) different, values in the parenthesis are % bioaccessible iron/calcium, MRB
– Maharashtra rabi bajra, TW – tap water, DMW – demineralized water, PC – Pressure cooking, G
– Germination.
Studies have report that contamination of iron originating from milling
equipment (mills equipped with iron-containing grindstones) led to a considerable
increase in bioaccessible iron, hence extrinsic iron supplied to food products by the
milling equipment could play a role in iron intake in developing countries (Valerie et
al 2011). Cooking water often contributes to mineral contamination influencing its
bioaccessibility. In view of this, tap water (previously passed through a water purifier)
Results and Discussion
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and de – mineralized water was used in processing treatments like boiling, pressure
cooking and germination respectively to see its effect on bioaccessible iron and
calcium content (Table 4.23). Although iron and calcium bioaccessibility of millet
processed using tap water was higher than de-mineralized water, the difference was
not significant.
Table – 4.24. Molar Ratios of Pearl Millet as Influenced by Processing
Processing [Phytate]/[Calcium]
1 [Phytate]/[Iron]
2 [Calcium]/[Phytate]
3 [Oxalate]/[Calcium]
4
K MRB K MRB K MRB K MRB
WF (Raw) 1.03 0.78 11.77 6.84 0.97 1.28 0.25 0.22
SRF 0.79 0.38 12.32 4.34 1.27 2.63 0.28 0.25
BRF 0.97 0.43 21.38 9.93 1.03 2.31 0.34 0.22
Boiling 0.64 0.65 15.20 7.30 1.57 1.55 0.15 0.13
PC 0.75 0.68 15.02 6.75 1.33 1.48 0.24 0.19
Roasting 0.55 0.70 11.40 9.60 1.82 1.43 0.23 0.18
Germination 0.75 0.42 8.40 6.90 1.33 2.40 0.16 0.10
1 Recommended critical value of [Phytate]/[Calcium] is 0.24, (Morris et al 1985)
2 Recommended critical value for [Phytate]/[Iron] is 1, (Hallberg et al 1989)
3 Recommended critical value for [Calcium]/[Phytate] is 6.1, (Oladimeji et al 2000)
4 Recommended critical value for [Oxalate]/[Calcium] is 1.0, (Davis, 1979)
K – Kalukombu, MRB – Maharashtra Rabi Bajra, WF – Whole flour, SRF – semi refined
flour, BRF – bran rich fraction, PC – pressure cooking.
Results and Discussion
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The bioavailability of minerals depends on the amount of antinutrients and the
ratio of antinutrients/minerals. These ratios are of significance when they are greater
than the recommended critical values. In such cases antinutrients (phytates and
oxalates) have a potential to complex with minerals (calcium/iron) thus impairing its
absorption. The molar rations for [Phytate/Calcium], [Phytate/Iron],
[Calcium]/[Phytate] and [Oxalate]/[Calcium] of raw and processed millet were
calculated to study the effect of oxalate and phytate contents on the bioaccessibility of
calcium and iron (Table 4.24). The phytate/calcium and phytate/iron molar ratios have
to be lower than 0.24 and 1 respectively (Morris et al 1985; Hallberg et al 1989).
Although, K and MRB exhibited molar ratios for phytate/calcium and phytate/iron
above the reference value, it decreased with the processing.
Furthermore, [Calcium]/[Phytate] and [Oxalate]/[Calcium] molar ratios of raw
and processed millet varieties were well below the recommended critical values of 1
and 6.1 respectively (Davis 1979; Oladimeji et al 2000). Oxalate forms insoluble
calcium salt with a 1:1 molar stoichiometry in the intestine thus, rendering calcium
unavailable for absorption. In view of this, the importance of the oxalate content in
limiting total dietary Calcium availability is of significance only when the calculated
molar ratios are greater than the recommended critical values. Since under these
circumstances the oxalate has the potential to complex not only the Calcium contained
in the plant but also that derived from other food sources (Davies 1979).
Results and Discussion
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Table – 4.25. Nutritionally Important Starch Fractions of Pearl Millet as
Influenced by Processing
Varieties Processing
Treatments
Dry Matter
(%)
Starch Fractions (g/100g as-eaten basis)
RDS SDS RS TS
K WF (Raw) 86.8 b ± 0.20 10.2 a ± 0.3 6.0 a ± 0.12 5.1 b ± 0.81 21.3 a ± 0.69
SRF 87.1 b ± 0.13 13.3
b ± 0.6 9.0
b ± 0.68 8.5
c ± 1.27 30.9
b ± 0.35
Boiling 83.9 b ± 1.11 16.9
d ± 0.2 15.7
d ± 0.29 3.3
ab ± 0.73 35.9
d ± 0.75
PC 84.7 b ± 0.97 14.0
b± 0.4 12.5
c ± 0.41 3.7
ab ± 0.85 30.1
b ± 0.51
Roasting 86.6 b ± 0.43 15.2
c ± 0.3 12.7
c ± 0.32 1.8
a ± 0.17 29.7
b ± 0.55
Germination 71.8 a ± 2.42 17.2
d ± 0.6 13.6
c ± 0.43 2.5
a ± 0.11 33.4
c ± 1.01
MRB WF (Raw) 85.9 b ± 0.11 11.4
a ± 0.6 7.6
a ± 0.48 4.0
b ± 0.90 23.0
a ± 0.35
SRF 86.3 b ± 0.30 12.7
b ± 0.4 7.7
a ± 0.80 10.3
c ± 0.47 30.7
b ± 0.74
Boiling 85.2 b ± 1.80 18.9
c ± 0.1 14.4
c ± 0.26 3.6
ab ± 0.37 36.3
c ± 0.58
PC 85.4 b ± 0.97 11.0
a ± 0.3 9.9
b ± 0.18 3.5
ab ± 0.65 24.4
a ± 0.55
Roasting 85.3 b ± 0.27 17.4
c ± 1.1 15.3
d ± 0.85 1.7
a ± 0.57 35.
0
c ± 0.38
Germination 74.4 a ± 2.13 20.2
d ± 0.5 17.1
e ± 0.31 3.7
ab ± 0.83 41.0
d ± 1.48
Values are means ± SD (n=4), Means with different superscripts (a, b, c, d) along the column
are significantly different (P ≤ 0.05), K – Kalukombu, MRB – Maharashtra Rabi Bajra, SRF –
semi refine flour, PC – pressure cooking, RDS – rapidly digestible starch, SDS – slowly
digestible starch, RS – resistant starch, TS – total starch,
Results and Discussion
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Starch is divided into 3 types considering the rate and extent of starch
digestion which includes rapidly digestible starch (RDS), slowly digestible starch
(SDS) and resistant starch (RS). Food processing is known to render some portion of
starch resistant to enzyme hydrolysis thereby influencing the starch fractions of food
(Englyst et al 1992). Changes in the starch fractions of pearl millet as a result of
processing are presented in Table 4.25. The raw and processed pearl millet flours
were gelatinized (flour to water ratio 1:4) prior to analysis and expressed on an as
eaten basis. K and MRB contained approximately 22% TS, 11% RDS, 7% SDS and
5% RS content. In general, the processing methods employed in this investigation
rendered the millet more digestible in comparison to the raw flour and also
correspondingly increased RS content. Milling, an important step in millet processing
has shown its influence on starch digestibility. The flour of pearl millet is coarse and
contains antinutrients like phytic acid, tannins and oxalates that form complexes with
nutrients leading to marked reductions in their digestibility (Arora et al 2003). Semi
refining of K variety drastically increased RS content. Although, bran which is a
physical barrier to enzymes and an important intrinsic factor limiting starch
hydrolysis was partially reduced or eliminated as a result of semi refining, it was high
in RS content. A combination of semi refining and gelatinization did not help in
improving starch digestibility. The high RS content could be explained by the fact that
the time taken for the process of gelatinization was perhaps too short to allow the
starch to completely gelatinize. Starch molecules present were entrapped inside the
granules which were not easily accessible to hydrolyzing enzymes (RS2) (Liljeberg,
2002). The seed coat/hull is an initial protective barrier for grains and plays an
important role in starch digestibility. The removal of hull renders the starch more
Results and Discussion
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accessible to hydrolytic enzymes leading to better digestibility. But in this study, the
slow rate of starch digestion in semi refined flour might be due to the presence of the
left out bran which led to the entrapment of starch in fibrous thick-walled cells
(Richard et al 2009, Asp 1994).
Millet subject to heat treatments (boiling, pressure cooking, roasting) reduced
the TS content. While, boiling or pressure cooking of pearl millet did not alter the RS
content a significant (P ≤ 0.05) drop in the millet subjected to roasting was noticed.
The process of cooking destroys the semi crystalline structure of raw starch granules
resulting in the loss of SDS and an increase of RDS. SDS content of food is important
as it gets hydrolyzed to glucose slowly yet completely in the small intestine, thereby
lowering the risk of chronic diseases such as cardiovascular diseases, obesity and
diabetes (Sureeporn et al 2010; Cousin et al 1996; Richard et al 2009). In this study
increase in the SDS and RDS content of heat treated millet in comparison to the raw
counterpart was seen. Increased starch digestibility after boiling/pressure cooking has
been reported in peas and beans (Richard et al 2009). The high RDS and SDS and low
RS content could be attributed due to heat treatments/gelatinization and dispersion of
the starch molecules rendering them more susceptible to attack by starch hydrolyzing
enzymes. A combination of high temperature and moisture caused greater disruption
of the cellular structure, increasing exposure of starch to amylolytic enzymes which
lead to a decrease in RS in boiled or pressure cooked millet.
