Enzymatic activity and quality characteristics of melon juice processed by high-intensity pulsed light

The aim of this study was to explore the use of pulsed light (PL) for inactivating peroxidase (POD), polyphenoloxidase (PP0) and pectin methylesterase (PME) in melon juice. The influence of treatments on the optical, physicochemical and rheological properties of the juice was also evaluated. PL fluences between 3.6 and 71.6 J cm(-2) caused a significant reduction in POD activity from 13% to 96% respectively. On contrary, PPO and PME activities were slightly or not significantly affected by the treatments. POD inactivation curve was successfully fitted with the first-order and Weibull-type models. Samples exposed to 35.8 and 71.6 J cm(-2) showed minor changes in pH, titratable acidity and total soluble solids content than non-treated juice along cold storage. PL treatments also better maintained the original colour of the fresh juice during storage. A slight but significant reduction in the apparent viscosity was observed due to PL exposure. Results indicated that pulsed light could be a useful technique for inhibiting POD activity and preserving the colour of melon juice along cold storage. Other preservation agent(s) in combination would need to be evaluated for better control of enzyme activity.