ENVIROPAKENVIROPAK

WP5. Development of WP5. Development of coating Techniquescoating Techniques(Maida Khan, Borges Chambal, (Maida Khan, Borges Chambal,

Asmina Sulemane, Izdine Opressa, Asmina Sulemane, Izdine Opressa, Sandra Chemane and Silvia Abdula)Sandra Chemane and Silvia Abdula)

November 2004November 2004

WP5. Development of coating WP5. Development of coating TechniquesTechniques

ObjectivesObjectives– To test the suitability of different coating To test the suitability of different coating

techniques on fruits and nutstechniques on fruits and nuts– To select and optimize the most suitable To select and optimize the most suitable

techniques on fruits and nuts for pilot techniques on fruits and nuts for pilot scale operationsscale operations

WP5. Development of coating WP5. Development of coating TechniquesTechniques

Results obtained on the work done during Results obtained on the work done during the first year:the first year:– Most suitable method to coat fruits and nuts was dipping Most suitable method to coat fruits and nuts was dipping

(sponge coating (fruits), pan coating (nuts) and spray (sponge coating (fruits), pan coating (nuts) and spray coating (both) not efficient. coating (both) not efficient.

Work done during the second year Work done during the second year – Coating of pears Coating of pears – Coating of litchisCoating of litchis– Evaluation of thickness and uniformity of films on Evaluation of thickness and uniformity of films on

cashew nuts, pears and litchis using light microscopy cashew nuts, pears and litchis using light microscopy and image analisysand image analisys

– studies for up scaling of coating processing of cashew studies for up scaling of coating processing of cashew nutsnuts

WP5. Development of WP5. Development of coating Techniquescoating Techniques

Work done during the second year Work done during the second year – Coating of pears Coating of pears – Coating of litchisCoating of litchis– Evaluation of thickness and uniformity of Evaluation of thickness and uniformity of

films on cashew nuts, pears and litchis films on cashew nuts, pears and litchis using light microscopy and image analisysusing light microscopy and image analisys

– studies for up scaling of coating studies for up scaling of coating processing of cashew nutsprocessing of cashew nuts

Coating of pearsCoating of pears

Studies performedStudies performed– Use of Low concentrated protein solutionsUse of Low concentrated protein solutions

13 %;11.52%;10.64%;9.76%;8.813 %;11.52%;10.64%;9.76%;8.8

– Use of different temperatures of pears (10, 23, 25 Use of different temperatures of pears (10, 23, 25 and 28ºC)and 28ºC)

– Addition of Citric acid in the coating solution in Addition of Citric acid in the coating solution in order to improve the quality of the coated pearorder to improve the quality of the coated pear

– Effect of temperature on whitening of pear

Coating of pearsCoating of pears

The solutions were prepared as The solutions were prepared as recommended by the casting method, but recommended by the casting method, but with reduced protein concentrations. with reduced protein concentrations.

The pears were let to stabilize the The pears were let to stabilize the temperature.temperature.

The range of the temperature of the The range of the temperature of the solutions was between 23solutions was between 23±1 to±1 to 30 30 ± 1± 1ºC. ºC. Relative Humidity of the environment Relative Humidity of the environment range was 50 to 80%. range was 50 to 80%.

The pH was measured for all solutions The pH was measured for all solutions

Coating of Pear – Results and Coating of Pear – Results and ConclusionsConclusions

Appearance was less glossy and Shining Appearance was less glossy and Shining effect increases with reduction of protein effect increases with reduction of protein content in the solution ( same effect was content in the solution ( same effect was found when apples were coated with zein found when apples were coated with zein solutions – Bai et al, 2003). solutions – Bai et al, 2003).

Intensity of whitening after coating was Intensity of whitening after coating was dependent of the temperature difference dependent of the temperature difference between the pear and the coating solution. between the pear and the coating solution.

Higher the temperature difference between Higher the temperature difference between the two, more intense was the whitening the two, more intense was the whitening effect and takes longer time to disappear. effect and takes longer time to disappear.

Coating of pear – Results and Coating of pear – Results and ConclusionsConclusions

When stored at low temperatures (10ºC) and brougth When stored at low temperatures (10ºC) and brougth to ambient temperature a whitening effect was to ambient temperature a whitening effect was observedobserved

During storage at ambient conditions no whitening During storage at ambient conditions no whitening effect on coated and dried pear was observedeffect on coated and dried pear was observed

Probable factor that contribute for the whitening effect Probable factor that contribute for the whitening effect on pears is water condensation due to temperature on pears is water condensation due to temperature

Use of citric acid no whitening effect was found just Use of citric acid no whitening effect was found just afetr coating. High concentration of citric acid results afetr coating. High concentration of citric acid results in jelly like films. in jelly like films.

Lowering the protein concentration on the coating Lowering the protein concentration on the coating solution improve the appearance of the coating on the solution improve the appearance of the coating on the pear.pear.

Other formulations were tested Other formulations were tested by CSIRby CSIR

Hyperlink to Sonya’s workHyperlink to Sonya’s work

Coating of LitchisCoating of Litchis

By dipping them 5, 10 and 15 seconds and By dipping them 5, 10 and 15 seconds and spraying them with:spraying them with:– Ethanol prepared solutionsEthanol prepared solutions– GAA prepared solutionsGAA prepared solutions

Litchis were let to dry at room Litchis were let to dry at room temperature. Stored in plastic bags and temperature. Stored in plastic bags and others without that at room temperature. others without that at room temperature. They were also kept in the refrigerator at They were also kept in the refrigerator at 10ºC.10ºC.

Coating of litchis - Coating of litchis - ConclusionsConclusions

Coated litchis unpacked and dried at Coated litchis unpacked and dried at room temperature have a whitening room temperature have a whitening problemproblem

GAA result in a burnt productGAA result in a burnt product More studies with other formulations More studies with other formulations

should be testedshould be tested HYperlink to work performed by UOMHYperlink to work performed by UOM

Evaluation of thickness and uniformity using Evaluation of thickness and uniformity using light microscopylight microscopy

* Light microscopy and image analysis were used

ConclusionsConclusionsThickness of films on coated fruits depends on Thickness of films on coated fruits depends on protein concentration protein concentration

Thickness reduces with decrease in protein Thickness reduces with decrease in protein content- Probable reason– viscosity decreasescontent- Probable reason– viscosity decreases

From the image can be seen that the films on From the image can be seen that the films on products seem to be uniform.products seem to be uniform.

Up scaling of coating Up scaling of coating aplicationaplication

A flow diagram for up scaling was developed based A flow diagram for up scaling was developed based on the dip coating method used in a lab scaleon the dip coating method used in a lab scale

It was mainly developed for coating of cashew nut, It was mainly developed for coating of cashew nut, but can be modified for litchis and probably pearsbut can be modified for litchis and probably pears

A tray with a mesh was made of stainless steelA tray with a mesh was made of stainless steel

Trials were performed using a tray dryer with forced Trials were performed using a tray dryer with forced airair

Drying curves were determined at 50Drying curves were determined at 50± 2ºC for kafirin ± 2ºC for kafirin and zein and zein coated cashew nuts to determine the drying coated cashew nuts to determine the drying timetime