Effects of Lacticaseibacillus casei fermentation on the physicochemical, nutritional, volatile, and sensory profile of synbiotic peach and grape juice during refrigerated storage

Both the application of probiotics and fermentation offer great potential in developing functional foods and, therefore, interesting health benefits. This study aimed to develop a synbiotic peach and grape juice (PGJ) containing probiotics (Lacticaseibacillus casei) and prebiotic (inulin), evaluating its probiotic viability, nutritional, volatile, and sensory profile before and after fermentation and digestion over 12 days of storage at 5 °C. Thus, PGJ containing inulin (PGJI) was inoculated with L. casei (10⁷ CFU/mL) and stored for 12 days at 5 °C, either as non-fermented (PGJI_PRO) or fermented for 48 h at 37 °C (PGJI_FER). Afterward, probiotic viability, physicochemical and nutritional properties, sensory attributes, and the volatile profile were evaluated over storage time. L. casei remained viable throughout storage (7.6 log CFU/mL) and even proliferated after fermentation (8.4 log CFU/mL) without decreasing after digestion. Nutritional properties were favorably affected after fermentation, providing lactic acid (1 g/L), vitamin B12 (1.05 µg/100 mL), and enhanced antihypertensive activity. Digestion boosted polyphenol content and antioxidant capacity by 64 % and 54 %, respectively. Regarding the volatile profile, fermentation greatly impacted delivering compounds related to lactic-butter attributes (e.g., acetoin, butanoic acid) and fermentation attributes (e.g., 3-pentanone, acetic acid). Nevertheless, storage time further affected the volatile profile, particularly after six days, increasing rancid flavor-related compounds. Sensory evaluation showed high acceptance of the synbiotic juice (90 %), reaching lower rates after fermentation (50 %). This study confirms the stability and health potential of L. casei in a fruit-based synbiotic beverage, highlighting its nutritional, functional, and sensory attributes.