42

CHAPTER II

PHYSICOPHYSICOPHYSICOPHYSICO----CHEMICAL, RHEOLOGICAL CHEMICAL, RHEOLOGICAL CHEMICAL, RHEOLOGICAL CHEMICAL, RHEOLOGICAL

PROPERTIES AND CHAPATI MAKING PROPERTIES AND CHAPATI MAKING PROPERTIES AND CHAPATI MAKING PROPERTIES AND CHAPATI MAKING

PROPERTY OF WHOLE WHEAT FLOURSPROPERTY OF WHOLE WHEAT FLOURSPROPERTY OF WHOLE WHEAT FLOURSPROPERTY OF WHOLE WHEAT FLOURS

42

2.1. INTRODUCTION

Chapati, an unleavened baked product made from whole wheat

flour, is the staple diet of majority of the population of India and its

subcontinent (Haridas Rao et al, 1986). Whole wheat flour is mixed

with water into a dough and the dough is normally given a minimum

rest period of 15-30 min, before it is sheeted to a thickness of about 2

to 3 mm. The dough thus sheeted is cut into a diameter of 12 to 15cm

and baked on a hotplate at 220°C and finally puffed on a live flame for

few seconds. It is generally consumed hot along with other adjuncts.

Complete and full puffing, soft and pliable textures as well as

wheatish brown color with dark brown spots are some of the

important attributes of good quality chapati.

The quality characteristics of chapati are mainly governed by

the quality of wheat used and the processing conditions employed for

converting it into flour (Austin & Ram, 1971; Leelavathi et al, 1986).

Based on the physicochemical properties, flour having particle size

distribution of upto 1000µm give good chapatis (Islam & Johansen,

1987). Factors reported to influence the chapati quality are damaged

starch content and water absorption of the flour (Haridas Rao et al,

1986; Abrol & Uprety, 1970; Haridas Rao et al, 1989 & Haridas Rao,

1993). The visco-elastic property of dough, which influences the

baking quality of wheat, depends on the quality and quantity of

protein. Wheat varieties having 9.5 to 10.5% protein are found to be

suitable for the preparation of chapati (Austin & Ram, 1971).

However, there are reports to indicate that wheat having higher

43

protein contents (>12%) are suitable for chapati making, indicating

the importance of quality or nature of proteins present in wheat in

determining chapati making quality (Srivastava et al, 2003).

The objectives were as follows

1. Physico-chemical properties, rheological properties of whole

wheat flour and the overall quality of chapati prepared from

wheat cultivars used in this study.

2. To correlate the physico-chemical and rheological properties to

the overall quality of chapatis.

44

2.2. MATERIALS AND METHODS

2.2.1. Procurement of wheat

Ten aestivum wheat varieties namely GW-322, HD-2189, HD-

2781, HD-2501, K-9644, MACS-2496, NIAW-34, and NI-5439 were

procured from Agharkar Research Institute, Pune and DWR-162 and

DWR-39 were procured from University of Agricultural Sciences,

Dharwad, India, for the studies.

2.2.2. Kernel hardness

Wheat kernel hardness was measured using a Universal Texture

Measuring System (Lloyds, LR 5K, UK). Measurement for 20 grains

from each variety was taken and the average calculated. The kernel

hardness was measured using the following settings: cross head

speed–100 mm/min; pre-load-200 gf; compression-50% of sample

original height; probe diameter-10 mm. The load cell capacity-100 Kgf.

The results are expressed in Newtons.

2.2.3. Milling of wheat

Cleaned wheat was milled into whole wheat flour (WWF) in a

commercial disc mill (plate mill) to obtain whole wheat flour, which

would pass through 400µ mesh. The flour obtained was cooled and

sieved 2-3 times for homogenization.

2.2.4. Chemical analysis

Moisture, total protein, total sugars and damaged starch of WWF

were determined according to the standard AACC methods (2000).

Values reported are the average of triplicate determinations.

45

2.2.5. Rheological characteristics

Farinograph, Amylograph and Extensograph studies were

carried out according to standard AACC methods (2000).

