The pasteurization of milk is recognized now by all groups of health workers as essential to community health. In many localities it is a legal requirement. The process of pasteurization consists of heating the entire quantity of milk to a temperature of 143° to 145° Fahrenheit, holding the temperature to this point for thirty minutes, and then rapidly cooling it to below 50° Fahrenheit. In order to maintain a low bacterial count in milk, it is important to maintain it at a low temperature from the time it is drawn until the time it is consumed.
Pasteurization is not intended to take the place of rigid sanitary control in the handling of milk ; it is merely an adjunct to cleanliness. Cleanliness in obtaining the milk, and careful handling of it, will do much toward making the milk more safe and desirable for human consumption. Nevertheless all raw milk is potentially dangerous, as cows may become diseased and their milk may be used for some time before the disease is recognized. Pasteurization, therefore, provides an important additional safeguard.
Safeguards Provided by Pasteurization
Pasteurization, if properly done, will destroy all disease-producing germs which may be present in the milk. It does not sterilize the milk, or destroy all the microorganisms in the milk, but it does get rid of the dangerous varieties. Bovine tuberculosis, undulant fever, scarlet fever, summer diarrhea, typhoid fever, dysentery, diphtheria, septic sore throat, and occasionally poliomyelitis, are diseases which have been most prominently associated with consumption of impure milk. Full protection from milk-borne diseases can be secured only when all milk is obtained from healthy cows, in a clean manner, properly cared for before consumption, and pasteurized as a final safeguard.
Certified milk which is not pasteurized may also be a potential source of infection. It is doubtful whether the strict regulations which are supposed to govern the production of certified milk are always adhered to in practice.'
The food constituents of milk are not changed by pasteurization, vitamin C excepted. The loss of this vitamin may be supplied by adding orange juice or tomato juice to the diet of infants, and for the adult, from a wider choice of foods.
A study was made of two groups of children. One group was fed pasteurized milk, and the other group was fed raw milk.2 No difference in the growth-producing qualities in the two types of milk could be observed. However, it was noted that children reared on heated milk had less diphtheria, scarlet fever, and tuberculosis. Pasteurization of milk protects human beings from all infections which may be milk borne.
The consumption of raw milk is one of the avenues by which man may ingest the Brucella organism which produces undulant fever. The organism is present in the milk and meat from infected cattle. The principal source of human infection, however, is the milk of infected cows. Present-day public-health facilities provide for frequent and careful inspection of dairy herds in an endeavor to eradicate this disease. Although much has been accomplished in this respect, it is still considered essential to pasteurize the milk in order to destroy organisms which may be present in the milk of unsuspected cattle. Undulant fever is important economically in the nation's health program, as it may be protracted over a Jong period of time, and usually incapacitates the patient during the acute phases of recurring attacks.
Tuberculosis, next to pneumonia, causes more deaths than any other specific infectious disease, and since it often leads to prolonged disability, it is a very important disease from the economic standpoint. The bovine type of bacillus tuberculosis is usually transmitted in the milk from tuberculous cattle. Children are particularly susceptible to infection from this form of the organism, while adults are rarely infected by it. About to per cent of all cases of tuberculosis in children under five years of age are due to bovine tubercle bacilli. The extensive practice of the pasteurization of milk has greatly reduced infection from the bovine form of the tubercle bacillus. The bovine type is usually associated with tuberculosis of the glands and bones in children. Pulmonary tuberculosis is usually caused by the human type of the bacillus.
Septic sore throat is a severe type of sore throat. It may be contracted through droplet infection, personal contact, or through raw milk. The milker who carries septic sore-throat germs may contaminate the milk directly, or may infect the udder of the cow through his unwashed hands. An abscess may form in the cow's udder and contaminate all milk produced for a given period of time. This milk may produce septic sore throat in all who consume it in the raw form.
"While it is possible to have milk so carefully handled that typhoid fever, dysentery, and other intestinal infections may be prevented, we insist that it is hardly possible to be sure that milk may not contain the germs of undulant fever and septic sore throat, and for this reason all milk should be pasteurized if it is to be drunk in an uncooked form." 3
D. L. B.
Burdon, Kenneth L., M.D., "A Textbook of Microbiology," Macmillan, New York, 1939, p. 283.
Chenoweth, Selkirk, and Bolt, "School Health Problems," Crofts, New York, 194o, p. 256.
Rice, Thurman B., M.D., ''A Textbook of Applied Microbiology and Pathology," Macmillan, New York, 1939, P. 204.
