Nth order kinetic modelling of peroxidase and polyphenol oxidase inactivation in kiwifruit juice during cold plasma and thermal treatment

Abstract

The current study examines the effect of thermal and cold plasma (CP) treatment on the inactivation of polyphenol oxidase (PPO) and peroxidase (POD) in kiwifruit juice. The residual activity of POD and PPO were fit to nth-order kinetics at a voltage, juice depth, and treatment time range of 18–30 kV, 2–10 mm, and 2–10 min, respectively. During thermal treatment, the inactivation order (n) value for POD and PPO were 1.07 and 1.06, whereas, for the cold plasma treatment, it was 2.07 and 2, respectively. The higher D-value of POD than PPO makes the former enzyme more resistant to plasma treatment. The Fourier-transform infrared spectroscopy (FTIR) revealed an increase in the proportion of β-sheet structure from 23 to 28% and a decrease in α-helix from 28 to 20% compared to the control sample. In comparison to thermal treatment, CP treatment effectively retained the biochemical attributes of juice. Industrial relevanceThe PPO and POD inactivation is necessary for preparing stable kiwifruit juice. A detailed kinetic study is mandatory for designing and optimizing the process, as both enzymes react in their way depending on the origin and experimental range. The generated kinetic model can be used to establish the optimum conditions for inactivating enzymes during CP treatment.