2.2.6. Water absorption of chapati dough

Water absorption of whole wheat flour required to obtain

chapati dough of optimum consistency was determined using

Research Water Absorption Meter according to Haridas Rao et al

(1986).

2.2.7. Preparation of chapati

Chapatis were prepared from WWF according to Haridas Rao et

al (1986) with slight modifications. Chapati dough was prepared by

mixing 200g flour and water equivalent to chapati water absorption in

a Hobart mixer (Model N-50) at speed 1 (61rpm) for 3 mins. The dough

was divided into pieces of 50g each and sheeted to a thickness of 1.5

mm in a specially designed platform to maintain uniform thickness.

The sheeted dough was cut into a circular shape of 12 cm diameter

using a die. The sheeted dough was baked on a hot plate maintained

at 215ºC for 70 s on side one, and 85 s for side two. The chapati was

then transferred to a heated gas tandoor (370ºC) in such a way that

side one was placed on the grill and heated for 10 s. The puffed

chapati from the tandoor was cooled and evaluated.

46

Fig. 2.1: Dough sheeted to chapati.

Fig. 2.2: Sheeted chapati cut with die.

Fig. 2.3: Chapati baked in an oven.

47

Fig. 2.4: Chapati placed in gas tandoor for puffing.

2.2.7.1. Objective evaluation of chapati and dough

Height of the puffed chapati was measured as soon as the chapati

was removed from the Tandoor oven according to Haridas Rao et al

(1986). The texture of chapati was evaluated by using the texture

analyzer (Stable Micro Systems, Model TA-HD, UK) using the Warner

Bratzler blade (HDP/BSW). Three strips measuring 4 X 2 cm from each

chapati were cut. One strip at a time was placed on the center of the

sample holder and allowed the blade to cut the chapati strip. The force

(Kg) required to cut the chapati strip into 2 pieces was recorded. The

speed was maintained at 1.70 mm/s. Measurement for four chapatis

were recorded and average value of these is reported.

2.2.7.2. Subjective evaluation of chapati

Sensory evaluation of chapatis was done by a panel of judges

using a 10 point scale. The product was evaluated for its color,

appearance (color of the spots and their uniformity), tearing strength,

48

pliability, mouthfeel (soft, tough, leathery), and taste and aroma

(sweetish, wheaty, bland) according to Haridas Rao et al (1986).

2.2.8. Statistical analysis

The experimental data, including sensory scores of chapati were

treated statistically by Duncan’s new multiple-range test to determine

the significance of results (Steel & Torrie, 1980).

49

2.3. RESULTS AND DISCUSSION

2.3.1. Physico-chemical characteristics of WWF

Physico-chemical and rheological characteristics of whole

wheat flour (WWF) are shown in Table 2.1 and Table 2.2, respectively.

The damaged starch content in WWF, which is crucial for chapati

making quality (Haridas Rao et al, 1989) varied from 12.3% (MACS-

2496) to 17.6% (DWR-39). Damaged starch content of the flour is

related to the kernel hardness and severity of grinding (Bass, 1988).

Harder the wheat kernel, higher would be the damaged starch content

and vice versa. Since the same conditions were followed for the

grinding of wheat, the differences in the damaged starch content of

flour mostly was related to the hardness of wheat kernels (Fig 2.5). The

results showed that wheat varieties MACS-2496, K-9644 and GW-322,

which had relatively lower kernel hardness showed lower damaged

starch content and wheat varieties with relatively higher kernel

hardness mostly had higher damaged starch content. The kernel

hardness and damaged starch contents in different wheat varieties

showed good positive correlation (r=0.74, p<0.05). Haridas Rao et al

(1989) highlighted that WWF having damaged starch content in the

range of 14.1 – 16.5% yielded good quality chapatis. The total protein

content of WWF samples ranged from 11.6% (HD-2781) to 14.6%

(MACS-2496) (Table 2.1). Majority of the Indian wheat varieties are

generally reported to have protein contents ranging from 8 to 15%

(Saxena et al, 1997; Srivastava et al, 2003).

