Surface engineered bacteria as Pickering stabilizers for foams and emulsions

The ability to manipulate the structure of food and increase the shelf life by enhanced stability using natural (e.g., biological) agents instead of synthetic surfactants is of interest to many food companies. Here we chemically modify the cell hydrophobicity of lactic acid bacteria Lactobacillus acidophilus (La5) using octenyl succinic anhydride (OSA) and investigate foams and emulsions produced with both the unmodified and modified cells in terms of the foamability, foam stability, emulsion storage stability and the microstructure. Cell hydrophobicity was effectively increased by OSA modification, and the modified bacteria adsorbed well on the oil-water or air-water interface to stabilize the foams or emulsions. Foamability and foam stability increased with OSA modification. Similarly, good emulsion stability against coalescence was observed over the studied period for the emulsions prepared with modified La5. Moreover, OSA modification only showed a modest lethal effect up to 6% OSA on bacteria based on the decline of cell viability and culturability depending on the degree of modification (0.5 log decrease for 6% OSA-modified cells but 5 log decrease for 10% OSA-modified cells in comparison to culturability of unmodified cells). From our results, we suggest that in future OSA-modified La5 cells may act as structural building blocks and fat substitution for food material creating texture and mouthfeel.