Rheological and physical properties of O/W protein emulsions stabilized by isoelectric solubilization/precipitation isolated protein: The underlying effects of varying protein concentrations

To better understand the potential of using isoelectric solubilization/precipitation (ISP)-isolated protein on emulsion-type meat products, the influences of protein concentration on the physical and rheological properties of protein emulsions were investigated. An oil-in-water (O/W) emulsion containing 20% soybean oil was stabilized by pale, soft and exudative (PSE)-like muscle protein (CON) and ISP-isolated PSE-like muscle protein (ISP) at the concentrations of 50, 100 and 150 mg/ml. Morphologically, the ISP-isolated protein demonstrated better emulsion capacity compared to the CON group, which formed uniform, long-lasting emulsions and dispersed smaller emulsified oil droplets. The apparent viscosity of all emulsion samples was fitted well by the Ostwald-de-Waele model (R² > 0.9). All emulsions exhibited non-Newtonian, pseudoplastic behaviors with the fitting parameters being highly dependent on both protein type and concentration. In the frequency sweep, all emulsion systems were classified as a “strong gel” because G’’ >> G’, especially when concentrations were 100 or 150 mg/ml. Based on a temperature sweep oscillatory curve, the heat-induced gelation behaviors of PSE-like protein emulsions were modified by ISP processing. In addition, the elasticity of the final emulsion gel was higher in the ISP group when compared to the CON group. The thermal gelling properties of ISP-isolated protein emulsions appeared to be impaired when the concentrations reached 150 mg/ml. It was concluded that ISP processing could effectively improve the emulsion properties of PSE-like meat protein.