Drying characteristics and quality evaluation in microwave-assisted hot air drying of cherry tomato

摘要

The aim of this work was to investigate the drying behavior of osmotic cherry tomatoes under different microwave powers and drying temperatures using a microwave assisted hot air dryer. The effective moisture diffusivity, physicochemical properties and bioactive compounds were studied under microwave powers of 300-600 watts (W) combined with drying temperatures of 60-80°C. It was clearly found that microwave power played an important role in moisture removal under microwave application conditions. In contrast, under conventional drying, drying air temperature was a key factor in moisture removal. Drying characteristics were consistent with moisture diffusivity and surface evaporation as a constant rate period was observed. Moisture diffusivity was significantly increased by increasing microwave power in combination with drying air temperature (p≤0.05). The color and textural properties of dried cherry tomatoes were higher than a conventional drying method (p≤0.05). However, the degree of shrinkage increased with the increase in drying conditions (p≤0.05) and contradicted with the decrease in drying time. Moreover, ascorbic acid, total phenolic compounds including flavonoids and lycopene were found superior in microwave assisted air drying compared to conventional air drying and commercial product (p≤0.05). The use of a microwave power of 450 W in combination with a drying air temperature of 60 °C was suggested for cherry tomatoes pretreated with non-nutritive sweetener, as nutrients were better stabilized than the other conditions.