Effect of post-harvest treatments on the level of glucosinolates in broccoli

Broccoli is a very perishable vegetable with a high water content (around 8 8%) which leads to rapid dehydration and probably to an alteration in compo sition if conditions after harvest are not controlled. This study evaluates the glucosinolate pattern and glucosinolate levels in the principal and se condary inflorescences of fresh broccoli cv 'Tokyodome', and after being su bmitted to some situations which are likely to occur during or after harves t: room temperature (+/-20 degrees C) for 5 days, kept in the fridge at 4 d egrees C for 5 days, and frozen after blanching. Another set of material wa s harvested 5 days later, simulating a post-maturation stage, and analysed. The highest total glucosinolate content was found at commercial maturation with 20 888 and 20 355 mu moles kg(-1) DW in the principal and secondary i nflorescences, respectively. Keeping the inflorescences at room temperature caused the most significant (P < 0.05) reductions in total and individual glucosinolates, except for 4-hydroxyindol-3-ylmethyl-, 2-hydroxy-2-phenylet hyl- and 2-phenylethyl-, when compared to the other situations. The highest levels (10 925 mu moles kg(-1) DW) of 4-methylsulphinylbutyl-, the precurs or of the anti-cancer isothiocyanate sulphoraphane, were found in the inflo rescences freshly harvested at commercial stage. Refrigeration at 4 degrees C and freezing were shown to be the best preservation processes for mainta ining high levels of these and other glucosinolates in contrast with the ot her situations. (C) 1999 Society of Chemical Industry.