Germination is a process which converts complex nutrients into simple ones
thereby improving its digestibility. Germination led to the significant increase in RDS
and SDS in both the varieties. A marked increase in the TS content as a result of
germination was seen. Degradation of starch in grains during germination led to the
Results and Discussion
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increase in dextrin and fermentable sugar. This change produces a special sweet
flavor in germinated brown rice (Kayahara, 2004). In germinated cereal grains,
hydrolytic enzymes are activated and decompose starch, non-starch polysaccharides,
and amino acids. The decomposition of high molecular weight polymers during
germination leads to the generation of bio-functional substances, and improvements in
organoleptic qualities due to the softening of texture and increase of flavor in cereal
grains (Kayahara 2004; Banchuen et al 2009).
Table – 4.26. Starch Digestion Index & Rapidly Available Glucose Values of
Processed Pearl Millet (g/100g)
Processing Starch Digestion Index Rapidly Available Glucose
K MRB K MRB
Whole flour (raw) 49 bc
± 2.1 50 b ± 2.3 13.7
a ± 0.2 13.2
a ± 0.7
Semi refined flour 43 a ± 2.0 41
a ± 0.5 17.5
b ± 0.6 17.3
c ± 0.5
Boiling 47 abc
± 1.0 51 b ± 0.2 20.5
c ± 0.3 22.4
e ± 0.3
Pressure cooking 46 ab
± 1.4 45 a ± 1.4 17.4
b ± 0.4 14.6
b ± 0.3
Roasting 51 c ± 0.5 51
b ± 1.1 18.6
b ± 0.2 20.9
d ± 0.6
Germination 52 c ± 0.4 49
b ± 0.8 22.8
d ± 0.5 26.3
f ± 0.4
Values are mean ± SD (n = 4), Means with different superscripts (a, b, c, d, f) along the column are
significantly different (P ≤ 0.05), K – Kalukombu, MRB – Maharashtra Rabi Bajra.
Results and Discussion
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Changes in the SDI and RAG content of processed pearl millet is presented in
Table 4.26. Overall, processing treatments significantly (P ≤ 0.05) affected the SDI
and RAG content of pearl millet. The changes in the SDI and RAG content of two
pearl millet varieties, however, were different. Semi refining decreased SDI
considerably. For example, raw flour of K and MRB varieties had SDI of 49 and 50
respectively; corresponding values were decrease to 43 and 41 after semi refining the
whole flour. Heat treatments and germination did not cause any significant changes in
the SDI of pearl millet.
Rapidly Available Glucose (RAG) content is a major determinant of the
magnitude of glycemic index. The % increase in RAG content for both the varieties
varied with processing techniques used. The raw flour of K and MRB had RAG value
of about 13%. The RAG content increased to about 27, 21, and 20% in germinated,
boiled and roasted millet respectively. Medium increase was seen in semi refined
flour and pressure cooked milled ranging from 14.6 to 17.5%.
Results and Discussion
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Table 4.27. Effect of Processing on % In–Vitro Protein Digestibility of Pearl
Millet
Processing % In-Vitro Protein Digestibility
Kalukombu MRB
Whole Flour 45.5 ab
± 1.1 49.3 a ± 7.9
Semi Refined Flour 54.8 abc
± 9.1 55. 3
a ± 7.9
Bran Rich Fraction 59.6 ac
± 4.0 69.9 bd
± 8.9
Boiling 32.5 a ± 4.3 58.2
ab ± 5.0
Pressure cooking 43.6 ab ± 4.1 45.5 a ± 3.1
Roasting 65.8 c ± 10.8 75.4 cd ± 1.4
Germination 88.2 d ± 6.6 78.9 d ± 7.8
Means followed by different letters (a, b, c) in the same column differ significantly (P ≤ 0.05),
MRB – Maharashtra rabi bajra.
Data in Table 4.27 indicated that protein digestibility of pearl millet was low
(45.5% for K and 49.3% for MRB variety). The relatively low protein digestibility
may be attributed to the influence of antinutrients such as enzyme inhibitors, lectins,
phytates, tannins and dietary fiber which inhibits protein digestion and also due to
presence of protein structures that resist digestion. Studies have demonstrated that
high-tannin sorghum varieties formed indigestible protein–tannin complexes which
are a major limiting factor in protein utilization (Chibber et al 1980). Semi refining of
the whole flour did not alter the protein digestibility, however, the BRF showed
Results and Discussion
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higher %IVPD than whole flour and was comparable to that of wheat bran (69%)
(Saunders et al 1972).
Results on the effect of heat treatments like boiling, pressure cooking and roasting
on IVPD significantly (P ≤ 0.05) varied between the two varieties. Wet heat
treatments such as boiling or pressure cooking did not alter the protein digestibility of
the millet which was in agreement with earlier reports on some cereals and legumes.
Protein cross-linking mainly through disulphide bonding and reduced protein
extractability in cooked samples appears to be the most important factor affecting
protein digestibility in cooked cereals (Aisha et al 2004; Vijayakumari et al 2007;
Singh et al 1981). In contrast, cooking improved %IVPD in foxtail, finger and
common millet (Ravindran 1992). Nevertheless, roasting markedly improved IVPD of
pearl millet from 45.5% to 65.8% in K variety and 49.3% to 75.4% in MRB
suggesting that dry heat treatment is more effective in improving protein digestibility.
The improvement as a result of dry heat treatment may be due to protein denaturation
and/or decreasing resistance of protein to enzyme attack (Sathe et al 1982).
Germination significantly (P≥0.05) improved the protein digestibility in both
varieties compared to the un-germinated millet (from 45.5% to 88.2% for K variety
and 49.3% to 78.9% for MRB variety). These findings are in agreement with an
earlier study on pearl millet (Anurag et al 1996). The increase in %IVPD can be
attributed to an increase in soluble proteins, due to partial hydrolysis of storage
proteins by endogenous proteases produced during the germination process. Such
partially hydrolyzed storage proteins may be more easily available for pepsin
digestion (Bhise et al 1988).
Results and Discussion
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Table 4.28. Association of % IVPD with Tannin and Dietary Fiber Content of
Pearl Millet
Dependent
variable
Independent
variable
Correlation
coefficient
% IVPD
Tannins 0.605**
IDF 0.034
SDF 0.168
TDF 0.046
** Correlation is significant at 0.01 level (2–tailed), IDF – Insoluble Dietary Fiber, SDF –
Soluble Dietary Fiber, TDF – Total Dietary Fiber
Tannins and dietary fiber are well known for their ability to bind and
precipitate protein. A correlation study was carried out between tannins, TDF, IDF
and SDF with %IVPD to ascertain whether protein digestibility of pearl millet was
influenced by these factors (Table 4.28). A positive correlation, was found between %
IVPD and tannin content (r = 0.605, P ≤ 0.01). For IDF, SDF and TDF the
correlations were positive although not significant. In this study, protein digestibility
of pearl millet showed a strong association with tannin levels. The low protein
digestibility of pearl millet was not due to tannins or dietary fiber content. It could be
due to other factors like interaction of proteins with non-protein components and the
proteins themselves thereby affecting their digestibility (Duodu et al 2003; Abdalla et
al 1997).
Results from the present study shows that relatively bioaccessible iron and
calcium content (in-vitro) was higher in MRB than K variety. Semi refining, heat
Results and Discussion
Page 154
treatments or germination of pearl millet improved the bioaccessible iron and calcium
in both varieties. Drastic improvement in bioaccessible iron content as a result of
various processing methods was seen in MRB, while increase in bioaccessible
calcium was similar in both varieties. Cooking effectively improved calcium
accessibility while the same was less effective in improving bioaccessible iron
suggesting that calcium and iron combined in a meal may decrease iron
bioaccessibility. Use of tap/de – mineralized water for boiling, pressure cooking or
germination led to an increase in the bioaccessible iron and calcium content,
nonetheless, this increase was not statistically significant. Changes in mineral and
antinutrient content during processing led to significant variations in the
antinutrient/mineral molar ratios which had a positive impact on the bioaccessible
iron and calcium content. Milling fractions like WF, SRF and BRF exhibited higher
RS values while a considerable decrease of the same due to heat treatment or
germination was seen due to complete starch digestion. Lower in-vitro protein
digestibility was seen in pearl millet. Milling, roasting and germination respectively
were more effective in improving the protein digestibility of pearl millet. A positive
correlation, was found between % IVPD and tannin content (r = 0.605, P ≤ 0.01). For
IDF, SDF and TDF the correlations were positive but not significant.
Results and Discussion
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CHAPTER – 5
UTILIZATION OF PEARL MILLET IN FOOD PRODUCTS
Pearl millet has a considerable potential to be used as foods and beverages. It
can be used as cooked, whole, dehulled or ground flour or else as a grain like rice.
The millet is mostly used as whole flour for traditional food preparation and hence
confined to traditional consumers and to people of lower economic strata. The flour
prepared out of pearl millet is coarse and has a grey to yellow color which imparts
bitter taste (Olatungi et al 1982).
Pearl millet is gluten-free and hence suitable for celiacs. Celiac disease is a
permanent gluten intolerance elicited in the genetically susceptible subject after
ingestion of gluten containing cereals (Laurin et al 2002). Celiac disease is a disorder
of considerable and increasing importance in Western countries occurring in 1 of 130
– 300 in the European population and in 1 of 111 of the US population (Green et al
2007; Joseph 1999). Celiac disease was recognized in northern India, primarily in
children, since the 1960s (Walia et al 1966).
