Cook the fruit slowly in a porcelain-lined or granite-ware kettle, using as little water as possible.  It is better to cook only small quantities at a time in one kettle.  Steaming in the cans is preferable to stewing, where the fruit is at all soft.  To do this, carefully fill the cans with fresh fruit, packing it quite closely, if the fruit is large, and set the cans in a boiler partly filled with cold water, with something underneath them to prevent breaking,—­muffin rings, straw, or thick cloth, or anything to keep them from resting on the bottom of the boiler (a rack made by nailing together strips of lath is very convenient); screw the covers on the cans so the water cannot boil into them, but not so tightly as to prevent the escape of steam; heat the water to boiling, and steam the fruit until tender.  Peaches, pears, crab apples, etc., to be canned with a syrup, may be advantageously cooked by placing on a napkin dropped into the boiling syrup.

Fruit for canning should be so thoroughly cooked that every portion of it will have been subjected to a sufficient degree of heat to destroy all germs within the fruit, but overcooking should be avoided.  The length of time required for cooking fruits for canning, varies with the kind and quality of fruit and the manner of cooking.  Fruit is more frequently spoiled by being cooked an insufficient length of time, than by overcooking.  Prolonged cooking at a boiling temperature is necessary for the destruction of certain kinds of germs capable of inducing fermentation.  Fifteen minutes may be considered as the shortest time for which even the most delicate fruits should be subjected to the temperature of boiling water, and thirty minutes will be required by most fruits.  Fruits which are not perfectly fresh, or which have been shipped some distance, should be cooked not less than thirty minutes.  The boiling should be very slow, however, as hard, rapid boiling will break up the fruit, and much of its fine flavor will be lost in the steam.

Cooking the sugar with the fruit at the time of canning, is not to be recommended from an economical standpoint; but fruit thus prepared is more likely to keep well than when cooked without sugar; not, however, because of the preservative influence of the sugar, which is too small in amount to prevent the action of germs, as in the case of preserves, but because the addition of sugar to the water or fruit juice increases its specific gravity, and thus raises the boiling point.  From experiments made, I have found that the temperature of the fruit is ordinarily raised about 5 deg. by the addition of the amount of sugar needed for sweetening sub-acid fruit.  By the aid of this additional degree of heat, the germs are more certainly destroyed, and the sterilization of the fruit will be accomplished in a shorter time.

Another advantage gained in cooking sugar with the fruit at the time of canning, is that the fruit may be cooked for a longer time without destroying its form, as the sugar abstracts the juice of the fruit, and thus slightly hardens it and prevents its falling in pieces.