50

Table 2.1: Physico-Chemical Properties of Different Wheat Varieties

Wheat Varieties

Kernel hardness (Newton)

Moisture (%)

Total Protein

(%)

Damaged Starch

(%)

Falling Number

Sugars* (%)

SDS Sedimentation

Value

DWR-162 102.0c ± 9.3 7.2b ± 0.1 12.7a ± 0.2 17.1f ± 0.1 420d ± 10 1.17b ± 0.02 59c ± 1

DWR-39 112.0c ± 11.1 7.3b ± 0.2 12.3a ± 0.3 17.6f ± 0.3 461f ± 12 1.22b ± 0.03 62c ± 2

GW-322 78.9b ± 3.7 7.2b ± 0.1 13.3b ± 0.1 12.6a ± 0.1 406d ± 11 1.15b ± 0.02 52a ± 1

NI-5439 121.0c ± 8.3 6.9a ± 0.1 13.5b ± 0.1 16.2e ± 0.1 390c ± 15 1.16b ± 0.04 54b ± 2

NIAW-34 119.7c ± 14.1 7.1ab ± 0.1 13.7b ± 0.1 14.8c ± 0.1 440e ± 11 1.41a ± 0.02 55c ± 2

HD-2781 167.0d ± 11.4 7.2b ± 0.1 11.6a ± 0.2 15.3d ± 0.2 360b ± 12 1.39a ± 0.04 62c ± 3

HD-2501 111.0c ± 8.4 7.2b ± 0.1 12.7a ± 0.2 14.8a ± 0.1 486g ± 17 1.06d,c ± 0.02 52a ± 2

K-9644 77.2b ± 6.0 6.9a ± 0.1 13.3b ± 0.2 13.8b ± 0.3 598h ± 17 1.41a ± 0.06 52a ± 1

HD-2189 110.0c ± 5.8 7.6c ± 0.1 12.0a ± 0.3 16.3e ± 0.2 464f ± 12 1.01c ± 0.04 50a ± 2

MACS-2496 65.3a ± 4.3 6.7a ± 0.1 14.6c ± 0.2 12.3a ± 0.1 370a ± 14 0.84d ± 0.04 53b ± 2

Data reported are as-is basis and expressed as mean ±SD of three determinations. Mean of the same column followed by different letters are significantly different (p<0.05). *Sugars: Sum of reducing and non-reducing sugars.

51

Reducing and non-reducing sugar content in these ten varieties

ranged from 0.84% (MACS-2496) to 1.41% (K-9644, NIAW-34) (Table

2.1). Higher sugar content in WWF has been reported to impart

sweetish taste to chapatis (Leelavathi & Haridas Rao, 1988).

Fig. 2.5: Effect of kernel hardness on damaged starch content of whole wheat flour.

2.3.2. Rheological characteristics of WWF

Water absorption of WWF as measured in Brabender

Farinograph, varied from 69.9% (HD-2501) to 77.8% (DWR-162) (Table

2.2). The results showed that mostly, the flours having higher

damaged starch content also had higher water absorption, with few

exceptions. For example, WWF from MACS-2496 even though had the

lowest damaged starch content had relatively higher water absorption

value.

0

2

4

6

8

10

12

14

16

18

20

0

20

40

60

80

100

120

140

160

180

DWR-

162

DWR-39 GW-322 NI-5439 NIAW-

34

HD-

2781

HD-

2501

K-9644 HD-

2189

MACS-

2496

Dam

aged s

tarc

h (%

)Kern

el h

ard

ness (N

)

Wheat varieties

Kernel hardness (Newton)

Damaged Starch (%)

52

Table 2.2: Rheological Characteristics of Whole Wheat Flour from Different Wheat Varieties

Wheat Varieties

Farinograph characteristics*

Amylograph characteristics* Extensograph Characteristics*

Water

absorption (%)

Dough Stability

(min)

Gelatinisation temperature

(⁰C)

Maximum viscosity

(BU)

Cold paste viscosity

(BU)

Resistance to

extension (R) (B.U.)

