STERILIZED FOOD. Food that has been subjected to an agent (usually heat) capable of destroying the germs of fermentation or disease which may be present. The articles of diet which are not usually prepared by heat before ingestion, and which are capable of conveying disease, are fresh fruits and certain vegetable,, water, and milk. The two latter are particularly likely to act as carriers of pathogenic microorganisms. Water may be rendered sterile by boiling or by distilla tion. It is then best kept for use in sterile bot ties, sealed, and maintained at a low- tempera ture. fee may be the means of carrying disease, since ninny bacteria, although retarded in their growth, are not killed by freezing.
Milk is the food around which the question of sterilization centres, because it is the sole nourishment of infants and swarms with bac teria, particularly during the summer months. Although it comes sterile from the breast of the suckling mother or the udder of the healthy cow, milk is almost a perfect culture medium tor many varieties of bacteria, pathogenic and non pathogenic, which multiply with astonishing ra pidity. It may become contaminated during the interval between milking and ingestion in vari ous ways. Unclean materials may be introduced into the milk from the udders of the cow- or the milker's hands. Impure water used either as an adulterant or for cleansing containers may be a means of contamination. Typhoid fever has been proved to have been conveyed in this manner. Exposure to the air alone is sufficient to intro duce, through dust, many different forms of bac terial life.
The diseases most likely to be propagated through milk are typhoid fever, tuberculosis, scarlet fever, cholera, suppuration, and especially the summer diarrhoea of children. Besides pro clueing their specific diseases bacteria produce poisonous elements in milk which are capable of giving rise to ptomaine poisoning (q.v.) in indi viduals who drink it. It has been proposed at various times to prevent the development of germs in milk by the addition of non-poisonous antiseptic substances. But it has been found
that even with such drugs as salicylic acid and horic acid quantities too large to be wholesome must be employed. Formalin has been exten sively used of late years to keep milk sweet and aseptic. Cold is a very imperfect means of sterilization. A low temperature retards devel opment of bacteria for a time, but does not destroy them nor their spores.
Milk is usually sterilized by boiling or by exposure to superheated steam. Germs existing in this fluid can be absolutely destroyed only by heating to 212° F. or higher on two or three suc cessive occasions. The ordinary method of steril izing milk is to place it in sealed jars or bottles containing sufficient for one feeding, which are then subjected to the action of steam. It is then cooled rapidly, kept scaled from the air, and placed on ice until needed. Exposure to such high temperatures alters the character of milk very materially. both as to its digestibility and nutritive qualities, and it is therefore ren dered unfit for use except as a makeshift in very hot weather and in cases of infantile summer diarrhea. Prolonged use of sterilized milk for children dependent solely upon it for nutriment has resulted in symptoms of scurvy. To obviate this difficulty milk is often subjected to a process known as pasteurization. This consists in heat ing it to a temperature of 167° F. and maintain ing it at this point for a period of twenty min utes. Pasteurization has been shown to be suf ficient to kill the micro6rganisms most common ly found in milk, and in particular those giving rise to diarrhoea] diseases, which are very vul nerable to heat. Spores, however, are not de stroyed. The tubercle bacillus is more resistant, but, as has been said before, tuberculosis is not often conveyed by milk. Pasteurized milk will keep two or three days at ordinary temperatures or several days on ice, and its taste, digesti bility, and nutritive value are believed to be un changed. Sec ADULTERATION ;