High pressure inactivation of polygalacturonase, pectinmethylesterase and polyphenoloxidase in strawberry puree mixed with sugar

• Enzyme inactivation is discussed during HPP of sugar rich strawberry puree.
• Impact of added sugar & high pressure process parameters is pointed out by RSM.
• Inactivation rate constants have been estimated from the RSM models for each enzyme.
• Polyphenoloxidase is more resistive than pectinmethylesterase & polygalacturonase.
• Addition of sugar enhanced high pressure induced inactivation of enzymes.

High pressure inactivation of polygalacturonase (PG), pectinmethylesterase (PME) and polyphenoloxidase (PPO) in strawberry puree was evaluated with different treatments (200–600 MPa, 40–80 °C, 2.5–10 min and 0–30% added sugar). Response surface methodology (RSM) and regression models were used to describe the effect of the parameters on the inactivation of each enzyme. Maximum of 80% inactivation of PG was observed; corresponding figures for PME and PPO were 67 and 50%, respectively. Kinetics of all enzymes were described with pulse effect (PE) followed by first order kinetics (for PME and PG) or fractional conversion model (for PPO). The kinetic parameters such as activation energy (Ea), activation volume (Va) and inactivation rate constant (k) values were estimated from the developed regression model. Under the experimental domain, k value increased with an increase in pressure; Ea and Va values decreased with an increase in pressure and temperature, respectively. Increased k values were obtained for sugar rich samples at same pressure and temperature condition compared to sample without sugar, depicting the positive effect of added sugar on the high-pressure induced inactivation process.

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