Canning is the process of putting up fruits or vegetables, either with or without sugar, in air-tight jars; preserving is the preparation of fruit with sufficient sugar to keep without fermentation whether the jars are air-tight or not. For home use, canning is the best and most desirable method of preparing fruits and vegetables.
Not only is it the easiest method, but it is the most economical and the most healthful. The fruit remains soft and juicy, which renders it more digestible.
There are several methods of canning, and the secret of success in each is absolute sterilization.
The best and easiest methods of canning are cooking the fruits in jars in an oven; cooking the fruits in a fireless cooker; cooking the fruits in jars in a steamer or in boiling water; and stewing the fruit before it is put into the jars.
Then there are also the cold water and hot water processes of canning and the sun-cooked preserves.
Some fruits, like rhubarb, green gooseberries and cranberries, may be preserved without cooking or the use of sugar, because their own acids are germ killers.
Although a vegetable, rhubarb is usually classed among the fruits. The stalks should neither be too tender and succulent nor too hard and sticky. The red variety is the best for canning or for making wine.
In canning fruits or vegetables, or in jelly or preserve making, it is most important that the food should be protected from the growth of molds as well as the growth of bacteria and yeasts.
To kill mold spores the food must be exposed to a temperature of from 150° F. to 212° F. After this it should be kept in a cool, dry place and covered that no floating spore can find a favorable place on its surface. Fruit for canning should be fresh, solid and not over-ripe. If over-ripe, some of the spores may survive the boiling, then fermentation will take place in a short time.
To prepare the fruit remove all stems, then peel with a silver knife, core or remove the seeds or pits, as the case may be. Peaches, pears or apples may be kept from discoloring if they are dropped, as they are pared, into cold water to which a little vinegar or lemon juice has been added.
Peaches, plums or tomatoes peel more easily if first immersed in boiling water, then for a moment or two in cold water, and drained.
Berries should be looked over one by one. If they have come from a sheltered field or if there has been recent rain, it may not be necessary to wash them. If not, they will have a more perfect flavor. Usually, however, they must be washed. Put them into a colander, one quart at a time; fill a large, deep pan with water, and gently lift the berries up and down several times. Never allow water to run from a faucet on delicate fruit.
When fruits or vegetables are brought into the house put them where they will keep cool and crisp until ready for use.
Glass is the most satisfactory jar to use in canning. Glass jars are becoming so universally in favor that they are taking the place of tin cans for everything, even for tomatoes. They are more economical than tin, for, although the glass costs more in the beginning, it lasts and can be used over and over again. While there are many kinds of jars, the preference should usually be given to those with wide mouths.
The jars must be thoroughly sterilized before using. Set in a kettle on a trivet and surround with cold water, then heat gradually to boiling point, boil for fifteen minutes, remove from the water, empty and fill while hot.
Examine and test the jars before sterilizing them. Put a little water in each, adjust the rubber, screw down the top, and invert. If the jar is not air-tight, it is better to discover the fact when it has only water in it than after it is filled with fruit. If the jar does not leak, be sure to keep it with its own cover; not every perfect cover will fit every perfect jar.
If a jar leaks, try another cover, or possibly an additional rubber. No jars should be used which have imperfections in them, not only on account of the danger of particles of glass being loosened and getting in the fruit, but because bacteria may be left there which will cause the fruit to spoil. Some of these places have been blisters in the glass, and when broken leave places from which one can never wash the color of the fruit last put in the can.
Jars of fruit or vegetables which have been put up for a long time are often very hard to open. The usual way is to pry up the edge of the cover, and pull the rubber out. There are easier and better ways: One is to place the jar top downward in a basin of boiling water. In a few minutes the cover will come off easily; another is to place a hot flat-iron on the cover of the can for a few minutes.
The rubbers should be new each season, and should be boiled for at least twenty minutes before using, that they may be sterilized and that they may not flavor the fruit. Black rubbers are more durable than the white. Be sure that the covers are a perfect fit and see that they are sterilized with all the other utensils that are to be used in the work. The lids and rubbers must not be handled after the boiling is fin ished. Sometimes it is possible to use old rubbers by dipping them in hot melted paraffin first.
When a jar of canned fruit is opened, the contents must be removed, for, unlike preserves, a portion cannot remain and the jar be sealed again. On this account there are pints, quarts and two-quart jars, so that cans which contain the requisite amount for the family may be purchased.
Absolute cleanliness and the best materials procurable are the first essentials for success in canning vegetables.
The vegetables should be as fresh as possible. Young vegetables are superior in flavor and texture to the more mature ones. Corn, peas and beans should be canned as soon as possible after gathering, as sweetness and flavor are absorbed by their pods and husks. All root vegetables and greens must be thoroughly washed.
The spoiling of vegetables is due primarily to bacteria. To this end vegetables must be thoroughly sterilized. Some vegetables spoil more readily than others, especially those rich in starchy constituents.
To defeat this propensity of the parent bacteria to reproduce itself, there must be not only the initial boiling, which disposes of the parent, but later boilings to kill the spores, which retain their vitality even in boiling water and germinate as soon as cooled. To make way with the bacteria, there must be successive boilings, preferably a day or two apart, or at least for five hours at a stretch.
When using canned vegetables in the winter, if the can is opened about two hours before serving and the contents turned into a shallow dish, much of the oxygen forced out by sterilization will re-enter the vegetables, so that one can hardly tell any difference between the fresh and the canned products.
When canning vegetables use a washboiler or a large preserving kettle. This must be furnished with a tight cover. An extra bottom must be provided for the boiler, as the cans would break if set flat on the bottom.
A wooden rack or a piece of wire netting cut to fit the container, with coils of rope or straw, or rolls of doth to keep the cans from touching each other, are also essentials.