Insights into effectiveness of tight ultrafiltration and frozen storage in bioactive compound retention in watermelon juice concentrate

Abstract

AbstractThe aim of this study is to evaluate the potential of tight ultrafiltration for the concentration of bioactive compounds in watermelon juice and also analyze the effectiveness of frozen storage for storing the juice concentrate. The concentration of the juice was performed at two different temperatures of 30 ± 2°C and 23 ± 2°C and at pressures of 2 and 3 bar for concentration factors of 1.5, 2, and 3. Total phenolic content in the concentrate was determined in terms of gallic acid and flavonoid concentration was analyzed in terms of rutin equivalent. Lycopene was determined spectrophotometrically using the hexane extraction method. The ultrafiltration (UF) process was successful in retaining a high percentage of bioactive compounds in the watermelon juice concentrate. Flavonoids showed the highest levels of concentration among the four important bioactive compounds. The ultrafiltration experimental set of T = 23 ± 2°C, P = 3 bar and volumetric concentration factor = 1.5 was found to be most feasible. Frozen storage at −18°C was successful in retaining a high percentage of bioactives in the concentrate after 1 month although vitamin C loss was on the higher side. Lycopene was highly preserved in the concentrate juice after frozen storage with retention of 93%.Practical ApplicationsOne of the major ways to reduce the amount of postharvest losses in watermelon is to convert it to juice by postharvest value addition. To make it available all through the year, the juice has to be processed in order to store it for longer periods. Membrane technology provides the best option to treat the juice in a nonthermal manner to retain its nutritional and sensorial characteristics after processing. Tight ultrafiltration can be a great tool for obtaining a juice concentrate that is rich in bioactive compounds. Watermelon has a significant amount of vitamin C, polyphenols, and also contains lycopene, a carotenoid with potential cancer preventive properties. Tight ultrafiltration can be useful in retaining these important components in the concentrated juice simultaneously reducing the water content, thereby increasing its shelf life. By optimizing different parameters associated with ultrafiltration, it can be possible to industrially scale up this process to make the juice available throughout the year.