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H. LI and H. S. Ramaswamy. Dept. of Food Science and Agricultural Chemistry, McGill Univ., 21,111 Lakeshore Road, Ste-Anne-De-Bellevue, QC H9X3V9, Canada The moisture sorption isotherm is an extremely valuable tool for food scientist because it can be used to predict potential changes in food stability; it can be used for packaging selection and for ingredient selection. Osmotic dehydration is recognized as a prosperous preconcentration method to obtain better quality product by removing moisture under mild conditions. Most of the sorption data for foods published in the literature has been obtained by simulating storage conditions. The influence of osmotic dehydration processing condition variance on sorption isotherm data change has rarely been studied. The objective of this study was to examine possible changes in sorption isotherm characteristics of osmotic preconcen-trated apple cylinders in combination with microwave and convective air dryig techniques and as related to osmotic variables and subsequent second stage drying. Sorption isotherms for dehydrated apple obtained by Freeze Drying (FD), Air Drying (AD), Osmotic Dehydration combined with conventional Air Drying (ODAD) and MicroWave assisted Osmotic Dehydration combined with conventional Air Drying (MWODAD) were established and fitted to the Guggenheim-Anderson-de Boer (GAB) model. Polynomial regression with the transferred GAB equation was used to calculate monolayer (Mo) moisture values. Results showed that sorption isotherms of osmotic dehydration (OD) and microwave assisted osmotic dehydration (MWOD) treatments shifted with respect to FD isotherms. Osmotic dehydration (OD) processing condition variables affected product's isothermal sorption monolayer value. OD pretreatment resulted in a less sugar intake than the conventional air dried product. The results suggested that osmotic dehydration processing conditions variables such as temperature, concentration and time, affect the adsorption isotherm of osmo-oven dried apple cylinders. GAB model gave the good fit for the experiment data. Calculated Mo content was influenced by total solids content change, caused by differences in binding properties of the products. The practical consequence was different processes resulted in different product responses to dehydration and rehydration processes.
Session 96, Fruit & Vegetable Products: General II
2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana |