The activity of myrosinase from broccoli (Brassica oleracea L. cv. Italica): Influence of intrinsic and extrinsic factors

The potential of some intrinsic (MgCl2, ascorbic acid, pH) and extrinsic (t emperature, pressure) factors for controlling/altering activity of myrosina se from broccoli was investigated in this paper. A combination of MgCl2 and ascorbic acid was found to enhance enzyme activity. Concentrations resulti ng in optimal activity were determined as 0.1 g/liter and 2 g/liter, respec tively. Both in the absence and presence of this enzyme activator, the opti mal pH was situated between 6.5 and 7, corresponding to the natural pH of f resh broccoli juice. At atmospheric pressure. the enzyme was optimally acti ve at a temperature about 30 degrees C. Application of low pressure (50 to 100 MPa) slightly enhanced the activity while at higher pressure (300 MPa), the activity was largely reduced. Future work should focus on the extensio n of this work to real food products in order to take cellular disruption i nto account. In intact vegetable tissues, the enzyme myrosinase is present in compartments separated from its substrate, the glucosinolates. Hence, en zymatic hydrolysis can merely occur after cellular disruption. In this resp ect, processes such as cutting, cooking, freezing, or pressurizing of the v egetables wilt have a large effect on the glucosinolate hydrolysis by myros inase. This work could then be the basis for controlling glucosinolate hydr olysis in food preparation and processing.