Properties and microstructures of golden thread fish myofibrillar proteins gel filled with diacylglycerol emulsion: Effects of emulsifier type and dose

In this study, diacylglycerol (DAG) emulsions stabilized by different concentrations of sodium caseinate (SCE) or Tween 80 (TWE) were prepared and characterized, and the effects of prepared emulsions as fillers on the gel properties, microstructures and molecular interactions of myofibrillar proteins (MP) gel were investigated. The particle size of SCE decreased gradually with the amount of sodium caseinate, and the minimum value was obtained with 2.5% sodium caseinate. The filling of SCE enhanced the whiteness, water-holding capacity (WHC), gel strength, and texture (P < 0.05), and facilitated the formation of a more compact gel network with sufficient emulsion droplets to be fixed in it. This positive effect was based on various interactions between SCE droplets and MP, and showed sodium caseinate dosage dependence within a certain range. In addition, TWE obtained the most effective particle size at 1.0% Tween 80 dosage, which had no adverse effect on gel properties. However, when Tween 80 concentration exceeded 1.5%, MP gel's water retention, strength, and texture properties showed a certain downward trend, accompanied by the weakening of gel network and the loss of more oil droplets. These results support that DAG emulsion stabilized by moderate sodium caseinate is a potential active filler, which can not only enhance the content of unsaturated fatty acids in gels, but also improve the gel properties.