Comparative Study of Functional Properties in Soy Beverages and Cow’s Milk Fermented by Selected Beneficial Bacteria

The fermentation of cow’s milk and soy beverages, a plant-based alternative, by lactic acid bacteria (LAB) and bifidobacteria strains shares the goal of creating functional products, but differs significantly in the substrates and final properties. The aim of this study was to compare the functional properties offered by 21 selected strains of LAB and bifidobacteria in the fermentation of soy beverages and cow’s milk. LAB and bifidobacteria strains showed a greater pH decrease in soy beverages, particularly in Lactiplantibacillus plantarum and Bifidobacterium pseudocatenulatum strains, which were only able to grow and ferment in soy beverages. Lacticaseibacillus rhamnosus and Lacticaseibacillus paracasei strains showed high proteolytic activity in both milk and soy beverages, while Streptococcus thermophilus and Lactococcus lactis strains showed greater proteolytic activity in cow’s milk, and most bifidobacteria strains did not show proteolytic activity. Fermentation mostly resulted in an increase in antioxidant activity in soy beverages, as measured by DPPH, and in cow’s milk by FRAP. Finally, all L. paracasei, L. rhamnosus, and bifidobacteria strains showed efficient production of daidzein and genistein in soy beverages. In conclusion, soy beverages are a better substrate for L. plantarum and bifidobacteria strains, and the production of bioactive isoflavones by many selected strains increases the functional potential of soy beverages.