Under this head we will discuss the methods of preparing perishable foods so they may be preserved for an indefinite length of time. Fruits which are in season only a few weeks during the year may, if properly preserved, be served at any time during the whole twelve months. The same is true of all the vegetables and meats, milk, butter, and even eggs. The essential condition for processes of decay to proceed are warmth, moisture, access of air. Reduction of temperature to near the freezing point stops all bacterial action. Removal of moisture also stops it; shutting out the air from substances already sterile will preserve them from decay. One of the simplest methods of food preservation is cold storage. This method carried on on such a large scale in the great population centers enables dealers to keep meats, butter, eggs, and certain fruits for many weeks, perhaps even months. While there is a certain amount of deterioration continually going on, which would eventually make the preserved food inedible and unwholesome, still the process, while it has limitations, is a most valuable one, and results in the preservation and use of millions of dollars' worth of food supplies which would otherwise have to be thrown away after having glutted the season's market. This cold-storage process facilitates a distribution of food products usually marketed in a season of limited length over a very much longer period of time, thus in a large measure equalizing the price of the food through the year. Cold storage is a process for the large dealer. Let us turn our attention now to processes that may be utilized in the home and in institutions, though they are also utilized on a large scale by producers and dealers. One of the simplest processes for food preservation is drying it. As revealed in the analytical tables given above, a very considerable proportion of all perishable foods is water. In fact, in some of these foods water makes as much as ninety per cent of the weight. If we can remove all or nearly all of the water, we will not only inhibit bacterial action, thus preserving the food for an indefinite time, but will also reduce the food greatly in volume and in weight, thus facilitating its easy storage and transportation.

In the earliest times fruits were dried. Those fruits rich in sugar are especially adapted to this process, and it is probable that the drying and storing of figs and dates has been followed for unnumbered ages in the Orient. Meats have been cured by drying by most primitive peoples. The only requisite to be observed in the drying of meat is to keep the flies away. This is accomplished by some Indians through tying strips of the meat to branches of trees twenty or thirty feet above the ground, thus out of the fly zone. In the drying of the meat it is customary to add some salt, this acting as a further preserving agent. Another modification frequently observed for meats, including fish, is smoking. The meat to be preserved is smoked over a smoldering fire. The heat of the fire dries the meat; the smoke flavors it. This smoked meat and fish possesses a flavor very pleasing to most people.

The drying of fruits and vegetables by removing so much water from the pulp of the fruit or vegetable makes it not only light and dry, but hard and unpalatable. In the preparation of such dried fruits and vegetables for the table it is necessary to introduce the water back into the tissues. This is best accomplished through soaking in cold water. Time should be given for the tissue gradually to take up the water and swell out to nearly its original size. After being thus soaked, the fruit or vegetable may be very quickly prepared for the table.

Treatment of perishable foods with various chemicals is another favorite method of preserving them. So far as possible, the substance used as the preservative should be a substance which is in itself either food or a recognized condiment. As an example of the first, sugar may be mentioned. Sugar solutions that are very heavy and syrupy do not readily ferment. Mold may collect upon the surface, but ordinary sugar fermentation cannot take place. Thus sugar came to be used very widely as a food preservative, especially for fruits. Jellies, jams, and preserves are examples of such products. When a small amount of sugar only is added, it is necessary also, in order to insure preservation against fermentation, to exclude the air from the preparation. This method is very widely used in modern times in the preservation of fruits and vegetables in tin and glass cans. In many of these canning processes only a very slight amount of sugar is added, perhaps in the case of some vegetables none at all. In this case the preservation is due simply to the exclusion of air from the sterile products, sterilization being an absolutely essential preliminary.

Another preservative widely used is common salt. While salt is a condiment widely used, there is a limit to the amount of it that is wholesome. Its use as a food preservative far exceeds the amount that is palatable in the food in question. It, therefore, becomes necessary in the preparation of salted meats and fish to remove a large part of the added salts as a preliminary, thus the method of removing this excess of salt is by soaking in cold water for a time. In the case of a salt fish, it may well be soaked ten or twelve hours, as overnight.

Another condiment widely used in the preservation of food and vegetables is vinegar. Vinegar as used in the kitchen is four per cent acetic acid, plus a minute proportion of extractives that give it flavor. When a vegetable or fruit is impregnated with vinegar, it may be kept for months without decaying or fermenting. In this way many varieties of pickles are prepared - both fruit and vegetable pickles. The addition of various spices in varying amounts and combinations, with or without sugar, in varying proportions, makes up an interminable list of fruit and vegetable pickles.

Antiseptic preservatives, such as salicylic acid, formaldehyd, boric acid, alum, sulphur, sulphur vapor, and benzoate of soda, have been used in attempts to preserve food materials for the market. Their use is most frequent in milk of the city markets and in canned meats and fruits.

While minute quantities of certain of these things, particularly of benzoate of soda, borax, boric acid, and sulphur, produce no disturbance of the normal functions, even when taken daily for months, still, it is very greatly doubted whether their use in any proportion should be permitted in the supplies of food presented in the markets. The contention made by Dr. Wiley, of the United States Department of Agriculture, that "the use of any of these preservatives, if permitted at all, is likely to be used by unscrupulous producers to make marketable food products that without such antiseptic agents could not be preserved," while very conservative, marks perhaps, in the long run, the wisest course to pursue. This thing is true, that food products in which decay has not already started may be easily preserved by methods given above, from beginning decay, and the use of these chemical antiseptics should not be necessary. On the other hand, it has also been conclusively demonstrated by a commission of Government experts that the use of a small amount of benzoate of soda may serve a valuable purpose in the preservation of fruit and vegetables by furnishing an added and final security against incipient fermentation, while, at the same time, this substance in particular is not deleterious when taken in the small quantities incident to its use in these materials as a food preservative.