Plant matrix concentration and redox status influence thermal glucosinolate stability and formation of nitriles in selected Brassica vegetable broths

Brassica vegetables are frequently consumed foods of nutritional interest, because they are rich in glucosinolates (GLSs). Among GLS breakdown products, especially isothiocyanates are known for their health-beneficial effects, while nitriles are less beneficial. To increase the understanding of the plant matrix's influence on GLS degra-dation, differently concentrated vegetable broths were prepared from selected Brassica vegetables (kohlrabi and red cabbage) and subsequently boiled. Altogether, heat stability and conversion of GLSs to the corresponding nitriles were both strongly influenced by vegetable type and plant matrix concentration in the broths. After boiling kohlrabi broths for 120 min, recovery of 4-(methylthio)butyl-GLS as nitrile was 55.5 % in 1 g/mL broth and 8.4 % in 0.25 g/mL broth. In follow-up experiments, a pronounced influence of the matrix's redox status was identified, with H2S being an important factor. A better understanding of these processes will help to preserve health-promoting effects of GLSs in Brassica vegetables in the future.

Automated summary

Brassica vegetables, rich in glucosinolates (GLSs), have health benefits due to the breakdown of GLSs into isothiocyanates. This study found that the heat stability and conversion of GLSs to nitriles in vegetable broths were influenced by vegetable type and plant matrix concentration. The redox status of the matrix, with H2S as an important factor, also played a role in these processes.