Application of Water-Based and Lipid-Based Stearin … of Water-Based and Lipid-Based Stearin Wax Coatings to Improve the Quality and Shelf-Life of Seedless Guava (Psidium Guajava

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)