Comparative Effects of Postharvest Ultraviolet-Light Treatments on Antioxidants Properties, Nutritional and Vitamin D Contents of Some Indigenous Green Leafy Vegetables

Ultraviolet lamps irradiation has been extensively used in water treatment, surface disinfection, and as a germicidal agent. Yet, activation of some essential reactions in fruits and vegetables occurs at low doses of irradiation, which in turn leads to an improvement of their shelf-life or bioactive compounds. In this study, postharvest effects of ultraviolet irradiation at different wavelengths were investigated on antioxidants properties, nutritional and vitamin D contents of six leafy vegetables. The six vegetables were each subjected to UV-A, B, and C lamps irradiation at wavelengths of 400, 315, and 230 nm respectively in irradiation chambers. The results revealed that ultraviolet irradiation increased the phenolic and flavonoid contents with a better-reducing power ability and antioxidant capacity in tested vegetables. More also, the essential amino acid contents were significantly (P ≤ 0.05) increased. In UV-A treatment, increased nutritional and antioxidant properties were significant (P ≤ 0.05) in M. oleifera leaf extract. On the other hand, a significant (P ≤ 0.05) increase in the level of vitamin D2 and D3 synthesis in the leaves of all the vegetables was observed under UV-B treatment. The results revealed that M. oleifera leaf responds more positively to ultraviolet irradiation than other treated vegetables. Therefore, this study shows that postharvest treatments with UV-A and B lamps may be a useful biological strategy for enhancing the antioxidant and nutritional quality of vegetables.