天然脂肪球主要由甘油三酯构成, 以不同大小的球状形式分泌而得。 不同大小的脂肪球的球体和膜组成成分不同, 从而影响了脂肪在乳中的存在形式和最终的乳品功能特性。 然而, 不同大小的脂肪球成分的差异尚未完全阐明。 利用拉曼光谱测定特定大小脂肪球及膜的脂质和脂肪酸组成。 拉曼光谱能够从单个脂肪球获得特定拉曼信号, 并且在不破坏天然脂肪球构型的情况下进行测定。 结果显示, 小脂肪球在2 885/2 850 cm-1处条带信号较高, 表明小脂肪球趋于形成结晶态的脂肪球膜包裹流动态的甘油三酯内核的结构。 此外, 小脂肪球与大脂肪球相比, 1 655/1 443 cm-1的条带信号较低, 表明小脂肪球的脂肪酸不饱和程度较高。 总之, 从本实验结果可以推断, 用特定的小脂肪球分离而得的稀奶油在熔化时较大脂肪球难熔化, 搅拌耗时更多, 但能形成更柔软的黄油。

Native fat globules composed mainly of triglycerides are secreted as droplets of variable size. The size of fat globules affects the form of fat in dairy products and final functionality, which depends mainly on the composition of the globules and membrane. However, the relation between the composition and size of fat globules has not been studied in detail. In this study, differences in the lipid content and fatty acid composition related to the size of native fat globules were investigated using confocal Raman spectroscopy, which offers the possibility of acquisition and analysis of the Raman signal without disruption of a single fat globule in natural suspension. The results showed small fat globules (SFG) had a higher ratio of band intensities at 2 885/2 850 cm-1, indicating SFG tend to have a triglyceride core in a fluid state with a milk fat globule membrane in a crystalline state. In addition, the SFG had a higher level of unsaturation compared to large fat globules, shown by a lower ratio at 1 655/1 443 cm-1. Using cream with selected SFG would allow a harder and more costly churning process but lead to a softer butter.