S-methyl-L-cysteine sulfoxide and glucosinolate levels in Australian-sourced Brassica vegetables before and after domestic cooking

Abstract

Currently no data exists on S-methyl-L-cysteine sulfoxide (SMCSO) levels in Australian-sourced vegetables and limited data exists for glucosinolates. The effect of various cooking methods on the retention of SMCSO and glucosinolates in Australian-sourced vegetables is also limited. This study measured SMCSO and ten glucosinolates in a selection of Australian-sourced Brassica vegetables, both raw and after steaming. We additionally measured SMCSO and glucosinolate levels in broccoli after microwaving, stir-frying and boiling. SMCSO contributed greater dry weight (0.6–1.9 %) than total glucosinolates combined (0.3–1.2 %) in these raw cruciferous vegetables. SMCSO levels from highest to lowest were: Brussels sprouts > broccoli > red cabbage > kale > cauliflower > white cabbage > Chinese cabbage; and glucosinolate levels were: Brussels sprouts > white cabbage > broccoli > kale > red cabbage > Chinese cabbage > cauliflower. Both SMCSO and the ten main glucosinolates quantified were relatively stable after light steaming across all vegetables measured, and after microwaving broccoli. Boiling and stir-frying broccoli led to significant losses in SMCSO and the two dominant glucosinolates, glucoraphanin and glucobrassicin (all p < 0.05). Mild steaming and/or microwaving were preferable in retaining SMCSO and glucosinolates, whilst boiling and stir-frying were least favorable.