HOME PRESERVING AND CANNING Primitive man early discovered that dried foods are more easily transported from place to place and have better keeping qualities than when fresh; and that the salt of sea-water and the smoke of the camp-fire have further preservative influence. Generations ago housekeepers found out that dense substances would keep longer than those that were watery, so they packed cooked meat in its own fat, and made preserves rich with honey, or sugar, and savory with spices. The air-tight tin can and glass jar, sterilization and cold-storage, have done much in solving one of the most complicated problems of modern civilization, but all the possibilities have not yet been fully investigated.
The efficiency of all ancient processes of food preservation is explained by the later knowledge of the habits of microorganisms. Failure in can ning and preserving is usually due to lack of knowl edge of these subjects. The essential points are these : Bacteria do not thrive in substances con taining less than 25 per cent of water, such as preserves or jellies thick with sugar ; they are destroyed by heat ; they do not flourish in the presence of acids, alcohol, salt, spices, or the sub stances deposited by smoke. Foods containing little nitrogenous matter are less liable to the attack of bacteria ; therefore bacteria are less troublesome in the preservation of fruits than of fish and meats.
Molds and ferments or yeasts are the common enemies of preserves, jellies and the like. (Figs. 237, 238.) These growths usually are killed in a few minutes at the temperature of boiling water, Fahr. A lower degree of heat continued for a longer period — half an hour or more— is often as effectual and less detrimental to the flavor and texture of the fruit. The spores, or undeveloped organ isms, resist heat that would be fatal to those fully grown, so in lab oratories or canning factories steam, under pressure, is used to secure a temperature much higher than 212° Fahr., and thus wholly to sterilize the food. Here the housekeeper cannot compete with the factories, and must practice intermittent sterilization as was done long before the existence and habits of these 'microorganisms were known. The material to be sterilized is heated to the boiling point and kept there for half an hour on three or more successive days. Between these scaldings it is left at an ordinary tempera ture, that the spores may germinate and become active organisms. These are then killed by the next
heating, and after the final boiling the exclusion of air prevents the entrance of others.
It is essential that everything exposed to the air, filled as it is with " germs," should be sterilized before it comes in direct or indirect contact with the food to be preserved. Fruits are constantly exposed while growing, or in market, and their skins harbor vast numbers of microorganisms; hence they must be thoroughly washed. The removal of skins from peaches, tomatoes and like products by scalding has more than one beneficial effect. If pared fruit must stand before cooking, it should be dropped into water with lemon juice or vinegar in it, to prevent the discoloration probably due to the action of a ferment.
The room in which such work is to be done should be as clean as the operating-room of a hospital. All possible dust should be removed with a damp cloth. Every utensil should be boiled ten minutes or more, and kept in the water till it is to be used. The jars had better be filled over the stove where the air is sterilized by heat and steam, rather than by an open window, where dust-laden air can come in contact with them.
We have become so accustomed to certain flavors in pickles and preserves that we forget that they are used primarily for their preservative effects and that they may retard digestion as much as the newer preservatives, the use of which is so justly condemned.
In her "Frugal Housewife," published in IS30, Mrs. Lydia Maria Child says, "Economical people will seldom use preserves, except for sickness. They are unhealthy, expensive and useless to those who are well." To a modern student of dietetics it seems singular to give the sick anything unsuitable for the well, but certain pharmaceutical values were ascribed to " conserves" in the early days of their manufacture. Thomas Tusser, who died in 1550, author of "Five Hundreth Pointes of Good Housekeeping" has this to say in their favor : "Good housewife provides, ere a sickness do come, Of sundry good things in her home to have some ; Conserves of barbary, quinces and such, With sirops, that easeth the sickly so much." The thorough sterilization of such articles is in their favor, and the value of sugar as a food is now recognized.