Rangsansarid Jongjit, Fukada Kazuhiro
Department of Biochemistry and Food Science, Faculty of Agriculture, Kagawa University, Ikenobe 2393, Miki-cho, Kagawa 761-0795, Japan.
J Colloid Interface Sci. 2007 Dec 15;316(2):779-86. doi: 10.1016/j.jcis.2007.07.040. Epub 2007 Jul 26.
Bovine serum albumin (BSA) was used as an emulsifier to disperse corn oil in aqueous media with various protein concentration, pH, and ionic strength. Quantitative estimation was made on the homogenizing activity of BSA and dispersion stability of oil particles by measuring particle size, turbidity, and creaming rate. Dispersion stability strongly depended on pH and became a minimum around pH 5.0 which was the isoelectric point of BSA. The interfacial tension between BSA solution and corn oil was minimized at pH 5.0. Interesting results were obtained concerning the ionic-strength dependence of stability. When the ionic strength was set below 30 mM, the emulsions became more stable with the increase of BSA concentration at pH 6.7 but the opposite behavior (enhanced destabilization) was confirmed at pH 5.0 with the BSA content. In high ionic strength conditions (ca. > or = 80 mM NaCl), however, BSA-stabilized emulsions became fairly stable even at pH 5.0. These results suggested that BSA molecules having no net charge induced some attractive interactions (e.g., bridging or depletion) in low ionic strength but steric stabilization in high ionic strength, respectively.
牛血清白蛋白（BSA）用作乳化剂，在具有不同蛋白质浓度、pH值和离子强度的水介质中分散玉米油。通过测量粒径、浊度和乳析率，对BSA的均质活性和油颗粒的分散稳定性进行了定量评估。分散稳定性强烈依赖于pH值，在BSA的等电点pH 5.0左右达到最小值。BSA溶液与玉米油之间的界面张力在pH 5.0时最小。关于稳定性的离子强度依赖性获得了有趣的结果。当离子强度设定在30 mM以下时，在pH 6.7下乳液随着BSA浓度的增加变得更稳定，但在pH 5.0下随着BSA含量的增加出现相反的行为（增强的不稳定）。然而，在高离子强度条件下（约≥80 mM NaCl），即使在pH 5.0时，BSA稳定的乳液也变得相当稳定。这些结果表明，不带净电荷的BSA分子在低离子强度下分别诱导了一些吸引相互作用（例如桥连或排空），而在高离子强度下诱导了空间稳定作用。
