European food research and technology vol:226 issue:3 pages:545-553
The activity of myrosinase, an enzyme found mainly in Brassicaceae, is influenced by some intrinsic (e.g. pH, ascorbic acid) and extrinsic (e.g. temperature, pressure) factors. In this study, the effect of intrinsic and extrinsic factors on the activity of mustard seed myrosinase (Sinapis alba L.) was determined in a buffer system and in broccoli juice. Ascorbic acid and to a much lesser extent MgCl2 were found to enhance the myrosinase activity. In buffer solution, the optimal temperature for myrosinase activity at atmospheric pressure was 60 degrees C. At elevated pressure, the reaction rate increased until 200 MPa and the optimal temperature shifted to 40 degrees C in a buffer system. In broccoli juice, mustard seed myrosinase behaved somewhat different compared to the buffer system. The highest enzyme activity was found at 60 degrees C, both at atmospheric and elevated pressures. In broccoli juice, the enzymatic reaction rate also increased up to pressures of 200 MPa. Enzyme inactivation could be described by first order kinetics.