Phytochemical Content in Broccoli Flower Buds During Postharvest Storage and Light Treatments

Broccoli (Brassica oleracea var. italica) is a popular vegetable rich in minerals,vitamins and potentially health-promoting phytochemicals. This study aims to explore the effects of postharvest storage and light treatments on the phytochemical content in broccoli flower buds, and also to compare and optimize methods for estimation of phytochemicals in fruits and vegetables. Freshly harvested broccoli heads were acclimated for 4 days at 4 °C in the dark before storage for 6 days at 4 °C or 10 °C. Light treatments with visible light (VIS) or a combination of VIS and UV-B radiation were conducted during storage at 10 °C and for 12 h per day. The content of phytochemicals in broccoli flower buds during storage was monitored by frequent sampling for chemical analyses. The contents of flavonols, total phenols, glucosinolates, ascorbic acid and soluble sugars were determined by HPLC and enzymatic assays, whereas qualitative changes in phytochemical profile were studied using a metabolomics platform based on UHPLC-ESI-qToF-MS. In addition, the flavonol content during storage was monitored by repeated measurements using a non-destructive method based on chlorophyll fluorescence. Results show that the phytochemical content in flower buds of broccoli heads stored under different light and temperature conditions differ markedly in both quantity and composition.