Processing (blanching, boiling, steaming) effects on the content of glucosinolates and antioxidant-related parameters in cauliflower (Brassica oleracea L. ssp. botrytis)

Five different varieties of cauliflower (Brassica oleracea L. ssp. botrytis); two white (cv. ‘Aviso’, ‘Dania’), one purple (cv. ‘Grafitti’), one green (cv. ‘Emeraude’) and one romanesco/green pyramidal (cv. ‘Celio’) cultivar have been studied. All samples were thermally processed and the effects on the levels of glucosinolates (GLS), total phenols (TP), total monomeric anthocyanins (TMA), l-ascorbic acid (l-AA) and antioxidant capacities (FRAP and ORAC) were investigated. Processing methods applied were: blanching (3 min), boiling (10 min) and steaming (10 min). Total GLS were significantly (p < 0.05) affected by processing with the highest losses, 55 and 42% on average, occurring for boiled and blanched samples, respectively. Significant effects were also noted for steaming, but to a lesser extent, i.e. 19% average reduction. Antioxidant-related parameters were similarly affected with average losses of 27, 33, 36 and 46% in boiled cauliflower and 16, 21, 22 and 28% in blanched for TP, FRAP, l-AA and ORAC, respectively. Blanching and boiling reduced TMA in purple cauliflower by 38 and 53%, respectively. Steaming affected the antioxidant-related parameters the least for all cultivars. l-AA was significantly reduced by 14% in all cultivars by steaming. Some differences in behaviour between cultivars were noted, especially between white and coloured cultivars for TP, FRAP and l-AA, but also for some GLS. The main losses were caused by leaching into the processing water.