Comparative effect of supercritical carbon dioxide and high pressure processing on structural changes and activity loss of oxidoreductive enzymes

TLDR: In this article, the influence of Sc-CO2 on enzyme inactivation was evaluated and the results were compared with those found using high pressure processing (HPP) (200-900 MPa/5-45 C/1-15 min).

Abstract: Due to the CO2 specific characteristics, it has been used as supercritical (Sc) fluid for several applications, including enzyme inactivation. The influence of Sc-CO2 (10–65 MPa/10–30 min/35–65 °C) on mushroom polyphenol oxidase (PPO) and horseradish peroxidase (POD) was evaluated and the results were compared with those found using high pressure processing (HPP) (200–900 MPa/5–45 °C/1–15 min). The free ion concentration was also studied to compare the enzymatic activity and changes in electrical conductivity. Additionally both enzymes, untreated or treated using either Sc-CO2 or HPP, were used as additives in the CuCl2 crystallization method. The resulting additive-specific CuCl2 patterns were characterized based on different structural features. Sc-CO2 was found to have a significant influence on PPO and POD activities, and an increased reduction in the residual activity of both enzymes was observed when the Sc-CO2 pressure was increased. However, PPO was more resistant to temperature and pressure than POD. The D-value calculated for POD was in the range of 38.3 and 592.0 min, and 60.6 and 291.5 min, for HPP and Sc-CO2 treatments, respectively; whereas for PPO varied from 103.1 to 284.3 min under HPP and from 83.4 to 303.0 min using the Sc-CO2 treatment. It can be concluded that the application of Sc-CO2 could be an effective tool for inactivating PPO and POD enzymes. Moreover, both enzymes and treatments could be differentiated significantly based on the resulting CuCl2 crystallization patterns.