Abstract: The aim of this study was to explore the stability and in vitro simulated gastrointestinal digestion properties of natural soybean and rapeseed oil body (OB) emulsions. The basic chemical compositions of soybean and rapeseed OB were analyzed. The particle size, viscosity and microstructure were analyzed with a laser scattering particle analyzer, a rotary rheometer and a confocal laser scanning microscope. Also, the stability of the two natural emulsions under various environmental stresses (pH, ion concentration and thermal treatment) was investigated, and changes in the protein profile and particle size during simulated gastrointestinal digestion were investigated. The results showed that the protein content of soybean OB was significantly higher (P < 0.05) than that of rapeseed OB while the lipid content was significantly lower (P < 0.05) than that of rapeseed OB. The particle sizes of the two emulsions decreased along with the increase in OB concentration, the particle size of soybean OB emulsion being significantly lower than that of rapeseed OB emulsion, as also demonstrated by the confocal laser scanning microscopic images. The droplet interface in soybean OB emulsion was covered with a large amount of oleosins. The viscosity of soybean OB emulsion was higher than that of rapeseed OB emulsion. Soybean OB emulsion showed large particle and was unstable at pH 4.0 and 100, 200 mmol/L NaCl concentration, whereas NaCl concentration caused little effect on the stability of rapeseed OB emulsion. Soybean OB emulsion was stable at 85 ℃ for 15 min, while rapeseed OB emulsion was sensitive to temperature. The two emulsions were consecutively treated with simulated gastric?fluid (SGF) and simulated intestinal fluid (SIF) for 180 minutes each.?The hydrolysis of protein in soybean OB emulsion was fast in the first 30 min of gastric digestion and then tended to level off. However, the protein of rapeseed OB emulsion was gradually hydrolyzed during the whole gastric digestion process. The particle size of the two emulsions was higher after the gastric digestion. The particle size of soybean OB emulsion was significantly reduced after the intestinal digestion, while the particle size of rapeseed OB emulsion showed no significant change.

Key words: oil body; natural emulsion; stability; gastrointestinal digestion