Besides being rich in iron, calcium, zinc and high level of fat, it is nutritionally
comparable and even superior to major cereals due to the energy and protein value
(Fasasi 2009; Anu Sehgal et al 2006; Malik et al 2002). Owing to its superior
nutritional quality, the aim of the present investigation was to explore the possibility
of using pearl millet flour in food products. These products were analyzed for
proximate composition, nutritionally important starch fraction, and mineral
bioaccessibility. Sensory and shelf life studies were also carried out. Products like
ladoo and burfi were stored in steel containers for 4 – 5 weeks while cookies were
stored in PET – PP and foil for 12 weeks. These products were analyzed for moisture
Results and Discussion
Page 156
content, free fatty acids and peroxide value. Acceptability studies as affected by
storage were also carried out.
Table – 4.29. Proximate Composition of Breakfast Items Prepared from Pearl
Millet (dry weight basis).
Breakfast
Items
Moisture
(g)
Protein
(g)
Fat
(g)
Ash
(g)
Iron
(mg)
Calcium
(mg)
Phosphorus
(mg)
Dosa
Rice (C) 56.9 b ± 1.7 7.8
b ± 0.2 5.0
a ± 0.1 1.67
a ± 0.1 0.7
2
a ± 0.0 18.4
a ± 0.1 152.6
a ± 2.6
K 51.6 a ± 0.7 5.3
a ± 0.3 6.9
b ± 0.7 2.90
b ± 0.1 3.24
b ± 0.2 56.4
b ± 5.1 271.1
c ± 28.0
MRB 51.6 a ± 0.9 6.0 a ± 0.4 6.0 ab ± 0.3 3.39 b ± 0.6 3.37 b ± 0.3 58.9 b ± 3.1 267.3 b ± 13.2
Roti
Rice (C) 65.0 b ± 1.0 7.4
b ± 0.3 5.4
b ± 0.4 2.
10
a ± 0.1 0.7
a ± 0.0 25.2
a ± 1.1 131.6
a ± 2.6
Ragi (C) 33.0 a ± 0.2 7.7
b ± 0.1 5.5
b ± 0.4 3.10
b ± 0.1 3.5
b ± 0.4 325.7
c ± 7.7 243.2
b ± 2.7
K 63.6 b ± 0.8 6.6
a ± 0.2 4.2
a ± 0.2 2.42
c ± 0.1 4.5
c ± 0.4 57.6
b ± 6.2 331.4
c ± 9.7
MRB 69.9 c ± 0.4 7.5
b ± 0.3 5.2
b ± 0.2 2.47
c ± 0.1 4.2
c ± 0.3 50.1
b ± 2.1 296.8
c ± 17.4
Puttu
Rice (C) 61.5 b ± 0.1 8.2
b ± 0.2 8.5
b ± 0.4 2.1
b ± 0.2 0.7
a ± 0.02 22.0
a ± 0.6 125.2
a ± 4.1
Ragi (C) 28.6 a ± 0.3 7.5
ab ± 0.4 6.6
a ± 0.4 1.8
a ± 0.0 3.5
b ± 0.4 377.6
c ± 11.8209.6
b ± 26.2
K 56.6 b ± 2.6 6.5
a ± 0.4 10.2
c ± 0.1 2.7
c ± 0.0 4.5
c ± 0.4 45.2
b ± 0.4 287.4
c ± 15.3
MRB 58.1 b ± 2.9 6.5
a ± 0.4 10.4
c ± 0.4 1.7
a ± 0.0 4.2
c ± 0.3 40.3
b ± 0.4 247.6
b ± 14.0
Means followed by different letters (a, b, c) in the same column differ significantly (P ≤ 0.05),
C – Control, K – Kalukombu, MRB – Maharashtra Rabi bajra.
Results and Discussion
Page 157
In order to evaluate the influence of pearl millet in product preparation,
selected breakfast items typical of Indian cuisine such as dosa, roti and puttu were
prepared and its nutritional profile was studied by comparing with traditionally
prepared breakfast meals containing rice/ragi as major ingredients. The data indicated
that incorporation of pearl millet in dosa significantly (P ≤ 0.05) lowered moisture
and protein content, while, increased the fat content (Table 4.29). For instance,
traditionally prepared rice dosa contained 56.9% and 7.8% of moisture and protein,
the corresponding values decreased to about 51% and 5.7% respectively upon
substitution with pearl millet, while the fat content increased from 5.0% to 6.5%.
Addition of pearl millet in dosa greatly increased ash content and therefore rich in
iron, calcium and phosphorus.
Traditionally prepared rotis based of rice and ragi was used for comparison.
The protein and fat content of MRB Roti was similar to that of rice and ragi roti
(ranging from 7.4 – 7.7% and 5.2 – 5.5% respectively), although, a lower protein
(6.6%) and fat (4.2%) content was seen in roti prepared using K variety. High ash and
mineral content was seen in pearl millet rotis. However highest increase in calcium
was seen in ragi roti. This is because ragi is a rich source of calcium than pearl millet
and rice.
Puttu prepared out of 100% pearl millet was compared with traditionally
prepared rice and ragi puttu. The protein content of pearl millet puttu was
significantly (P ≤ 0.05) lower than those of rice and ragi puttu. Significant (P ≤ 0.05)
increase in the fat, ash and mineral content was seen in pearl millet puttu; however
ragi puttu had the highest levels of calcium.
Results and Discussion
Page 158
In general, the results indicated that breakfast items prepared by either partial
or 100% substitution increased fat, ash and minerals like iron, calcium and
phosphorus. The nutrient profile of breakfast items prepared out of K and MRB was
similar.
Table – 4.30. In-Vitro Bioaccessible Iron and Calcium Content of Breakfast
Items Prepared from Pearl Millet (per 100g)
Breakfast
products
Bioaccessible Iron Bioaccessible Calcium
Mg/100g % Mg/100g %
Dosa
Rice (C) 0.125 a ± 0.01 17 5.00
a ± 0.4 27
Kalukombu 0.330 c ± 0.12 10 33.50 c ± 2.1 59
MRB 0.210 b ± 0.03 6 32.30
b ± 2.5 55
Roti
Rice (C) 0.135 a ± 0.00 19 5.6
a ± 0.7 23
Ragi (C) 0.533 c ± 0.06 15 71.2
c ± 8.5 22
Kalukombu 0.311 b ± 0.00 7 35.8
b ± 3.1 62
MRB 0.350 b ± 0.09 8 29.4 b ± 2.7 59
Puttu
Rice (C) 0.425 b ± 0.01 28 8.99
a ± 0.5 41
Ragi (C) 0.280 a ± 0.01 13 83.03 c ± 4.7 22
Kalukombu 0.680 bc
± 0.19 13 20.3 b ± 1.8 45
MRB 0.540 bc ± 0.17 12 20.20 b ± 1.1 50
Means followed by different letters (a, b, c) in the same column differ significantly
(P ≤ 0.05), C – Control, MRB – Maharashtra Rabi bajra.
Results and Discussion
Page 159
The bioaccessible iron content of dosa, roti and puttu prepared from rice flour was
0.125, 0.135 and 0.425 mg/100g, respectively (Table 4.30). Whole or partial
incorporation of pearl millet flour into these products brought about a significant (P ≤
0.05) increase in the bioaccessible iron content, for example, the corresponding values
increased to about 0.27, 0.33 and 0.61mg/100g respectively. However, these values
were lower compared to ragi based roti and puttu. Ragi is a rich source of iron and
calcium and hence it showed a positive influence on bioaccessible iron and calcium.
Although bioaccessible iron content of pearl millet based products increased, its %
bioaccessibility remained lower than rice products. The highest % bioaccessible iron
content was registered for rice than pearl millet or ragi based products.
The addition of pearl millet enhanced bioaccessible calcium content (mg/100 g) as
well as % bioaccessibility in all the products. The % bioaccessibility of calcium was
even higher than ragi based products. The highest increase in bioaccessible calcium
was seen in roti followed by puttu prepared using pearl millet.
Results and Discussion
Page 160
Table – 4. 31: Nutritionally Important Starch Fractions (In-vitro) of Breakfast Items from Pearl Millet (g/100g)
Breakfast
Products Dry matter TS RDS SDS RS SDI RAG
Dosa
Rice (C) 43.2 a ± 2.03 48. 6 b ± 0.03 25.8 c ± 0.08 19.6 c ± 0.11 3.1 a ± 0.21 53 b ± 0.17 34.7 c ± 0.09
Kalukombu 47.5 a ± 0.01 48.1
b ± 0.94 20.4
b ± 0.63 13.2
b ± 0.73 15.6
b ± 0.35 42
a ± 2.11 30.2
b ± 0.27
MRB 48.4 a ± 1.13 37.9
a ± 0.58 15.4
a ± 0.52 10.7
a ± 0.39 12.3
b ± 0.21 41
a ± 1.17 24.5
a ± 0.22
Roti
Rice (C) 34.9 b
± 1.29 37.8 a ± 2.06 21.5
a ± 1.05 11.8
a ± 1.01 4.5
b ± 0.28 57
a ± 0.46 24.4
a ± 1.11
Ragi (C) 66.9 c ± 0.21 41.4 b ± 0.73 26.5 b ± 1.00 14.6 b ± 0.26 0.24 a ± 0.24 64 c ± 1.29 29.5 b ± 0.20
Kalukombu 36.4 b ± 0.94 34.5 a ± 0.23 20.7 a ± 0.25 10.2 a ± 0.44 3.6 b ± 0.20 60 b ± 0.41 24.5 a ± 0.20
MRB 30.3 a ± 0.62 35.0
a ± 0.33 20.7
a ± 0.39 9.9
a ± 0.51 4.3
b ± 0.37 59
ab ± 0.79 25.3
a ± 0.40
Puttu
Rice (C) 38.5 a ± 0.14 45.0
a ± 1.82 24.0
a ± 0.43 13.6
a ± 0.85 7.2
b ± 0.44 54
a ± 1.31 28.6
a ± 0.63
Ragi (C) 73.9 b ± 2.86 47.2 a ± 0.87 27.4 b ± 0.21 19.2 c ± 0.58 0.92 a ± 0.11 58 a ± 0.64 30.5 b ± 0.23
Kalukombu 43.4 a ± 3.21 56.3 c ± 2.18 31.3 d ± 0.59 16.9 b ± 0.87 8.1 b ± 0.20 56 a ± 2.69 37.7 c ± 2.65
MRB 41.9 a ± 3.50 52.1 b ± 0.59 29.2 c ± 1.08 13.7 a ± 0.29 9.2 b ± 0.76 56 a ± 0.62 36.9 c ± 0.09
Means followed by different letters (a, b, c) in the same column differ significantly (P ≤ 0.05), MRB – Maharashtra Rabi bajra, C –
Control, TS – Total starch, RDS – Rapidly digestible starch, SDS – Slowly digestible starch, RS – Resistant starch, SDI – Starch
digestion index, RAG – Rapidly available glucose.
