A novel procedure for routine milk fat extraction based on dichloromethane

A novel method for the extraction of milk fat using dichloromethane (CH2Cl2)–ethanol was compared to the Rose-Gottlieb (IDF Standard 1D, 1996) extraction procedure. The new extraction method consisted of a fast (approximately 30 min for 20 samples) and simple procedure involving direct mixing of raw cow milk samples with a dichloromethane–ethanol solution (2/1, v/v). The fatty acid (FA) proportions and FA groups as obtained through gas chromatography (GC) analysis of fatty acids methyl esters (FAME) showed that there was no relevant difference of the extraction procedure on the individual fatty acid proportions (%FAME). None of the main milk FA groups, such as the sum of monounsaturated (MUFA), polyunsaturated (PUFA), odd- and branched-chain (OBCFA) and saturated (SFA) FA showed any significant difference between the Rose-Gottlieb and dichloromethane methods. Total milk fat as gravimetrically determined did not differ between the two extraction procedures, although numerically a slightly lower amount (2.8% less) was extracted with the new procedure (P = 0.919). In general, the new dichloromethane extraction method was found to be much faster, less hazardous to health (shorter exposure time) and more cost efficient (lower cost based on solvent price and amount used); overall, it is much more suitable for gas chromatography analysis of milk fatty acids than the older, more widely used Rose-Gottlieb extraction method.