High performance liquid chromatographic and gas chromatographic methods for lipid analysis

Abstract

Milk fat contains a number of diVerent lipids, but is predominately made up of triacylglycerols (TAG) (98%). The remaining lipids are diacylglycerols (DAG), monoacylglycerols (MAG), phospholipids, free fatty acids (FFA) and sterols. Milk fat contains over 250 diVerent fatty acids, but 15 of these make up approximately 95% of the total (Banks, 1991); the most important are shown in Table 19.1. The unique aspect of bovine, ovine and caprine milk fat, in comparison to vegetable oils, is the presence of high levels of short-chain volatile FFAs (SCFFA), which have a major impact on the Xavor/aroma of dairy products. Most cheeses are produced from either bovine, ovine or caprine milk and the diVerences of their FFA proWle are responsible for the characteristic Xavor of cheeses produced from such milks (Ha and Lindsay, 1991). Milk fat composition and esterase/lipase activity are also very important in the dairy industry in terms of Xavor, functionality and nutrition. Therefore, it is necessary to have accurate methods to enable quantiWcation of the key milk fat components and lipolytic activity. Methods speciWcally relating to the quantiWcation of esterase and lipase activity are described in detail in Chapter 11. However, methods incorporating chromatography forthe determination of lipolytic activity are described brieXy in this chapter together with a detailed account of chromatographic methods used to quantify individual FFAs, MAGs, DAGs and TAGs.