ENVIROPAK WP5. Development of coating Techniques (Maida Khan, Borges Chambal, Asmina Sulemane, Izdine Opressa, Sandra Chemane and Silvia Abdula) November 2004

WP5. Development of coating Techniques Objectives Objectives –To test the suitability of different coating techniques on fruits and nuts –To select and optimize the most suitable techniques on fruits and nuts for pilot scale operations

WP5. Development of coating Techniques Results obtained on the work done during the first year: Results obtained on the work done during the first year: –Most suitable method to coat fruits and nuts was dipping (sponge coating (fruits), pan coating (nuts) and spray coating (both) not efficient. Work done during the second year Work done during the second year –Coating of pears –Coating of litchis –Evaluation of thickness and uniformity of films on cashew nuts, pears and litchis using light microscopy and image analisys –studies for up scaling of coating processing of cashew nuts

WP5. Development of coating Techniques Work done during the second year Work done during the second year –Coating of pears –Coating of litchis –Evaluation of thickness and uniformity of films on cashew nuts, pears and litchis using light microscopy and image analisys –studies for up scaling of coating processing of cashew nuts

Coating of pears Studies performed Studies performed –Use of Low concentrated protein solutions  13 %;11.52%;10.64%;9.76%;8.8 – Use of different temperatures of pears (10, 23, 25 and 28ºC) –Addition of Citric acid in the coating solution in order to improve the quality of the coated pear – –Effect of temperature on whitening of pear

Coating of pears The solutions were prepared as recommended by the casting method, but with reduced protein concentrations. The solutions were prepared as recommended by the casting method, but with reduced protein concentrations. The pears were let to stabilize the temperature. The pears were let to stabilize the temperature. The range of the temperature of the solutions was between 23±1 to 30 ± 1ºC. Relative Humidity of the environment range was 50 to 80%. The range of the temperature of the solutions was between 23±1 to 30 ± 1ºC. Relative Humidity of the environment range was 50 to 80%. The pH was measured for all solutions The pH was measured for all solutions

Coating of Pear – Results and Conclusions  Appearance was less glossy and Shining effect increases with reduction of protein content in the solution ( same effect was found when apples were coated with zein solutions – Bai et al, 2003).  Intensity of whitening after coating was dependent of the temperature difference between the pear and the coating solution. Higher the temperature difference between the two, more intense was the whitening effect and takes longer time to disappear.

Coating of pear – Results and Conclusions  When stored at low temperatures (10ºC) and brougth to ambient temperature a whitening effect was observed  During storage at ambient conditions no whitening effect on coated and dried pear was observed  Probable factor that contribute for the whitening effect on pears is water condensation due to temperature  Use of citric acid no whitening effect was found just afetr coating. High concentration of citric acid results in jelly like films.  Lowering the protein concentration on the coating solution improve the appearance of the coating on the pear.

Other formulations were tested by CSIR Hyperlink to Sonya’s work Hyperlink to Sonya’s work

Coating of Litchis By dipping them 5, 10 and 15 seconds and spraying them with: By dipping them 5, 10 and 15 seconds and spraying them with: –Ethanol prepared solutions –GAA prepared solutions Litchis were let to dry at room temperature. Stored in plastic bags and others without that at room temperature. They were also kept in the refrigerator at 10ºC. Litchis were let to dry at room temperature. Stored in plastic bags and others without that at room temperature. They were also kept in the refrigerator at 10ºC.

Coating of litchis - Conclusions Coated litchis unpacked and dried at room temperature have a whitening problem Coated litchis unpacked and dried at room temperature have a whitening problem GAA result in a burnt product GAA result in a burnt product More studies with other formulations should be tested More studies with other formulations should be tested HYperlink to work performed by UOM HYperlink to work performed by UOM

Evaluation of thickness and uniformity using light microscopy * Light microscopy and image analysis were used Conclusions Thickness of films on coated fruits depends on protein concentration Thickness reduces with decrease in protein content- Probable reason– viscosity decreases From the image can be seen that the films on products seem to be uniform.

Up scaling of coating aplication A flow diagram for up scaling was developed based on the dip coating method used in a lab scale A flow diagram for up scaling was developed based on the dip coating method used in a lab scale It was mainly developed for coating of cashew nut, but can be modified for litchis and probably pears It was mainly developed for coating of cashew nut, but can be modified for litchis and probably pears A tray with a mesh was made of stainless steel A tray with a mesh was made of stainless steel Trials were performed using a tray dryer with forced air Trials were performed using a tray dryer with forced air Drying curves were determined at 50± 2ºC for kafirin and zein coated cashew nuts to determine the drying time Drying curves were determined at 50± 2ºC for kafirin and zein coated cashew nuts to determine the drying time