Characterization of probiotic lactobacilli and development of fermented soymilk with improved technological properties

Two human-originated bacterial strains Limosilactobacillus reuteri NCDC958 and Lacticaseibacillus rhamnosus NCDC953, previously characterized as extracellular B12-producers, were tested in the current study for the in vitro probiotic potential, and for the development and technological characterization of probiotic fermented soymilk. During in vitro probiotic testing, both strains showed 1.6 to 2.2 log reduction at pH 3, tolerate 0.3% bile salt, exhibited auto- (36–47%) and co-aggregation features (28–32%), along with moderate hydrophobicity (26–63% for xylene, ethyl acetate, and chloroform) and noticeable (≥13 mm inhibition zone) antimicrobial activity against food-related pathogenic indicators (Escherichia coli, Bacillus cereus, Salmonella typhimurium, Enterococcus faecalis, Staphylococcus aureus). Both cultures lacked hemolytic activity and showed variable susceptibility and resistance towards clinical antibiotics. The addition of 0.1% modified starch and 1% vanilla flavor improved sensory, rheological and textural properties of both the fermented soymilks with final acceptability above 7 on a 9-point hedonic scale. No significant differences (P > 0.05) were observed in acidity, pH, and microbiological counts. According to obtained results, fermented soymilks developed using probiotic strain NCDC958 or NCDC953 were found satisfactory on all technological and sensorial attributes under evaluation and may be forwarded for scale-up fermentation.