Comparison of Sous-vide methods and traditional hydrothermal treatment on GLS content in Brassica vegetables

Abstract

Brassica vegetables are a source of many biologically active compounds, including glucosinolates (GLS). At present, GLS attract a special attention because of their healthy properties. Four Brassica vegetables: cauliflower, Romanesco-type cauliflower, Brussels sprouts, and broccoli were examined. Analyses of GLS were done in raw, sous-vide cooked, traditionally cooked, and steamed vegetables as well as in samples stored for 5 days at 2 ± 1 °C. In the examined vegetables, 9 GLS were identified. The content of vitamin C was also determined. Moreover, microbiological analyses were performed. Among the investigated vegetables, the highest content of GLS was observed in the steamed samples. The traditional cooking of broccoli and Romanesco-type cauliflower causes a significant decrease of GLS as compared to the raw materials. The same explicit tendency was also observed in the case of cooking by the sous-vide method of Romanesco-type cauliflower and Brussels sprouts. Brussels sprouts, cooked by the sous-vide method, contained almost 40% less GLS than those cooked in water. Storage of the treated vegetables at 2 ± 1 °C led to a further reduction of the GLS level. It must be emphasized that the highest losses were observed in broccoli after sous-vide cooking (over 30%). Our results indicate that sous-vide method can be an advantageous technique of processing broccoli destined only for direct consumption.