Effect of carbonic maceration pre-treatment on the drying behavior and physicochemical compositions of sweet potato dried with intermittent or continuous microwave

ABSTRACT

Drying behavior and change of physicochemical compositions of sweet potato in intermittent microwave drying (IMD) and continuous microwave drying (CMD) combined with or without carbonic maceration (CM) pre-treatment were investigated. A quantity of 100 g of fresh or CM pre-treated samples were dried in IMD at 700 W with power on–off ratio of 1/6 (5 s/30 s, t_on/t_off) or dried in CMD with power density of 1 W/g. The results indicated that the process of CM + IMD as compared with IMD, CMD, and CM + CMD had the shortest drying time, the lowest activation energy (E_a), and the biggest effective moisture diffusivity (D_eff) and exhibited the highest total content of phenols, anthocyanins, flavonoids, β-carotene, ascorbic acid retention rate, as well as scavenging free radical capability 2,2-diphenyl-1-picrylhydracyl of dried product. Meanwhile, color measurements indicated that CM + IMD could get the most desirable color of dried sweet potatoes. Therefore, CM pre-treatment is promising for industrial application.

KEYWORDS:

• Antioxidant capability
• carbonic maceration
• chemical composition
• intermittent microwave
• product quality
• sweet potatoes