Extensibility (E)

(mm)

Ratio R/E

DWR-162 77.8 2.8 67.7 470 581 435 112 3.9

DWR-39 75.5 2.5 67.3 530 728 425 108 3.9

GW-322 70.9 1.9 64.7 567 809 315 100 3.2

NI-5439 73.4 1.9 67.6 501 699 213 120 1.8

NIAW-34 76.2 1.3 66.0 479 690 560 108 5.2

HD-2781 76.0 1.5 63.6 478 658 315 116 2.7

HD-2501 69.9 1.8 66.1 527 691 220 122 1.8

K-9644 70.6 2.6 66.4 555 736 393 127 3.1

HD-2189 72.5 1.7 76.5 472 717 193 118 1.6

MACS-2496 74.9 2.9 75.8 480 763 595 96 6.2

* Average of two values.

53

This higher water absorption can also be due to higher protein

content in this variety. It is well known that besides starch, proteins

also influence water absorption of flour along with pentosans (Meuser

& Suckow, 1986). On the other hand, WWF from HD-2189 and NI-

5439 varieties even though had relatively higher damaged starch

content did not have comparatively higher water absorption values.

Gelatinization temperature ranged from 63.6ºC (HD-2781) to 76.5ºC

(HD-2189) on determining the amylograph characteristics. The GW-

322 wheat variety had the highest paste viscosity of 567 BU and cold

paste viscosity of 809 BU (Table 2.2).

Measurement of extensibility properties of WWF in Brabender

Extensograph indicated that resistance to extension (R) varied

between 193 B.U. (HD-2189) to 595 B.U. (MACS-2496) (Table 2.2).

The extensibility (E) properties of dough varied from 96 mm (MACS-

2496) to 127 mm (K-9644). The R/E ratio of these ranged from 1.6

(HD-2189) to 6.2 (MACS-2496). Ratio that indicates stiffness of the

dough, showed that varieties which had high protein contents viz.,

MACS-2496, NIAW-34 had relatively stiff dough. The total protein

content and dough stiffness were positively well correlated (r=0.72.

p<0.05).

2.3.3. Objective evaluation of chapati

Physical characteristics of chapatis prepared from ten wheat

varieties are shown in Table 2.3. The results showed that the puffed

height of chapatis varied from 4.7 cms (K-9644) to 5.5 cms (DWR-

162). The higher puffed height is said to be due to higher water

54

absorption of flour, which helps in generating sufficient steam for

puffing the chapati (Haridas Rao et al, 1986). Earlier it was noted that

WWF from K-9644 had relatively lower water absorption compared to

NIAW-34. On the other hand, other varieties namely, GW-322, HD-

2189, and HD-2501 even though showed relatively lower water

absorption, similar to K-9644, had relatively higher puffed height (Fig.

2.6).

Table 2.3: Chapati Making Properties of Whole Wheat Flour from Different Wheat Varieties

Wheat Varieties Puffed height (cms)

Cutting Force (N)

DWR -162 5.5c ± 0.12 5.8c ± 0.13

DWR - 39 5.3c ± 0.11 5.6c ± 0.12

GW - 322 4.9a ± 0.09 5.1b ± 0.41

NI - 5439 4.8a ± 0.08 5.4b ± 0.20

NIAW - 34 5.2b ± 0.13 5.5bc ± 0.18

HD – 2781 5.1b ± 0.08 7.0d ± 0.21

HD - 2501 4.9a ± 0.08 5.6bc ± 0.18

K – 9644 4.7a ± 0.09 4.2a ± 0.51

HD – 2189 5.1b ± 0.09 6.7d ± 0.15

MACS - 2496 5.0b ± 0.09 4.5a ± 0.58

Data reported are as-is basis and expressed as mean±SD of three determinations. Means of the same column followed by different letters are significantly different (p<0.05).

It is possible that, similar to bread, where gas retention

properties are governed by the visco-elastic gluten matrix, resulting in

higher loaf volume, the chapati dough should have a gluten matrix

which is capable of retaining more steam resulting in higher puffed

height. Haridas Rao et al (1986) reported that poor puffed height of

chapati is attributed to poor quality gluten. Fig. 2.7 shows chapati

puffed height verses protein content of WWF. Our studies showed a

55

poor negative correlation between protein content and puffed height of

chapati (r=-0.28, p<0.05).

