Nondestructive quantification of organic compounds in whole milk without pretreatment by two-dimensional NMR spectroscopy

In this study, various organic compounds in commercial whole milk were quantified simultaneously by H-1 1D and H-1-C-13 HSQC 2D NMR spectra without any pretreatment. 2D NMR spectroscopy was applied to quantification of milk compounds for the first time. Milk fat content was easily determined to be 3.6 +/- 0.1%, and the lactose content was 47.8 +/- 1.0 mg/mL by H-1 NMR spectra. From H-1-C-13 HSQC spectra, the concentrations of citrate, N-acetylcarbohydrates, and trimethylamine were determined to be 3.2 +/- 0.2, 2.9 +/- 0.1, and 4.0 +/- 0.6 mM, respectively. The latter two compounds were quantified in milk for the first time. Butyric acid, total monounsaturated fatty acids, and total polyunsaturated fatty acids of triacylglycerols were 6.2 +/- 0.5, 9.1 +/- 0.9, and 2.9 +/- 0.3 mM, respectively. The fatty acid compositions (mol %) of triacylglycerols were then calculated and were observed to be in good agreement with reference values. The results indicated that H-1 1D and H-1-C-13 HSQC 2D NMR spectroscopy is useful for the rapid and nondestructive determination of various compounds in milk.