Kinetic modeling of high-pressure induced inactivation of polyphenol oxidase in sugarcane juice (Saccharum officinarum).

BACKGROUND

Polyphenol oxidase (PPO) is the main enzyme in sugarcane juice associated with rapid browning and degradation of organoleptic properties. High-pressure processing (HPP) (300-600 MPa) of sugarcane juice in combination with moderate temperatures (30-60 °C) for different processing times (10-25 min) has shown promising results in minimizing PPO activity while preserving the juice's freshness.

RESULTS

A maximum PPO inactivation of 98% was achieved at 600 MPa/60 °C/25 min, while the corresponding value for thermal treatment at 0.1 MPa/60 °C was only 66%. The nonlinearity in the inactivation data was well described by the Weibull distribution model with a high adjusted R and reduced χ values at all levels of pressure and temperature. The PPO inactivation data were fitted at shape parameter, β = 1 (log linear) and β ≠ 1. A refitted Weibull model was used to predict kinetic parameters such as the inactivation rate constants (k), activation energy (E ) and activation volume (V ), which govern PPO inactivation in HPP-treated sugarcane juice. A secondary kinetic model was formulated to predict the k values as a function of pressure (P) and temperature (T), incorporating E and V .

CONCLUSIONS

Combined high-pressure and temperature processing has been considered a reliable alternative to conventional heat treatment for inhibiting PPO activity in sugarcane juice. While the isothermal inactivation of PPO followed first-order kinetics, inclusion of high pressure resulted in a strong deviation from log linear kinetics. Identification of suitable kinetic models describing these inactivation processes is expected to aid product development and process control of high-pressure processed sugarcane juice. © 2018 Society of Chemical Industry.