In milk

C12H24O, CH3 [CH,]io COOH. Needles, m.p. 44 C, b.p. 225"C/I00mm. A fatty acid occurring as glycerides in milk, spermaceti, laurel oil, coconut oil, palm oil and other vegetable oils. The metal salts are widely used. 

CH3-[CHi]5.CH CH-[CH2]g-C02H. A white solid, m.p. 43-44°C, which is present in small quantities in animal fats and in milk. It is the only naturally occurring fatty acid with the trans configuration. 

This enzyme, sometimes also called the Schardinger enzyme, occurs in milk. It is capable of " oxidising" acetaldehyde to acetic acid, and also the purine bases xanthine and hypoxanthine to uric acid. The former reaction is not a simple direct oxidation and is assumed to take place as follows. The enzyme activates the hydrated form of the aldehyde so that it readily parts w ith two hydrogen atoms in the presence of a suitable hydrogen acceptor such as methylene-blue the latter being reduced to the colourless leuco-compound. The oxidation of certain substrates will not take place in the absence of such a hydrogen acceptor. 

In milk fat, cholesterol is associated with Hpoproteins in the milk fat globule. It is also a component of animal membranes and controls rigidity and permeabihty of the membranes. Cholesterol has interesting surface properties and can occur in Hquid crystalline forms. Plants contain sterols such as P-sitosterol [83-46-5] (4b) or stigmasterol [83-48-7] (4c). Their functions in plant metaboHsm are not yet well understood. Analysis of sterols has proven useful for detection of adulteration of edible fats (9). 

Table 2. Pharmaceuticals Produced in Milk or Blood of Transgenic Farm Animals...

Irradiation. Although no irradiation systems for pasteurization have been approved by the U.S. Food and Dmg Administration, milk can be pasteurized or sterilized by P tays produced by an electron accelerator or y-rays produced by cobalt-60. Bacteria and enzymes in milk are more resistant to irradiation than higher life forms. For pasteurization, 5000—7500 Gy (500,000—750,000 tad) are requited, and for inactivating enzymes at least 20,000 Gy (2,000,000 rad). Much lower radiation, about 70 Gy (7000 tad), causes an off-flavor. A combination of heat treatment and irradiation may prove to be the most acceptable approach. 

The leading states in milk production in decreasing order are Wisconsin, Minnesota, New York, California, and Pennsylvania. These states produce - 45% of the U.S. milk supply. Less than 5% of the total production is used on farms and the remainder is sold for commercial purposes. Whereas milk and cream were formerly shipped in 19-, 30-, or 38-L cans from the farm to the plant, in the 1990s most commercial production, particularly for fluid milk, is moved in bulk from the cows to refrigerated farm tanks to insulated bulk tmck tankers and to the manufacturing plant. The investment in equipment and the cost of hired labor are associated with large, capital-intensive production centers. 

The methylene blue and resazurin reduction methods indirectly measure bacterial densities in milk and cream in terms of the time interval required, after starting incubation, for a dye—milk mixture to change color (methylene blue, from blue to white resazurin, from blue through purple and mauve to... 

Sediment. The sediment test consists of filtering a definite quantity of milk through a white cotton sediment test disk and observing the character and amount of residue. Efficient use of single-service strainers on dairy farms has reduced the use of sediment tests on milk as deflvered to receiving plants. Although the presence of sediment in milk indicates unsanitary production or handling, its absence does not prove that sanitary conditions always existed. 

Nutritional Value of Milk Products. Milk is considered one of the principal sources of nutrition for humans. Some people are intolerant to one or more components of milk so must avoid the product or consume a treated product. One example is intolerance to lactose in milk. Fluid milk is available in which the lactose has been treated to make it more digestible. The consumption of milk fat, either in fluid milk or in products derived from milk, has decreased markedly in the 1990s. Whole milk sales decreased 12% between 1985 and 1988, whereas the sales of low fat milk increased 165%, and skimmed milk sales increased 48% (35). Nutritionists have recommended that fat consumed provide no more than 30 calories, and that consumption of calories be reduced. Generally, a daily diet of 2000—3000 cal/d is needed depending on many variables, such as gender, type of work, age, body responses, exercise, etc. Further, there is concern about cholesterol [57-88-5] and density of fat consumed. Complete information on the nutritive value of milk and milk products is provided on product labels (36) (see also Table 4). 

One technology uses bovine somatotropin (bST) produced by recombinant technology (38). Somatotropin [9002-72-6] is a growth hormone. The bST-supplemented cows provide an increase in milk output per cow or an increased feed efficiency. Recombinant bST, also known as recombinant bovine growth hormone (rBGH) is the synthetic analogue of a natural hormone that increases milk production in cows (39). The use of recombinant technology was approved by the FDA in 1993. The Commission of the European Community has recommended that the moratorium on commercial use of BGH be delayed until the year 2000. 

Xanthine oxidase, mol wt ca 275,000, present in milk, Hver, and intestinal mucosa (131), is required in the cataboHsm of nucleotides. The free bases guanine and hypoxanthine from the nucleotides are converted to uric acid and xanthine in the intermediate. Xanthine oxidase cataly2es oxidation of hypoxanthine to xanthine and xanthine to uric acid. In these processes and in the oxidations cataly2ed by aldehyde oxidase, molecular oxygen is reduced to H2O2 (133). Xanthine oxidase is also involved in iron metaboHsm. Release of iron from ferritin requires reduction of Fe " to Fe " and reduced xanthine oxidase participates in this conversion (133). 

Alkaline sizing agents are especially effective in milk-carton board and printing and writing grades that utilize calcium carbonate fillers. 

Lactose occurs in milk, mainly free, but to a small extent as a component of higher oligosaccharides. Cow and goat milks contain about 4.5% lactose human milk contains about 7.0%. Lactose is used as an excipient in tablets to provide bulk and rapid disintegration. It is also used in some food products where it contributes body with only about 40% the sweetness of sucrose and enhances colors and flavors. 

A useful property of the red seaweed extracts is their abiUty to form gels with water and milk. Kappa-carrageenan reacts with milk protein micelles, particularly kappa-casein micelles. The thickening effect of kappa-carrageenan in milk is 5—10 times greater than it is in water at a concentration of 0.025% in milk, a weak thixotropic gel is formed. 

Cellulose gum is the accepted common name for purified CMC. It may be used in milk products, dressings, jellies, symps, beverages, and other select products. It is permitted in food contact and packaging appHcations. 

In milk approximately 90% of the yellow color is because of the presence of -carotene, a fat-soluble carotenoid extracted from feed by cows. Summer milk is more yellow than winter milk because cows grazing on lush green pastures in the spring and summer months consume much higher levels of carotenoids than do cows ham-fed on hay and grain in the fall and winter. Various breeds of cows and even individual animals differ in the efficiency with which they extract -carotene from feed and in the degree to which they convert it into colorless vitamin A. The differences in the color of milk are more obvious in products made from milk fat, since here the yellow color is concentrated. Thus, unless standardized through the addition of colorant, products like butter and cheese show a wide variation in shade and in many cases appear unsatisfactory to the consumer. 

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