FOAM MAT DRYING OF CUSTARD APPLE PULP AND STORAGE STABILITY OF CUSTARD APPLE POWDER

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Date
2017
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COLLEGE OF AGRICULTURAL ENGINEERING AND TECHNOLOGY ANAND AGRICULTURAL UNIVERSITY, GODHRA
Abstract
The foaming properties (foam expansion, foam density and foam stability) of custard apple pulp were carried out at concentration of egg albumen (0, 5, 10, 15 and 20%, w/w) with concentration of methyl cellulose (0.0, 0.125, 0.25, 0.375 and 0.50%, w/w) and whipping time (5, 10, 15, 20 and 25 min). The drying experiments of optimized foamed custard apple pulp were carried out at temperature 60, 65, 70 & 75°C and at drying thickness of 2, 4, 6 and 8 mm. Drying characteristics of thin layer custard apple pulp were evaluated. Mathematical models were fitted to fit drying data of foamed custard apple pulp. The different biochemical parameters, powder recovery and sensory evaluation of different drying treatments were observed during the experimental work. The storage stability of optimized custard apple powder was evaluated at 30 days interval of storage period using laminated aluminum foil pouch & polyethylene bag. The compromised optimum condition for maximum expansion, stability and minimum density was obtained at egg albumin concentration, methyl cellulose concentration and whipping time of 15%, 0.37% and 17.32 min respectively. The drying time to reach final moisture content for custard apple pulp were 90 to140, 120 to 210, 150 to 290 and 180 to 370 min at drying thickness of 2, 4, 6 and 8 mm, respectively for selected temperature range (60-75°C). Twelve commonly used models were tested to fit the experimental data of foamed custard apple pulp. The R2 value of Hii’s model was higher (0.9956), and corresponding χ2 (0.0005) and RMSE (0.0175) values were lower than other models, which indicate that the model fitted very well to the experimental data. The average values of effective diffusivities of foamed custard apple pulp were varied from 2.01 × 10-08 to 2.04 × 10-07. The activation energy varied from 29.99 to 50.52 kJ/mol with an average value of 41.45 kJ/mol. The maximum ascorbic acid and total sugar were 11.36 mg/100g and 10.53 g/100g observed at 60 and 65°C with thickness of 2 and 4 mm and maximum sensory evaluation 8.25 was observed at 65°C at thickness of 4 mm. During the storage, the average colour-L* values decreased, whereas coloura* values, colour-b* values and total colour deference (ΔE) value increased with storage period. Colour change was more pronounced in packages without vacuum and glass bottle as compared to laminated aluminium foil pouch and Polyethylene bag with vacuum. The average ascorbic acid, total sugar and overall acceptability were more in case of packaging (laminated aluminium foil pouch and polyethylene bag) under vacuum condition as compared to glass bottle followed by (laminated aluminium foil pouch and polyethylene bag) without vacuum condition. The zero-order model is recommended for the prediction of colour-L*, colour-a* value, moisture content, ascorbic acid and total sugar of custard apple powder during storage period due to higher R2 and lower χ² and RMSE values.
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