Antibacterial activity of bioemulsifiers/biosurfactants produced by Levilactobacillus brevis S4 and Lactiplantibacillus plantarum S5 and their utilization to enhance the stability of cold emulsions of milk chocolate drinks

Chocolate milk drink, one of the most popular and widely consumed milk products among the population, independent of their age, has as its main challenge the problem of its physical instability. The aim of this study was to assess the stabilizing effect of bioemulsifiers/biosurfactants (BE/BS) from two lactobacilli strains in a cold chocolate milk drink. The strains Levilactobacillus brevis S4 and Lactiplantibacillus plantarum S5 isolated from pendidam were screened for their ability to produce BE/BS. The produced BE/BS were characterized, their antimicrobial activities were assessed, and their ability to stabilize cold chocolate milk drinks was determined. The results obtained showed BE/BS yields of 3.48 and 4.37 g/L from L. brevis S4 and L. plantarum S5, respectively. These BE/BS showed emulsifying and surface activities that remained stable after treatment at different temperatures, pH, and salinity. The emulsions formed using BE/BS were stable for 72 h at room temperature (25 ± 1°C). The BE/BS exhibited antimicrobial activity against Staphylococcus aureus S1 and Escherichia coli E1. When applied to cold chocolate milk drinks at 0.2% (w/v), the BE/BS from L. brevis S4 and L. plantarum S5 showed interesting solubility indexes and water absorption capacities, which led to the successful stabilization of the drinks. The results of this study demonstrate the stabilizer potential of BE/BS from L. brevis S4 and L. plantarum S5 and suggest their use in the dairy and food industries. The issue of the physical instability of chocolate milk drinks, a popular and widely consumed milk product among the population independent of their age, has led to the search for stabilizers. The green alternative proposed in this study was the bioemulsifiers/biosurfactants (BE/BS) from Levilactobacillus brevis S4 and Lactiplantibacillus plantarum S5. These biomolecules demonstrated good in vitro emulsifying, emulsion stabilizing and antimicrobial activities. Thanks to their interesting solubility indexes and water absorption capacities, the BE/BS have successfully stabilized the cold chocolate milk drinks, thus suggesting their potential use in the dairy industry as well as the food industries as a substitute for chemical stabilizers.