Preparation of Soybean Oil Body Complex Emulsions by Ultrasonic Treatment and Transport of β-Carotene

In this study, soybean oil bodies were used as raw materials and emulsifiers to prepare soybean oil body complex emulsions by ultrasonication, to optimise the ultrasonication conditions and to use the oil body complex emulsions for the transport of fat-soluble bioactives. The mechanism of ultrasonic treatment to enhance the stability of oil-body complex emulsions was revealed through the study of the physicochemical properties of the emulsions. The effect of oil-body complex emulsions on the transport of β-carotene was also examined. As a result, soybean oil body complex emulsion was successfully prepared by ultrasonication, and the oxidative and storage stability of the emulsion was best at a power of 450 W (10 min). At this time, the average particle size of emulsion was 1537 nm, and the shape of droplets was round and evenly distributed. The results of Fourier transform infrared spectroscopy indicated that the ultrasound-induced cavitation effect increased the physical forces, such as turbulence and shear forces. This caused partial unfolding of the protein polypeptide chains in oil bodies, leading to the rearrangement of hydrogen bond networks within the proteins. Consequently, the protein secondary structure changed: The relative content of α-helix structures decreased and the relative content of β-sheet structures increased. The electrophoresis results showed that there were no significant changes in the composition of protein subunits. But with the ultrasound intensity increased, the adsorption of extrinsic proteins at the droplet interface was enhanced. The results of storage stability showed that ultrasonic treatment (450 W) could inhibit the generation of oxidation products and improved the oxidation stability of emulsions. The soybean oil body-β-carotene emulsions could be successfully prepared by ultrasonic treatment, and the encapsulation rate of β-carotene was the highest (94.9%) at 450 W, and the retention rate was 81.8% after 11 days of room temperature storage. This study provides insights into the application of soybean oil bodies as emulsifiers for the delivery of fat-soluble bioactive substances.