Fermentation of Grapefruit Juice with Lacticaseibacillus rhamnosus and Enzymatic Debittering by Naringinase

Growing consumer awareness of the link between diet and health has increased interest in functional foods, including fermented juices. Grapefruit juice has potential health-promoting properties, but its bitter taste limits its acceptance by consumers. This study aimed to develop a fermentation process for debittering grapefruit juice at natural pH using Lacticaseibacillus rhamnosus and naringinase. Grapefruit juice was fermented with Lactic. rhamnosus using free naringinase and naringinase immobilized on carob gum and chitosan supports at 30 ± 0.2 °C for 72 h. Naringin concentration, bacterial cell count, total phenol content, organic acids, carbohydrates, antioxidant activity, and pH were analyzed. Naringinase immobilized on carob gum demonstrated the highest efficiency, hydrolyzing over 42% of naringin after 24 h (from 418.20 to 241.19 μg/mL). The free enzyme reduced the naringin concentration to 155.28 μg/mL after 48 h. The highest Lactic. rhamnosus cell count (2.05 × 10⁹ CFU/mL) was achieved with the free enzyme. Total phenol content decreased from 42.24 to 16.58 mg GAE/100 mL when using naringinase immobilized on chitosan. The combined use of naringinase and Lactic. rhamnosus enables the development of an integrated process that improves consumer acceptance with potential applications in the functional beverage industry.