Effect of Citric Acid Extracted from June Plum on the Antioxidant Properties of Watermelon Juice (Citrullus spp.)

Objective: This study was conducted to evaluate the antioxidant properties of watermelon juice preserved with citric acid extracted from June plum. Materials and Methods: The Box-Behnken experimental design of response surface methodology was employed in the experimental design. The independent variables for watermelon juice preserved with citric acid were citric acid concentration (0.5-10 g), pasteurization time (10-20 sec), storage temperature (0-30°C) and pasteurization temperature which was kept constant at 75°C. To make watermelon juice, the fruit was washed, diced, juiced and pasteurized (75°C) to ensure safety and extend shelf life. As part of the production process for citric acid crystals from June plum, pH was adjusted, filtration was performed, CaCl2 was added, heating, acidification and evaporative crystallization occurred. Results: The dependent variables: phenolic acid, flavonoid, vitamin A, Vitamin C and E and lycopene ranged from 0.54-1.14 mg GAE/100 mL, 3.15-3.84 μg QE mL–1, 1.71-1.87 mg, 8.10-9.66 mg, 3.06-3.37 mg, 3.80-4.56 mg L–1, respectively. Conclusion: The research findings revealed that the antioxidant properties of the watermelon juice were strongly affected by citric acid extracted from June plum.