Characterization and synergistic antimicrobial activities of food-grade dilution-stable microemulsions against Bacillus subtilis

The physicochemical characterization of a food-grade glycerol monolaurate (GML)/ethanol/Tween 20/sodium lactate (SL)/water microemulsion system and the antimicrobial activities against Bacillus subtilis have been studied in this paper. The influence of ethanol and SL on oil solubilization capability was clearly reflected in the phase behavior of these systems. The addition of ethanol in GML/Tween 20/water system greatly improved the oil solubilization and induced the formation of a U-type microemulsion system, while a transition from U-type to S-type microemulsion system was observed with the increasing concentration of sodium lactate. Two microemulsion formulations were obtained and remained stable by physical stability studies. Antimicrobial results showed that the microemulsions were effective in inhibiting the viable bacteria cells and the bacteria growth. Later it was found that the microemulsions had synergistic antimicrobial activities with a major contribution of GML and the solubilization of SL enhanced the antimicrobial effects. This work indicated that microemulsions are promising delivery vectors for antimicrobial applications in food industry.