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Pre-treatments influence on the osmotic dehydration of star fruit slices

Osmotic dehydration (OD) of star fruit (Averrhoa carambola L.) in sucrose solution was studied, aiming at optimizing the process. At a first set of trials, edible coating (pectin or pectin+starch) was applied on the slices followed by OD (50%, w/w, 27°C). On a second set of trials, the coatings partial drying in the oven, before OD, was also assessed. At a third set of trials, the addition of the CaCl2 in the osmotic solution itself was tested. The pectin based and pectin+starch based coatings, moist or oven-dried before the osmotic dehydration, were not viable on the process efficiency improvement (maximum water loss/solute gain) due to the high moisture retention and the easy sucrose impregnation of them. The vegetal tissue, uncoated, restrained more of the solute transfer and allowed a higher water output. The use of 0.04M CaCl2 concentration in the sucrose osmotic solution itself improved the process efficiency slightly in relation to the solution without salt. These pre-treatments also yielded positive results on the sensorial evaluation of the air-dried (60 and 70°C) star fruit slices, in comparison with the non-treated fruit, and the best temperature was 60°C

calcium chloride; edible coatings; sensory analysis; drying; mass transfer


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