REQUIMTE/LAQV, Department of Chemistry and Biochemistry, Faculty of Science, University of Porto, Rua do Campo Alegre 687, 4169-007 Porto, Portugal.
Departamento de Química-Física, Facultad de Química, Universidade de Vigo, 36310 Vigo, Spain.
Molecules. 2021 Oct 7;26(19):6058. doi: 10.3390/molecules26196058.
Surfactants have been used for decades in the food industry for the preparation of lipid-based emulsified food stuffs. They play two main roles in the emulsification processes: first they decrease the interfacial tension between the oil and water, facilitating droplet deformation and rupture; second, they reduce droplet coalescence by forming steric barriers. However, addition of surfactants to binary oil-water mixtures also brings up the formation of three-dimensional interfacial layers, surrounding each emulsion droplet, that significantly alter chemical reactivity. This is the case, for instance, in the inhibition reaction between antioxidants and the lipid radicals formed in the course of the spontaneous oxidation reaction of unsaturated lipids, which are commonly employed in the preparation of food-grade emulsions. The rate of the inhibition reaction depends on the effective concentrations of antioxidants, which are mostly controlled by the amount of surfactant employed in the preparation of the emulsion. In this work, we analyze the effects of the surfactant Tween 20 on the oxidative stability and on the effective concentrations of two model antioxidants derived from cinnamic acid, determining their interfacial concentrations in the intact emulsions to avoid disrupting the existing equilibria and biasing results. For this purpose, a recently developed methodology was employed, and experimental results were interpreted on the grounds of a pseudophase kinetic model.
几十年来，表面活性剂一直被用于食品工业中制备基于脂质的乳化食品。它们在乳化过程中发挥着两个主要作用：首先，它们降低油和水之间的界面张力，促进液滴变形和破裂；其次，它们通过形成空间位阻屏障来减少液滴聚结。然而，向二元油-水混合物中添加表面活性剂也会导致形成三维界面层，包围每个乳液液滴，这会显著改变化学活性。例如，在抗氧化剂与不饱和脂质自发氧化反应过程中形成的脂质自由基之间的抑制反应中就是如此，不饱和脂质通常用于制备食品级乳液。抑制反应的速率取决于抗氧化剂的有效浓度，而抗氧化剂的有效浓度主要受制备乳液时使用的表面活性剂的量控制。在这项工作中，我们分析了表面活性剂 Tween 20 对氧化稳定性和两种源自肉桂酸的模型抗氧化剂的有效浓度的影响，通过在完整乳液中确定它们的界面浓度，避免破坏现有的平衡并产生偏差结果。为此，采用了一种新开发的方法，并根据拟相动力学模型对实验结果进行了解释。
