Food Chemistry and Technology Department, Teagasc Food Research Centre , Moorepark, Fermoy, County Cork, Ireland.
School of Food and Nutritional Sciences, University College Cork , Cork, Ireland.
J Agric Food Chem. 2016 Aug 31;64(34):6546-54. doi: 10.1021/acs.jafc.6b01722. Epub 2016 Aug 23.
Milk has been used commercially as a carrier for phytosterols, but there is limited knowledge on the effect of added plant sterols on the properties of the system. In this study, phytosterols dispersed in milk fat at a level of 0.3 or 0.6% were homogenized with an aqueous dispersion of whey protein isolate (WPI). The particle size, morphology, ζ-potential, and stability of the emulsions were investigated. Emulsion crystallization properties were examined through the use of differential scanning calorimetry (DSC) and Synchrotron X-ray scattering at both small and wide angles. Phytosterol enrichment influenced the particle size and physical appearance of the emulsion droplets, but did not affect the stability or charge of the dispersed particles. DSC data demonstrated that, at the higher level of phytosterol addition, crystallization of milk fat was delayed, whereas, at the lower level, phytosterol enrichment induced nucleation and emulsion crystallization. These differences were attributed to the formation of separate phytosterol crystals within the emulsions at the high phytosterol concentration, as characterized by Synchrotron X-ray measurements. X-ray scattering patterns demonstrated the ability of the phytosterol to integrate within the milk fat triacylglycerol matrix, with a concomitant increase in longitudinal packing and system disorder. Understanding the consequences of adding phytosterols, on the physical and crystalline behavior of emulsions may enable the functional food industry to design more physically and chemically stable products.
牛奶已被商业用作植物甾醇的载体，但对于添加植物甾醇对体系性质的影响知之甚少。在这项研究中，将水平为 0.3%或 0.6%的植物甾醇分散在乳脂肪中，然后与乳清蛋白分离物（WPI）的水相分散体进行均质化。研究了乳液的粒径、形态、ζ-电位和稳定性。通过使用差示扫描量热法（DSC）和同步加速器小角和广角 X 射线散射来研究乳液的结晶性质。植物甾醇的富集影响了乳液液滴的粒径和物理外观，但不影响分散颗粒的稳定性或电荷。DSC 数据表明，在较高水平的植物甾醇添加下，乳脂肪的结晶被延迟，而在较低水平下，植物甾醇的富集诱导成核和乳液结晶。这些差异归因于在高植物甾醇浓度下，植物甾醇在乳液中形成单独的晶体，这一点通过同步加速器 X 射线测量得到了证实。X 射线散射图谱表明，植物甾醇能够整合到乳脂肪三酰基甘油基质中，同时纵向堆积和系统无序度增加。了解添加植物甾醇对乳液物理和结晶行为的影响，可能使功能性食品行业能够设计出更具物理和化学稳定性的产品。
