Biopolymers and Colloids Laboratory, Department of Food Science, University of Massachusetts, Amherst, Massachusetts 01003, USA.
J Agric Food Chem. 2010 Jun 9;58(11):7059-66. doi: 10.1021/jf100990r.
Nanoemulsions are finding increasing utilization in the food and beverage industry to encapsulate and protect lipophilic functional components. Low-intensity methods, such as the phase inversion temperature (PIT) approach, are of particular interest for forming food-grade nanoemulsions because of their ease of formation and relatively low energy costs. Nevertheless, this type of emulsion tends to be highly unstable to droplet coalescence after preparation. In this study, we develop a potential solution to this problem using model water/surfactant (Brij 30, C(12)E(4))/oil (tetradecane) systems. The PIT and system morphology were determined by monitoring the temperature dependence of the electrical conductivity, turbidity, and microstructure of the emulsions. Nanoemulsions were formed by holding water/surfactant/oil mixtures at their PIT and then rapidly cooling them. The influence of storage temperature on emulsion stability was investigated, which indicated that the optimum temperature (13 degrees C) was about 27 degrees C lower than the PIT (approximately 40 degrees C). Higher storage temperatures resulted in an increase in droplet growth rate due to coalescence, while lower temperatures led to gelation. Nanoemulsions that were relatively stable to coalescence could be formed at ambient temperatures by adding either Tween 80 (0.2 wt %) or SDS (0.1 wt %) to displace the Brij 30 from the droplet surfaces. We propose that these surfactants increase nanoemulsion stability by changing the optimum curvature of the interfacial layer, as well as by increasing the repulsive interactions (steric or electrostatic) between the droplets. This study may lead to a novel approach to create stable nanoemulsion-based delivery systems that are suitable for utilization within the food industry.
纳米乳剂在食品和饮料工业中越来越多地被用于包裹和保护疏水性功能性成分。低强度方法，如相转变温度 (PIT) 方法，由于其易于形成和相对较低的能量成本，对于形成食品级纳米乳剂特别感兴趣。然而，这种类型的乳液在制备后往往对液滴聚结非常不稳定。在这项研究中，我们使用模型水/表面活性剂 (Brij 30、C(12)E(4))/油 (十四烷) 系统为这个问题开发了一个潜在的解决方案。通过监测乳液的电导率、浊度和微观结构随温度的变化，确定了 PIT 和系统形态。通过将水/表面活性剂/油混合物保持在其 PIT 并迅速冷却来形成纳米乳剂。研究了储存温度对乳液稳定性的影响，结果表明最佳温度 (13 摄氏度) 比 PIT (约 40 摄氏度) 低约 27 摄氏度。较高的储存温度会由于聚结而导致液滴生长速率增加，而较低的温度会导致凝胶化。通过向混合物中添加吐温 80（0.2wt%）或 SDS（0.1wt%）取代 Brij 30 从液滴表面，可在环境温度下形成相对稳定的纳米乳剂。我们提出，这些表面活性剂通过改变界面层的最佳曲率以及增加液滴之间的排斥相互作用（静电或空间位阻）来增加纳米乳剂的稳定性。这项研究可能会导致一种创建适合在食品工业中使用的稳定纳米乳液输送系统的新方法。
