Polyglycerol polyricinoleate (PGPR) is a food emulsifier with a unique yield stress reducing efficacy in fat-based suspensions. There are many commercially available PGPRs, and the different products vary in their impact on the yield stress. Choosing the right PGPR for a specific formulation is often based on empirical data and the experience of the formulator. Lack of fundamental understanding of why these differences exist hampers reformulation efforts to replace PGPR. Therefore, this study aimed to link the yield stress reducing efficacy of PGPR to its molecular properties. Five commercial PGPR samples were studied (3 g/kg) in a concentrated suspension of icing sugar (650 g/kg, ≈ 530 mL/L) in sunflower oil (with naturally-occurring surface-active molecules removed). Rheological analysis revealed Herschel-Bulkley yield stress variations of between 0.90 ± 0.06 Pa and 1.90 ± 0.18 Pa, compared to 57.6 ± 15.8 Pa in the absence of PGPR. Yield stress was correlated to critical micelle concentration, obtained from oil-water interfacial tension data. Applying molecular characterisation techniques revealed that the presence of a hydroxyl group on the fatty acid at the end of the polyricinoleate estolide chain could be linked to inferior yield stress reducing efficacy.

聚甘油聚蓖麻油酸酯 (PGPR) 是一种食品乳化剂，在脂肪基悬浮液中具有独特的屈服应力降低功效。市售的 PGPR 有很多，不同的产品对屈服应力的影响各不相同。为特定配方选择正确的 PGPR 通常基于经验数据和配方设计师的经验。缺乏对为什么存在这些差异的基本理解阻碍了重新制定替代 PGPR 的努力。因此，本研究旨在将 PGPR 的屈服应力降低功效与其分子特性联系起来。研究了五种商业 PGPR 样品 (3 g/kg) 在向日葵油中的糖粉 (650 g/kg, ≈ 530 mL/L) 浓缩悬浮液（去除了天然存在的表面活性分子）。流变分析显示 Herschel-Bulkley 屈服应力变化在 0.90 ± 0.06 Pa 和 1.90 ± 0.18 Pa 之间，而在没有 PGPR 的情况下为 57.6 ± 15.8 Pa。屈服应力与临界胶束浓度相关，从油水界面张力数据中获得。应用分子表征技术表明，聚蓖麻油酸酯酯链末端脂肪酸上羟基的存在可能与降低屈服应力的效果较差有关。