Endogenous and exogenous enzymolysis of vegetable-sourced glucosinolates and influencing factors

Glucosinolates are naturally abundant in many vegetable sources. These compounds have limited health benefit in their original forms, however their derived product, sulforaphane, has been shown to be hugely health beneficial in protecting against certain types of cancer. This work investigated the conversion of glucosinolates (glucoraphanin) to sulforaphane using either an endogenous myrosinase or an exogenous myrosinase under various enzymolysis conditions. It was found that an optimum degradation of glucosinolates to sulforaphane by the endogenous method was achieved under the following conditions: a liquid–solid ratio of 3 ml/g, an enzymolysis time of 8 h, at 25 °C, at pH 4.0, and with the addition of ascorbic acid 0.02 mg/g. This gave 35% conversion rate of glucosinolates to sulforaphane. However, the exogenous approach appeared to be much more efficient in converting glucoraphanin to sulforaphane. At a combined condition of a liquid–solid ratio of 1000 ml/g, 3 h enzymolysis, at 35 °C and pH 5.0, and in the presence of 0.02 mg/g ascorbic acid, as much as 68% of glucoraphanin was found to be degraded to form sulforaphane.