Assessment of Lactic Acid Bacteria Growth Rate, Physicochemical Parameters, Vitamin Contents, and Antioxidant Potentials of Probiotic-Fortified Fruit Juices

This study aimed to assess the impact of probiotic fortification on the microbiological qualities, growth rate of lactic acid bacteria (LAB), physicochemical properties, vitamin content, and antioxidant potential of fruit juices derived from watermelon, pineapple, and orange. Using standard analytical methods, both non-probiotic-fortified and probiotic-fortified juice samples were compared. Probiotic was achieved by inoculating juices with Lactobacillus casei and Lactobacillus fermentum, which significantly reduced coliform counts (from 7.20 × 10³ to 4.00 × 10² colony forming unit [CFU]/mL) and fungal counts (from 2.40 × 10² to 4.00 × 10¹ CFU/mL) and enhanced LAB viability (from 0.4 × 10⁴ to 1.8 × 10⁴ CFU/mL), especially when both strains were combined. Probiotic-fortified juices demonstrated notable improvements in physicochemical parameters, including increased titratable acidity (0.20-0.56%), reduced pH (5.50-3.17), and decreased soluble solids (17.90-7.90% brix), indicative of successful fermentation. Orange juice with both probiotic strains contained the highest potassium content (234.75 mg/100 mL), while pineapple juice with both strains had the highest vitamin B12 content (17.80 mg/100 mL). Antioxidant potential, measured using 1,1-diphenyl-2-picrylhydroxyl and other radical-scavenging assays, was significantly higher in probiotic-enriched juices, with synergistic effects observed for multi-strain combinations. Organoleptic evaluation confirmed good acceptability of the functional beverages. These findings demonstrate that fortifying tropical fruit juices with probiotic LAB not only improves microbial safety and nutritional value but also enhances antioxidant properties, supporting the development of innovative, inclusive, non-dairy functional beverages suitable for health-conscious and lactose-intolerant individuals.