Effect of dielectric barrier discharge plasma excitation frequency on the enzymatic activity, antioxidant capacity and phenolic content of apple cubes and apple juice

Cold plasma is a potential alternative to traditional thermal conservation methods because of its high efficiency in the preservation and retention of quality parameters. The objective of this study was to evaluate the application of atmospheric cold plasma on some qualitative aspects of apple cubes and apple juice. The research used dielectric barrier discharge plasma and studied different excitation frequencies of plasma: 50, 200, 400, 600, and 900 Hz. The effects of plasma application were evaluated on enzymatic activity (PPO and POD), total phenolic compounds, antioxidant capacity, and colorimetry. Plasma treatment partially inactivated the polyphenol oxidase enzyme in apples cubes and juice. Inactivation of peroxidase occurred only in apple juice. Total phenolic content and antioxidant capacity presented no significant difference between the treated and control samples of apple cubes, while significant changes were observed in apple juice. The changes in color parameters were slight and did not compromise the product quality. Plasma application was able to partially inactivate the enzymes responsible for browning while maintaining the quality and sensory properties of apple cubes and juice.