Application of Water-Based and Lipid-
Based Stearin Wax Coatings to Improve
the Quality and Shelf-Life of Seedless
Guava (Psidium Guajava L).
Abd. Rashid, N.*, Amin Zaki, E.N. & Mohd Som, H.Z.
Faculty of Applied Sciences, Universiti Teknologi MARA Shah Alam, Selangor, MALAYSIA.
*e-mail: [email protected]
Universiti Teknologi MARA
40450 Shah Alam, Selangor, MALAYSIA.
Tel : (+603) 5544 4644 Fax : (+603) 5544 4562
Http: www.fsg.uitm.edu.my
ISO 9001:2000 (Certificate No. : KLR 0404074)
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IntroductionEdible coating
wax was the first edible coating used for fruits
applied on oranges & lemons in the 12th & 13th centuries by theChinese (Park, 1999).
made from 4 major types of materials namely lipids, resins,polysaccharides and proteins (Baldwin et. al, 1995).
Palm stearin
by-product of palm oil fractionation, of less valuable and cheapsource of fat fraction.
available in wide range of MP and IV depending on thefractionation conditions.
OBJECTIVE:
To study the potential of using hard palm stearin (IV 32) as water-based and lipid-based coatings in improving the quality andshelf-life of seedless guavas.
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Previous related studies
Baldwin et. al (1995): edible coating delay ripening of climacteric fruit,
delay color changes in non-climacteric fruit, reduce water loss, reduce
decay & improve appearance.
Garcia et. al (1998): starch-based coating applied on strawberry and
polyvinyl acetate coating on citrus fruit (Garcia, 2001).
Hagenmaier and Baker (1997): micropholine-free wax microemulsion on
oranges and polyethylene-candelilla coating for ‘Valencia’ oranges
(Hagenmaier, 2000).
Maftoonazad (2004): postharvest shelf-life extension of avocados using
methyl cellulose-based coating.
Mohamed (1992): 20% palm oil surface coating was the best treatment for
maintaining the quality of fresh guava stored for 2 months compared to
starch, liquid paraffin, fatty acid sugar esters.
Olorunda & Aworth (1984): coating fruits with semi-permeable film
influenced the fruit physiology to retard ripening and post harvest
metabolism
Yaman and Bayoundurh (2002): effect of edible coating and cold storage
on shelf-life and quality of cherries.
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Materials and Methods
Materials
RBD hard PS (IV 32, SMP 52.5˚C) and PKOo - Cargill Specialty Oils
& Fats Sdn. Bhd. Port Klang, Malaysia.
Seedless guavas
Seedless guavas (index 2) - Sui Yuan Fruit Trading, Ladang
Bikam, Bidor, Perak, Malaysia .
Selected based on uniformity of size, weight, shape and colour.
Coating solution preparation
Lipid-based coating: blending 1:1 hard PS with PKOo
Water-based stearin wax coating: using stearin-to-water
microemulsion-making method (Hagenmaier and Baker, 1994).
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Materials and Methods
Sample preparationseedless guavas were cleaned & immersed in 0.5% potassiumsorbate.
both coatings were applied by hand-wiping technique usingsponge followed by air drying and stored at room temperature(22˚-25˚C).
effectiveness of coatings were monitored in terms of thefollowing parameters at day 1, 3, 6, 9, 12, 14 and 16.
i. % weight loss
ii. firmness by Texture Analyzer (TAXT2)
iii. surface colour development by Konica Minolta Chromameter
iv. titratable acidity (AOAC, 2005)
v. ascorbic acid content (AOAC, 2005)
vi. oxygen concentration by MOCON Pac Check Model 350
vii. carbon dioxide and ethylene concentration by GC
RESULTS & DISCUSSION
Universiti Teknologi MARA
40450 Shah Alam, Selangor, MALAYSIA.
Tel : (+603) 5544 4644 Fax : (+603) 5544 4562
Http: www.fsg.uitm.edu.my
ISO 9001:2000 (Certificate No. : KLR 0404074)
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Weight loss
Fig. 3.1: Effect of Different Coating Formulations on Percent Weight Loss of Seedless Guavas
weight loss increases withstorage time
both coatings significantlyreduced water evaporation& weight loss.
these coatings provide amoisture barrier; resultedin delay migration ofmoisture from fruits toenvironment.
result agrees with otherresearchers’ findings thatreported coatings madefrom lipids have good watervapour barrier properties.
