Comparative study on preparing dehydrated fruits and vegetable slices using various drying methods & packaging materials

Abstract

Dehydration is one of the oldest and commonly used preservation techniques where water activity of the food is reduced thereby not providing a conducive environment for microbes to survive. However during dehydration, the nutritional quality parameters of the food get deteriorated. In this research work, pumpkin, which is a commonly grown vegetable was selected to study dehydration while varying the pretreatment methods that affect its nutritional qualities. Blanching and osmotic dehydration were used as pretreatment methods prior to dehydration of pumpkin slices. The effect of blanching methods (water / steam), the concentrations of osmotic solutions (50°brix/ 55°brix/ 60°brix/ 65°brix/ 70°brix) on nutrient retention in dehydration and the packaging material (aluminum/polythene) on dehydrated product storage was studied. Retained total carotenoid and vitamin C contents of the dehydrated pumpkin slices were found to be highly affected by the blanching method, osmotic solution concentration and the packaging material during the drying process. Water blanching had led to higher nutrient destruction when compared to steam blanching. The presence of residual water content also had shown a significant effect on nutrient retention. Water activity of osmotic-dehydrated pumpkin had decreased at higher sugar syrup concentrations retaining the nutrient value of the product for a considerably longer period. Exposure to light had also proved to be highly influential in nutrient retention in terms of aluminum and polythene packaging.