Quantification of Free Short-Chain Fatty Acids in Raw Cow Milk by Gas Chromatography-Mass Spectrometry

Abstract

Free short-chain fatty acids (FSCFAs) are a momentous contributor to the flavor of the raw cow milk. Hence, the purpose of this research was to build an approach for the quantification of 10 FSCFAs in raw cow milk. Raw cow milk samples are acidified by hydrochloric acid ethanol (0.5%) solution pretreatment and then processed on the gas chromatography-mass spectrometry. With the exception of iso C5:0 and anteiso C5:0 co-flux, the remaining eight FSCFAs were effectively separated by chromatography. The methodological validation data revealed that the linear relationship satisfied the assay requirements (coefficient of determination >0.999), the limits of quantification were 0.167 to 1.250 μg mL^-1, the recoveries ranged from 85.62% to 126.42%, the coefficients of variation were 1.40~12.15%, and no SCFAs in the triglyceride form were potential degradation, and the precision ranging from 0.56% to 9.09%. Our easy, fast, and robust method successfully determined three FSCFAs in raw cow milk without derivatization. Some characteristic features of FSCFAs have been discovered in raw cow milk such as its higher percentages of C4:0 and C6:0. Our research has provided a very valuable method for the future quality and safety control of raw milk and nutritional studies.

Keywords: free short-chain fatty acids; gas chromatography-mass spectrometry; milk.

Figure 1

Total ion chromatogram of 10 FSCFAs by GC-MS. (a) Red line, total ion chromatogram of standards in water (b) Blue line, total ion chromatogram of raw cow’s milk. 1, C2:0; 2, C1:0; 3, C3:0; 4, iso C4:0; 5, C4:0; 6, iso C5:0; 7, anteiso C5:0; 8, C5:0; 9, iso C6:0; 10, C6:0; IS, anteiso C6:0.