Rampon V, Genot C, Riaublanc A, Anton M, Axelos M A V, McClements D J
Laboratoire d'Etude des Interactions des Molécules Alimentaires and Laboratoire de Physico-Chimie des Macromolécules, Institut National de la Recherche Agronomique (INRA), Rue de la Géraudière, 44316 NANTES Cedex 03, France.
J Agric Food Chem. 2003 Apr 23;51(9):2482-9. doi: 10.1021/jf026168g.
The displacement of a globular protein (bovine serum albumin, BSA) from the surface of oil droplets in concentrated oil-in-water emulsions by a nonionic surfactant (polyoxyethylene sorbitan monolauarate, Tween 20) was studied using front-face fluorescence spectroscopy (FFFS). This method relies on measurement of the change in intensity (I(MAX)) and wavelength (lambda(MAX)) of the maximum in the tryptophan emission spectrum. A series of oil-in-water emulsions (21 wt % n-hexadecane, 0.22 wt % BSA, pH 7.0) containing different molar ratios of Tween 20 to BSA (R = 0-131) were prepared. As the surfactant concentration was increased, the protein was progressively displaced from the droplet surfaces. At R > or = 66, the protein was completely displaced from the droplet surfaces. There was an increase in both I(MAX) and lambda(MAX) with increasing Tween 20 concentration up to R = 66, which correlated with the increase in the ratio of nonadsorbed to adsorbed protein. In contrast, there was a decrease in I(MAX) and lambda(MAX) with Tween 20 concentration in protein solutions and for R > or = 66 in the emulsions, which was attributed to binding of the surfactant to the protein. This study shows that FFFS is a powerful technique for nondestructively providing information about the interfacial composition of droplets in concentrated protein-stabilized emulsions in situ. Nevertheless, in general the suitability of the technique may also depend on protein type and the nature of the physicochemical matrix surrounding the proteins.
使用前表面荧光光谱法（FFFS）研究了非离子表面活性剂（聚氧乙烯山梨醇单月桂酸酯，吐温20）将球状蛋白质（牛血清白蛋白，BSA）从浓水包油乳液中油滴表面置换出来的过程。该方法依赖于测量色氨酸发射光谱中最大值处的强度变化（I(MAX)）和波长变化（lambda(MAX)）。制备了一系列含有不同吐温20与BSA摩尔比（R = 0 - 131）的水包油乳液（21 wt%正十六烷，0.22 wt% BSA，pH 7.0）。随着表面活性剂浓度的增加，蛋白质逐渐从液滴表面被置换出来。当R≥66时，蛋白质完全从液滴表面被置换出来。在R = 66之前，随着吐温20浓度的增加，I(MAX)和lambda(MAX)均增加，这与未吸附蛋白质与吸附蛋白质的比例增加相关。相反，在蛋白质溶液中以及乳液中R≥66时，I(MAX)和lambda(MAX)随吐温20浓度的增加而降低，这归因于表面活性剂与蛋白质的结合。本研究表明，FFFS是一种强大的技术，可原位无损地提供有关浓蛋白质稳定乳液中液滴界面组成的信息。然而，一般来说，该技术的适用性也可能取决于蛋白质类型以及蛋白质周围物理化学基质的性质。
