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Kinetic modeling was used as a tool to quantitatively estimate glucosinolate thermal degradation rate constants. Literature shows that thermal degradation rates differ in different vegetables. Well-characterized plant material, leaves of broccoli and Chinese kale plants grown in two seasons, was used in the study. It was shown that a first-order reaction is appropriate to model glucosinolate degradation independent from the season. No difference in degradation rate constants of structurally identical glucosinolates was found between broccoli and Chinese kale leaves when grown in the same season. However, glucosinolate degradation rate constants were highly affected by the season (20-80% increase in spring compared to autumn). These results suggest that differences in glucosinolate degradation rate constants can be due to variation in environmental as well as genetic factors. Furthermore, a methodology to estimate rate constants rapidly is provided to enable the analysis of high sample numbers for future studies.

Brassica vegetables are the predominant dietary source of glucosinolates (GLS) that can be degraded in the intestinal tract into isothiocyanates, which have been shown to possess anticarcinogenic properties. The effects of pilot-scale long-term boiling on GLS in white cabbage (Brassica oleracea L. ssp. capitata f. alba cv. `Bartolo¿) was experimentally determined and mathematically modeled. Cabbage was boiled, resulting in a dramatic decrease of 56% in the total GLS levels within the plant matrix during the first 2 min. After 8¿12 min of boiling, the decrease progressed to over 70%. Progoitrin had an exceptionally higher decline rate in comparison to all other GLS. As boiling progressed the concentration of all GLS continued to decrease at a lower rate for the remaining cooking period. A mathematical model was used to describe the concentration profile of the GLS in the plant matrix, based on leaching of GLS to the water phase due to cell lysis and thermal degradation of the GLS both in the plant matrix and in the water phase. The model described the concentration profiles very well. Estimated lysis and degradation rate constants for white cabbage differed from those reported in the literature for red cabbage. The degradation rate constants found were significantly higher in the plant matrix when compared to those in the water phase for all GLS. Identification of the kinetics of decline of GLS during cooking can aid in designing processing and preparation methods and determining the conditions for the optimal effects of ingestion of Brassicaceae toward cancer prevention.

Total and individual levels of glucosinolates (GSs) were measured in red cabbage after various microwave treatments varying in time and intensity of the treatments. Furthermore, the myrosinase enzyme activity of the microwave-heated vegetables was determined. The retention of GSs in the cabbage and the residual activity of the hydrolytic enzyme as a result of microwave preparation were compared with untreated cabbage. In general, high total GS levels were observed for all of the applied microwave treatments. Strikingly, many of the time/energy input combinations resulted in levels exceeding the total GS content of the untreated cabbage material. Moreover, the increase in levels seems to be associated with the energy input applied. A possible explanation for this behavior is an increased extractability of GS from heat-treated cabbage as compared to raw cabbage. Substantial myrosinase activity was retained in cabbage treated at low (24 min, 180 W) and intermediate microwave powers (8 min, 540 W) while microwave cooking for 4.8 min at 900 W (259.2 kJ energy input) resulted in a complete loss of hydrolytic activity. In this respect, differences in observed temperature profiles of the various microwave treatments play an important role. Higher retention of GSs and controllable amounts of active myrosinase can offer increasing health-promoting properties of microwave-prepared Brassica vegetables.