Knowledge of binary emulsifiers' influence on the formation and stability of emulsion-based products is still limited. The aim of this study was to investigate the emulsifying properties of Quillaja saponin-egg lecithin mixtures at different concentration ratios (r = 5:0, 4:1, 3:2, 2:3, 1:4, and 0:5) with total emulsifier concentration set to 0.5% or 1.0% (w/w). For this, oil-in-water emulsions (10% oil, pH 7) were prepared via high-pressure homogenization. Furthermore, emulsion stability against different environmental stresses was tested. All the binary emulsifier mixtures formed submicron sized emulsions upon homogenization. The most stable emulsions among the mixed emulsifiers were obtained at low Quillaja saponin concentration at r = 1:4 that showed similar physical stability over time to emulsions stabilized by Quillaja saponins and egg lecithin alone. The data suggested that the mixtures of Quillaja saponins and egg lecithins built mixed interfacial layers that were prone to changes over time. Emulsions stabilized by the binary mixtures were in general less stable against changes in pH and ionic strength than the emulsions stabilized by the individual emulsifiers. An exception were the emulsions at r = 1:4 that showed improved stability at pH 2 over the phase separated Quillaja saponin-stabilized emulsions at the same pH. Moreover, all the emulsions were heat stable up to 90 °C. On the other hand, none of the emulsions were stable upon freeze-thawing. These results increase our understanding of technofunctionality of binary emulsifier systems. PRACTICAL APPLICATION: Food-grade and natural emulsifier mixtures composed of Quillaja saponins and egg lecithin may be used in selected emulsion-based food or personal care product applications to replace synthetic surfactants due to issues with consumer acceptance and regulatory restrictions.

中文翻译：

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Quillaja皂苷-鸡蛋卵磷脂混合物稳定乳液的形成和稳定性

二元乳化剂对乳液基产品的形成和稳定性的影响的知识仍然有限。本研究的目的是研究不同浓度比（r = 5:0、4:1、3:2、2:3、1:4 和 0:5）的槐树皂苷-鸡蛋卵磷脂混合物的乳化特性乳化剂总浓度设置为 0.5% 或 1.0% (w/w)。为此，通过高压均化制备了水包油乳液（10% 油，pH 7）。此外，还测试了针对不同环境压力的乳液稳定性。所有二元乳化剂混合物均化后形成亚微米级乳液。混合乳化剂中最稳定的乳液是在 r = 1 的低 Quillaja 皂苷浓度下获得的：图 4 的物理稳定性与单独由 Quillaja 皂苷和鸡蛋卵磷脂稳定的乳液相似。数据表明，Quillaja 皂苷和鸡蛋卵磷脂的混合物构建了易于随时间变化的混合界面层。与由单个乳化剂稳定的乳液相比，由二元混合物稳定的乳液通常对 pH 值和离子强度的变化更不稳定。一个例外是 r = 1:4 的乳液在 pH 2 下显示出比在相同 pH 下相分离的 Quillaja 皂苷稳定的乳液更高的稳定性。此外，所有乳液在高达 90 °C 时都是热稳定的。另一方面，没有一种乳液在冻融时是稳定的。这些结果增加了我们对二元乳化剂系统技术功能的理解。实际应用：