Enhancement of nutritional and flavor properties of red-fleshed pitaya juice via Lacticaseibacillus paracasei fermentation

In this study, the changes in physicochemical properties, antioxidant activity, and volatile/non-volatile metabolites of red-fleshed pitaya (Hylocereus polyrhizus) juice during Lacticaseibacillus paracasei fermentation were comprehensively investigated. The results indicated that L. paracasei significantly increased the total polyphenols, flavonoids, and anthocyanins contents, with the total phenolic content increasing from 0.16 ± 0.03 mg/mL to 0.38 ± 0.03 mg/mL. L. paracasei fermentation enhanced the antioxidant activities, lipase inhibition, and α-glucosidase activities of red-fleshed pitaya juices. A total of 78 volatile compounds were detected. The increased abundance of volatile compounds significantly enhanced the flavor profile, adding floral, fruity, buttery, and sweet flavors. Furthermore, metabolomic analysis demonstrated that L. paracasei significantly altered the non-volatile compounds of red-fleshed pitaya juice, particularly increasing ornithine, asparagine, glutamine, and indole-3-lactic acid. These metabolites are involved in carbohydrate metabolism, amino acid synthesis/metabolism pathways, suggesting their potential roles in nutritional improvement. These improvements demonstrated its potential as a functional beverage.