Milk composition

In 1877, O. Hammarsten identified the three principal proteins in milk casein, lactalbumin and lactoglobulin. It is now known that bovine mUk is a complex liquid which contains many hundreds of different compounds in various states of dispersion. 

There is some variation in the average composition of milk taken from different animal species, but the same major classes of compound are always present (Table 12.11). Average physical properties are indicated in Table 12.12. Milk phosphoproteins are mostly present in the caseins but also to a smaller extent in the numerous enzymes (e.g. phosphatases, lipases, ribonucleases). 

Annual world production of cows milk has increased by over 50% in the past 40 years and now exceeds 400 x 10 tons per annum. The average yield per cow in Western Europe has more than doubled over the past century. 

Not only is cows mUk used directly for food, but much of it is converted to butter and cheese (see below). Milk is also the source of cream, casein, milk powder and other products. 

The proportions of milk production utilised in these products vary very much from one country to another. Practical non-food applications are discussed in Section 12.17. 

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Munro G L, Grieve P A and Kitchen B J (1984), Effects of mastitis on milk yield, milk composition, processing properties and yield and quality of milk products , Australian Journal of Dairy Technology, 39, 7-16. 

Politis I and Ng-Kwai-Hang K F (1988a), Effect of somatic cell counts and milk composition on cheese composition and coagulating properties of milk , Journal of Dairy Science, 71, 1711-1719. 

Politis I, Bizelis I, Tsiaras A and Baldi A (2004), Effect of vitamin E supplementation on neutrophil function, milk composition and plasmin activity in dairy cows in a commercial herd , Journal of Dairy Research, 71, 273-278. 

Butler, G., Nielsen, J.H., Slots, T., Sanderson, R.A., Eyre, M.D. and Leifert, C. (2007a), Effect of low input dairy management systems on milk composition - I. Fatty acid profiles . Journal of Dairy Science, submitted. 

Hamann, J. (2001), Relationships between somatic cell count and milk composition, in Proceedings of the IDF World Summit, Auckland/New Zealand. 

In view of the lack of satisfactory data, the evidence for substantial inter-individual differences in milk composition is limited, and satisfactory conclusions must await further study of both inter-individual and intra-individual differences. The available data suggest that interindividual differences may be substantial and important in the case of ascorbic acid, folic acid, and vitamin B12. 

Lactation Detectable amounts of the drug have been identified in the milk of mothers receiving medroxyprogesterone. In nursing mothers treated with medroxyprogesterone, milk composition, quality, and amount are not adversely affected. Infants exposed to medroxyprogesterone via breast milk have been studied for developmental and behavioral effects through puberty no adverse effects have been noted. 

The role of milk in nature is to nourish and to provide immunological protection to the mammalian young. The nutritional value of milk is high. It comes from various sources, such as human, goat, buffalo, sheep, and yak, and has been a food for humans since prehistoric times. It is also a very complex food with many thousands of different molecular species found in it. There are several factors that can affect milk composition. An approximate composition of milk can be given as follows ... 

Dostal, L.A., Weaver, R.P. Schwetz, B.A. (1987a) Transfer of di(2-ethylhexyl) phthalate throngh rat milk and effects on milk composition and the mammary gland. Toxicol, appl. Pharmacol., 91, 315-325... 

Jensen, R.G. (ed.) (1995) Handbook of Milk Composition, Academic Press, San Diego. 

Cowie, A.T. and Tindal, J.S. (1972) The Physiology of Lactation, Edward Arnold, London. Jensen, R.G. (ed.) (1995) Handbook of Milk Composition, Academic Press, San Diego. 

With the recent commercial availability of ultrafiltration, it has become possible to increase the concentration of casein, thus levelling out seasonal variations in milk composition and consequently in gel characteristics and... 

Milk composition expressed in terms of the contents of water (or total solids = 100 - water), fat, protein, lactose, and ash is called gross composition. Protein is often calculated as crude protein by multiplying total N by 6.38, but sometimes it is corrected to true protein 6.38 (TN -NPN) in a few studies, casein and whey protein have been calculated separately. Lactose should be expressed on an anyhydrous basis, but as pointed out previously, this has not always been done. For bovine milk the sum of fat, true protein, anhydrous lactose, and ash would be expected to fall about 0.2-0.3 percentage units short of the total solids contents because of the materials (citrate, NPN, and mis-... 

Inherited Variation. Genetically controlled variation in milk composition is evident from both interbreed and intrabreed studies. Some comparative studies of breed differences involve sampling from individual cows others use herd milk comparisons. Surveys with both kinds of sampling, summarized in Table 1.12, give a reasonably consistent picture of differences among breeds in the gross composition of milk. 

Seasonal Variation and the Influence of Temperature. In temperate latitudes, rather characteristic seasonal variations in milk composition are commonly observed. Both fat and solids-not-fat contents are lower in summer than in winter. In the survey by Overman (1945) of individual cows at the University of Illinois, monthly extremes for fat were 4.24 and 3.81% in January and August and for protein were 3.61 and 3.37% in January and July, respectively. Nickerson (1960) found significant seasonal differences in 18 components of bulk milks from six areas in California. Seasonal differences in fat and protein contents were similar to those observed in Illinois. Seasonal variations in milk composition could conceivably be caused by differences in temper-... 

Laben, R. C. 1963. Factors responsible for variation in milk composition. J. Dairy Sci. 46, 1293-1301. 

Kurtz, F. E. 1974. The lipids of milk Composition and properties. In Fundamentals of Dairy Chemistry. B.H. Webb, A. H. Johnson and J.A. Alford (Editors). AVI Publishing Co., Westport, Conn. pp. 125-210. 

Table 6.1. Milk Composition of Domesticated and Experimental Mammals.

There appears to be no effect of environmental conditions, stage of lactation, lactation number, or nutritional level of the animal on milk density, aside from the effects of these parameters on milk composition. 

Eley, R. M., Collier, R. J., Brass, M. L., Horn, H. H. van and Wilcox, C. J. 1978. Interrelationships between heat stress parameters and milk composition and yield in dairy cattle. J. Dairy Sci. 67(Suppl. 1), 147. 

World Health Organization (WHO) Task Force on Oral Contraceptives. Effects of hormonal contraceptives on breast milk composition and infant growth. Stud Fam Plann 1988 19(6 Pt l) 361-9. 

TABLE 1.1 Milk composition and percent contribution to the daily dietary reference intake of some nutrients in 0.5 I whole milk and their main health effects... 

Petit, H.V. 2002. Digestion, milk production, milk composition, and blood composition of dairy cows fed whole flaxseed. J. Dairy Sci. 85, 1482-1490. 

Petit, H.V., Dewhurst, R.J., Proulx, J.G., Khalid, M., Haresign, W., and Twagiramungu, H. 2001. Milk production, milk composition, and reproductive function of dairy cows fed different fats. Can. J. Anim. Sci. 81, 263-271. 

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