Author:

Keywords:

high hydrostatic-pressure, x ananassa, temperature inactivation, pectin methylesterase, partial-purification, mild-heat, peroxidase, enzymes, fruits, vegetables, Science & Technology, Life Sciences & Biomedicine, Biochemistry & Molecular Biology, Food Science & Technology, HIGH HYDROSTATIC-PRESSURE, X ANANASSA, TEMPERATURE INACTIVATION, PARTIAL-PURIFICATION, PEROXIDASE, ENZYMES, PRODUCTS, FRUITS, HEAT, PH, 0908 Food Sciences, Food Science, 3006 Food sciences

Abstract:

Polyphenol oxidase (PPO) was isolated from strawberries (Fragaria ananassa) and some of its biochemical characteristics were studied. The optimum pH for strawberry PPO activity was pH = 5.0. K(m)and V(max)values were 5.95 mm and 133.8 A(420nm)/min using a 50 mm catechol substrate solution. Kinetic studies showed that the thermal inactivation of strawberry PPO followed biphasic kinetics, resulting in an activation energy of 314.1 kJ/mol for the labile fraction and 321.3 kJ/mol for the stable fraction. Pressure/temperature inactivation of the stable fraction of strawberry PPO can be adequately described by a first-order model. Pressure and temperature were found to act synergistically, except in the high temperature-low pressure region where an antagonistic effect was observed. A second-degree polynomial model was successfully applied to describe the temperature/pressure dependence of the inactivation rate constants of the stable strawberry PPO fraction.