Objective measurement of texture of chapati showed that

cutting force for chapatis ranged from 4.2 to 8.5 N (Table 2.3).

Chapatis made from NIAW-34 and HD-2189 had higher cutting force

values compared to chapatis made from other varieties. Austin and

Ram (1971) reported that good quality chapatis should give minimum

resistance to tearing. Haridas Rao et al (1986) reported that chapatis

made from flour with high protein content were chewy with high

tearing resistance and vice versa.

Fig. 2.6: Effect of water absorption on puffed height of chapatis.

In the present study, it was observed that WWF from K-9644

and NIAW-34 varieties, which have relatively less protein content (13.3

& 13.7%), required significantly higher cutting force. However, in

4.2

4.4

4.6

4.8

5

5.2

5.4

5.6

64

66

68

70

72

74

76

78

80

DWR -162 DWR - 39 GW - 322 NI - 5439 NIAW - 34 HD – 2781 HD - 2501 K – 9644 HD – 2189MACS - 2496

Puffe

d h

eig

ht (c

ms)W

ate

r absorp

tion

(%

)

Wheat varieties

Water absorption (%) Puffed height (cms)

56

relation to chapati making a protein content of 13.5% cannot be

considered as low. The variety, MACS-2496 which had relatively

higher protein content, required lower cutting force. Thus, the results

indicate that total protein content alone may not influence the cutting

force of chapatis, instead protein composition and other parameters

may have a role in chapati quality.

Fig. 2.7: Effect of protein content on puffed height of chapatis.

2.3.4. Sensory characteristics of chapati

Sensory evaluation scores of chapatis are shown in Table 2.4.

Chapatis prepared from wheat varieties DWR-162, DWR-39, NIAW-34,

GW-322, and NI-5439 had very appealing wheatish brown color with

uniform dark spots. On the other hand, color of chapatis made from

wheat varieties MACS-2496 and K-9644 was relatively darker.

Chapatis made from varieties HD-2501 and HD-2189 were not as

4.2

4.4

4.6

4.8

5

5.2

5.4

5.6

0

2

4

6

8

10

12

14

16

DWR -162 DWR - 39 GW - 322 NI - 5439 NIAW - 34 HD – 2781 HD - 2501 K – 9644 HD – 2189 MACS -

2496

Puffe

d h

eig

ht (c

ms)

Pro

tein

(%

)

Wheat varieties

Total Protein Puffed height (cms)

57

dark as the latter two varieties. Assessment of the tearing strength of

chapatis showed that DWR-162, DWR-39, GW-322 and NI-5439 had

higher scores. On the other hand, chapatis made from HD-2501 were

very fragile giving low scores. Sensory scores for the remaining

varieties were in-between those of the former two scores. However,

unlike in bread, where softer bread generally gets higher score, it is

not very easy to evaluate the required cutting or tearing strength in a

highly acceptable chapati. It is desired that chapati should not be too

fragile with easy to tear properties, but it should offer some resistance

to tearing as well as chewing. Chapatis made from wheat varieties

DWR-162, DWR-39, GW-322 and NIAW-34 were very pliable.

Leelavathi et al (1986) explained that higher water absorption capacity

of flour renders chapatis soft and pliable. However, in relative terms

the WWF from HD-2781 variety, even though had the highest water

absorption, produced chapatis that were relatively less pliable.

Highest sensory scores for taste and aroma were recorded for the

varieties DWR-162, DWR-39, GW-322 and K-9644. These chapatis

had wholesome sweetish aftertaste (Table 2.1).

The wheat varieties MACS-2496 and HD-2189 recorded

significantly lower scores for taste due to their bland taste. These two

varieties incidentally had relatively lower sugar content. It is possible

that the amount of sugar present in the flour even though is very

small, would enhance the wholesome taste in chapatis.

