Zhao Yuan, Guan Yue, Pan Yuanjie, Nitin Nitin, Tikekar Rohan V
Program in Culinary and Food Science, Drexel University, Philadelphia, PA 19104, USA.
Department of Food Science and Technology, University of California-Davis, Davis, CA 95616, USA.
Food Res Int. 2015 Aug;74:269-274. doi: 10.1016/j.foodres.2015.05.008. Epub 2015 May 9.
The materials encapsulated within oil-in-water emulsions are prone to oxidation due to the permeation of oxidative species across the oil-water interface and into the lipid phase. Thus, the oxidative barrier properties of the interfacial layer are pivotal in reducing oxidation within emulsified oils. To enhance these barrier properties, we explored an approach of stabilizing emulsions using 'silica-polymer microparticles'. We hypothesize that these microparticles will enhance the barrier properties of emulsion interfaces by mechanisms such as higher interfacial thickness and quenching of oxidative species before they permeate into the emulsions. Silica-ε-polylysine (Si-EPL) microparticles were synthesized by electrostatic aggregation of anionic silica nanoparticles and cationic ε-polylysine in the aqueous phase. Formation of Si-EPL microparticles was validated using particle size, ζ-potential and scanning electron microscopy measurements. These microparticles were subsequently used for emulsion stabilization. Emulsions stabilized by silica nanoparticles alone were used as control. Oxidative barrier properties were determined by measuring the rate of permeation of peroxyl radicals from the aqueous to the oil phase of the emulsion using fluorescence based methods. The rate of permeation of peroxyl radicals was significantly lower in emulsions stabilized by Si-EPL microparticles compared to that stabilized by silica nanoparticles. One of the mechanisms responsible for the observed effect was enhanced quenching of peroxyl radical by Si-EPL microparticles before they can permeate inside the oil phase. To further validate the results, stability of a model bioactive compound, retinol, encapsulated in these emulsions was compared. Consistent with peroxyl radical permeation measurements, emulsion stabilized by Si-EPL microparticles significantly improved the oxidative stability of retinol compared to that stabilized by silica nanoparticles alone. Thus, by engineering the physical properties of the interfacial layers, the oxidation of the encapsulants in emulsions can be controlled.
水包油乳液中包裹的物质容易被氧化，这是由于氧化物质透过油水界面进入脂质相所致。因此，界面层的抗氧化屏障特性对于减少乳化油中的氧化至关重要。为了增强这些屏障特性，我们探索了一种使用“二氧化硅-聚合物微粒”来稳定乳液的方法。我们假设这些微粒将通过诸如增加界面厚度以及在氧化物质渗透到乳液之前将其淬灭等机制来增强乳液界面的屏障特性。二氧化硅-ε-聚赖氨酸（Si-EPL）微粒是通过阴离子二氧化硅纳米颗粒和阳离子ε-聚赖氨酸在水相中的静电聚集而合成的。使用粒径、ζ电位和扫描电子显微镜测量对Si-EPL微粒的形成进行了验证。随后将这些微粒用于乳液稳定化。仅用二氧化硅纳米颗粒稳定的乳液用作对照。通过基于荧光的方法测量过氧自由基从乳液水相到油相的渗透速率来确定抗氧化屏障特性。与用二氧化硅纳米颗粒稳定的乳液相比，用Si-EPL微粒稳定的乳液中过氧自由基的渗透速率显著更低。观察到的这种效果的一个机制是Si-EPL微粒在过氧自由基渗透到油相之前对其进行了增强的淬灭。为了进一步验证结果，比较了包裹在这些乳液中的模型生物活性化合物视黄醇的稳定性。与过氧自由基渗透测量结果一致，与仅用二氧化硅纳米颗粒稳定的乳液相比，用Si-EPL微粒稳定的乳液显著提高了视黄醇的氧化稳定性。因此，通过设计界面层的物理性质，可以控制乳液中封装剂的氧化。
