INFLUENCE OF MICROWAVE HEATING ON MASS TRANSFER DURING OSMOTIC DEHYDRATION OF APPLES
 
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Pol. J. Food Nutr. Sci. 2007;57(Special issue 4B):317–323
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ABSTRACT
The aim of this work was to analyse the influence of microwave heating on mass transfer during osmotic dehydration of apples. The samples in 10 mm-cube shape were pre-dried at 200 and 300W microwave power for 10 min. After that, osmotic dehydration of apples was carried out in a glucose solution of 49% concentration at 30 and 50oC temperature. Osmotic process time was 15 and 30 min. An influence of microwave heating on mass transfer in osmodehydrated apples was found. Mass loss from apples with microwave treatment before osmotic dehydration was 3-10 times lower than in the samples without pretreatment. Microwave application decreased water content (14-28%) and increased water loss (15-46%). However, there was no significant effect on water activity in the investigated apples. The highest effect of microwave pretreatment was observed in solids gain. It was 2-3 times higher than in apples without pretreatment. Moreover, in apples exposed to microwave treatment the water loss to solids gain ratio was 2-5 times smaller than in apples without pretreatment. Microwave treatment before osmotic dehydration caused slightly more darkness of apples in comparison with non-treated samples.
ISSN:1230-0322