Abstract: Crude oil bodies (COB) rich in exogenous proteins and purified oil bodies (POB) practically free from exogenous proteins were extracted from soybean by aqueous extraction followed by deionized water washing and alkaline washing, respectively. The physicochemical and rheological properties of COB and POB were analyzed and the effects of different environmental factors (pH, Na+ concentration and temperature) on the stability of COB and POB were determined. The results showed that the main protein components in soybean POB were oleosins, while COB contained a large number of exogenous proteins deside oleosins, mainly including glycinin and β-conglycinin. Compared with POB (whose average particle size and zeta-potential were (475.06 ± 4.49) nm, and (–14.00 ± 1.86) mV, respectively), the presence of exogenous proteins resulted in larger average particle size ((552.93 ± 9.40) nm) and lower zeta potential ((–35.03 ± 0.60) mV) of COB. The isoelectric point of COB was around pH 4.5, which was close to that of glycinin and β-conglycinin, while the isoelectric point of POB was around pH 5.5. At different pH and Na+ concentrations, POB exhibited better stability than COB, which might be due to the fact that the presence of exogenous proteins in COB makes it susceptible to the environment, causing changes in electrostatic and hydrophobic interactions and thus leading to its poor stability. However, thermal treatment had little effect on the stability of COB and POB. In addition, both COB and POB had shear thinning properties, but the viscosity of COB was higher than that of POB, which further proves the influence of the presence of exogenous proteins on the processing properties of soybean oil bodies, and provides an idea for the development of different oil body-based products.

Key words: soybean; exogenous proteins; crude oil bodies; purified oil bodies; stability