In the preservation of fruit the most essential thing is to keep the fruit, as well as the utensils used, sterile. This should be observed from the earliest stage in the preparation of the fruit to the final sealing and storing. To sterilize a substance or thing is to destroy all life and source of life in it. It is necessary to do more than exclude the air, for investigations of scientists, particularly Pasteur, have shown that it is not the oxygen of the air which causes fermentation, but bacteria and other microscopic organisms. Yeast and nearly all kinds of bacteria require oxygen, but certain species grow equally well without it, so that the exclusion of air is no protection if one of these bacteria is sealed in the can.
Every housekeeper is familiar with molds which under favorable conditions grow on any kind of organic matter. Molds develop from spores which are always floating about in the air. When a spore falls upon a substance containing moisture and suitable food, it sends out a thread which branches and works over the entire surface; in a short time spores are produced and the work of reproduction goes on. Ordinarily molds do not cause fermentation and are not as injurious as bacteria and yeasts. They do not as readily penetrate jellies and the liquids of canned fruits, and generally settle in a thick film on top, but if given time they will finally work their way through the entire contents of the jar, and a musty taste is the result.
Since air and water as well as the fruit contain bacteria and may take up mold spores, all utensils for preserving are liable to be contaminated. For this reason everything that is used should be absolutely clean and properly sterilized. In order to accomplish this, place the clean utensils in a pan of cold water, heat to the boiling point, and let them boil at least ten minutes.
The would-be economical housekeeper who buys cheap, inferior fruit under the impression that it is good enough for preserving, makes a grave mistake. While small fruit, provided it is fresh and free from contamination of mold or insects, can be used for jams and jellies, the best developed fruit of any variety is preferable for canning. For any kind of preserve that requires the juices to become jellied, the fruit should be rather under than over ripe; in fact, some unripe fruits are most excellent for tart jellies, as gooseberries, grapes, and apples.
The initial expense of buying suitable jars and glasses for preserving is quite an item, and to distribute expenditure along these lines evenly, it is wise to buy a few jars at a time early in the year, and add to them gradually when special sales are on. In this way when the time comes for buying the fruit and sugar, the glasses will be ready. The practice of using jelly and fruit glasses in the kitchen during the year is wasteful, for many will be broken before preserving time comes round. The best way is to wash each glass as soon as it is empty, wrap it in clean paper, and set it on an unused pantry shelf or pack in a box. The addition of a few glasses each fruit season will then insure a good supply from year to year. The covers, too, should be washed, well dried, and wrapped with the glasses. Another economy consists in saving all glasses and jars that come into the house during the year, such as those which contain olives, peanut butter, and various condiments. Even should some of these glasses be small, they will do for the finer jellies, bar-le-duc, or fancy conserves. If the family is small, such a glass serves for one meal. They are also very desirable for remembering a sick friend, or some old lady to whom a little glass of homemade preserves is a great treat.