Synergistic impact of agar microsphere surface charge on the physical and oxidative stability of Pickering emulsions

Polysaccharide-based food-grade particles have remarkable potential to improve the physicochemical stability of emulsions. This study prepared four agar microspheres (AM1-AM4) with different surface charges via emulsion curing and investigated their effects on emulsion stability. Results showed that emulsion stability increased with the surface charge of AMs (AM1 > AM2 > AM3 > AM4). Adjusting the pH and salt ion concentration to modify the surface charge of AM1 revealed that alkaline conditions (pH 11) increased the charge to -57.00 mV, preventing oil-water separation of the emulsion within 30 days. By contrast, salt ions caused phase separation through charge neutralization. Notably, emulsion oxidative stability remained consistent across pH 5-11, demonstrating adaptability to charge fluctuations. At 55 °C, AM1 inhibited lipid oxidation with primary (11.99 mmol/kg) and secondary (1.45 mmol/kg) oxidation products, and these values were significantly lower than those of the control group. These findings indicated that charge-mediated stabilization offered dual protection, enhancing physical stability and reducing lipid oxidation, providing a basis for developing stable, clean-label emulsified foods.