Multi-scale structuring of the oil-water interface in fat crystal-stabilized emulsions

脂肪结晶对黄油、人造黄油、冰淇淋和低脂巧克力等食品油包水(W/O)乳状液的形成和质量属性有显著影响，在这些乳状液中，水以细小的液滴形式分散在连续的油/脂网络中。在这类产品中，‘Pickering’三酰甘油(TG)晶体包裹分散的水滴，有助于产品质地和长期稳定性，防止液滴合并和视觉相分离。卢梭实验室的两项最新发现正在为在分子和微结构长度尺度上系统构建脂肪晶体稳定的W/O乳剂的物理性质铺平道路。我们最近已经证明，通过使用具有与TGS相容的分子结构的界面吸附的液态表面活性剂，可以将原本表面不活跃的脂肪晶体直接在分散的水滴表面结晶。其次，脂肪晶体稳定的W/O乳状液在受限环境中的剪切冷却会导致脂肪晶体团聚成球状、蚕茧状的微结构。我们的研究导致了一种新型的Pickering稳定剂的开发，这种稳定剂将分散的水滴包裹在厚厚的晶壳中。目前处于起步阶段，对这些现象的机械理解对于充分理解和利用这些结构化的乳剂是必要的。将使用包括拉曼光谱、流变学和显微镜在内的众多研究工具。我的团队还建议使用同步辐射X射线衍射法来原位确定TGS和表面活性剂在乳化液-水界面的真实取向。这些技术结合在一起，将允许在分子和微结构长度范围内专门设计和建造创新的结构化Pickering稳定的W/O乳液。获得的基本认识将导致更好的乳状液稳定性，从而延长食品和其他应用的保质期。此外，随着W/O食品乳液越来越多地被食品加工者视为减少卡路里的载体，这项高度可行的研究将成为开发更健康的加工食品的新工具。

Fat crystallization has a pronounced influence on the formation and quality attributes of food water-in-oil (W/O) emulsions such as butter, margarine, ice cream and low-fat chocolate, where water is dispersed as fine droplets within a continuous oil/fat network. In such products, 'Pickering' triacylglycerol (TG) crystals englobe dispersed water droplets and contribute to product texture and long-term stability against droplet coalescence and visual phase separation. Two recent discoveries in the Rousseau laboratory are paving the way to the systematic structuring of the physical properties of fat crystal-stabilized W/O emulsions at the molecular and microstructural length scales. We have recently shown that it is possible to 'coerce' otherwise surface-inactive fat crystals into crystallizing directly at the surface of dispersed water droplets by using interfacially-adsorbed liquid-state surfactants with a molecular structure compatible with the TGs. Secondly, shear-cooling of fat crystal-stabilized W/O emulsions within a confined environment induces fat crystal agglomeration into spheroidal, cocoon-like microstructures. Our research has led to development of a new form of Pickering-type stabilization where dispersed aqueous droplets are encapsulated within thick crystal shells. Currently in its infancy, a mechanistic understanding of these phenomena is necessary to fully understand and exploit these structured emulsions. Numerous research tools including Raman spectroscopy, rheology and microscopy will be used. My group also proposes the use of synchrotron X-ray diffraction to establish in-situ the true orientation of TGs and surfactants at the emulsion oil-water interface. Together these techniques will permit the dedicated design and construction of innovative structured Pickering-stabilized W/O emulsions at the molecular and microstructural length scales. The fundamental understanding gained will result in better emulsion stability and therefore increased shelf life for foods and other applications. As well, as W/O food emulsions are increasingly seen as vehicles for calorie reduction by food processors, this highly-feasible research will be a novel tool for the development of healthier processed foods.