Inactivation of peroxidase and polyphenol oxidase in red beet (Beta vulgaris L.) extract with high pressure carbon dioxide

The inactivation of peroxidase (POD) and polyphenol oxidase (PPO) in red beet extract with high pressure carbon dioxide (HPCD) was investigated. HPCD treatment at 37.5 MPa for POD and 22.5 MPa for PPO (55 °C, 60 min) resulted in a reduction of their activities by approximately 86% and 95%, respectively. Compared with thermal treatment (55 °C), the decimal reduction time (D) of POD and PPO was reduced from 555.56 min to 74.63 min and 161.29 min to 38.31 min, respectively, by the HPCD treatment. The inactivation process followed first-order kinetics (R2 > 0.84, p < 0.05) with D values declining with the rise of pressure and temperature. The activation energy of the inactivation was reduced by the HPCD treatment from 92.54 kJ/mol to 68.63 kJ/mol and 57.06 kJ/mol to 53.58 kJ/mol for POD and PPO, respectively. Analysis of the kinetic parameters of the inactivation showed that both POD and PPO were less sensitive to pressure changes under supercritical than subcritical conditions.Industrial relevanceThere is a strong interest in the food industry in developing non-thermal processing techniques to produce fresher, safer and higher quality food. High pressure carbon dioxide (HPCD) is one of the emerging non-thermal technologies for inactivating microorganisms and enzymes in food products. Peroxidase (POD) and polyphenol oxidase (PPO) are two common enzymes that can cause quality deterioration in many food products. This work explores the feasibility of inactivating POD and PPO in red beet extracts by HPCD and establishes the inactivation kinetic models. These models are useful in understanding the responses of POD and PPO activities to changes in the HPCD parameters including pressure, temperature and process time. The models may also be used in assisting the design of industrial-scale HPCD processes.