Wan Zhi-Li, Wang Li-Ying, Wang Jin-Mei, Yuan Yang, Yang Xiao-Quan
Research and Development Center of Food Proteins, Department of Food Science and Technology, South China University of Technology , Guangzhou 510640, People's Republic of China.
J Agric Food Chem. 2014 Jul 16;62(28):6834-43. doi: 10.1021/jf502027u. Epub 2014 Jun 30.
The adsorption of the mixtures of soy glycinin (11S) with a biosurfactant stevioside (STE) at the air-water interface was studied to understand its relation with foaming properties. A combination of several techniques such as dynamic surface tension, dilatational rheology, fluorescence spectroscopy, and isothermal titration calorimetry (ITC) was used. In the presence of intermediate STE concentrations (0.25-0.5%), the weak binding of STE with 11S in bulk occurred by hydrophobic interactions, which could induce conformational changes of 11S, as evidenced by fluorescence and ITC. Accordingly, the strong synergy in reducing surface tension and the plateau in surface elasticity for mixed 11S-STE layers formed from the weakly interacting mixtures were clearly observed. This effect could be explained by the complexation with STE, which might facilitate the partial dissociation and further unfolding of 11S upon adsorption, thus enhancing the protein-protein and protein-STE interfacial interactions. These surface properties were positively reflected in foams produced by the weakly interacting system, which exhibited good foaming capacity and considerable stability probably due to better response to external stresses. However, at high STE concentrations (1-2%), as a consequence of the interface dominated by STE due to the preferential adsorption of STE molecules, the surface elasticity of layers dramatically decreased, and the resultant foams became less stable.
研究了大豆球蛋白（11S）与生物表面活性剂甜菊糖苷（STE）的混合物在气-水界面的吸附情况，以了解其与发泡性能的关系。采用了多种技术相结合的方法，如动态表面张力、扩张流变学、荧光光谱和等温滴定量热法（ITC）。在中等浓度的STE（0.25 - 0.5%）存在下，STE与本体中的11S通过疏水相互作用发生弱结合，这可能会诱导11S的构象变化，荧光和ITC结果证明了这一点。因此，对于由弱相互作用混合物形成的11S - STE混合层，在降低表面张力方面有很强的协同作用，并且表面弹性出现平台期，这一现象很明显。这种效应可以通过与STE的络合来解释，这可能会促进11S在吸附时的部分解离和进一步展开，从而增强蛋白质-蛋白质和蛋白质-STE的界面相互作用。这些表面性质在由弱相互作用体系产生的泡沫中得到了积极体现，这些泡沫表现出良好的发泡能力和相当的稳定性，可能是由于对外部应力有更好的响应。然而，在高浓度的STE（1 - 2%）下，由于STE分子的优先吸附导致界面由STE主导，层的表面弹性急剧下降，所产生的泡沫变得不太稳定。
