Impact of electric field intensity and frequency on polyphenol oxidase inactivation and quality parameters of tender coconut water during Ohmic heating

Abstract

Coconut water is well recognized for its refreshing flavor and nutritional value. However, its commercial use is limited by rapid spoilage, primarily due to enzymatic browning and oxidative reactions. This study investigates the application of Ohmic heating, an emerging thermal method that incorporates electric field exposure, to improve the stability of coconut water through combined thermal and non-thermal effects. Treatments were performed at different electric field strengths (20–30 V/cm) and frequencies (50–10,000 Hz). Key quality attributes including polyphenol oxidase activity, total soluble solids, pH, acidity, turbidity, color, total phenolic content, and antioxidant capacity (2,2-diphenyl-1-picrylhydrazyl (DPPH) assay) were assessed. The study showed that Ohmic heating at 25 V/cm and 500 Hz enabled rapid temperature rise, limited physicochemical alterations, and improved enzyme inactivation efficiency. Ohmic heating at 90 °C for 5 min resulted in more effective polyphenol oxidase inactivation than conventional heating (77.6% vs. 43.9%). These findings support the potential of Ohmic heating as a mild pasteurization approach that maintains product quality while enhancing safety.