Edible foam based on Pickering effect of probiotic bacteria and milk proteins

We report the preparation and characterization of aqueous Pickering foams using bio-particles constituted by lactic acid bacteria surface modified by oppositely charged milk proteins. Cell surface modification was shown by zeta potential measurements. Foams stabilized by bacterial Pickering bio-particles showed improved stability compared to purely milk protein stabilized foams. The stability of foams increased with the bacterial concentration whereas the foam volume (foamability) decreased. On the other hand, protein concentration was correlated with foamability but not with the foam stability. Optical and fluorescence microscopy revealed organized cell structures around and in between the air bubbles providing for an internal network that effectively stabilizes the foam. Therefore, entirely food grade stable foams can be produced by using modified health promoting bacterial cells and surface active milk proteins. Such Pickering systems can potentially be utilized in bottom up construction of more complex hierarchical food structures and further improve properties such as foam stability.