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The effect of blanching and freezing on osmotic dehydration of pumpkin

Kowalska, H., Lenart, A., Leszczyk, D.
Journal of food engineering 2008 v.86 no.1 pp. 30-38
water content, pumpkins, pretreatment, blanching, freezing, drying, osmotic treatment, sucrose, glucose, starch, syrups, aqueous solutions, mass flow, mass transfer, diffusion, diffusivity, solids, water activity, drying quality, kinetics, Cucurbita, equations
The aim of this work was to analyze the influence of pretreatment (blanching, freezing) on osmotic dehydration of pumpkin. Pumpkin cubes (10 x 10 x 10 mm) were dehydrated in sucrose, glucose and starch syrup solutions. The process took 180 min. Peleg's and exponential equations can be satisfactory applied to describe osmotic dehydration of raw and pretreated pumpkin. Osmotic dehydration of pumpkin in sugar solution at 30 °C depended on the pretreatment. Both pretreatments before osmotic dehydration of pumpkin under these conditions gave higher water loss and especially increase solids gain in comparison to samples without pretreatment. The highest water loss from blanched osmodehydrated during 180 min pumpkin took place by using starch syrup solution (4.5 gH2O/g i.d.m.) and the smallest from frozen samples and dehydrated in sucrose solution (1.6 gH2O/g i.d.m.). But the highest value of WL/SG (to 9.4) parameter was obtained during osmotic dehydration of raw pumpkin. Pretreatment such as blanching and freezing did not have significant influence on the diffusion coefficient for water and solids during osmotic dehydration.