This section is from the book "Elements Of The Theory And Practice Of Cookery", by Mary E. Williams. Also available from Amazon: Elements Of The Theory And Practice Of Cookery; A Textbook Of Domestic Science For Use In Schools.
Fruit and tomatoes are the easiest foods to can because they are the easiest to sterilize. The reasons for this are three. 1. They are attacked chiefly by yeasts, and by bacteria which do not bear spores, both of which are quickly killed by boiling. 2. They are acid, and hot acid helps to kill microorganisms. 3. They are readily penetrated by heat. Our aim in canning is to sterilize the fruit without injuring its appearance and flavor.
One secret of success in canning is cleanliness. Cleanliness means fewer microorganisms to be killed. For this reason, keep the room as free as possible from dust; keep the table, your hands, and your clothes clean while you work; and wash all the utensils just before beginning work, rinse them with boiling water, and let them dry without wiping. Dish-towels are not sterile.
Put the jars in a pan or pail, cover with cold water, let it come to a boil and boil for ten minutes. This is an extra precaution, not necessary except when fruit is cooked before being put into jars. When it is done, covers and rings should be sterilized in a smaller vessel in the same way.
Fill a jar with water, fasten on ring and cover, and invert. If it leaks, either the jar is imperfect or the rubber poor. Use no jar that cannot be made absolutely tight.
Utensils used in Canning.
Sealing Fruit Jars.
Can each fruit in its season when it is best and cheapest. It is best for canning just before it is quite ripe. The better the condition of the fruit the easier it is to sterilize. So use only fresh, clean, sound fruit, and see that no soft berries or spoiled bits get into the cans.
Wash all fruit. Hull berries. Take out stems and trash. Peel or pare large fruits. Pour hot water over peaches and tomatoes to loosen the skin. Core and quarter apples and quinces. Quarter large tomatoes. Can small ones whole. Peaches may either be canned whole, or halved and stoned. Halves pack better. A few peach stones canned with them improves the flavor. Stoned cherries pack closer than whole ones and can be sterilized quicker. Prick whole cherries and plums. If peeled fruits are not to be put in jars at once, drop them into water made slightly acid with lemon-juice or vinegar.
It is the simplest method. It best retains the flavor of the fruit. It avoids exposing the fruit after it has been sterilized.
This method requires the following outfit: a wash boiler, pail, or any vessel with a tight-fitting cover, large enough to hold several cans; a rack to fit the bottom of the boiler and keep the jars from bumping and breaking when the water boils (this may be a piece of heavy wire netting or it may be made at home of strips of wood); quart or pint glass jars (the jars with glass covers and metal springs are best); a new rubber ring for each jar (old rubber may not be air-tight); large bowl or enamelled pan for fruit; plated knife and fork; plated or enamelled spoon; quart measure; half-pint measure; scales; saucepan for syrup. Avoid iron and tinware in canning.
Fruit to be used for cooking may be canned without sugar. If to be used for sauce, it is best to sweeten it when it is canned. The sugar should be proportioned to the acidity of the fruit. The easiest way to do this is to dissolve the right amount for each jar (usually from two to four ounces for a pint jar) in hot water and pour it in, filling up the jar with more hot water if necessary. The water should be proportioned to the juiciness of the fruit. This regulates itself fairly well, as in general the juiciest fruits are the small ones that pack close and leave little space for liquid. The sugar may be made into a syrup. For a light syrup, use one-half pound of sugar to one quart of water. Boil together until the sugar is dissolved. If a scum rises, remove it. A sweeter syrup may be used for more acid fruits and for small fruits which leave little space for syrup. It may be necessary to find by trial how much syrup one can of fruit will hold before determining the proportions of sugar and water.
Add salt to vegetables, using one-fourth to one-half teaspoonful to a pint jar, and fill up with cold water.
