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Dilution and aging of a sugar solution after its multiple uses in an osmotic dehydration process of lowbush blueberries

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Paper number  046142,  2004 ASAE Annual Meeting . (doi: 10.13031/2013.16984) @2004
Authors:   Michèle Marcotte, Dominique Maxime, Ali R. Taherian
Keywords:   Solution Dilution, Osmotic Dehydration, Solution Aging, Lowbush blueberries, Sugar solution

Osmotic dehydration occurs upon the immersion of biological pieces in hypertonic aqueous solutions. Two major counter-current flows are generated. Water comes out from the biological structure and solutes migrate from the solution. There has been an increasing R&D interest but only few examples of successful industrial implementation. Few options are available to overcome the problem of the solution dilution. Sugar can be added continuously but the result is an undesirable solution build-up. Another alternative is to concentrate the dilute solution by membrane processing or evaporation. However, these operations can be very costly. Little has been reported on the quality and aging of solutions after multiple uses. The objective of the study was to osmotically dehydrate batches of lowbush blueberries. Baskets of blueberries were immersed in a batch reservoir that was either opened or closed. The process was performed at 60oC for 3 hours. The sucrose solution was recirculated (30 L/min) with a ratio of 10:1 (solution:blueberries). Various chemical changes (e.g. pH, sucrose, glucose, fructose, anthocyanins) were measured. The pH of the solution decreased to reach an equilibrium value of 3.6. It was found that there was a significant inversion of sucrose into glucose and fructose in the solution. If the osmotic process was performed using an open reservoir, the natural evaporation was sufficient to compensate for the dilution of the solution. Using the same solution, anthocyanin content and pH values were found to reach equilibrium after 4 uses, limiting further losses of fruits components.

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