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Firmness
Fig. 3.2: Effect of Different Coating Formulations on Firmness of Seedless Guavas
Stearin wax coating had
significantly maintained the
firmness of seedless
guavas compared to
control.
The ability of the stearin
wax to maintain the
seedless guavas firmness
could be related to the
lower weight losses, similar
to studies on strawberry,
(Mali & Grossman, 2003;
Del-Valle et al., 2005),
apple (Moldao-Martins et
al., 2003), and sweet
cherry (Yaman &
Bayoundurh, 2002 &
Romero et al., 2005).
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Surface colour development
Table 3.3(a): Lightness (L*) of seedless guavas during storage
Days Control Lipid based Water-based
1 75.66 0.25Ca 86.70 0.16Ba 88.80 0.3AAa
3 70.55 0.27Cb 76.61 0.48Bb 80.28 0.39Ab
6 60.73 0.21Cc 68.55 0.19Bc 72.99 0.25Ac
9 50.29 0.23Cd 57.66 0.46Bd 61.88 0.29Ad
12 46.63 0.21Ce 53.86 0.38Be 57.55 0.28Ae
14 40.08 0.28Cf 50.77 0.21Bf 52.47 0.38Af
16 38.75 0.23Cg 49.93 0.67Ag 50.49 0.40Ag
• Water–based coating
did not affect the
normal colour and
had maintained the
natural glossiness of
the seedless guavas.
• However, the lipid-
based coating had
slightly affected the
surface appearance
and the colour of
seedless guavas after
application due to the
uneven spreadability
of the coating itself. It
had also caused the
loss of natural fruit
glossiness and gave
a slightly pale green
colour.
Means with same capital letters across the column are not
significantly different (p<0.05)
Means with same small letters down the row are not significantly
different (p<0.05)
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Surface colour development
Table 3.3(b):Greeness (a*) of seedless guavas during storage
Days Control Lipid based Water-based
1 -18.41 0.35Ag -20.9 0.64Bg 21.69 0.24Bg
3 -14.63 0.29Af -18.62 0.27Bf -19.53 0.39Cf
6 -9.38 0.40Ae -15.45 0.37Be -18.41 0.32Ce
9 -8.02 0.19Ad -13.64 0.23Bd -16.72 0.28Cd
12 -6.35 0.24Ac -9.48 0.34Bc -12.51 0.35Cc
14 -5.38 0.14Ab -8.28 0.17Bb -10.50 0.28Cb
16 -3.14 0.10Aa -7.59 0.34Ba -8.46 0.15Ca
Stearin wax coating
had significantly
retarded the colour
changes of seedless
guavas by retaining
the green colour
longer compared to
the uncoated ones
throughout storage
Means with same capital letters across the column are not
significantly different (p< 0.05)
Means with same small letters down the row are not significantly
different (p<0.05)
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Surface colour development
Means with same capital letters across the column are not significantly different (p< 0.05)Means with same small letters down the row are not significantly different (p< 0.05)
Days Control Lipid
based
Water-based
1 31.09 0.14Af 27.29 0.83Bf 23.82 1.16Cf
3 34.49 0.48Ae 28.92 0.19Be 25.85 0.45Ce
6 37.74 1.07Ad 31.01 0.20Bd 26.17 0.30Ce
9 40.88 0.63Ac 31.55 0.61Bd 28.07 0.56Cd
12 41.24 0.39Ac 32.81 0.25Bc 30.07 0.45Cc
14 42.50 0.15Ab 34.60 0.47Bb 33.55 0.69Cb
16 44.01 0.18Aa 35.88 0.27Ba 35.45 0.28Ba
Table 3.3(c): Yellowness (b*) of seedless
guavas during storage Uncoated seedless guavas begin
to attain full yellow colour as early at
the 1st day of storage while lipid-
based and water-based was at 7th or
12th day, respectively
Indicated that uncoated guavas
experienced faster ripening process
than the coated fruits.
Visual appearance
Day 3
Day 1
Day 6
Day 9
Day 12
Day 14
Day 16
Control Lipid-based Water-based
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Ascorbic acid content
Fig 3.4: Effect of Different Coating Formulations on Ascorbic Acid Content of Seedless Guavas
The ascorbic acid content
significantly decreased for both
coated and uncoated fruits with
increase of storage time.
However, coating had slowed the
amount of ascorbic acid loss from
guavas compared to that of the
control. Ascorbic acid loss is due to
the activities of the phenoloxidase
and ascorbic acid oxidase (Yaman
and Bayoundurh, 2002).
Coating should reduce the ascorbic
acid losses since it acts as an oxygen
barrier which lowers the activity of
these enzymes.
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Titratable acidity
Fig 3.5: Effect of Different Coating Formulations on
Titratable Acidity of Seedless Guavas.
Stearin wax coating had
significantly delayed the decrease
in the titratable acidity of the fruits
compared to the control fruits.
A decline in acidity demonstrated
maturation development. This is
expected as the organic acids are
substrates for enzymatic reactions
of respiration. As the fruit respires,
organic acids will be used up and
this reduced the tiratable acidity.
Yaman and Bayoundurh (2002)
reported that coatings reduced the
respiration rate, hence delayed the
utilization of organic acids. This
indicated that both stearin wax
coatings were able to act as
protective oxygen barrier.
Oxygen concentration
Fig 3.6: Effect of Different Coating Formulations on Oxygen Concentration of Seedless Guavas.
Lower values of oxygen
concentrations were obtained for
seedless guavas treated with stearin
wax coating compared to those of
control fruits.
This is because when coating is
applied it will acts as a barrier towards
oxygen (Hagenmaier, 2000).
Oxygen concentration is also related
to total acidity and weight loss. The
results obtained revealed that coating
made from palm stearin was able to act
as an oxygen barrier that slowed down
the respiration rate of guavas hence
delaying the organic acid utilization and
decreasing the weight loss.
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Carbon dioxide concentration
Fig 3.7: Effect of Different Coating Formulations on Carbon Dioxide Concentration of Seedless Guavas.
The stearin wax coatings had
significantly reduced the carbon
dioxide concentration compared to
the control guavas.
This indicates that the stearin
wax coatings had slowed down the
respiration rate thus decrease the
weight loss. These effects being
similar to those obtained with other
edible coatings (Romero et al,
2005; Maftoonazad et al., 2006).
Lipid-based coating is known to
be an excellent water barrier but
relatively permeable to gases.
However, this study shows
different results, where coating
made from palm stearin is not only
a good moisture barrier but is also
a good gas barrier.
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Ethylene production
Fig. 3.8: Effect of Different Coating Formulations on
Ethylene Production of Seedless Guavas
The ethylene production of
uncoated seedless guavas
decreased significantly after three
days of storage, with the third day
storage as the climacteric peak
where the highest amount of
ethylene was produced.
Stearin wax coatings delayed the
maximum ethylene production from
3rd day to 9th day of storage,
indicating the ripening process has
been delayed.
Ethylene production is related to
respiration rate where low oxygen
and high carbon dioxide
concentrations retard the ethylene
production, therefore delaying
ripening process.
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Conclusions
Application of water-based and lipid-based stearin wax coatingswas able to improve the quality and shelf-life of seedless guavasthroughout 16 days of storage time at room temperature.
