Characterisation of myrosinase in polish varieties of rapeseed

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Abstract
It has been shown that the myrosinase activity in rapeseed and in white mustard seeds is similar and does not depend on the variety of rapeseed. The two molecular forms of rapeseed myrosinase with different isoelectric points, Km values towards sinigrin, response to ascorbic acid and stability were isolated. The enzyme was strongly stimulated by ascorbic acid and had the same hydrolytic potential against rapeseed glucosinolates as the myrosinase from white mustard. However, the rapeseed enzyme was much less stable during storage. The fast inactivation of myrosinase in both, flaked and intact seeds was achieved after incubation at 90–100°C and 90–100% relative humidity. In the flaked seeds, however, a substantial amount of the endogenous glucosinolates had already been decomposed before complete inactivation of the enzyme. Thus, it is suggesting that the enzyme should be inactivated in the intact seeds before processing.