comparative analysis of shelf-life extension of grape juice by ohmic heating and ultrasonication

Grapes are consumed as a fresh fruit or as a fresh juice. Grape juice has higher antioxidant properties. These antioxidants help reduce free radicals. Grapes are stored best at a 0-5°C temperature. About 10-15% of fresh grapes lose their market value and consumer acceptance due to poor post-harvest techniques. The water activity of grape juice is high, and therefore juice is highly susceptible to microbial growth. So, it is not easy to store it for a long period without processing. Ohmic heating and ultrasonication are novel techniques that were used in this research for the shelf life of grape juice. These non-thermal techniques have a positive effect on the shelf life of grape juice. Grape juice was treated by taking seven different treatment groups; T0 was the control sample, while T1, T2, and T3 were heated ohmically at 20V/cm for 10, 20, and 30 seconds, respectively, and T4, T5, and T6 were treated with ultrasonication at 20 kHz for 10, 20, and 30 minutes, respectively. The best treatment was determined to be storing grapes for up to 7 days at 4°C. Both treatments showed slight changes in the physicochemical parameters of grape juice. Both treatments at set voltages and different times caused changes in pH. A greater decrease in pH was observed by Ohmic heating as compared to ultrasonication. A decrease in pH was considered to protect the juice from microbial deterioration, and it could be stored for one week. A microbiological analysis of grape juice treated by Ohmic heating and ultrasonication revealed that Ohmic heating caused a reduction in the total plate count and total coliform count more effectively as compared to the ultrasonicated grape juice. Therefore, Ohmic heating was considered more effective as it provides uniform and rapid heating during processing, and it was found that grape juice treated by this treatment can be stored for up to 7 days.