Vitamin C in broccoli (Brassica oleracea L. var. italica) flower buds as affected by postharvest light, UV-B irradiation and temperature

Abstract

In this study, the changes in vitamin C, l-ascorbic acid (AA) and l-dehydroascorbic acid (DHA) levels in broccoli flower buds were examined during pre-storage and storage periods, simulating refrigerated transport with wholesale distribution and retail, respectively. Broccoli heads were pre-stored for 4 or 7 days at 0°C or 4°C in the dark and then stored for 3 days at 10°C or 18°C. During storage the broccoli heads were exposed for 12h per day to three different levels of visible light (13, 19 or 25μmolm−2s−1) or a combination of visible light (19μmolm−2s−1) and UV-B irradiation (20kJm−2d−1), or they were stored in the dark. The vitamin C content in broccoli flower buds during storage was significantly affected by pre-storage period and temperature. Higher vitamin C levels in flower buds after storage were observed for broccoli heads pre-stored for 4 days or at 0°C as compared to those pre-stored for 7 days or at 4°C. Storage temperature also affected vitamin C in broccoli flower buds, with higher levels observed for broccoli stored at 10°C than at 18°C. Hence, vitamin C in broccoli flower buds was demonstrated to decrease together with increasing pre-storage period, pre-storage temperature and storage temperature. AA in broccoli flower buds was influenced mainly by storage temperature and to a minor extent by pre-storage temperature. The DHA level and DHA/AA ratio were stable in flower buds of broccoli pre-stored for 7 days, whereas increasing tendencies for both DHA level and ratio were observed after pre-storage for 4 days. These results indicate a shift in the ascorbate metabolism in broccoli flower buds during storage at low temperatures, with its higher rate observed for broccoli pre-stored for shorter time. There were no effects of the light and UV-B irradiation treatments on vitamin C, AA and DHA levels in broccoli flower buds.