B. - Philogenetic and Ecological Variation in the Fatty Acid Composition of Milks

Abstract

This chapter discusses philogenetic and ecological variation in the fatty acid composition of milks. Lipid is the most variable constituent of milk among species. Since the time of early studies on milk fatty acids, two things have been apparent. First, milk fatty acid composition differs markedly among species, both in the degree of unsaturation and in chain length. Second, milk fatty acids originate, to varying degrees, directly from the diet. In this chapter, factors which contribute to differing fatty acid patterns among taxonomic groups briefly reviewed and the analytical techniques necessary to accurately identify and quantify milk fatty acids. Diet may be a key factor affecting the fatty acid composition of most nonruminant species. Additionally, sampling and the methods of extraction, transesterification, and gas–liquid chromatography analysis will also greatly influence milk fatty acid data. Fatty acids may be susceptible to autooxidation during storage and, thus, it is preferable that samples be extracted or placed in lipid solvents as soon as possible after collection. The accurate analysis of milk fatty acid composition requires efficient separation of all components, correct identification of peaks, and accurate quantitation of peak areas. General patterns in milk fatty acid composition can be discerned along phylogenetic and ecological lines.