Milk and dairy products are major components of the human diet in Western countries, providing about 30% of dietary proteins and lipids. The current annual production of milk is 560 x 106 tonnes, of which 85, 11, 2 and 2% are bovine, buffalo, caprine and ovine, respectively. Although some raw milk is still consumed, the vast majority of milk is processed to at least some extent. Liquid milk is a major food item in all developed dairying countries, representing 30% of total milk production. The remainder is processed into one of several thousand products, making dairy products the most diverse and flexible group of food products. The flexibility of milk as a raw material resides in the chemical and physico-chemical properties of its constituents, many of which are unique. The principal constituents of milk can be modified by enzymatic, chemical and/or physical methods, permitting the production of new products. However, the concentrations and properties of milk constituents are variable and hence the processability of milk and the properties of dairy products are inconsistent, although much of this variability can be eliminated by employing modern technology, which exploits certain features of milk constituents. Today, most milk is processed in very large, highly mechanised and automated factories, where consistency in processing properties is essential. The resulting products are distributed through large wholesale and retail outlets, where consistency is, again, paramount. Finally, today's consumers expect consistency. The consistency expected by the processor, distributor and consumer can be achieved only if the properties of milk constituents are understood at the molecular level.
This communication will describe:
The chemical and physico-chemical properties of the principal constituents of milk, i.e. lactose, lipids, proteins and salts,
Variations in milk composition and in the properties of its constituents and the influence of dairy husbandry practices thereon,
Exploitation and significance of the chemical and physico-chemical properties of milk constituents in the production and properties of the principal groups of dairy foods, i.e. liquid milk products, cheese, butter, fermented milks, functional milk proteins and lactose.
Process modifications which may be used to overcome variations in the properties of milk constituents.