Effect of Soybean Soluble Polysaccharides and Fe²⁺ on Physical Stability and Rheological Properties of O/W Emulsion

The effects of soybean soluble polysaccharides (SSPS) and different concentrations of Fe²⁺ on the physical stability and rheological properties of soy isolated protein (SPI) stabilized oil-in-water emulsions were investigated. The turbiscan stability index (TSI), steady rheology, particle size and distribution and Zeta-potential of the emulsions containing SSPS and different concentrations of Fe²⁺ within 14 days were determined. The results showed that the TSI of the SSPS-SPI emulsion was significantly lower than that of the SPI emulsion, and the surface area average diameter (d_{3, 2}) and volume average diameter (d_{4, 3}) of the droplets increased, the viscosity coefficient increased and the absolute value of Zeta-potential decreased, indicating that SSPS increased the viscosity of the SPI emulsion and improved the physical stability of the emulsion. After addition of 0.1 mmol/L Fe²⁺, the TSI was the lowest, and the particle size was the smallest with the d_{3, 2}and d_{4, 3} of 0.686, 2.136 μm, respectively, the viscosity of emulsion increased, its physical stability was better. With increasing of Fe²⁺ concentration, the TSI increased significantly (p<0.05), the particle size became larger and the distribution range became wider, indicating that 0.2~0.5 mmol/L Fe²⁺ decreased the physical stability of the emulsions. In a word, the addition of SSPS and 0.1 mmol/L Fe²⁺ improved the physical stability of the SPI-stabilized O/W emulsion.