Aspects of the value and the limitations of milk protein as a food material.

It is generally accepted that milk and milk-based products constitute a valuable source of dietary protein. In the last few years considerable advances have been made in understanding the chemistry of milk proteins and in particular in the elucidation of their primary chemical structures so that it is now possible to examine this general conclusion concerning the worth of milk proteins, their value and limitations as foodstuffs in the light of an almost complete knowledge of their basic chemistry, a situation which, it may be noted in passing, exists for no other dietary protein. It is also feasible at least to begin to consider some of the implications of the utilization of milk proteins in non-traditional forms. Before proceeding to considerations of this kind, mention should be made of a major limitation to the further utilization of milk protein which ha! little direct connection with an evaluation of its nutritional worth. This concerns the acceptability of the form in which it is presented as a foodstuff. While this paper is concerned largely with the intrinsic properties of milk proteins and not with the production of new acceptable food forms, it should be remembered that the requirement of acceptability does exist and is indeed of overriding importance. In any assessment of the significance of milk protein as food consideration should be given to the amount of it consumed. In 1977 the milk protein produced for human consumption in this country amounted to slightly more than ++oooo tons which it may be calculated was sufficient to supply everyone in the country with about 25% of his total requirement for protein and accounted for about 65% of his animal protein intake. These figures are reasonably representative of the situation in Western Europe as a whole and in the United States. They are not universally applicable, since in India and Pakistan it has been estimated (Smith, 1970) that only about 8-10’30 of the protein intake originates in milk and elsewhere in Asia the figure is as low as I-2Y0. It is therefore the populations of the developed areas which rely on milk and milk-based products for protein and this they clearly do to a highly significant extent. Whatever their nutritional value may be there is no disputing the present commercial value of milk proteins. Any increase in their utilization in this type of market will have to take place in the form of food products of some sophistication. The questions may be asked, therefore, what are these proteins and how are they constituted? Milk protein is, with the possible exception of that derived from eggs, the only major dietary component which in Nature is produced specifically for the nourishment of young. In this functional respect it differs from other dietary animal proteins, vegetable proteins and unconventionally produced proteins. However it is only with man that these proteins are included in the diet throughout the entire life span, a point which will be mentioned again later.