de Wolf Johanna R, Ali Kawthar, Legtenberg Chris G, Verveld Wietske, Bosschaart Nienke
Department of Biomedical Photonic Imaging, Faculty of Science and Technology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands.
Foods. 2024 Dec 20;13(24):4124. doi: 10.3390/foods13244124.
The refractive index (RI) of human milk serum (also known as whey, milk soluble fraction or milk plasma) depends on the individual molecular species dissolved in the serum and their concentrations. Although the human milk serum RI is known to influence milk analysis methods based on light scattering, the RI dependency on human milk serum composition is currently unknown. Therefore, we systematically evaluate how the RI depends on natural variations in macronutrient concentrations in the soluble fraction. We measure RI variations in serum simulating samples with controlled macronutrient concentrations, as well as skimmed and whole fore-, bulk, and hindmilk from 19 donors. For both types of samples, we relate the measured RI to the macronutrient composition. From the serum simulating samples, we observe that the RI depends more on variations in whey protein, than carbohydrate concentrations, while minerals have negligible influence. For all donated samples, the average RI was 1.3470 (range 1.3466-1.3474). Per donor, no significant differences were observed in RI between fore-, bulk, and hindmilk. We conclude that protein and solids-not-fat (i.e., the total contribution of carbohydrates, proteins and minerals present in milk) concentrations are most predictive for human milk serum RI.
人乳血清（也称为乳清、乳可溶部分或乳血浆）的折射率（RI）取决于溶解在血清中的各个分子种类及其浓度。虽然已知人乳血清RI会影响基于光散射的乳汁分析方法，但目前尚不清楚RI与人乳血清成分之间的关系。因此，我们系统地评估了RI如何取决于可溶部分中常量营养素浓度的自然变化。我们测量了模拟血清样本中RI的变化，这些样本的常量营养素浓度是可控的，同时还测量了来自19位捐赠者的脱脂和全脂初乳、批量乳和末乳的RI。对于这两种类型的样本，我们将测量的RI与常量营养素组成联系起来。从模拟血清样本中，我们观察到RI对乳清蛋白变化的依赖性比对碳水化合物浓度的依赖性更大，而矿物质的影响可忽略不计。对于所有捐赠样本，平均RI为1.3470（范围为1.3466 - 1.3474）。对于每个捐赠者，初乳、批量乳和末乳之间的RI没有观察到显著差异。我们得出结论，蛋白质和非脂固形物（即乳汁中存在的碳水化合物、蛋白质和矿物质的总含量）浓度对人乳血清RI的预测性最强。
