Thermal and high pressure inactivation kinetics of blueberry peroxidase

- Blueberry peroxidase (POD) is thermolabile with complete inactivation at 0.1 MPa and 80 °C.
- Biphasic thermal inactivation of POD indicating isoenzymes of different stability.
- High pressure activates POD with a maximum of 40% activation at 395 MPa and 70 °C.
- High pressure inhibits the thermal inactivation of POD.
- This may lead to quality degradation of high pressure processed blueberries.

This study for the first time investigated the stability and inactivation kinetics of blueberry peroxidase in model systems (McIlvaine buffer, pH = 3.6, the typical pH of blueberry juice) during thermal (40-80 °C) and combined high pressure-thermal processing (0.1-690 MPa, 30-90 °C). At 70-80 °C, the thermal inactivation kinetics was best described by a biphasic model with ∼61% labile and ∼39% stable fractions at temperature between 70 and 75 °C. High pressure inhibited the inactivation of the enzyme with no inactivation at pressures as high as 690 MPa and temperatures less than 50 °C. The inactivation kinetics of the enzyme at 60-70 °C, and pressures higher than 500 MPa was best described by a first order biphasic model with ∼25% labile fraction and 75% stable fraction. The activation energy values at atmospheric pressure were 548.6 kJ/mol and 324.5 kJ/mol respectively for the stable and the labile fractions.