Results and Discussion
Page 161
Nutritionally important starch fractions of breakfast products prepared from
two pearl millet varieties (K and MRB) and rice/ragi (control) were analyzed in vitro
and exhibited in Table 4.31. Pearl millet was used in the preparation of roti, dosa and
puttu. Dosa is a fermented breakfast item while puttu is a streamed product. Total
starch content of dosa prepared out of rice and K variety (48%) were similar while
MRB had low starch content (37.9%). Starch in rice dosa was rapidly available
(25.8%) with low levels of SDS (19.6%) and RS (3.1%). Higher starch digestibility
was found in rice dosa (control) as it was prepared with higher amounts of rice along
with some minor ingredients. Replacement of rice with pearl millet reduced RDS and
SDS to about 17.9% and 12% respectively, while, greatly increased RS to 14%.
Significant reduction in RAG and SDI was also noticed.
The rotis were prepared by adding warm water and a pinch of salt to the
respective flour and mixed into dough, then flattened into round shaped roti and
shallow fried (150 – 200oC) on a pan. Cereal and millet based rotis were used as
controls. TS content of ragi roti (41.4%) was higher than rice (37.8%) and pearl millet
roti (35%). Ragi roti had significantly (P ≤ 0.05) higher RDS (26.5%) and SDS
(14.6%) content, where as rice and pearl millet rotis were low in RDS and SDS which
of about 21% and 10.7% respectively. Ragi roti was found to contain minor amounts
of RS (0.24%), whereas, higher RS was found in rice and pearl millet roti ranging
from 3.6 to 4.5%. SDI and RAG values were higher for ragi roti and lower for rice
and pearl millet roti respectively.
Puttu is a steamed product served with desiccated coconut and sugar. Cereal
(rice) and millet (ragi) based controls were used for comparison. Unlike dosa and roti,
rice and ragi puttu were found to have low TS and RDS content. Compared to ragi
Results and Discussion
Page 162
dosa or roti, puttu prepared out of ragi had considerable amount of RS (0.92%), yet, it
was lower than rice and pearl millet based puttu. SDI was similar for all the products
while RAG values ranged from 28.6% for rice to about 37% for pearl millet based
products.
Table – 4.32. Sensory Analysis of Breakfast Items Prepared from Pearl Millet
Breakfast
products Color Flavor Texture Taste
Overall
Acceptability
Dosa
Rice (C) 7.7 c ± 0.69 7.6
b ± 0.55 7.8
b ± 0.60 7.9
b ± 0.79 7.7
b ± 0.63
K 6.8 b ± 0.76 6.7 a ± 1.06 7.0 a ± 0.89 6.7 a ± 1.00 6.8 a ± 0.83
MRB 6.2 a ± 1.15 6.7
a ± 1.18 6.6
a ± 1.52 6.6
a ± 1.60 6.8
a ± 1.28
Puttu
Rice (C) 7.6 b
± 0.96 7.0 ab
± 0.88 7.3 a ± 0.97 7.1
b ± 1.16 7.
3
b ± 0.92
Ragi (C) 6.7 a ± 0.99 7.5
b ± 0.84 7.2
a ± 1.03 7.2
b ± 0.75 7.3
b ± 0.63
K 6.8 a ± 1.21 6.9
ab ± 1.03 6.9
a ± 1.08 7.0
b ± 1.02 7.1
ab ± 0.84
MRB 6.7 a ± 1.15 6.8
a ± 1.03 6.8
a ± 1.09 6.4
a ± 1.19 6.6
a ± 1.06
Roti
Rice (C) 7.8 b ±0.90 7.4
b ±0.76 7.4
b ±1.04 7.7
ab ± 0.91 7.7
b ± 0.83
Ragi (C) 6.8 a ±1.12 7.5 b ±0.90 7.6 b ±0.72 7.7 b ± 0.78 7.5 ab ± 0.77
K 6.4 a ±0.97 7.2
ab ± 0.86 7.3
ab ± 0.92 7.7
ab ± 1.03 7.4
ab ± 0.89
MRB 6.4 a ± 0.93 6.7 a ± 1.01 6.8 a ± 0.96 7.1 a ± 1.01 7.0 a ± 0.93
Means followed by different letters (a, b, c) in the same column differ significantly (P < 0.05),
C – Control, K – Kalukombu, MRB – Maharashtra Rabi bajra.
Results and Discussion
Page 163
The sensory evaluation of breakfast products is presented in Table 4.32. The
sensory evaluation results for dosa prepared from rice and pearl millet respectively,
revealed that the scores for parameters like color, flavor, texture and overall
acceptability obtained for rice dosa were higher than that of pearl millet dosa. Based
on the hedonic ratings, pearl millet dosa was less preferred by the panelists than rice
dosa. The color score of pearl millet puttu was lower than rice puttu, while, no
significant difference was found with the color scores of ragi puttu. Replacement with
pearl millet did not affect the flavor, taste, texture and overall acceptability of puttu.
Roti prepared from MRB had the lowest scores for all the parameters while; roti from
K variety had scores similar to those prepared from rice or ragi. In a hedonic scale of
9 points, a score of 6 is considered a quality limit (Munoz et al 1992).The three
different products prepared from rice, ragi and pearl millet respectively exhibited
scores appreciably higher than the quality limit (6.2 to 7.9). Overall, pearl millet
incorporation substantially affected the color of the products; however the scores were
in the acceptable range.
Results and Discussion
Page 164
Table 4.33. Proximate Composition of Wheat flour (Control) and Pearl Millet
Cakes
Cake Moisture
(g)
Fat
(g)
Proteins
(g)
Ash
(g)
Iron
(mg)
Calcium
(mg)
Phosphorus
(mg)
Control 13.9 b ± 0.3 25.7
a ± 0.6 5.9
a ± 0.4 0.62
a ± 0.1 2.2
a ± 0.1 13.9
b ± 0.2 112.6
a ± 0.8
K 12.30a ± 0.2 25.6
a ± 0.4 6.3
b ± 0.2 0.84
c ± 0.0 4.4
c ± 0.0 13.2
a ± 0.2 124.8
b ± 0.6
MRB 13.3 b ± 0.1 26.7
b ± 0.6 8.5
c ± 0.5 0.69
b ± 0.0 2.8
b ± 0.0 15.8
c ± 0.7 134.0
c ± 2.0
Means followed by different letters (a, b, c) in the same column differ significantly (P ≤ 0.05), K –
Kalukombu, MRB – Maharashtra Rabi bajra.
Cakes were baked by replacing refined wheat flour with 40% pearl millet and
compared with cake prepared with 100% refined wheat flour. Data in Table 4.33
presents proximate composition of cake incorporated with 40% pearl millet (K and
MRB). The fat content of the cake increased when fortified with 40% MRB. Since
pearl millet is richer in protein content than refined wheat flour, incorporation of
cakes with pearl millet enhanced protein content (increased from 5.9 (control) to 6.3
and 8.5 for K and MRB). The mineral content of cakes baked with 40% pearl millet
was also higher.
Results and Discussion
Page 165
Table 4.34. Proximate Composition of Wheat flour (Control) and Pearl Millet
Buns
Bun Moisture
(g)
Fat
(g)
Proteins
(g)
Ash
(g)
Iron
(mg)
Calcium
(mg)
Phosphorus
(mg)
C 26.2 c ± 0.6 11.4
b ± 0.3 12.3
c ± 0.5 1.1
a ± 0.10 1.3
a ± 0.0 40.1
a ± 0.0 108.9
a ± 0.8
K 27.8 b ± 1.2 10.8
a ± 0.6 11.4
b ± 0.4 1.6
b ± 0.10 1.5
b ± 0.0 56.0
b ± 0.8 143.5
b ± 0.4
MRB 22.4 a ± 0.2 13.2 c ± 0.9 9.7 a ± 0.3 1.6 b ± 0.00 1.8 c ± 0.0 60.5 c ± 0.4 155.7 c ± 0.5
Means followed by different letters (a, b, c) in the same column differ significantly (P ≤ 0.05),
C – Control, K – Kalukombu, MRB – Maharashtra Rabi bajra.
