Concentrated O/W Pickering emulsions stabilized by soy protein/cellulose nanofibrils: Influence of pH on the emulsification performance

In this work, concentrated Pickering emulsions had been prepared by using soybean protein isolate (SPI) and TEMPO-oxidized bacterial cellulose (TOBC) complex as solid stabilizers. The effects of solid particle content, pH and oil phase volume fraction on the morphology, stability and rheological behaviors of the emulsions had been investigated. It indicated that the emulsion droplets had uniform particle size distribution when the ratio of SPI/TOBC was controlled to 12.5:1 (wt/wt). The emulsification performance could be improved with the increase of solid complex particles content from 1.0% to 3.0%. Moreover, the pH played an important role in regulating the structure and properties of the emulsions. With microscopic observation, the emulsions at pH 7.0 had smaller droplet size (10-15 mu m) than that (15-40 mu m) of the emulsions at pH 3.0. While the emulsions at pH 3.0 maintained a low creaming index (CI) value than those at pH 7.0, and uniform cellular network structure could be seen by SEM observation. It suggested that the electrostatic complexation between soy proteins and anionic bacterial cellulose nanofibrils at pH 3.0 was more favorable for stabilizing emulsions than those at pH 7.0. This work would provide some guidance for regulating the properties of emulsions that stabilized by soy protein and cellulose nanofibrils.