Regulation of Enzymatic Browning of Mung Bean Sprout by Heat-Shock Treatment

Abstract

Mung bean sprouts turn brown during cold storage. Here we showed that heat-shock treatment inhibited this browning by repressing the induction of phenylalanine ammonia-lyase (PAL) activity and the biosynthesis of polyphenols during cold storage. Mung bean sprouts were soaked in warm water at 50°C for 60 s as heat-shock treatment and then stored at 8°C for 6 days. Heat-shocked mung bean sprout turned less brown than that of the control sprout. The PAL activity in the control significantly increased during cold storage, while that in heat-shocked mung bean sprouts did not. The polyphenol content in heat-shocked mung bean sprouts was lower than that in the control at 3 and 6 days. There was no significant difference in polyphenol oxidase activity between the control and heat-shocked mung bean sprouts during cold storage. These results show that mild heat treatment inhibited the enzymatic browning of mung bean sprouts by repressing the induction of PAL activity during cold storage and the accumulation of polyphenols.