Buns were prepared by incorporating 40% pearl millet (K and MRB) and
compared with bun prepared using 100% refined wheat flour (Table 4.34). Buns
fortified with Pearl millet contained fat and protein higher than control. Incorporation
of pearl millet had higher levels of ash content thereby contributing to higher levels of
mineral content. Minerals such as iron, calcium and phosphorus were considerably
high in buns baked using 40% pearl millet than 100% refined wheat flour.
Results and Discussion
Page 166
Table – 4. 35a. Sensory Analysis of Wheat flour (Control) and Pearl Millet Cakes
Cake Color Flavor Texture Taste Overall
Acceptability
Control 7.7 b ± 0.96 7.6 b ± 0.74 7.5 a ± 0.80 7.8 b ± 0.79 7.8 b ± 0.72
K (40%) 6.9 a ± 0.96 7.6
b ± 0.97 7.2
a ± 0.99 7.6
ab ± 1.05 7.6
b ± 0.82
MRB (40%) 6.7 a ± 0.95 6.8
a ± 1.02 7.2
a ± 0.87 7.1
a ± 1.02 7.1
a ± 0.84
Means followed by different letters (a, b, c) in the same column differ significantly (P ≤ 0.05),
Control – 100% wheat flour, K – Kalukombu (60:40 wheat flour: pearl millet flour), MRB –
Maharashtra Rabi bajra (60:40 Wheat flour: Pearl millet flour)
Table – 4. 35b: Sensory Analysis of Wheat flour (Control) and Pearl Millet Buns
Bun Control K MRB
Wt. of Bun (g) 63.784 b ±0.80 48.589
a ±0.99 48.573
a ±0.95
Vol. of Bun (mL) 190 b ±2.1 140
a ±2.5 140
a ±2.9
Crust shape Normal Normal Normal
Crumb grain Medium fine Medium fine Slightly soft
Texture Soft Very soft Slightly soft
Eating quality Typical Appealing
wholesome taste Typical
Means followed by different letters (a, b) in the same column differ significantly (P ≤ 0.05), K
– Kalukombu, MRB – Maharashtra Rabi bajra.
Results and Discussion
Page 167
As shown in Table 4.35a, the color score was higher for control cake (7.7)
than 40% pearl millet cake (6.9 for K and 6.7 for MRB). However, these sensory
scores were within the acceptable range. Flavor scores were similar for control and
40% K variety cakes (7.6 each) than those prepared with 40% MRB flour (6.8).
Texture, taste and overall acceptability scores for control, 40% K and 40% MRB flour
fortified cakes were similar and were markedly higher than 6, which are considered as
the quality limit of a product. All the sensory scores given by the panelists revealed
that the cakes prepared by fortifying with 40% K or MRB flour were acceptable.
The data presented in Table 4.35b showed that incorporation of pearl millet
flour (40%) decreased the weight and volume of buns significantly (P ≤ 0.05) from 63g
to about 48g in weight and from 190ml to 140 ml in volume. The crust shape of
control and pearl millet buns was normal, while crumb grain which was medium fine
in case of control and K bun, was slightly soft in case of MRB bun. On the whole, the
addition of pearl millet particularly K variety flour improved the eating quality of the
bun and resulted in a wholesome appealing taste.
Results and Discussion
Page 168
Table 4.36. Effect of Storage of Bun at Room Temperature on Mould Growth.
Bun Mould growth appearance
Control First evidence of mould growth on 4th day of storage
Kalukombu First appearance of mould growth on 5th
day of storage
MRB First appearance of mould growth on 3rd
day of storage
MRB – Maharashtra Rabi bajra
Table 4.37: Effect of Storage of Cake at Room Temperature on Mould Growth
Cake Mould growth appearance
Control First appearance of mould growth on 13th day of storage
Kalukombu First appearance of mould growth on 12th
day of storage
MRB First appearance of mould growth on 11nt
day of storage
MRB – Maharashtra Rabi bajra
Buns and cakes baked using pearl millet flour was packed in airtight polythene
covers and were placed in an area sterilized with alcohol. They were observed for
mould growth and compared with the standard (conventionally prepared). Appearance
of mould growth in conventionally prepared bun and cake was observed on 4th and
13th day of storage respectively (Table 4.36 & 4.37). While those prepared by addition
of MRB (40%) had mould growth on 3rd
and 11th
day of storage and K variety (40%)
showed mould growth on the 5th and 12th
day respectively. The appearance of mould
Results and Discussion
Page 169
growth in standard and pearl millet flour (40%) buns and cakes was almost same and
was storable up to about 3 – 4 days for buns and 11 – 12 days for cake.
Table – 4. 38: Proximate Composition of Traditional Sweets Prepared from
Pearl Millet.
Sweets Moisture
(g)
Fat
(g)
Proteins
(g)
Ash
(g)
Iron
(mg)
Calcium
(mg)
Phosphorus
(mg)
Ladoo
C 0.11a ± 0.0 17.17 b ± 0.3 9.20 c ± 0.2 1.84b ± 0.0 2.49a ± 0.0 21.70b ± 0.0 203.2 c ± 5.5
K 0.22c ± 0.0 16.18
a ± 0.0 7.75
a ± 0.5 0.91
a ± 0.0 4.98
b ± 0.1 19.21
a ± 0.7 175.7
b ± 1.3
MRB 0.18b
± 0.0 19.06 c ± 1.0 8.73
b ± 0.1 1.95
b ± 0.0 6.43
c ± 0.1 27.56
c ± 0.7 163.6
a ± 1.1
Burfi
C 0.12b
± 0.0 25.8 c ± 0.3 9.37
b ± 0.3 1.6
b ± 0.0 2.64
a ± 0.0 30.90
c ± 0.7 191.2
a ± 2.1
K 0.13c ± 0.0 19.9
b ± 0.3 7.80
a ± 0.2 1.0
a ± 0.0 5.51
b ± 0.0 20.88
b ± 0.7 217.1
b ± 0.6
MRB 0.11a ± 0.0 16.0 a ± 0.7 9.20 b ± 0.5 0.9 a ± 0.0 6.03 c ± 0.1 13.36 a ± 0.0 194.4 a ± 3.1
Means followed by different letters (a, b, c) in the same column differ significantly (P ≤ 0.05),
C – control, K – Kalukombu, MRB – Maharashtra rabi bajra.
Results and Discussion
Page 170
Indian traditional sweets such as ladoo and burfi were prepared using pearl
millet flours (K and MRB) and compared with traditionally prepared sweets for its
nutrient composition (Table 4.38). The moisture content of ladoo and burfi prepared
from K was higher than the control. Traditionally prepared sweets had higher protein
content while those prepared using pearl millet were comparatively low in protein.
However, significantly higher iron content was found in pearl millet sweets than those
prepared using gram flour. The higher values of iron in pearl millet sweets can be
attributed to the higher iron content in the millet.
Table – 4. 39: Sensory Analysis of Traditional Sweets Prepared from Pearl
Millet.
Traditional
sweets Color Flavor Texture Taste
Overall
Acceptability
Ladoo
Control 7.2 b ± 0.98 6.5 a ± 0.84 6.6 a ± 0.83 6.3 a ± 0.81 6.2 a ± 0.90
Kalukombu 6.5 ab
± 1.23 7.4 b
± 0.71 7.0 a ± 0.90 7.6
b ± 0.57 7.4
b ± 0.71
MRB 6.0 a ± 1.07 6.5
a ± 1.08 6.6
a ± 1.02 6.7
a ± 1.21 6.6
a ± 1.07
Burfi
Control 7.1 b
± 0.87 6.4 a ± 1.01 6.4
a ± 0.90 6.8
ab ± 1.03 6.8
a ± 1.01
Kalukombu 6. 4
a ± 0.76 7.1
a ± 0.83 6.5
a ± 0.90 7.4
b ±x 0.76 7.1
a ± 0.70
MRB 6.2 a ± 0.53 6.4
a ± 0.96 6.1
a ± 0.91 6.6
a ± 0.95 6.4
a ± 0.76
Means followed by different letters (a, b, c) in the same column differ significantly (P < 0.05),
MRB – Maharashtra rabi bajra.
Results and Discussion
Page 171
Ladoo and burfi are the two traditional sweets prepared using gram flour as a
base ingredient. In this study these traditional sweets were prepared with pearl millet
and compared with the traditionally prepared. The control burfi and ladoo had a high
color score of 7.2 and 7.1 respectively (Table 4.39). While those prepared out of pearl
millet had low scores ranging between 6 – 6.5. The flavor, taste, texture and overall
acceptability scores for ladoo and burfi made from K variety were higher than control
and MRB. The scores for all the sensory parameters of ladoo and burfi made from
gram flour and pearl millet were higher than 6, suggesting that these products were
acceptable.
