Effect of microwave freeze-drying on microbial inactivation, antioxidant substance and flavor quality of Ashitaba leaves (Angelica keiskei Koidzumi)

Abstract

To decrease microbial quantity and conserve antioxidant substances of Ashitaba leaves, microwave freeze-drying was conducted at 1, 1.5, and 2 W/g in pilot scale. After drying, microbial inactivation and quality parameters of color, chlorophylls, flavonoids, moisture content, and flavor of dried Ashitaba leaves were evaluated. After drying, the highest contents of chlorophylls and flavonoids maintained 14.62 g/kg and 15.75 mg/g, respectively; microbial colonies decreased by about 2-log; various tastes of dried sample were improved. It could be a suitable dehydration in processing of Ashitaba leaves.