english

The milk of the domestic cow is an important protein source for man and particularly children. Milk is an aqueous solution of protein, lactose, minerals, and certain vitamins (A, C, D) the carries emulsified fat globules and colloidally dispersed casein micelles consisting of protein together with phosphate, citrate, and calcium. Besides its use as a food for direct consumption and bakery products, it is employed for making cheese, butter, casein, ice-cream, lactic acid, and lactose chemicals.

Milk has been called "the most nearly perfect food" because it is an outstanding source of these nutrients. But milk is not "tha perfect food" because it lacks enough iron and does not provide all vitamins. Carbohydrates are major source of energy for the body. The carbohydrate content of milk is mainly lactose, or milk sugar. In addition to providing energy, lactose helps the body absorb the minerals calcium and phosphorous in milk. Because cow’s milk contains proportionally more casein and lactose than human milk, it is usually recommended that specially adapted formulas be given to babies under nine month of age.

Fats, like carbohydrates, provide energy. Fat gives milk its rich flavour.

Milk is an excellent source of calcium. Calcium and phosphorous occur in milk in the right amount for the intestinal absorption and for the normal skeletal development.

Vitamins are essential for growth, maintaining body tissue, and the prevention of such diseases as beriberi and rickets.

Milk conteins the fat soluble vitamin A and carotene, its precursor, but the amount varies considerably according to the food of the lacting animal. Since green food is the main source of thia vitamin in the diet of cows, summers milk usually contains more than whinter milk. The fat-soluble vitamin D, the water-soluble B complex and vitamin C are also persent.

Milk protein is of high nutritional value, since it contains all the essential amino acids which man needs for building blood and tissue but cannot synthesize in quantities sufficient for his needs. In the stomach of the young it is precipitated as a soft curd in which the globules of fat are enclosed. Digestion can thus proceed smootly whitout the disturbance which the ingestion of fatty foods often causes.

If the fat is removed from whole milk, we call the product skimmed or skim milk. If the casein is then precipitated out by reducing the pH to 4.6 (at 20�C), the residue is know as the whey or serum. Much fo the production of milk is used in foodstuff manufactured in the form of dried milk, or milk powder, which is made largerly from skin milk.

Cooling milk to temperatures slightly above the freezing point markedly reduces the rate of multiplication of the bacteria and the amount of chemical change they produce and consequently, increases the length of time milk continues to be palatable.

TIPES OF MILK

Raw milk, or milk that has not been heated contains microorganism that eventually cause it to become sour to the taste and curdle. During the milking, handling and trasportation, it may become contaminated with organisms that cause disease in man.

	Pasturized milk is milk that has been heated to about 72�C for 15 seconds. Pasteurization kills all disease- prodicing organisms and a large proportion of those causing souring. If milk is pasteurized in closed containers and kept from contamination there after, it will continue to be a safe milk. It should be kept refrigerated to minimize the growth of remaining harmless bacteria which can produce unpleasant flavours.
	Homogenized milk is milk that has been treated by sonic vibration to break up the fat globules and distribute them evenly in the liquid. The nutritional value of homogenized milk is similar to that of pasturized milk
	The ultra-high temperature (UHT) treatment of milk at a temperature of about 130�C for one or two seconds is use to product UHT or long-life milk which is packed aseptically into special containers to protect it form light and from oxigen.
	Sterilized milk is prepared from homogenized milk which is bottled and then heated to about 140�C for 20-60 minutes.
	Evaporated milk is prepared by concetration of milk at low temperature. Then the milk is sterilized in cans at 115�C for 15 minutes.
	Sweetened condensed milk, formerly used widely where refrigeration was not available, is prepared similarly, but the processing temperature is lower since it conteins added sucrose.

TESTING

Laboratory technicians check the odour, taste, and appearance of the milk. They also measure the fat content, the number of bacteria, the amount of milk solids, and the acidity. Technicians further test the milk during and after processing. All this testing helps ensure the quality and purity of the milk.

Odour, taste, and appearance are tasted by smelling, testing, and observing the milk upon arrival and during and after processing.

	The methilene blue test is a simple method of indicating the approximate number of bacteria in milk. This blue dye is sdded to a small quantity of milk which is heatede and examined every hour. The longer it takes the blue colour to disappear, the fewer bacteria are present.
	The acidity test shows the amount of acid in milk. Milk that conteins too much acid testes sour and cannot be properly processed. An alkaline solution is added to a sample of milk, and a colour indicator, such as Phenophthalein, shows the acid contein.
	The standard plate count is Way of counting bacteria in milk. Milk diluted with sterile distilled water is placed in a germ-free dish and mixed with a solution called "sterile agar medium". After you count the bacteria.