Results and Discussion
Page 172
Table – 4.40: Effect of Storage on Sensory Attributes of Pearl Millet Ladoo
LADOO Color Flavor Texture Taste Overall
Acceptability
Control
Week – 0 7.2 ab ± 0.98 6.5 a ± 0.84 6.6 ab ± 0.83 6.3 ab ± 0.81 6.2 a ± 0.90
Week – 1 7.9 b
± 0.88 7.1 a ± 1.14 6.7
ab ± 1.01 7.2
c ± 1.25 7.2
b ± 1.12
Week – 2 7.6 ab
± 0.87 7.2 a ± 0.72 7.0
b ± 0.64 7.4
c ± 0.83 7.2
b ± 0.72
Week – 3 7.4 ab ± 0.84 7.0 a ± 0.77 6.8 ab ± 0.54 7.0 bc ± 0.89 6.9 ab ± 0.63
Week – 4 6.9 a ± 1.58 6.4
a ± 1.77 6.1
a ± 1.83 6.1
a ± 1.98 6.3
a ± 1.68
Kalukombu
Week – 0 6.5 a ± 1.23 7.4
a ± 0.71 7.0
a ± 0.90 7.6
a ± 0.57 7.4
a ± 0.71
Week – 1 6.7 a ± 0.88 7.5 a ± 0.81 7.1 a ± 0.86 7.6 a ± 1.13 7.5 a ± 1.00
Week – 2 6.1 a ± 1.61 7.4
a ± 0.67 7.4
a ± 0.73 7.6
a ± 0.74 7.6
a ± 0.68
Week – 3 7.0 a ± 1.10 7.4 a ± 0.94 7.2 a ± 1.03 7.4 a ± 1.13 7.4 a ± 1.02
Week – 4 6.8 a ± 1.72 7.4
a ± 1.52 7.4
a ± 1.69 7.5
a ± 1.52 7.8
a ± 0.73
MRB
Week – 0 6.0 ab
± 1.07 6.5 a ± 1.08 6.6
a ± 1.02 6.7
a ± 1.21 6.6
a ± 1.07
Week – 1 6.7 b
± 0.66 6.6 a ± 1.35 7.1
a ± 0.78 7.2
a ± 1.02 6.9
a ± 0.98
Week – 2 5.5 a ± 1.52 6.4 a ± 1.06 6.9 a ± 0.93 6.5 a ± 1.29 6.6 a ± 0.73
Week – 3 6.0 ab
± 1.36 6.8 a ± 0.97 6.7
a ± 1.11 6.6
a ± 1.16 6.6
a ± 1.06
Week – 4 6.4 b ± 1.62 6.9 a ± 1.55 6.7 a ± 1.46 6.6 a ± 1.49 6.7 a ± 0.91
Means followed by different letters (a, b, c) in the same column differ significantly (P ≤ 0.05),
MRB – Maharashtra Rabi bajra.
Results and Discussion
Page 173
Initially, the overall acceptability scores for of control, K and MRB ladoo was
6.2, 7.4 and 6.6 respectively (Table 4.40). K ladoo was preferred over control or MRB
ladoo. Color is an important sensory attribute of a food product. The color scores for
control ladoo (7.2) were higher than K (6.5) and MRB (6.0) on day 0. This indicated
that the yellowish color of the control ladoo was preferred by the panelists as
compared with the grayish color of the pearl millet ladoo. However, the color scores
for K and MRB ladoo increased to 6.8 and 6.4 respectively over the storage period,
indicating that the panelist liked the color of pearl millet ladoo after they got adapted
to it over the storage period of 4 weeks. The scores for all the sensory parameters of
control ladoo decreased from 2nd
week onwards, while the scores of pearl millet ladoo
(K and MRB) remained constant until the end of the study period. In particular,
sensory scores for flavor, texture, taste and overall acceptability showed no significant
differences throughout the study period.
Results and Discussion
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Table – 4.41: Effect of Storage on Sensory Attributes of Pearl Millet Burfi
BURFI Color Flavor Texture Taste Overall
Acceptability
Control
Week – 0 7.1 a ± 0.87 6.4 a ± 1.01 6.4 a ± 0.90 6.8 b ± 1.03 6.8 ab ± 1.01
Week – 1 7.4 a ± 0.85 6.7
a ± 0.99 6.8
a ± 0.80 7.0
b ± 0.98 7.0
b ± 0.81
Week – 2 7.7 a ± 0.96 6.7
a ± 0.92 6.5
a ± 0.91 7.0
b ± 1.09 6.8
ab ± 0.91
Week – 3 7.1 a ± 1.26 6.4 a ± 1.12 6.6 a ± 1.26 6.4 ab ± 0.98 6.4 ab ± 0.90
Week – 4 7.2 a ± 1.58 6.0
a ± 1.58 6.3
a ± 1.55 5.6
a ± 1.67 5.9
a ± 1.71
Kalukombu
Week – 0 6.4 ab
± 0.76 7.2 bc
± 0.83 6.5 a ± 0.90 7.4
b ± 0.76 7.1
abc ± 0.70
Week – 1 6.4 ab ± 0.67 6.5 a ± 0.86 6.7 a ± 0.91 6.7 a ± 0.88 6.6 a ± 0.89
Week – 2 5.9 a ± 1.75 7.3
c ± 0.66 6.6
a ± 1.18 7.5
b ± 0.78 7.3
b ± 0.74
Week – 3 6.5 ab ± 1.15 6.8 ab ± 1.09 6.4 a ± 1.21 6.7 a ± 1.31 6.6 abc ± 1.17
Week – 4 6.6 b ± 1.64 7.3
c ± 1.36 6.9
a ± 1.51 7.4
b ± 1.40 7.2
c ± 1.40
MRB
Week – 0 6.2 a ± 0.53 6.4
a ± 0.96 6.1
a ± 0.91 6.6
ab ± 0.95 6.4
ab ± 0.76
Week – 1 6.7 a ± 0.92 6.9
a ± 0.83 7.0
b ± 0.93 7.1
b ± 1.04 7.1
b ± 0.91
Week – 2 5.7 a ± 1.60 6.2 a ± 1.20 6.2 ab ± 1.00 6.5 ab ± 0.98 6.4 ab ± 0.94
Week – 3 5.6 a ± 1.47 6.5
a ± 1.09 6.3
ab ± 1.22 5.9
a ± 1.49 6.3
ab ± 1.20
Week – 4 5.9 a ± 1.63 6.1 a ± 1.60 6.4 ab ± 1.52 6.1 ab ± 1.73 6.0 a ± 1.52
Means followed by different letters (a, b, c) in the same column differ significantly (P ≤ 0.05),
MRB – Maharashtra rabi bajra
Results and Discussion
Page 175
Sensory evaluation of burfi as affected by storage is presented in Table 4.41.
Similar to ladoo, the color score of control burfi (7.1) was higher than K (6.4) and
MRB (6.2). However, the scores for color increased for burfi prepared from K over
the storage period of 4 weeks. The color scores of control burfi remained highest
throughout the storage period, while, values for taste and overall acceptability
decreased after 3 weeks of storage. Significantly, burfi made from pearl millet
retained acceptability throughout the storage period of 4 weeks. Therefore it may be
concluded that prolonged storage of pearl millet burfi may have induced desirable
changes in taste, texture and flavor. Burfi from K was more favored than MRB. It was
also noticed that scores for color, flavor, taste and overall acceptability of burfi from
K was highest at the end of 4th
week compared to MRB.
Results and Discussion
Page 176
Bars with different letters (a, b, c) differ significantly (P ≤ 0.05), C – Control, K – Kalukombu, MRB –
Maharashtra Rabi bajra.
Figure 4.9: Moisture, Peroxide value and Free Fatty Acid Content of Ladoo and
Burfi Prepared from Two Pearl Millet Varieties as Affected by Storage
Results and Discussion
Page 177
Moisture content is an important determinant of the shelf life of a product.
Migration of moisture produces changes in the texture, water activity and flavor of the
product. The moisture content of the ladoo and burfi prepared from pearl millet was
about 0.24% initially which increased to about 0.48% at the end of the storage period
(Fig. 4.9). The moisture content of pearl millet-burfi was higher while that of ladoo
was lower than their traditional counterparts. This increase did not affect the texture
of pearl millet sweets at the end of the 5th
week of storage; however those prepared
traditionally, were soggy at the end of 5th
week.
The peroxide value (PV) of an oil or fat is used as an indicator of rancidity
reactions that have occurred during storage. Peroxide value is the most widely used
method for determining autoxidation (oxidative rancidity), by measuring the amount
of iodine formed by the reaction of peroxides (formed in oil or fat) with iodide ion.
The peroxide value is the number that express, in milliequivalents of active oxygen,
the quantity of peroxide contained in 100g of fat. When fatty acids react with oxygen
they become peroxy radical. Hydroperoxides are unstable intermediates formed
during oxidation process. They further disintegrated to form a wide range of products
that are also unstable, in turn undergo oxidation to form stable products most of which
are responsible for disagreeable flavors associated with rancid oils (Eskin et al 2001).
There was a significant difference in the peroxide values between control and
pearl millet burfi/lodoo (Fig. 4.9). The peroxide value for traditional and pearl millet
burfi and ladoo was 0.00% which increased to about 1.41%. The differences between
the PV of traditional and pearl millet products although significant, were not large.
Free fatty acid (FFA) is a measure of hydrolytic rancidity in fats. A large
majority of fats are triglycerides which is a combination of glycerol with 3 fatty acids
Results and Discussion
Page 178
attached. Hydrolysis of triglycerides, in presence of water causes cleavage of ester
bonds that attach fatty acids residue to glycerol thus setting it free from glycerol. The
detached fatty acids from triglycerides are called free fatty acids. Essentially how
soon the triglycerides deteriorate, determines the shelf life of a product. A fatty acid
radical has an unpaired electron. Therefore they are short lived and are highly reactive
as they seek a partner for their unpaired electron.
Pearl millet triglycerides contains about 74% unsaturated fatty acids
(oleic, linolic and linolenic acids) and the remaining fraction is made up of saturated
fatty acid residues (palmitic and steric acids). Pearl millet germ is proportionally
larger than other cereal grains and has major fraction (88%) of lipids stored in the
germ. The relatively high proportions of polyunsaturated fatty acids that constitute the
triglycerides negatively affect the shelf life of pearl millet flour (Lai et al 1980;
Taylor 2004). Hydrolysis of triglycerides and subsequent oxidation of the released
de – esterified unsaturated fatty acids occur during the ambient storing conditions.
