Chapter One

T. Huppertz, A.L. Kelly and P.F. Fox

1.1 Introduction

Milk is the fluid secreted by the female of all mammalian species, primarily to meet the complete nutritional requirements for the neonate, such as energy, essential amino acids and fatty acids, vitamins, minerals and water. Milk is an effective and balanced source of lipids, proteins (caseins and whey proteins), carbohydrates (mainly lactose), minerals (e.g. calcium and phosphate), enzymes, vitamins and trace elements.

The primary role of the lipids in milk is to provide a source of energy to the neonate. From a practical viewpoint, milk lipids derive a high level of importance from the distinctive nutritional, textural and sensory properties they confer on a wide variety of dairy products such as liquid milk, cheese, ice cream, butter and yoghurt. Milk lipids were long regarded as the most economically valuable constituent of milk and, as a result, the milk price paid to farmers was for many years determined primarily by the concentration of lipids in the milk; only more recently has the concentration of milk proteins attained an equal, or even higher, weighting factor in the determination of milk price. In this chapter, the aim is to provide an overview of the composition, origin and properties of milk lipids. The focus is primarily on the lipids of cow's milk, but comparisons with milk from other major dairy species are made where appropriate.

1.2 Composition of milk lipids

Lipids are esters of fatty acids and related compounds that are soluble in apolar organic solvents and (nearly) insolu