Biotechnological Features of a Functional Non-Dairy Mixed Juice Fermented with Lacticaseibacillus paracasei SP5

In the present study, a wild-type Lacticaseibacillus paracasei SP5 (L. paracasei SP5) potential probiotic strain (previously isolated from kefir grains) was applied for the 1-day fermentation of an apple-orange-carrot mixed juice. After the fermentation, the mixed juice was refrigerated in cold storage at 4 degrees C, and the microbiological stability, characterization of volatiles, physicochemical properties (pH, total titratable acidity (TTA), residual sugar content and organic acids content), the sensorial validation (aroma, taste and overall acceptability) of the juice, and the viability of the potential probiotic strain were analyzed. The stored juice exhibited zero colonies of yeasts/fungi and simultaneously the viability of L. paracasei SP5 was retained to 8.28 Log CFU/mL, even after the 4th week of cold storage. The pH values ranged from 3.80 to 3.35 and the TTA values ranged from 0.1344% to 0.1844% lactic acid for the unfermented juice up until the 4th week of cold storage. Furthermore, the organic acids content consisted mostly of lactic acid (4.6 to 9.1 g/L), while malic acid (3.7 to 1.5 g/L), acetic acid (0.6 g/L) and propionic acid (0.3 g/L) were detected only after the 4th week of cold storage. Residual sugar content ranged from the initial value of 122.2 g/L and 106.6 g/L at the end of cold storage. As far as the volatiles' characterization is concerned: 9 esters, 2 organic acids, 12 alcohols, 3 aldehydes, 1 ketone, 6 terpenes and 4 sesquiterpenes (37 in total) were detected in the unfermented mixed juice and 33 compounds in the fermented juice after 4 weeks of cold storage. The sensorial properties (aroma, taste and overall acceptability) of the fermented mixed juice samples were positively influenced. Consequently, L. paracasei SP5 potential probiotic strain may be applied for the production of probiotic mixed juices, with satisfying viability, volatile profile and organoleptic results.