Effect of the interfacial layer composition on the properties of emulsion creams.
Effect of the interfacial layer composition on the properties of emulsion creams.
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DOI：
10.1021/jf0636925
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发表时间：
2007-06
影响因子：
6.1
通讯作者：
A. Mackie;M. Ridout;G. Moates;F. Husband;P. Wilde
中科院分区：
文献类型：
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作者：
A. Mackie;M. Ridout;G. Moates;F. Husband;P. Wilde
我们量化了观察到的由蛋白质和低分子量表面活性剂稳定的乳剂在微观结构和流变性质的差异。在这项研究中，我们从单一的母体乳液中制备了两组乳液，它们只是在界面组成（即蛋白质或表面活性剂）上有所不同。所研究的蛋白质为分离乳清蛋白。通过混合阴离子（SDS）和非离子（brij35）表面活性剂来控制表面活性剂稳定乳液的zeta电位，使其与蛋白质稳定乳液的zeta电位相匹配。尽管如此，超声乳化测量和共聚焦显微镜显示，在两组乳剂之间，乳膏层内的结构是不同的。蛋白质稳定的乳剂似乎减缓或阻止了乳剂内部的堆积，导致乳剂液滴密度较低的网络，而表面活性剂乳剂液滴则更快地重新排列成一个堆积良好、浓缩的乳剂层。乳液的流变学分析表明，尽管蛋白质稳定乳液具有较低的分散相体积分数，但其弹性模量约为表面活性剂稳定乳液的30倍。这些差异是由蛋白质在液滴周围形成高粘弹性界面网络的能力引起的，其中可能包括分子间共价交联。在近距离内，层间相互作用的粘附性质有助于浓缩乳液的微观结构和流变性。这是第一次对这种定义明确的乳液体系进行详细的研究，既可以非侵入性地研究其对乳化的影响，也可以侵入性地研究其对体积流变性能的影响。
We have quantified observed differences in the microstructure and rheology of creaming emulsions stabilized by protein and low molecular weight surfactants. In this study, we made two sets of emulsions from a single parent emulsion, which differed only in their interfacial composition (i.e., either protein or surfactant). The protein studied was whey protein isolate. The zeta potential of the surfactant-stabilized emulsion was controlled by mixing anionic (SDS) and nonionic (Brij 35) surfactants to match the zeta potential of the protein-stabilized emulsion. Despite this, ultrasonic creaming measurements and confocal microscopy showed that the structures within the cream layers were different between the two sets of emulsions. The protein-stabilized emulsions appeared to slow or arrest the packing within the cream, leading to a lower density network of emulsion droplets, whereas the surfactant emulsion droplets rearranged more quickly into a well-packed, concentrated cream layer. Rheological analysis of the creams showed that despite the protein-stabilized emulsions having a lower dispersed phase volume fraction, their elastic modulus was approximately 30 times greater than that of a comparable surfactant-stabilized emulsion. These differences were caused by the ability of the protein to form a highly viscoelastic interfacial network around the droplets which may include intermolecular covalent cross-links. At close range the adhesive nature of the interaction between the layers contributes to the microstructure and rheology of concentrated emulsions. This is the first time that such well-defined emulsion systems have been studied in detail both noninvasively to look at the impact on creaming and also invasively to look at the impact on bulk rheological properties.