Microbial cells as colloidal particles: Pickering oil-in-water emulsions stabilized by bacteria and yeast

• Thermally-inactivated lactic acid bacteria and yeast cells used as micron-sized Pickering colloidal particles
• Oil-in-water emulsions can be stabilized solely by lactic acid bacteria and yeast cells.
• Kinetically stable high internal phase ratio emulsions possible with lactic acid bacteria and yeast cells

ABSTRACTThermally-inactivated baker's yeast (Saccharomyces cerevisiae) and lactic acid bacteria (Lactobacillus acidophilus and Streptococcus thermophilus) were used to generate and stabilize model oil-in-water (O/W) emulsions containing up to 80 wt.% dispersed oil. With optimized compositions, cell-covered dispersed oil droplets were stable against droplet coalescence and bulk phase separation for over four months. From a textural perspective, these emulsions were self-supporting and exhibited a mayonnaise-like consistency. The microbial cells acted as Pickering-type stabilizers by residing at the oil–water interface. The three-phase contact angle of the yeast at the oil–water interface measured using confocal microscopy was 30 ± 9°, demonstrating its ability to stabilize O/W emulsions. These microbial cells may be used in the design of processed food emulsions with an ‘all-natural’ designation as well as for the replacement of common synthetic surfactants to permit clean label declarations.

Adsorbed cells on oil droplets: a) S. thermophilus; b) L. acidophilus; c) S. cerevisiae.Figure optionsDownload as PowerPoint slide