If packed in quart jars, sterilize berries from ten to twenty minutes, other small fruits and cut-up fruits for twenty-five, pears and whole peaches for thirty, quinces for one hour or more, according to size of pieces, tomatoes fifteen to twenty minutes. The time for quinces may be shortened and the quinces improved by cooking them for ten or fifteen minutes before putting them in the jars. For fruit in pint cans, only two-thirds as much time is required.1 The water must boil every minute.
Pack fruit compactly in jars. To make it pack better, it may be put in a strainer or piece of cheesecloth and lowered into boiling water for about one minute. This is called "blanching." Blanch fruit in small lots, that the water may not be cooled much. Press fruit gently down in jars with spoon or small wooden spatula. Fill jars with syrup. Release any air-bubbles by slipping knife or spatula down between fruit and jar. Put on rings and cover without fastening them down. Place jars on rack in boiler. Pour in cold or warm water (warm saves time) to a depth of two or three inches. Put on the boiler cover. Bring water to a boil and boil as long as required. Remove from the heat, fasten down covers, take jars out, and let them cool as quickly as possible. Letting them cool down slowly in the water softens the fruit and makes the juice cloudy. If, when sterilization is complete, there is more than half an inch of space between fruit and cover, the contents of one jar may be used to fill the rest before the covers are fastened down. Five minutes more boiling is then required. This is troublesome and is unnecessary if jars have been properly packed.
1 These directions apply to fruit bought in towns and cities. Less time is required for fruit freshly picked. Ten minutes for quart jars, five minutes for pint jars of freshly picked berries is sufficient. The shorter the time of sterilization the better the berries retain their flavor, shape, and color.
A steamer may be used instead of a boiler to sterilize fruit in jars. Or the jars may be set in a pan of water or on a sheet of asbestos in the oven. The oven method shrinks the fruit more and takes more fuel.
Cook the fruit in the syrup in an enamelled kettle until it is tender. Take jars, rings, and rubbers as you need them from hot water in which they have been sterilized. While filling the jar let it stand on a hot wet cloth. Transfer the fruit quickly from kettle to jar, using a wide-mouthed funnel and a dipper or large spoon. Fill jar to overflowing with syrup. Put on ring and cover and fasten cover down. Wipe off jar.
Strawberries may be canned to advantage by this method without the addition of water, which they do not need. Hard fruits such as quinces and pineapples should be cooked in clear water before sugar is added.
Meat, fish, and many vegetables, notably corn and beans, are hard to sterilize because they contain spore-bearing bacteria and are not acid. In factories, these and many other foods are canned by steam under pressure. Vegetables may be canned at home by boiling them several times, generally on three successive days, to kill spores which have developed after previous boilings. This method is called intermittent sterilization. Canning outfits, some for steaming under pressure, are made for home use in the country. It does not pay city-people to buy vegetables to can. They cost too much and are not fresh enough.
If fresh from the garden and tender, these may be canned like fruit. Wash and string them, and break them into short pieces. Blanch from five to ten minutes, removing them when soft enough to bend without breaking. Pack in jars, fill with cold water, and add one teaspoonful of salt to a quart jar. Boil quart jars one hour. If beans are not freshly picked, boil for one hour, fasten down covers, remove jars, set aside till the next day, and boil again for one hour.
Pickling is preserving in brine or vinegar, to which sugar and spice are often added. Now that fresh or canned vegetables can be obtained the year round, there is not the need for pickling them that there was in our grandmothers' day. Even as a condiment, pickles and spiced preserves should be used sparingly, and not at all by children. They stimulate digestion, but tend to weaken it in the long run.
For further development of topics treated in this section see: -
Olsen : Pure foods. Ch. 12.
Rose : Preservation of food in the home. Parts 1, 2, 3. Cornell reading course.
U. S. Dept. of Agriculture : Farmers' bulletins: (359, Canning vegetables in the home; 203, Canned fruits, preserves, and jellies. Also circulars on girls' canning and home demonstration work.)
North Carolina Dept. of Agriculture. V. 31, No. 5, May, 1900. Home canning of fruits and vegetables. (Sent free to citizens.)