Effect of Vacuum Microwave Drying on the Quality and Storage Stability of Strawberries
The aim of this study was to determine how vacuum assisted microwave drying (VMD, 50C, 6 kPa for 3 h) affects the quality attributes and shelf life of dehydrated strawberries. Changes of quality attributes such as color, texture, and rehydration, shrinkage, polyphenol contents, antioxidant activity, and physicochemical and sensory properties were assessed after VMD. Vacuum packed, dehydrated strawberries were stored at 20C in the dark for 6 months. Decay of anthocyanins, flavonoids and polyphenols, and antioxidant activity was determined and modeled according to first order kinetics. VMD resulted to minimum color difference. Texture changed by increased mechanical resistance and stiffness, and decreased toughness after VMD. Sensory attributes were between 3.5 and 4.3 on 5 point intensity hedonic scale. Anthocyanins were the most unstable components in strawberries after VMD and storage, assessing the strawberry shelf life to 68 days. Finally, VMD is a promising technology that can be used to maintain fruit quality and extend shelf life. Practical Applications Drying is particularly important for handling and distribution of agricultural products with high moisture content and limited shelf life such as fruits and vegetables. The main objective of drying is to reduce moisture content to a level where microbial spoilage and deteriorative chemical reactions of agricultural products are minimal. However, the degradation of nutrients in food during convective hot air drying results to quality loss. Therefore, new drying equipment and drying techniques have to be designed and studied. Vacuum assisted microwave drying is an emerging dehydration method that may be efficient to preserve quality characteristics of food and additionally leads to shorten effective drying time. The purpose of this study was to determine the effects of vacuum assisted microwave drying and subsequent product storage on the quality attributes and shelf life of strawberry fruits. This preservation technique may avoid freezing or refrigeration of fruit.