GLUCOSINOLATE COMPOSITION OF BRASSICA IS AFFECTED BY POSTHARVEST, FOOD PROCESSING AND MYROSINASE ACTIVITY

The aim of this study is to evaluate the effect of postharvest conditions and food processing on beneficial glucosinolates (GLs) present in Brassicacea plants. Also, we evaluate the role of endogenous enzyme, the myrosinase, on natural GL degradation. The myrosinase activity (MA) was measured either by spectrophotometric and high-performance liquid chromatography (HPLC) methods and the GLs were identified and quantified by HPLC. The samples were submitted to a different temperature regime for 72 h, and to three different cooking methods. The results showed a different MA between cultivars, however not significantly different. The GLs were affected by temperature and by cooking method, depending however on cultivar (P < 0.05). The highest total GLs were obtained under refrigerator (1,784.7 mu moles center dot 100/G dry weight [DW]). The steam method contributed to the higher GL preservation and in opposition the classic method (boiling water) led to higher losses in GL content (57% in Brassica oleracea and 81% in Brassica rapa cultivars). PRACTICAL APPLICATIONS This manuscript intends to present a batch of results in order to understand the variation of beneficial glucosinolates (GLs), with postharvest treatments (temperature regime and period) and cooking methods (boiling, steaming and microwave). In a practical way, it intends to demonstrate not only the effect of storage conditions but also the influence of endogenous enzyme myrosinase on natural GL hydrolysis and therefore on their availability. In a practical way, the major outcome is to show the consumers what the main possibilities are and what could be the best choices in food preservation and confection of Brassicacea plants in a real situation at their homes. We also want to emphasize that this study is one of the few that have been made in Portugal, where the Brassicaceae plants assume a great importance, being widely cultivated and widely consumed, but whose results can be extended to the entire international community.