Enzymatic, Phyto-, and Physicochemical Evaluation of Apple Juice under High-Pressure Carbon Dioxide and Thermal Processing
Ayesha Murtaza, Aamir Iqbal, Krystian Marszałek, Muhammad Amjed Iqbal, Shinawar Waseem Ali, Xiaoyun Xu, Siyi Pan, Wanfeng Hu
Abstract
In this study, the changes in enzyme activities, total polyphenols, phenolic profile, and physicochemical properties from thermally (25–75 °C) and high-pressure carbon dioxide (HP-CO2) (25–65 °C/20 MPa)-treated apple juice were investigated. The HP-CO2 exhibited complete inactivation of polyphenol oxidase (PPO) at 65 °C, whereas PPO was still active at 75 °C under thermal processing (TP). Similarly, the relative activity of peroxidase (POD) significantly decreased by 71% at 65 °C under HP-CO2 processing, whereas TP was less effective. HP-CO2 and TP treatments at 65 °C reduced the browning degree (BD) value to 0.47 and 0.89, respectively. Thus, HP-CO2 inhibits the browning reactions caused by PPO and POD enzymes at each operating temperature. The concentration of epicatechin and catechin increased significantly with increasing temperature above 45 °C in TP-treated juices. HP-CO2 treatment increased the same phenolic compounds at 35 °C and 9 MPa, whereas high-temperature and -pressure conditions caused insignificant changes in concentration of epicatechin and catechin. Changes in others phenolic compounds were insignificant under TP and HP-CO2 treatment. Overall, HP-CO2 is a promising technology to get high-quality juices with lower enzyme activity.