Fermentation of enzymatical feijoa fruit juice by probiotic bacteria: nutritional composition, bioactive phenolics, and antioxidant activities.

Five commercial lactic acid bacteria—Lactobacillus bulgaricus 57 (Lb57), Lactobacillus gasseri 07 (Lg07), Streptococcus thermophilus 08 (St08), Pediococcus pentosaceus 57 (Pp57), and Bifidobacterium adolescentis 68 (Bba68)—were employed to investigate their impact on physicochemical and nutritional properties of feijoa juice pretreated with enzymatic hydrolysis. The results showed that feijoa fruit juice was a favorable food matrix for probiotics and the viable counts remained above 9.0 log CFU/mL at the end of fermentation. Total soluble solids (TSS), vitamin C (VC), and sucrose were decreased, whereas glucose, quininic acid, adipic acid, and antioxidant capacity were increased by 36-h fermentation. Bba68 and St08 demonstrated robust malolactic conversion abilities, yielding over 1.65 mg/L of lactic acid. The phenolic content in feijoa juice varied significantly, with gallic acid reaching 16.12 mg/L and 16.46 mg/L after 36-h fermentation by Bba68 and St08, respectively. Compared to other strains, Bba68 displayed excellent 2,2-diphenyl-1-picrylhydrazyl (DPPH) (2.68 mmol Trolox/L), 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid (ABTS) (6.60 mmol Trolox/L), and ferric ion reducing antioxidant potential (FRAP) (28.11 mmol Trolox/L) capacities. Pearson correlation analysis demonstrated that enhanced antioxidant activities positively correlated with gallic acid content. Furthermore, the functional evaluation of the probiotic revealed that Bba68 possessed the highest acid-producing capacity (14.50 g/L) and bile salt tolerance (3.04%). Given this, these results may offer a possible pathway for screening strains with specific functions and industrial-scale fermentation conditions to manufacture novel value-added feijoa fruit products. [ABSTRACT FROM AUTHOR]