This hydrolysis is catalyzed by lipase enzyme. It is these chemical changes that are
manifested as undesirable tasted and odors in millet flours that has been stored
(Taylor 2004).
In this study, the free fatty acid value is expressed as palmitic acid
equivalents/100g of ladoo/burfi. FFA content increased progressively during storage
of ladoo and burfi (Fig. 4.9). The free fatty acid levels increased more rapidly in the
sweets prepared from pearl millet compared to those traditionally prepared. The free
fatty acid for stored control, K and MRB ladoo increased from 0.63, 0.69 and 0.74 to
0.89, 1.15 and 1.13% while FFA for stored control, K and MRB burfi increased from
0.46, 0.78 and 0.8 to 1.09, 1.15 and 1.10% respectively within 5 weeks of storage.
Results and Discussion
Page 179
This was due to entry of moisture as indicated by a marked increase of moisture in the
sweets. However this increase did not affect the sensory quality of the products. The
burfi and ladoo of pearl millet remained sensorialy acceptable during the entire one
month storage without any adverse effect on their acceptability by consumers,
whereas those of the traditional sweets, the overall acceptability scores decline after 3
weeks of storage.
Pearl millet flour is not stable during storage, as it develops disagreeable
sensory flavors. Hence, the millet flour was roasted prior to its use in these products.
Roasting stabilized lipids by inhibiting lipase activity in the pearl millet. Pearl millet
can be successfully used in preparation of sweets that is preferred by consumers.
Table. 4.42. Proximate Composition of Refined Wheat Flour (control) and
Pearl Millet Cookies
Cookies Moisture
(g %)
Fat
(g %)
Proteins
(g %)
Ash
(g %)
Iron
(mg %)
Calcium
(mg %)
Phosphorus
(mg %)
Control 2.57 b
±0.14 16.95 a ±1.21 6.80
a ±0.22 0.38
a ±0.02 2.48
a ±0.34 18.26
a ±0.16 86.76
a ±
5.4
K 0.58 a ±0.03 19.71 a ±1.09 8.63 b ±0.23 0.93 c ±0.05 6.39 b ±0.01 25.70 b ±0.54 208.10 b±10.2
MRB 0.34 a ±0.03 17.82
a ±0.22 8.50
b ±0.33 0.77
b ±0.02 6.71
b ±0.10 29.36
c ±0.54 189.99
b ±6.2
Means sharing the same superscripts are not significantly different from each other (Tukey’s
– B significant difference test, P ≤ 0.05), K – Kalukombu, MRB – Maharashtra rabi bajra.
Results and Discussion
Page 180
Data in Table 4.42 presents proximate composition and mineral content of the
cookies prepared out of refined wheat flour and pearl millet. The moisture content of
control cookies (100% refined wheat flour) was significantly (P ≤ 0.05) higher than
pearl millet cookies. This difference can be attributed to the use of roasted millet
flour. Higher moisture content of cookies results in a soggy and soft texture which is a
major cause for lower consumer acceptability. Fat content remained similar for
control and millet cookies. Cookies fortified with pearl millet was had significantly (P
≤ 0.05) higher protein, ash and minerals like iron, calcium and phosphorus.
Approximately 2.7 fold increase in the iron content was observed in pearl millet
cookies. Other minerals such as calcium and phosphorus increased by 1.6 and 2.2
times respectively in the pearl millet cookies.
Table – 4.43. Physical Characteristics of Refined Wheat flour (Control) and
Pearl millet Cookies.
Parameters Control Kalukombu MRB SEM
±
Diameter (mm) 88.0b 87.0a 86.7a 86.7
Thickness (mm) 10.6a 10.9
a 11.1
b 0.20
Spread ratio (D/T) 8.30b 7.98
a 7.81
a 0.10
Spread factor 83.01b 79.81a 78.10a 0.50
Breaking strength (g) 1600a 1650
b 1680
b 10
SEM – Standard error of means at 15 degrees of freedom, mean in the same row followed by
different superscripts differ significantly (P ≤ 0.05), MRB – Maharashtra Rabi Bajra.
Results and Discussion
Page 181
Physical characteristics of cookies such as diameter, thickness, spread ratio
and breaking strength were determined and are presented in Table – 4.43. The data
showed that the diameter of control, K and MRB cookies did not vary between each
other. Thickness of cookies prepared out of wheat flour (control) and K where similar
while that of MRB increased. Spread ratio is based on the values obtained for
thickness and diameter of the cookies. The spread ratio of the cookies decreased from
8.30 to 7.98 and 7.81 for K and MRB cookies respectively. Similarly, the breaking
strength values for control, K and MRB cookies were 1600, 1650 and 1680g
respectively indicating that the texture of the pearl millet cookies did not vary
between varieties. Pearl millet cookies had light and crisp texture.
OQ – overall quality, C – Control, K – Kalukombu, MRB – Maharashtra Rabi bajra
Figure 4.10. Sensory Profile of Wheat flour (Control) and Pearl Millet Cookies
Results and Discussion
Page 182
Research findings from a study on the influence of flour mixes on the quality
of gluten-free biscuits indicated that a mixture containing millet flakes was one
among the three best mixtures selected based on sensory data (Tilman et al 2003).
This shows that millets could exert beneficial influence on the quality of biscuits.
However, in a comparative study on sorghum cookies and pearl millet cookies, latter
were dark, less gritty and more fragile than the former (Badi et al 1975). A point to be
noted here is that there was a wide variation in the composition and relative
proportion of ingredients of the products studied, which, in all probability, resulted in
the diverse quality of the products. In the present study, control cookies had off-white
color and crisper texture. Perceptible vanilla – like aroma, baked cereal aroma and
sweet taste in control cookies were found to be low which consequently reduced its
overall quality (8.1). On the other hand, pearl millet cookies (K&MRB varieties) had
closely matching sensory profile (Fig. 4.10) which differed significantly from control
in key attributes such as color, vanilla-like aroma, baked cereal aroma and sweet taste.
Higher perceived intensities of these desirable sensory parameters significantly and
positively impacted the overall quality of pearl millet cookies rated at 10.7 for K and
9.2 for MRB respectively as compared to control (8.1). These finding indicated that
the pearl millet cookies were acceptable. Sensory panelists opined that pearl millet
cookies had a combination of desirable and lasting vanilla – like aroma coupled with
typical baked millet aroma. In addition, crisp and crumby texture was perceived in
these cookies which further enhanced their sensory appeal making them highly
palatable. High acceptability for pearl millet cookies in a similar study was reported
(Archana et al 2004) where depigmentation of pearl millet was carried out. Results
showed that native or pigmented pearl millet cookies were rated slightly less for the
Results and Discussion
Page 183
stated sensory attributes compared to depigmented cookies. However, in the present
study, it was found that dark color of the pearl millet cookies did not adversely affect
its acceptability, instead; it provided an interesting visual appeal.
Results and Discussion
Page 184
Results and Discussion
Page 185
C – Control, K – Kalukombu, MRB – Maharashtra rabi bajra,
Figure 4.11: Sensory Profile of Wheat Flour (Control) and Pearl Millet Cookies
as Affected by Storage
Results and Discussion
Page 186
Cookies prepared from wheat flour (control) and two pearl millet varieties (K
and MRB respectively) were storage in two different packaging materials for a period
of 12 weeks (Fig. 4.11) Cookies packed in PET-PP and foil packaging materials were
withdrawn fortnightly and subjected to sensory descriptive analysis. Results of
sensory analysis showed that experimental samples prepared using two pearl millet
varieties had better sensory quality compared to the traditionally prepared cookies
containing refined wheat flour, at the end of 12 weeks of storage.
Traditionally prepared cookies packed in PET – PP pouches were off-white in
color which turned pale brown during the course of storage. Initially, the samples
were crisp (6.2) in texture with slightly perceptible vanilla – like (4.3) aroma and
moderately intense baked cereal aroma, with an overall quality score of 8.1. During
subsequent withdrawals, perceptible decrease in crispness and loss of vanilla-like
aroma were observed. By the end of 4 weeks, perceptible ‘staleness’ and ‘rancid’
notes had developed. The trend continued with increasing intensity, rendering the
product ‘not acceptable’ with an Overall Quality (OQ) score of 6.1 at the end of 8
weeks.
Conventionally prepared cookies packed in foil showed a similar trend which
was just acceptable at the end of 2 weeks. However, by the end of 4 weeks, a sharp
decrease in crispness and increase in ‘stale’ and ‘rancid’ notes were observed in this
sample, which was reflected in reduced OQ score of 5.9 compared to 8.1 of initial
sample. Consequently, further sensory evaluation of these samples was discontinued.
Cookies from K variety, packed in PET-PP had initially higher scores for
crispness, vanilla – like aroma and baked cereal aroma resulting in a desirable high
overall quality score of 10.7. Slight textural changes were observed during the course
Results and Discussion
Page 187
of storage which was not significant. Color (brownish with black spots) and
appearance of the cookies remained the same throughout the study. However, a
perceptible and significant reduction in vanilla – like aroma and baked cereal aroma
was observed by the end of the study. Most notably, the cookies had no ‘stale’ and
‘rancid’ notes at the end of the study. The intensity of most of the desirable attributes
remained at satisfactory levels indicating that the product was acceptable with an OQ
score of 9.0 at the end of 12 weeks.
