Lactic-acid bacteria fermentation-induced effects on microstructure and interfacial properties of oil-in-water emulsions stabilized by goat-milk proteins

An oil-in-water emulsion stabilized with goat milk proteins was subjected to processing from lactic acid bacteria fermentation and the effects on emulsion microstructure and droplet characteristics were investigated. Optical microscopy and Turbiscan analyses were used to monitor the microstructure and droplet size during the fermentation. pH-driven effects led to milk protein conformational changes as indicated by the determination of total thiol groups and affected the protein interfacial composition. This phenomenon coincided (pH<5.5, T>37.9 °C) with the increase in average droplet size, which was attributed to flocculation phenomena due to reduced electrostatic repulsion. Casein solubility was enhanced during the initial stages of fermentation (1 hr - 3 hr) and was precipitated at pH<4.8. LC-MS/MS analysis confirmed that caseins (αs1-, αs2-, β- and κ-casein) were the dominant protein species at oil-water interface at the end of the fermentation process and contributed to the stability of the emulsion by reducing the droplet diameter (1.24 μm).