Inactivation effects and kinetics of polyphenol oxidase from Litopenaeus vannamei by ultra-high pressure and heat

• UHP could activate PPO extracted from Litopenaeus vannamei at 100–300 MPa.
• UHP could inactivate PPO extracted from Litopenaeus vannamei at 400–600 MPa.
• Inactivation of PPO followed the first-order reaction kinetics at 400–600 MPa.
• When Shrimp was directly treated at 400–600 MPa, activation of PPO in shrimp occurred.
• UHT must combine with temperature or inhibitors to inactivate PPO in shrimp completely.

Using heat treatment (40–100 °C) as the control, the effects of ultra-high pressure (UHP, 100–600 MPa) on activity of polyphenol oxidase (PPO) from Litopenaeus vannamei (whiteleg shrimp, also known as Pacific white shrimp) were investigated, and the kinetic models of PPO inactivated by UHP were established. The results showed that PPO activity was significantly reduced (p < 0.05) with increasing temperature. For UHP treatment, PPO was activated and increased maximally by 57.61% when the pressure was lower than 300 MPa, and PPO activity reduced significantly (p < 0.05) when the pressure was above 300 MPa. PPO was completely inactivated using 2-min exposures to 500 MPa. Inactivation of PPO by heat (60–100 °C) and UHP (400–600 MPa) all followed first-order reaction kinetics. At 400–600 MPa PPO from the crude extracts was effectively inactivated, but PPO was activated directly in shrimp. If the PPO in shrimp was completely inactivated, higher pressure would probably be needed or the pressure would need to be combined with temperature or other melanosis inhibitors. It is a reference for the application of high pressure to inactivate PPO of Litopenaeus vannamei.Industrial relevanceUltra-high pressure (UHP) has the potential to destroy food-borne microorganisms and inactivate enzymes while minimally affecting the sensory and nutritional quality of food products. Litopenaeus vannamei is one of the aquatic products with high nutritional value and accounts for 90% of global aquaculture shrimp production. However, melanosis induced by polyphenol oxidase (PPO) from shrimp has been of great concern to food scientists and food processors. UHP is a good technology to inactivate PPO. However, little work has been reported on PPO from shrimp processed by UHP. The available data are provided for the evaluation and application of UHP, and the present work is inactivation effects and kinetics of polyphenol oxidase from Litopenaeus vannamei by ultra-high pressure in order to explore the feasibility of processing shrimp using UHP.