Both coatings were good moisture and gas barriers which wereable to slow down the ripening process by decreasing the weightloss, reducing the respiration rate and ethylene production,maintaining the firmness, titratable acidity and ascorbic acidcontent and retarding the changes of surface colour of theseedless guavas.
Palm stearin has the potential to be used as a cheap source ofedible coating for fruits and vegetables.
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References
Baldwin, E.A., Nisperos-Carriedo, M.O. and Baker, R.A. (1995). Edible coating for lightly processed fruitsand vegetables. HortScience. 30, 35-38.
Federal Agricultural Marketing Authority (2006). Analysis of the guava industry. Vol- 6576/2006/B1, Ministryof Agriculture and Agro-Based Industry Malaysia.
Garcia, M. A., Martino, M.N. and Zaritzky, N.E. (1998). Starch–Based Coatings: Effect on RefrigeratedStrawberry (Fragaria ananassa) Quality. Journal Science Food Agriculture, 76, 411-420.
Garcia, J. (2001). Agricultural Research Services, USDA in Food-grade Polyvinyl Acetate New Edible,Food-Grade Fruit Coating, Retrieved September 5, 2005 from www.ars.usda.gov
Hagenmaier, R.D. and Baker R.A. (1997). Edible Coating from morpholine-freewax microemulsion. J.Agric. Food Chemistry, 45, 349-352.
Hagenmaier, R.D. (2000). Evaluation of a polyethylene-candelilla coating of ‘Valencia’ oranges.Postharvest Biology and Technology, 19, 147-154.
Hagenmaier, R.D. (2000). Reduction in gas exchange of citrus fruits by wax coating. Journal Agriculture ofFood Chemical 41 (2), 283-287.
Hagenmaier, R.D. and Baker R.A. (1994). Wax microemulsions and emulsions as citrus acid coating.Journal of Agriculture Food Chemistry. 42 (4): 899-902.
Maftoonazad, N., (2004). Postharvest shelf-life extension of avocados using methyl cellulose-basedcoating. Department of Food Science, McGill University, Canada, 12.
Mohamed, S., Kyi M.M.K., Idris, A.Z.,Yusof, S. and Osman, A. (1992). Effects of various treatments (palm oil, liquid paraffin, samperfresh or starch surface coatings and LDPE wrappings) on storage life of guava (Psidium Guava) at 10oC. Acta Horticulturae 321:786-794.
Olorunda, A.O. and Aworth, O.C (1984). Effect of pro-long, a surface coating agent on the shelf-life andquality attributes of plantain, J. Sci Food Agric, 35, 573-578.
Ko, W.H. and Kunimoto, R.K. (1980). Guava fruit firm rot induced by bruising. HortScience 15, pp. 722–723.Yaman, O. and Bayoundurh, L. (2002). Effects of an edible coating and cold storage on shelf-life and quality of
cherries. Lebesm-Wiss. U. Technol., 35, 146-150.
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Acknowledgment
Ministry of Science, Technology and
Innovation Malaysia (MOSTI) for
Sciencefund Grant
Universiti Teknologi MARA (UiTM)
Cargill Specialty Fats, Port Klang, Malaysia
Universiti Teknologi MARA
40450 Shah Alam, Selangor, MALAYSIA.
Tel : (+603) 5544 4644 Fax : (+603) 5544 4562
Http: www.fsg.uitm.edu.myISO 9001:2000 (Certificate No. : KLR 0404074)
Hand-wiping using sponge
Lipid-based Stearin wax Water-based Stearin wax
THANK YOU
Universiti Teknologi MARA
40450 Shah Alam, Selangor, MALAYSIA.
Tel : (+603) 5544 4644 Fax : (+603) 5544 4562
Http: www.fsg.uitm.edu.my
ISO 9001:2000 (Certificate No. : KLR 0404074)
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