Effect of Aqueous Phase pH and Na⁺ on the Stability of Microcrystalline Cellulose-Lard Pickering Emulsion

The effects of aqueous phase pH and Na⁺ concentration on the stability of Pickering emulsions formed by microcrystalline cellulose (MCC) and lard were investigated. MCC-lard Pickering emulsions were prepared by mixing the aqueous phase containing 1% MCC with an equal volume of oil phase at different pH and Na⁺ concentrations, and the changes in the appearance, emulsion index, microstructure, particle size, zeta potential and rheological properties of the emulsions were measured at different pH (pH4~9) and Na⁺ concentrations (0~500 mmol/L). The results showed that the MCC-lard Pickering emulsions did not show significant delamination at pH5~8, and the emulsion index did not change, and the particle size of the emulsion droplets was smaller than those at pH4 and pH9, with better viscosity and shear resistance, among which the best stabilization effect was achieved at pH6. When the Na⁺ concentration was 300 mmol/L and above, the emulsion stability decreased more rapidly with increasing resting time. It was observed that at a Na⁺ concentration of 400 mmol/L, the emulsions would delaminate after three days of standing. With the increasing of Na⁺ concentration, the electrostatic shielding effect made the particle size of emulsion increased, the absolute value of zeta potential decreased, and the viscosity and shear resistance decreased. The MCC-lard Pickering emulsions had good emulsion stability at low to medium pH (pH5~8) and low Na⁺ concentration (≤300 mmol/L) in aqueous phase, but the emulsions were less stable at pH4 and pH9 and high Na⁺ concentration (>300 mmol/L) in aqueous phase. The effects of different pH and Na⁺ concentrations on the emulsification stability of MCC-lard Pickering emulsions and their principles were investigated to provide some reference for the processing and application of functionalized pre-emulsified meat products.