Structural Rearrangement of 尾-Lactoglobulin at Different Oil鈥揥ater Interfaces and Its Effect on Emulsion Stability

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• 作者：Jiali Zhai ; Tim J. Wooster ; S酶ren V. Hoffmann ; Tzong-Hsien Lee ; Mary Ann Augustin ; Marie-Isabel Aguilar
• 刊名：Langmuir
• 出版年：2011
• 出版时间：August 2, 2011
• 年：2011
• 卷：27
• 期：15
• 页码：9227-9236
• 全文大小：990K
• 年卷期：v.27,no.15(August 2, 2011)
• ISSN：1520-5827

文摘

Understanding the factors that control protein structure and stability at the oil鈥搘ater interface continues to be a major focus to optimize the formulation of protein-stabilized emulsions. In this study, a combination of synchrotron radiation circular dichroism spectroscopy, front-face fluorescence spectroscopy, and dual polarization interferometry (DPI) was used to characterize the conformation and geometric structure of 尾-lactoglobulin (尾-Lg) upon adsorption to two oil鈥搘ater interfaces: a hexadecane鈥搘ater interface and a tricaprylin鈥搘ater interface. The results show that, upon adsorption to both oil鈥搘ater interfaces, 尾-Lg went through a 尾-sheet to 伪-helix transition with a corresponding loss of its globular tertiary structure. The degree of conformational change was also a function of the oil phase polarity. The hexadecane oil induced a much higher degree of non-native 伪-helix compared to the tricaprylin oil. In contrast to the 尾-Lg conformation in solution, the non-native 伪-helical-rich conformation of 尾-Lg at the interface was resistant to further conformational change upon heating. DPI measurements suggest that 尾-Lg formed a thin dense layer at emulsion droplet surfaces. The effects of high temperature and the presence of salt on these 尾-Lg emulsions were then investigated by monitoring changes in the 味-potential and particle size. In the absence of salt, high electrostatic repulsion meant 尾-Lg-stabilized emulsions were resistant to heating to 90 掳C. Adding salt (120 mM NaCl) before or after heating led to emulsion flocculation due to the screening of the electrostatic repulsion between colloidal particles. This study has provided insight into the structural properties of proteins adsorbed at the oil鈥搘ater interface and has implications in the formulation and production of emulsions stabilized by globular proteins.