Journal of food process engineering vol:29 issue:3 pages:269-286
Polyphenol oxidase (PPO) was extracted from white grapes (var Victoria, South Africa) and partially purified by ammonium sulfate precipitation. Detailed kinetic studies on thermal and high-pressure inactivation of grape PPO were preformed in McIlvaine buffer (pH = 4.0), in reconstituted grape must and in grape must. Thermal inactivation of PPO in McIlvaine buffer followed a first-order model while in reconstituted grape must and grape must a biphasic inactivation behavior has been observed. Under all conditions investigated, a first-order kinetic model could describe the pressure inactivation data. It was found that PPO is more thermostable and pressure-stable in must than in reconstituted grape must and McIlvaine buffer at the same pH=4.0.