Abstract: Enzyme-linked immunosorbent assay cannot detect the adulteration of heat-treated cow milk in goat milk. In this study, N-acetylglucosamine was revealed by gas chromatography-mass spectrometry to be a non-protein biomarker present in cow milk that discriminates it from goat milk, and a high performance liquid chromatographic method was developed for quantitative detection of cow milk adulteration in goat milk. Samples were derivatized with 1-phenyl-3-methyl-5-pyrazolone at 70 ℃ for 60 min, followed by chromatographic separation of the marker on a reversed-phase C18 column and detection at 245 nm. The amount of cow milk added to goat milk was calculated according to the N-acetylglucosamine content in the samples. The limit of detection and limit of quantification of the method were 0.3% and 1.0%, respectively. The method showed good linearity in the range of 1%–100% cow milk addition with correlation coefficient of 0.999 4. The recoveries of spiked samples were 100.4%–105.1%, and the intra-day and inter-day precisions (relative standard deviations) at spiked concentrations of 10, 50 and 100 mg/L were 1.8% and 2.0%, 1.7% and 3.7%, 2.6% and 2.7%, respectively. This method proved to be highly sensitive, accurate and precise, and therefore could be suitable for quantitative analysis of cow milk adulteration in goat milk.

Key words: goat milk; cow milk; adulteration; N-acetylglucosamine; high performance liquid chromatography