58

Table 2.4: Subjective Evaluation of Chapatis

Data expressed as mean ±SD, Mean followed by different letters in the same column box differ significantly (p<0.05).

Wheat Varieties

Appearance

(10)

Tearing strength

(10)

Pliability

(10)

Taste and Aroma

(10)

Eating quality

(20)

Overall quality

(60)

DWR – 162 8.6d ± 0.2 8.5c ± 0.3 8.4c ± 0.2 8.5d ± 0.3 18.4f ± 0.3 52.4c ± 0.4

DWR – 39 8.7d ± 0.3 8.5c ± 0.2 8.4c ± 0.3 8.5d ± 0.3 18.2f ± 0.6 52.3c ± 0.4

GW – 322 8.2c ± 0.5 8.6c ± 0.2 8.6c ± 0.3 8.3d ± 0.3 16.0e ± 0.4 49.7b ± 0.3

NI – 5439 8.2c ± 0.3 8.0b ± 0.2 7.8b ± 0.2 7.7c ± 0.3 16.6e ± 0.6 48.3b ± 0.4

NIAW – 34 8.8d ± 0.4 7.7b ± 0.5 8.1c ± 0.2 7.1b ± 0.2 14.6c ± 0.5 46.3b ± 0.4

HD – 2781 7.9b ± 0.2 7.4a ± 0.3 7.3a ± 0.5 7.9c ± 0.2 13.4a ± 0.2 43.9a ± 0.7

HD – 2501 7.7b ± 0.3 7.1a ± 0.5 7.4a ± 0.6 7.9c ± 0.3 14.6c ± 0.2 44.7a ± 0.5

K – 9644 7.1a ± 0.3 7.3a ± 0.2 7.9b ± 0.3 8.3d ± 0.5 15.2d ± 0.4 45.8a ± 0.4

HD – 2189 7.3a ± 0.3 7.7b ± 0.2 7.6a ± 0.4 6.5a ± 0.2 13.8a ± 0.5 42.9a ± 0.5

MACS – 2496 7.3a ± 0.3 7.4a ± 0.6 7.2a ± 0.3 6.2a ± 0.3 14.2a ± 0.9 42.3a ± 0.3

59

Sensory evaluation of chapatis for their eating quality properties

showed that DWR-162, DWR-39, NI-5439 and GW-322 had relatively

higher scores. These chapatis were neither tough nor hard to chew.

They were not weak, offering less resistance to chewing but had

optimum chewing properties. On the other hand, chapatis made from

varieties HD-2781 and HD-2189 were somewhat tough to chew, hence

had the least score. Objective measurement studies also showed that

chapatis made from these two varieties had high cutting force values

(Table 2.3). Chapatis made from K-9644 also had good chewing

properties.

Evaluating the overall quality of chapatis, it is clearly seen that

the varieties DWR-162, DWR-39 and GW-322 produced highly

acceptable chapatis. This was closely followed by those prepared from

NI-5439 and NIAW-34. It is important to note here that chapatis made

from K-9644 scored less, only for their dark color while they had

excellent pliability and eating qualities. Among the ten varieties tested,

MACS-2496 had the least overall score, mostly because of its bland

and insipid taste, undesirable texture and color and poor pliability.

Earlier, Srivastava et al (2003) reported that varieties NI-5439, NIAW-

34 grown, in a different geographical location, did not show good

chapati making properties. The protein and damaged starch contents

reported for were 11.4 and 12.8% for NI-5439 and 15.1 and 13.9% for

NIAW-34, respectively. In the present study, these values are different

and the damaged starch content was found to be higher for these

varieties. On the other hand, varieties, MACS-2496 and HD-2189 had

60

shown poor chapati making properties in both studies (Table 2.1).

Thus, the variations in the chemical and chapati making properties of

these varieties may be due to variation in soil and environmental

conditions as they were grown in different geographical locations.

Earlier, reports indicate that agronomic measures such as nitrogen or

sulfurfertilization, climatic conditions such as rain fall, temperature

and other factors do affect bread making quality (Kolster & Vereijken,

1993).