The effect of surfactant crystallization on partial coalescence in O/W emulsions
The effect of surfactant crystallization on partial coalescence in O/W emulsions
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DOI：
10.1016/j.jcis.2017.04.021
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发表时间：
2017-08-15
影响因子：
9.9
通讯作者：
Faure, Chrystel
中科院分区：
文献类型：
--
作者：
Goibier, Lucie;Lecomte, Sophie;Faure, Chrystel
部分聚结是分散相部分结晶的乳液中普遍存在的不稳定现象。当乳状液用蛋白质稳定时，界面僵硬和远程排斥表面力阻碍了这种类型的不稳定性。低分子表面活性剂的加入改变了界面性质和表面作用力，通常会促进部分聚结。本文研究了不同结晶温度的表面活性剂(吐温80、棕榈酸和单甘酯)在酪蛋白酸钠稳定的O/W模型乳状液中诱导部分聚结的能力。最初的流体乳液被提交给回火循环，导致体系的凝胶化。通过测量体储能模数来评价材料的部分聚结程度。DSC用于确定油相和表面活性剂的熔融范围，而偏光显微镜、拉曼成像和表面流变学测量则用于表征油/水界面。首次探索了在吐温80存在下，液滴大小、表面活性剂与蛋白质的摩尔比和回火历史等有利于部分聚结的实验条件。我们发现，当加入可结晶表面活性剂时，部分聚结是相当边缘的，而与液体表面活性剂一起加入时，部分聚结更明显。这一结果背后的现象，特别是表面活性剂的界面结晶现象得到了证实和讨论。(C)2017 Elsevier Inc.保留所有权利。
Partial coalescence is a ubiquitous instability in emulsions whose dispersed phase is partially crystallized. When emulsions are stabilized with proteins, interfacial stiffness and long-range repulsive surface forces hinder this type of instability. The addition of low molecular weight surfactants modifies the interfacial properties and surface forces, generally promoting partial coalescence. In the present work, various surfactants (Tween 80, palmitic acid and monoglycerides) differing in their crystallization temperature were probed for their ability to induce partial coalescence in model O/W emulsions stabilized by sodium caseinate. The initially fluid emulsions were submitted to a tempering cycle leading to the gelation of the system. The extent of partial coalescence was evaluated by measuring the bulk storage modulus. DSC was used to determine the melting range of the oil phase and surfactants, while polarized microscopy, Raman imaging, and surface rheology measurements were performed to characterize the oil/water interface. The experimental conditions in terms of droplet size, surfactant-to-protein molar ratio and tempering history favoring partial coalescence were first explored in presence of Tween 80. We show that partial coalescence is rather marginal when crystallizable surfactants are added, and pronounced with liquid surfactants. The phenomena underlying this result, especially interfacial crystallization of surfactants, are evidenced and discussed. (C) 2017 Elsevier Inc. All rights reserved.