Mass Transfer Considerations in Osmotic Dehydration of Plantain (Musa Paradisiaca) Chips

J. S. Alakali, S. V. Irtwange, P. A. Yusuf

Abstract


The influence of process variables and the kinetics of water loss during osmotic dehydration of plantain (Musa paradisiaca) chips in sugar solutions was determined to provide information necessary for further drying and to enable processors maintain its quality. A 3 x 4 factorial in Complete Randomized Design (CRD) experimental design comprising of three sucrose concentrations 29, 33 and 41oBrix and four temperatures 40, 50, 60 and 80oC were used for the study. For each sucrose concentration, plantain slices each 20 g were immersed in sugar solutions contained in 500ml glass beaker which were maintained at 40, 50, 60 and 80oC respectively in agitated water bath while maintaining the syrup to fruit ratio at 5:1 in order to minimize errors arising from changes in syrup concentrations due to mass transfer. Osmotic dehydration kinetics of plantain slices was analyzed based on the models reported by Azoubel and Murr (AMM), and Zungarramudi and Lupin (ZLM). The analysis of variance shows a highly significant syrup concentration, temperature and interaction effect. As the temperature increased, water loss increased and residual water decreased. At all sucrose concentrations studied, water loss was observed to increase with temperature. Results of evaluation of the mass transfer characteristics during osmotic dehydration indicate that both AMM and ZLM gave high regression coefficients ranging from 0.789 to 0.997 for AMM and 0.821 to 0.996 for ZLM. The values of the mean relative deviation modulus (%E) used to evaluate the goodness of fit of the models for AMM and ZLM were generally low, less than 10% indicating that the two models gave good fit to experimental data with ZLM predicting the experimental data better than AMM. The apparent diffusivity (Da) values generally increased with both temperature and sucrose concentration with the values ranging between 3.489x10-12 to 1.857x10-6 m2/s.

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