Effect of Lipophilization of Soy Protein on Its Emulsion Stabilizing Properties

Effect of lipophilization of the soy protein (SP) molecule on emulsion stabilizing properties (ES) was investigated by comparing the properties of alcohol-modified, acetylated, partially hydrolyzed and unmodified SP. The modified SPs showed high ES even in the slightly acidic region, where the protein solubility remained at low level, whereas the ES of unmodified SP decreased with the decrease of protein solubility. The hydrophile-lipophile balance (HLB) number of SP at pH 4.5 decreased and its ES increased as a result of modifications. Both the exposed tyrosine of SP determined by ultraviolet difference spectra and the hydrophobic region on the surface of the SP molecule compared with relative fluorescent intensity was increased by ethanol-modification. The ES of the modified SP were found to increase almost linearly with the increase in fluorescent intensity and intrinsic viscosity. Considering these facts and the nature of effect of alcohols on globular proteins, it was concluded that lipophilization of the SP molecule is one of the primary factors which increase the ES in the slightly acidic region.