Acidification and tissue disruption affect glucosinolate and S-methyl-l-cysteine sulfoxide hydrolysis and formation of amines, isothiocyanates and other organosulfur compounds in red cabbage (Brassica oleracea var. capitata f. rubra)

Abstract

Cabbages are rich in sulfur-containing metabolites like glucosinolates (GLSs) and S-methyl-l-cysteine sulfoxide (SMCSO). Tissue disruption initiates hydrolysis of these compounds and bioactive volatile hydrolysis products such as isothiocyanates (ITCs), sulfides, and thiosulfinates are formed. However, nitriles, epithionitriles, or amines can also result from GLSs. Here, the influence of hydrolysis time, extent of tissue disruption (chopping vs. homogenization), and addition of lemon juice or vinegar on the outcome of enzymatic hydrolysis of GLSs and SMCSO was investigated in red cabbage. Chopping led to partial hydrolysis of GLSs, whereas homogenization completely degraded GLSs but only had a small effect on SMCSO. Homogenization increased amine formation from alkenyl and methylthioalkyl ITCs, but not from methylsulfinylalkyl ITCs. Acidification inhibited formation of products from SMCSO. Further, it reduced nitrile and epithionitrile formation and stopped amine formation, thereby increasing ITC levels. Therefore, acidification is a valuable mean to enhance ITC levels in fresh Brassica foods.

Keywords: Amine; Glucosinolate; Hydrolysis; Isothiocyanate; S-Methyl-l-cysteine sulfoxide; Thiosulfinate; Volatile organosulfur compounds.