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 (<i>Hylocereus polyrhizus</i>) juice during <i>Lacticaseibacillus paracasei</i> fermentation were comprehensively investigated. The results indicated that <i>L. paracasei</i> 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. <i>L. paracasei</i> 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 <i>L. paracasei</i> 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.