Nelis Veronique, De Neve Lorenz, Balcaen Mathieu, Dewettinck Koen, Courtin Timothee, Martins José C, Van der Meeren Paul
Particle and Interfacial Technology Group, Department of Green Chemistry and Technology, Ghent University, Coupure Links 653, B-9000 Gent, Belgium; Food Structure & Function Research Group, Department of Food Technology, Safety and Health, Ghent University, Coupure Links 653, B-9000 Gent, Belgium.
Particle and Interfacial Technology Group, Department of Green Chemistry and Technology, Ghent University, Coupure Links 653, B-9000 Gent, Belgium.
J Colloid Interface Sci. 2021 Sep 15;598:314-323. doi: 10.1016/j.jcis.2021.04.039. Epub 2021 Apr 20.
It is expected that low resolution (LR) NMR diffusometry enables (more) accurate water droplet size determination for solid-fat based water-in-oil (W/O) emulsions with (sub)-micron size water droplets in comparison to liquid-oil based W/O emulsions due to hindered extra-droplet water diffusion.
W/O emulsions with a volume-weighed mean diameter of about 1 µm and a solid fat content (SFC) ranging from 0% to 74% were produced. The aqueous phase contained the ionic marker tetraphenylphosphonium chloride (TPPCl). The water droplet size was estimated using LR and high resolution (HR) NMR diffusometry.
HR-NMR diffusometry showed that the diffusion behavior of water and TPPCl was different, indicating water diffusion beyond the droplet's interfacial boundaries. From a certain SFC onwards, a slower echo decay was observed for the water molecules, thus decreasing the overestimation of the water droplet size in (sub)micron W/O emulsions. For those emulsions, the solid fat matrix is believed to hinder extra-droplet water diffusion, which is most likely to be related to the increased tortuosity of the diffusive path in the porous fat crystal network. Using LR-NMR, it can be verified whether the water echo attenuation is mono-exponential or bi-exponential by increasing the gradient pulse duration for the maximum gradient strength, which is more convenient for routine analysis compared to HR-NMR.
预计低分辨率（LR）核磁共振扩散测量法能够比基于液态油的水包油（W/O）乳液更准确地测定基于固体脂肪的水包油乳液中（亚）微米级水滴的大小，因为液滴外水的扩散受到阻碍。
制备了体积加权平均直径约为1μm且固体脂肪含量（SFC）范围为0%至74%的W/O乳液。水相中含有离子标记物四苯基氯化鏻（TPPCl）。使用LR和高分辨率（HR）核磁共振扩散测量法估计水滴大小。
HR-NMR扩散测量法表明，水和TPPCl的扩散行为不同，表明水在液滴界面边界之外扩散。从一定的SFC开始，观察到水分子的回波衰减变慢，从而减少了（亚）微米W/O乳液中水滴大小的高估。对于这些乳液，认为固体脂肪基质阻碍了液滴外水的扩散，这很可能与多孔脂肪晶体网络中扩散路径曲折度增加有关。使用LR-NMR，可以通过增加最大梯度强度下的梯度脉冲持续时间来验证水回波衰减是单指数还是双指数，这与HR-NMR相比，对于常规分析更方便。
