Effects of UV-B on vitamin C, phenolics, flavonoids and their related enzyme activities in mung bean sprouts (Vigna radiata)

In this study, ultraviolet-B radiation (UV-B) was used to effect the accumulation of vitamin C, phenolics and flavonoids in mung bean sprouts. Results indicate that the content of vitamin C and flavonoids increased during the initial period, and after a brief decline, reached peak levels of 25.29 ± 1.02 mg/100 g FW and 726.67 ± 7.35 mg/100 g DW, respectively, at 2.5 h (1.845 kJ m−2), while the peak levels of the phenolics were 10741.33 ± 68.04 mg/100 g DW. The thiobarbituric acid reactive substances (TBARS) content decreases with the increase in irradiation time. The activities of the related enzymes, including phenylalanine ammonia-lyase (PAL), L-galactono-1, 4-lactone dehydrogenase (GalLDH), peroxidase (POD), polyphenol oxidase (PPO) and chalcone isomerase (CHI) were determined, which showed strong correlations with the change in the content of vitamin C, phenolics and flavonoids. In conclusion, the accumulation of vitamin C, phenolics and flavonoids in mung bean sprouts can be promoted by a low-dose UV-B irradiation.