Effects of fructooligosaccharide and soybean protein isolate in the microencapsulation of walnut oil

The purpose of this study was to evaluate the effects of different proportions of fructooligosaccharide/soy isolate protein as wall materials on the physical properties and structural characterization of walnut oil microcapsules. Different ratios of oligofructose/soy protein isolate microcapsules were prepared to encapsulate walnut oil. The protective effect of microcapsules on walnut oil was evaluated by accelerated oxidation experiment. The microcapsules were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy and thermogravimetric analysis. The results show that fructooligosaccharide had no effect on the two-level structure of soy protein isolate, but its encapsulation efficiency could be improved by reducing the particle size of the emulsion and increasing the viscosity of the emulsion. In addition, fructooligosaccharide can improve the encapsulation efficiency by maintaining the structure of the protein during the freeze-drying process. The addition of fructooligosaccharide reduces the water content and hygroscopicity of the microcapsules. The accelerated oxidation results show that microencapsulation can significantly improve the oxidation stability of walnut oil. After accelerated oxidation, the peroxide value and thiobarbituric acid value of walnut oil in the control group were significantly higher than those of microencapsulated walnut oil (p < 0.05). The peroxide value of unencapsulated walnut oil is 2.8 times higher than that of encapsulated walnut oil. The results show that fructooligosaccharide/soy isolate protein could be used as the wall material of microcapsules to embed sensitive, active substances.