Effects of pressure/temperature treatments on stability and activity of endogenous broccoli (Brassica oleracea L. cv. Italica) myrosinase and on cell permeability

Broccoli contains glucosinolates, which can be hydrolysed by myrosinase (EC 3.2.1.147) after cell disruption, to yield a range of products, of which some have anticarcinogenic properties. Since thermal processing results in myrosinase inactivation, the use of a high pressure/temperature treatment (HP/T), which can induce cell permeabilisation at moderate conditions, can be an alternative. In this research it was investigated at which conditions it was possible to induce glucosinolate conversion through processing. The effect of thermal and HP/T treatments on the stability and activity of endogenous myrosinase in broccoli was studied, as well as the effect of temperature and HP on cell permeability. The thermal stability (50–60 °C) of myrosinase in broccoli could be described by a consecutive step kinetic model while for the HP/T stability (50–500 MPa; 15–60 °C) a first order model was adequate. Moderate pressure (50–250 MPa) only had a limited effect on myrosinase activity. The effect of HP/T processing on cell permeability showed pressure to have a large influence. Finally it was shown that HP/T treatments can be used to induce glucosinolate conversion, necessary to create the health promoting hydrolysis products.