Effect of ohmic heating parameters on inactivation of enzymes and quality of not-from-concentrate mango juice

Background and Objective: Ohmic heating (OH) is one of the electrothermal technologies that used recently for food processing to inactivate microorganisms and enzymes. In present study, effect of OH parameters (voltage gradients and temperature) on inactivation of polyphenoloxidase (PPO) and pectinmethylesterase (PME) of not-from-concentrate (NFC) mango juice was investigated.

Multiple response surface methodology (RSM) was used to optimize the OH parameters, where the effect of voltage gradient and temperature on PPO and PME in the NFC mango juice was evaluated. After optimization, the NFC mango juice was produced with optimized OH conditions. Methodology: The PPO and PME activity, total phenolic, total carotenoids, ascorbic acid, cloud value, color as well as physical properties were determined and compared with mango juice reported by conventional heating (CH).

Results: The PPO activity was completely inactivated for mango juice produced by OH (at 40 V cmG-1, 80°C and holding time for 60 sec) and CH (at 90°C holding time for 60 sec), while the inhibition of PME activity were 96 and 90%, respectively. The reduction in the ascorbic acid for OH (11.3%) was significantly lower than for CH (20%) treated samples.

The total phenolic content was increased by 8 and 5% for the OH and CH treated samples, respectively. The reduction in total carotenoids level was significantly lower in the OH (10.9%) than in the CH (19.4%) treated sample. Conclusion: Overall, OH is a potential mild thermal treatment in the production of mango juice with improved functional properties instead of conventional methods.