Quantitation of Fatty Acids in Milk by Gas Chromatography

AN-BANG WU, WEN-HUI JUAN, HUI-WEN CHENG, CHIN-WEN LIN* AND CHAU-YANG CHEN

Graduate Institute of Pharmaceutical Sciences, Taipei Medical College, Taipei, Tawian 11O, R.O.C.
*Department of Animal Science, National Taiwan University, Taipei, Taiwan 106, R.O.C.

ABSTRACT

   This study investigated a reliable method for quantitation of fatty acids (FA) in milk by gas chromatography. Milk samples were treated with CHCl3/CH30H(2:1, v/v) to extract the fats, A transesterification reaction using fat plus AcCl/CH30H(1:10, v/v) as a reagent to prepare fatty acid methyl esters (FAME) was carried out at 60 ??? for 90 min. The recoveries of FAME derived from standard FA were 98.2±3.2% for the high concentration group; 97.5±4.1% for the low concentration group. When FAME derived from each milk sample was injected into a gas chromategraph, a total of 9 corresponding FA were separated and detected. The FA portion was found to constitute more than 85% of total fat. The content of C4-C12 short-chain FA was also found to be slightly different between the various brands of marketing pasteurized milk and milk powder (reconstituted milk). The content of various FA in long-life milk is essentially similar to pasteurized milk; in flavored milk obvious differences were found due to a variety of additives blended. Raw cow and goat milk contain more short-chain FA than human milk.

Key words : Fatty acids, FAME, milk, gas chromatography