Vitamin A Emulsion Encapsulated with Whey Protein Isolate–Soybean Lecithin Enhances Surimi Gel Structure and Protein Conformation

In this study, whey protein isolate-soybean lecithin-encapsulated vitamin A emulsion (V_A-WSE) with different oil-to-water ratios was prepared and characterized. The impact of V_A-WSE on the physicochemical characteristics of <i>Nemipterus virgatus</i> surimi at varying concentrations was determined. The V_A-WSE emulsion exhibited the best stability when the oil-to-water (O:W) ratio was 1:1 (<i>w</i>/<i>w</i>). Composite gels prepared by mixing V_A-WSE (O:W = 1:1, <i>w</i>/<i>w</i>) with surimi at different ratios showed significantly improved gel properties. In particular, the hardness, chewiness, gel strength, and water-holding capacity of the composite gel with a V_A-WSE concentration of 8% (<i>w</i>/<i>w</i>) reached the highest values of 2629.00 g, 2051.27 g, 292.16 g·cm, and 87.10%, respectively. Similarly, the observed voids in the microstructural images gradually decreased with rising V_A-WSE concentration and were the smallest in the 8% sample group. Surimi gels showed remarkably enhanced hydrogen bonds in the V_A-WSE concentration range of 0-8%, increasing from 0.001 to 0.025 mg/mL (<i>p</i> < 0.05). Furthermore, it was observed that the energy storage modulus (G') was larger than the loss modulus (G″), suggesting the dominant elastic characteristics of the composite gels. The solubility and total sulfhydryl group contents significantly increased from 30.33 to 88.29% and from 4.90 to 28.19 nmol/mg, respectively. In summary, V_A-WSE can promote the unfolding of the myofibrillar protein (MP) structure and improve the gel properties of surimi gels. These results support the development of functional surimi products.