Composition of Milk and Evaluation of Quality

Milk is a complex biological fluid comprising of numerous similar and dissimilar molecules. These molecules are present in several states of dispersion and interact with each other in several ways. Any change in these interactions leads to change in properties of milk. The knowledge of all the components in milk in terms of their chemistry is therefore essential for understanding properties of fresh milk and effect of storage and processing on chemical quality of milk. Milk contains major and minor components and these components determine its nutritive quality. Since, milk is used as human food; there is natural interest in its chemical composition for several purposes.

Milk is composed of water, carbohydrate (lactose), fat, protein, minerals and vitamins. While each component can be discussed separately, it is important to remember that milk is secreted as a complex mixture of these components. The properties and importance of milk are greater and more complex than the sum of its individual component parts. The basic components of milk from different species are shown in Table 1.  Significant variations from the average values can be observed and these are influenced by the breed and species of the milk animals, feeding, maintenance, lactation period as well as health and age of the animals.