Fermented Java Plum (Syzygium cumini (L.) Skeels) Juice Using Lactiplantibacillus plantarum: Effect of Fermentation on Its Antioxidant Capacity, α-Glucosidase Inhibition, and Sensory Properties

Fruit juices are recently being explored to create functional beverages that promote health and well-being. This study explored the development of fermented Java Plum (Syzygium cumini (L.) Skeels) juice using L. plantarum as a functional beverage with high antioxidants. Java plum juice inoculated with L. plantarum was fermented for 96 hours and its physicochemical, phenolic content, antioxidant activity, α-glucosidase inhibition, and phenolic profile were investigated against an unfermented Java plum juice. Results showed that fermented and unfermented samples were not significantly different in terms of their phenolic and flavonoid content. In contrast, the hydrogen peroxide (H2O2) radical scavenging activity of the juice samples were 1.7 times higher while the 2,2’-azino-biz-(3-ethylbenzothiazoline-6-sulfonic) acid) (ABTS) radical scavenging activity of the juice samples were 4.7 times higher compared to the radical scavenging activity of 0.1% BHT. Also, the fermented juice exhibited a significant one-fold increase in α-glucosidase inhibition activity than its unfermented counterpart at α = 0.05. HPLC analysis revealed that gallic acid is the predominant phenolic acid in the juice followed by catechin and rutin hydrate. In addition, sensory evaluation using the 9-point hedonic scale showed that the Java plum fermented juice is generally acceptable. With these, fermentation can be a viable process in the development of a Java plum juice with its antioxidant capacity conserved while improving its α-glucosidase inhibition activity and sensory attributes.