Inactivation of polyphenol oxidase from Pacific white shrimp by dense phase carbon dioxide

The inactivation of polyphenol oxidase (PPO) from Pacific white shrimp exposed to dense phase carbon dioxide (DPCD) treatment was investigated. PPO activity showed a dramatic loss at 4–25 MPa and 37 °C. At the lower pressure (4–15 MPa), the experimental data of inactivation followed the first-order reaction kinetic model, the pressure sensitivity (ZP) of the kinetic parameters was 49.02 MPa and the activation volume (△ V≠) was − 120.88 cm3/mol. At the higher pressure (20 and 25 MPa), the experimental data of inactivation followed the biexponential kinetic model. The kinetic rate constant kF and kS of fast and stable fractions were 2.45 and 0.08 min− 1, respectively. The decimal reduction time DF and DS were 0.94 and 29.43 min at 25 MPa and 37 °C, respectively. After DPCD treatment, the loss activity of PPO had no restoration storing for 6 days at 4 °C. The results of SDS-PAGE and activity staining also showed that DPCD treatment had the obvious inhibitory effect on PPO from Pacific white shrimp. The PPO activity in vivo was easier to be inactivated than that in crude PPO extracts under the same DPCD treatment conditions.Industrial relevanceThere is a growing interest in non-thermal pasteurization methods, which could retain food's freshlike physical, nutritional, and sensory qualities. Pacific white shrimp accounts for 90% of the global aquaculture shrimp production, they are becoming increasingly popular. However, enzymatic browning of shrimp has been of great concern to food scientists and food processors. Dense phase carbon dioxide (DPCD) may be an adequate tool to obtain high quality since PPO activity could not be inactivated totally by high pressure under 400 MPa yet. The present work deals with the inactivation of PPO from Pacific white shrimp exposed to DPCD treatment in order to explore the feasibility of shrimp by DPCD process.

Research highlights
► The inactivation conformed to the first-order reaction kinetics in low pressure (≤ 15 MPa).
► The experimental data of inactivation followed the biexponential kinetic model at the higher pressure (20–25 MPa).
► After DPCD treatment, no restoration of PPO residual activity was observed during the 6 days at 4 °C storage period.
► SDS-PAGE and PPO activity staining further confirmed the inhibitory effect of DPCD on white shrimp PPO.
► The PPO activity in vivo was easier to be inactivated than that in crude PPO extracts under the same DPCD conditions.