Pasteurization

“ The pasteurization of milk can be done in such a manner as to impart to it good keeping qualities and to insure its freedom from pathogenic bacteria, and yet not impair its physical and chemical properties, but much of the so-called pasteurized milk placed on the market is not treated in accordance with proper hygienic methods. ”

“ It maintains that pasteurization kills benign germs essential to the life of milk, and that after benign germs are killed, pasteurized milk, if exposed to infection, is more dangerous than raw milk, for the rapid growth of harmful germs is no longer contested by benign germs fighting for supremacy. ”

“ The receptacles in which the milk is allowed to stand, the vessels in which it is measured, and the person who handles it must be absolutely clean, and the nurse must keep in mind the fact that pasteurization does not completely destroy the bacterial growth in milk, that it merely diminishes it, and she must see that the milk which has undergone the pasteurizing process is kept cold, otherwise the microörganisms which are present, even if to a less extent than in raw milk, will undoubtedly multiply. ”

“ Finally, because raw milk even from clean dairies may contain germs of typhoid, scarlet fever, or tuberculosis, pasteurization is demanded to kill every germ. There are advocates of pasteurization that deprecate the practice and deny that raw milk is necessarily dangerous; they favor it for the time being until farms and shops have acquired habits of cleanliness. Likewise many would prefer private pasteurization or laws compelling pasteurization of all milk offered for sale ”

“ While pasteurizing can be performed on a small scale by the individual, the process can also be adapted to the commercial treatment of large quantities of milk. The apparatus necessary for this purpose is not nearly so expensive as that used in sterilizing, a factor of importance when other advantages are considered. In this country pasteurization has made considerable headway, not only in supplying a milk that is designed to serve as children's food, but even for general purposes. ”

“ Efficient pasteurization can be more readily accomplished in a closed receptacle such as is most frequently used in the commercial treatment of milk, than where the milk is heated in open bottles or open vats. ”

“ Sometimes a second pasteurization is practiced, the milk being purposely allowed to stand at 70° to 80° for 12 to 24 hours after the first pasteurization for the germs which escaped destruction to develop into full-grown bacteria. They are then killed by the second heating before the milk is finally chilled to stop any further growth. ”

“ Practically, then, these bacteria that resist the moderate heat of Pasteurization are of no serious importance in connection with the healthfulness of milk. Pasteurized milk has been deprived of all its strictly pathogenic bacteria, and the germs still left will commonly have no opportunity to grow very much before the milk is consumed. It is therefore the confident belief of many that Pasteurization is actually a safer method of treating milk than sterilization. ”

“ But the explanation is essentially that heat is cheaper than cold. Because of the subsequent Pasteurization this company does not feel it necessary to demand that the milk should reach them in as cool a condition as is required by the other companies. While their business rivals insist that they shall receive milk not warmer than 4° C., this Pasteurizing company receives it as warm as 10° C., and this saving in the cooling largely pays for the Pasteurization. The mechanical bottling enables them to employ a cheaper grade of help than is necessary when the milk is peddled in carts. ”

“ Purging magistrates' courts of their leniency toward dealers in impure, dangerous milk is better than purging milk of germs. Boiling milk receptacles will save more babies than boiling milk. Teaching mothers about the care of babies will bring better results than giving them a false sense of safety, because only one of many dangers has been removed by pasteurization. Educating consumers to demand [265] clean milk and to support aggressive work by health departments leaves fewer evils unchecked than covering up uncleanliness by pasteurization. ”

“ The temperature, however, is not sufficient to destroy all bacteria, and for this reason is looked upon with disfavor by those who feel that what is needed is an absolute destruction of all bacteria. The Germans, who like to do things thoroughly, do not take readily to Pasteurization, and there are others besides Germans who insist that this treatment does not make the milk safe. But if one is looking for practical possibilities rather than theoretical success, there is perhaps at present more to be said in favor of Pasteurization than sterilization. ”

“ It is recognized that some of our dangerous epidemics are transmitted from house to house by means of milk, which furnishes a good medium for their growth. If pasteurization is sufficient to kill the disease-germs, and if at the same time it delays the souring from twenty to forty hours, and if the milk thus treated retains the taste of fresh milk, and permits the cream to rise on it in the natural way, it is plain that it is a process highly to be recommended. ”

“ When a child must subsist upon boiled milk for a long period, he should be given the juice of an orange each day. Children are not usually strong and normal when fed upon milk of this character for indefinite periods. All living bacteria (except the spores or eggs) may be destroyed by boiling milk for one or two minutes.
PASTEURIZATION
When baby is to use the milk within twenty-four hours, "pasteurization" is better than boiling as a method of destroying microbes. ”

“ American experiment stations established the temperatures and the time of exposure necessary for best results, and no one has done more for the introduction of pasteurization than the New York philanthropist, Nathan Straus, who has established pasteurizing plants and milk distributing stations in many localities, thereby contributing so largely to the lowering of the death rate among the children of the poor. ”

“ Pasteurization of market milk..The spread of the pasteurizing process as applied to market milk has been rapid. This has been due to the recognition of the fact that only by this process can a safe milk i.e., one free from pathogenic bacteria, be obtained. As previously mentioned a small proportion of all human beings that have suffered from typhoid fever become bacillus carriers. It is impossible to examine all persons who may be concerned in the handling of milk in order to ascertain whether they belong to this dangerous and unfortunate class of people. ”

