โ Scribed by J.S.H.
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I935, XVIII, 2I-3O) discusses the problem of food preservation in relation to public health. Milled cereals, sugar, and refined vegetable oils form considerably more than one-half of the daily caloric intake of man; yet these foods supply scarcely any of the mineral elements and vitamins, and leave much to be desired with respect to their protein constituents. These deficiencies are supplied and health is maintained by adequate consumption of dairy products, succulent vegetables and fruits. In order to make these perishable products generally available, some form of preservation is necessary, e.g., drying and dehydration, curing and smoking, fermentation and pickling, canning, refrigeration above or below freezing, and chemical preservatives. In sun-drylng and in dehydration by means of an air current of controlled temperature and humidity, the antiscorbutic vitamin, water-soluble C, is inadequately preserved; cured and smoked products are practically devoid of this vitamin. Fermentation and pickling apparently have no effect on vitamins A and B, and fermentation in the absence of oxygen does not injure vitamin C. Fruits and vegetables are usually canned with added sirup or brine, which must be eaten also in order to obtain the full nutritive value.
The process of canning does not affect vitamins A, D, G, and E, may produce a material loss of vitamin B (F) in leafy vegetables like spinach, but practically no loss of this vitamin in peas and other vege.tables. The destruction of vitamin C by canning is extremely slight in the fruits, and may be appreciable in vegetables, but practically always is less than the destruction produced by cooking similar market products in an open kettle by the usual kitchen methods. The heat of sterilization in canning increases the availaability of the food calcium for use by the animal body. While the vitamin C content of raw fruits and vegetables may deteriorate during transportation and holding under refrigeration above freezing, yet those species which normally are rich in that vitamin still retain an adequate quantity of it. Frozen vegetables and fruits are still in the experimental stage; they must be kept frozen until consumed ; and vegetables must be heated sufficiently to inactivate their native enzymes prior to freezing. As to chemical preservatives, they should be restricted to the utmost practicable extent, since several foods from different manufacturers but preserved with the same chemical compound may be eaten at the same time, and since preservatives may exert a cumulative effect after being ingested regularly during a long period of time.
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