‘K’ cookies packed in foil showed a similar pattern but for better retention of
texture. However, loss of vanilla – like aroma was more drastic in this sample at the
end of 12 weeks. This effect was observed to be more pronounced after 8 weeks of
storage. No ‘stale’ or ‘rancid’ notes were perceived in this product. Samples were
found to be acceptable with an OQ score of 8.6 at the end of 12 weeks
Although there was a decrease in OQ compared to that of initial samples, this
may be attributed to slight loss of texture (crispness) and vanilla – like aroma.
Sensory profile of ‘MRB’ cookies stored in PET – PP pouches closely
matched that of ‘K’ cookies except for minor differences such as the former was less
crumbly and the latter had slightly higher baked cereal aroma at the end of 12 weeks.
There was no development of off – odors or off – taste in the product during storage.
The cookies were found to be acceptable within an OQ score of 9.0 at the end of
storage period, which was very close to that of initial sample.
‘MRB’ cookies packed in ‘Foil’ had sensory quality similar to that of its
counterpart packed in ‘PET – PP’. A feature repeatedly noted in this sample also was
better retention of texture (crispness) and baked cereal aroma. No perceptible ‘off –
Results and Discussion
Page 188
notes’ were observed in this sample by the end of 12 weeks. Overall quality of this
cookie (8.8) was close to that of initial sample (9.2).
On the basis of sensory data of cookies during storage, it may be concluded
that experimental cookies prepared using pearl millet had better sensory quality and
could keep well for 12 weeks compared to traditionally prepared sample containing
refined wheat flour. At the end of 12 weeks of storage, there was no significant
difference in the sensory quality of ‘K’ and ‘MRB’ cookies. However, ‘MRB’ cookies
had overall quality scores closer to initial samples compared to ‘K’ cookies. As a
packaging material, ‘Foil’ was a better option for better retention of crispness in
cookies. Although there was reduction in perceptible vanilla – like aroma in the
cookies by the end of 12 weeks, it did not adversely affect their overall quality scores.
There was no perceptible off – note in the experimental cookies. Both ‘K’ and ‘MRB’
cookies were acceptable and found to be highly palatable throughout the storage
study.
Results and Discussion
Page 189
Bars with different letters (a, b, c) differ significantly (P ≤ 0.05), MRB – Maharashtra rabi bajra.
Figure 4.12: Equilibrium Relative Humidity of Wheat Flour (Control) and Pearl
Millet Cookies as Affected by Storage
Results and Discussion
Page 190
Water content is one of the most important properties in the food domain.
Water is essential for growth and metabolism of microbes and many chemical
reactions that occur in the product. Water occurs in a food system in both free and
bound states. Free water supports the growth of microorganisms, chemical reactions
and acts as a transporting medium for compounds. Whereas bound water is tied up by
water soluble compounds such as sugar, salt, gums etc. The amount of water that is
available to microorganisms is termed as water activity (aw). Many microorganisms
prefer an aw of 0.99 to grow. Relative humidity and aw are related. Water activity
refers to the availability of water in a food or beverage. Relative humidity refers to the
availability of water in the atmosphere around the food or beverage. Equilibrium
relative humidity (ERH) is a valuable tool for food product packaging development as
it is an indicator of what chemical reactions may occur during distribution and of how
much packaging protection should be designed for the product to give it the required
shelf life. During storage, foods in the semi-moist rubbery state can become partially
crystalline as sugar is crystallized out as seen in milk based powders, soft cookies,
chocolates and cake glazes or they can harden by several different chemical reactions
including protein aggregation (Labuza et al 2004, Zhou et al 2008, Labuza et al 1970;
Barbosa et al 2007).
The relationship between moisture content and water activity of control and
pearl millet cookies stored at room temperature are presented in Figure 4.12. The
cookies were exposed to a wide range of water activities (0.31, 0.64 and 0.76) to find
out its effect on the texture. This was done by placing cookies in a petridish inside
desiccators containing various saturated solutions equilibrated at certain relative
humidities. The moisture content of the cookies was measured at weekly intervals up
Results and Discussion
Page 191
to 8 weeks using a moisture analyzer (Mettler Toledo, Switzerland). The initial
moisture content of control, K and MRB cookies were 2.57, 0.58 and 0.34%
respectively. The corresponding values increased to 2.90, 1.47 and 1.44% respectively
at an aW of 0.31 by the end of the 8th week. At 0.64 and 0.76 aW, pearl millet cookies
gained about 3.5% and 5% moisture while control cookies gained 4.4% and 5.4%
moisture respectively. Highest moisture gain in the control and pearl millet cookies
was seen when they were stored at a water activity of 0.64 and 0.76. Texture is an
important sensory attribute for many cereal based foods and the loss of desired texture
leads to a loss in product quality and a reduction in shelf life (Nielsen 1979). The
texture of cookies was altered by changes in the water activity due to moisture gain
resulting in loss of crispness or hardness. At the end of the study period (week 8)
cookies became softer and soggy. From the results, at an aW of 0.31, control and pearl
millet cookies were stable with respect to texture and mold growth. Thereafter,
cookies became soggy and lost its crispness due to moisture uptake associated with
increase in the water activity (0.31 to 0.72).
Results and Discussion
Page 192
Bars with different letters (a, b, c) differ significantly (P ≤ 0.05), MRB – Maharashtra Rabi bajra.
Figure 4.13: Moisture Content of Wheat flour (Control) and Pearl Millet Cookies
as Affected by Storage.
Results and Discussion
Page 193
Cookies prepared from wheat flour (control) and two pearl millet varieties (K
and MRB respectively) were packaged in two different packaging materials (PET –
PP and Foil) and stored for a period of 12 weeks. Cookies packed in ‘PET-PP’ &
‘Foil’ packaging materials were withdrawn fortnightly and analyzed for moisture,
peroxide value and free fatty acid.
The moisture content of the cookies is presented in Figure 4.13. Moisture
content is a marker of shelf life of a particular product. The initial moisture content of
control, K and MRB cookies were 2.57%, 0.46% and 0.34% respectively. The
corresponding values increased to 3.41, 1.00 and 1.31 after 12 weeks of storage in
PET – PP packaging material while, cookies packed in foil showed a marginal
increase in the moisture content. K and MRB cookies packed in foil exhibited lower
moisture content throughout the storage period retaining its crispy texture which is
associated with freshness and quality of a product, its loss might be a chief cause of
consumer rejection.
Results and Discussion
Page 194
Bars with different letters (a, b, c) differ significantly (P ≤ 0.05), MRB – Maharashtra Rabi bajra.
Figure 4.14: Peroxide Value of Wheat Flour (Control) and Pearl Millet Cookies
as Affected by Storage
Results and Discussion
Page 195
The peroxide value of the cookies is presented in Figure 4.14. The peroxide
value is expressed as milli equivalents KOH /100g of fat. The data on peroxide value
of control, K and MRB cookies packed in PET – PP and foil respectively showed that
there was an increase in the peroxide value (PV) during the storage period of 12
weeks. The initial PV of control, K and MRB was 0.90, 0.92 and 0.92% respectively.
A higher content of PV was found in control cookies (6.55%), followed by K (1.87%)
and MRB (1.4%) packed in PET – PP, while, those packed in foil comparatively
showed a lower increase of 4.78, 1.2 and 1.1% respectively during storage period.
Results and Discussion
Page 196
Bars with different letters (a, b, c) differ significantly (P ≤ 0.05), MRB – Maharashtra Rabi bajra.
Figure 4.15: Free Fatty Acid Content of Wheat Flour (Control) and Pearl Millet
Cookies as Affected by Storage
Results and Discussion
Page 197
The free fatty acids (FFA) present in the fat extracted from cookies are
presented in Figure 4.15. Free fatty acid content is one of the main criteria for
checking the quality of oil. The free fatty acid value is expressed as palmitic acid
equivalents /100g of fat. The cookies on fresh basis contained 0.23 and 0.24 FFA for
control and pearl millet. These values were comparable to the reported values (Aftab
et al, 2008). During storage, FFA content increased to 0.69, 0.46 and 0.40 for control,
K and MRB cookies packed in PET – PP, While, for cookies packed in foil, a minor
increase of 0.25, 0.3 and 0.24 respectively was seen. Cookies packed in PET – PP
showed a significant increase while those packed in foil had constant values through
the storage period. The level of FFA indicates a higher level of oil hydrolysis and
usually freshly processed edible oils contain less than 0.1% FFA. This indicated that
cookies packed in foil can be stored up to 12 weeks, without any apparent undesirable
changes.
Findings of the study demonstrated that complete/or partial replacement of
potentially low cost pearl millet flour improved the overall nutritional quality of the
prepared food products. A considerable increase in total iron, calcium and phosphorus
content as well as bioaccessible iron and calcium of dosa, roti, puttu prepared from
pearl millet was seen. Nutritionally important starch fractions of the breakfast items
prepared from pearl millet revealed low RDS and SDS with increased RS content.
The sensory scores of baked items (bun and cakes) prepared with 40% pearl millet
flour as well as traditional sweets (ladoo and burfi) and cookies prepared from 100%
pearl millet flours were in the acceptable range (6.6 – 7.8). The acceptability scores of
the stored traditional sweets and cookies packed in various packing materials
remained constant until the end of study period. Lower moisture, FFA and PV values
Results and Discussion
Page 198
of cookies packed in foil indicated that foil is a suitable packaging material for storage
of cookies up to 12 weeks or more without any apparent undesirable changes. Thus
the highly beneficial pearl millet could be a successfully used in the production of
value-added, nutritious convenience foods for the human consumption.