“ Notwithstanding the care exercised by boards of health, it is impossible at any time to be sure of the purity of the milk supply; hence the need is urgent that it be made safe by Pasteurization, which is, in reality, simply subjecting the milk to the lower temperature of 150° to 160° F., instead of 212° F., as was formerly done, and is called thus in deference to Pasteur, who long ago found that the ordinary germs of fermentation and bacteria would be destroyed by this temperature, and recommended such, a process for their destruction and for the preservation of foods. ”

“ The truth is probably that strong pasteurization at a temperature above 157° and holding the heated milk unnecessarily long at such high temperature do change the properties of the milk so as to make it harder to digest, but that the main difficulty is in the change of diet from raw to pasteurized milk or vice versa. Let the child get used to the change by making it gradual, diminishing the amount of one and increasing the amount of the other from day to day in a week, until the change is completed, and there will usually be little if any trouble. ”

“ It is only necessary to bear in mind the great part played by sterilization in the laboratory, and pasteurization on the fermentation industries and in the preservation of food materials. Pasteur first formulated the idea that bacteria are responsible for the diseases of fermented liquids; the corollary of this was a demand for pure yeast. He recommended that yeast should be purified by cultivating it in a solution of sugar containing tartaric acid, or, in wort containing a small quantity of phenol. ”

“ In the making of butter there are a number of processes that the maker can use when he finds himself obliged to utilize poor milk. The milk can be pasteurized and the harmful bacteria thus destroyed; desirable kinds can then be added in the form of a pure-culture starter. Pasteurization also drives off some of the volatile by-products of the first acid fermentation. By the use of these means, the maker can prepare a very good product from poor material. ”

“ Milk also furnishes a splendid medium for bacterial growth, and if left exposed to the air, put into unclean receptacles, or kept in a warm place, will immediately become more or less contaminated, after which it is unwise to use it. Sterilization and pasteurization will in a measure overcome the bacterial contamination, but milk purchased from a dairy which is not clean or milked under unsanitary conditions will remain dirty, hence unfit for [Pg 84] human consumption. ”

“ It is important to select the best possible milk for pasteurizing, for if the milk has not been milked under clean conditions, it is likely to be rich in the spore-bearing bacteria. Old milk, or milk that has not been kept at a low temperature, is much richer in germ-life than perfectly fresh or thoroughly chilled milk.
The true standard for selecting milk for pasteurization should be to determine the actual number of bacterial spores that are able to resist the heating process, but this method is impracticable under commercial conditions. ”

“ If, however, milk is produced with the refinements outlined above, pasteurization becomes superfluous. Many dairies produce milk with less than 10,000 bacteria per cubic centimeter, some as low as 1,000. By extreme care and intelligent supervision such milk is not much more expensive than ordinary market milk and the outcome of the war waged against poor milk supplies will probably bring such milk within the reach of every one. ”

“ It would appear, then, that this method of Pasteurization by a central company offers the most hopeful solution of this feature of the problem which is growing with the growth of cities. The milk companies could probably arrange, without great expense, such a plan of Pasteurizing large amounts of milk. This only emphasizes the conclusion, already reached, that the most hopeful method of dealing with the problem in our cities is through properly organized companies that can handle milk on a large scale, and will do it conscientiously, and not wholly from the standpoint of money-making. ”

“ The cost of producing certified milk places it beyond the reach of the great majority of consumers. But such care and cleanliness as can be observed by the farmer and the milkman without extra expense should 38be insisted upon, and milk which nevertheless contains a large number of bacteria can be made safe by pasteurization. ”

“ The tendency, moreover, of pasteurization is to put a premium upon dirt, which gains entrance to milk chiefly through careless methods in milking and caring for milk after it leaves the cow which carries with it a great multitude of bacteria and is the most important source of bacteria contamination of milk. ”

“ Destruction of disease bacteria. While milk should be pasteurized so as to destroy all active, multiplying bacteria, it is particularly important to destroy any organisms of a disease nature that might find their way into the same. Fortunately most of the bacteria capable of thriving in milk before or after it is drawn from the animal are not able to form spores and hence succumb to proper pasteurization. Such is the case with the diphtheria, cholera and typhoid organisms. ”

“ Babies fed on home-pasteurized milk did not develop manifest scurvy. The difference in the two processes consists mainly in the amount of handling during the process of heating and the subsequent aging which the milk undergoes. An interval of forty-eight hours usually elapses between commercial pasteurization and the delivery of the milk to the consumer. In New York city most of the better-grade milk is pasteurized at the farm, so that it is subjected to a longer period of aging than the poorer grade, which is not pasteurized until it reaches the city. ”

“ The sterilization and Pasteurization of milk have doubtlessly saved the lives of many children, but every intelligent physician knows that even the most careful mother or nurse often fails to secure a milk that is altogether safe. ”

“ Before use, warm the milk—in the bottles—to blood heat. Never pour it into another vessel.
8. The milk must not be used for children later than twenty-four hours after pasteurization. Never use remnants.
30In a Continuous Pasteurizer a constant stream of milk is fed into the machine, heated by flowing over a metal surface with steam or hot water on the opposite side, and cooled by running over a cooler furnished with a stream of cold water or ice water. ”

“ In the treatment of market milk, care should be taken to use only that in which the acidity has not materially increased. A fair standard is about 0.2 per cent. High acid milk usually means old milk or dirty milk, either of which is very likely to contain many more spore-bearing bacteria than clean, fresh milk. The greater the number of spores, the more rapidly will the pasteurized milk spoil. If it is possible to exercise any selection of milk prior to pasteurization, the rapid test for determination of acidity will prove of great advantage. ”