Effect of some variables of Ohmic pasteurization on quality Attributes of Passion (Passiflora edulis) Fruit Juice

Passion fruit (Passiflora edulis) juice was highly preferred for consumption due to its excellent antioxidants, fibers, carbohydrates, minerals useful for health benefits. It's commonly passed various processing steps such as removal of the insoluble particles, skin, and seeds and pasteurization to eliminate microbial load and enzyme activity. Conventional heating caused serious deterioration for the fruit juice characteristics. Ohmic heating was a thermal treatment as an alternative to overcome disadvantages of conventional method by passing alternating electric current through sample in a short period of time. In this research, passion fruit juice were treated by ohmic heating in different temperatures (60, 65, 70, 75, 80 degrees C) at 60 Hz frequency using voltage gradients (30, 35, 40, 45, 50 V/cm). The final passion fruit juice was then sampled to evaluate polyphenoloxidase and peroxidase activities; ascorbic acid, total phenolic and carotenoid content. Results showed that polyphenoloxidase and peroxidase activities were significantly inactivated by ohmic heating. Ascorbic acid and carotenoid content were nearly stable at temperature below 65 degrees C and voltage below 35 V/cm. Accelerating temperature as well as voltage, ascorbic acid, and carotenoid content would be decreased gradually. Meanwhile, total phenolic content increased from voltage 30 V/cm to 40 V/cm and decreased afterward. It's suggested that the best formula in ohmic heating should be 65 degrees C and 35 V/cm to effectively inactivate enzyme activities while retaining the most valuable phytochemical and functional components.