Assessing the dry inactivation mechanism of polyphenol oxidase (PPO) and peroxidase (POD) employing catalytic infrared treatment based on experiments and molecular simulations

Abstract

An innovative catalytic infrared (CIR) dry enzyme inactivation method was developed in this study to replace wet-heat methods. The residual activities and structural changes of peroxidase (POD) and polyphenol oxidase (PPO) after heat treatment were assessed experimentally. Molecular dynamics and docking studies were employed to compare the thermal and radiation effects of CIR. The results demonstrated complete inactivation (100 %) of PPO and POD after 65 min at 70 °C. This was attributed to both thermal and radiation effects of CIR, which disrupted hydrogen bonds, induced disordered secondary structure, loosened molecular conformation, encapsulated active sites, and reduced binding energy, thereby leading to enzyme inactivation. The thermal effect was more destructive to PPO and POD than the radiation effect, loosening by 1.81 % and 1.21 % of surface area, reducing by 0.87 % and 2.27 %, 2.85 % and 1.32 % of intra- and intermolecular hydrogen bond and 6.71 % and 4.21 % of binding energy, respectively. The mechanism of dry enzyme inactivation by CIR was elucidated. CIR is a promising alternative to wet-heat methods, offering energy savings and enhanced safety.

Industry relevance

Enzymatic browning, driven by polyphenol oxidase (PPO) and peroxidase (POD), is a significant concern in global fruit and vegetable processing. Conventional enzyme inactivation methods, such as wet-heat treatments, suffer from high energy and water consumption and contribute to environmental pollution. This increases processing costs and compromises product quality. In contrast, CIR is promising to be a new dry enzyme inactivation technology instead of wet-heat enzyme inactivation methods, which is energy-efficient, environmentally friendly, and capable of achieving optimal enzyme inactivation. This study conveys a better understanding of CIR mechanisms and optimal conditions of dry enzyme inactivation for its effective use in food processing applications on an industrial scale.