1634. To Can Fresh Fruit

1634.    To Can Fresh Fruit. Procure a sufficient number of tin cans of suitable size, fill them quite full with the fruit, and solder them securely. Next pierce a small pin-hole in the top of each can, to allow the air to be expelled; place the cans in a boiler as deep as the cans are high, pour boiling water into the boiler until within 1/2 inch of the top of the cans; keep the water hot over a moderate fire, but not boiling, until the air ceases to escape from the cans, and then seal the air holes with solder before removing the cans from the water. The cans should then be taken out, wiped dry, and allowed to cool; when cold, if the cans have been closed perfectly air-tight, the vacuum inside will cause the top and bottom of the cans to become concave or hollowed inwards. {See No. 1611 (To Can Meat).) Tomatoes are also kept fresh in this manner.

1635. To Insure Success in Canning Fruit

1635.    To Insure Success in Canning Fruit. Select fresh fruit that is perfectly ripe; but, at the same time, perfectly sound. One unsound berry may injure all in contact with it.

The boiling water poured into the boiler will be considerably cooled by contact with the cans; care must be taken not to let the water return to the boil while the cans are in it; and yet it must become hot enough to expel the air from the cans.

The surest way to attain the desired object is to keep the bulb of a thermometer in the water. A heat of 200° to 208° Fahr. will answer best, but it must never exceed the latter degree. To ascertain when all the air possible has been expelled, put one drop of hot water on the air hole; the cessation or absence of air bubbles passing through it will denote that the cans are ready for final sealing.

1636. To Can Berries

1636.    To Can Berries. Peaches, apples, pears, plums, etc., can be kept perfectly fresh in tin cans in the manner described in No. 1634, and will retain their fresh flavor almost, if not entirely, intact. Raspberries, strawberries, etc., are kept in better condition by adding 1/2 pound white sugar to each pound of fruit, letting them come to the boil, and then filling the cans quite full, soldering the lid of the can immediately. The hot fruit will, to all intents, expel the air from the can. No water should be used with fruits, except in cases where a little is necessary to dissolve the sugar, as it tends to render them insipid. Most vegetables can be kept in cans in this way, omitting the sugar, and scalding them in water sufficient to cover them.

1637. To Expel the Air from Cans

1637.    To Expel the Air from Cans. Air, by heating, expands many times its own bulk; consequently, if you take a jar and cover it tightly with the exception of a hole the size of a pin through the cover, and set it in boiling water, as air expands 20 times its bulk by heating, it is obvious that 19/20 of the air pases out through the pin hole in the cover; now drop a little sealing wax or solder over the pin hole and you have but 1/20 of the air in the jar that was in it before heating it. Of course the fruit and syrup, if put into the jar cold, displaces most of the air; but putting it in as hot as it can be, and filling as full as possible, expels the air to all intents and purposes. Cans managed in this way, when made of sheet metal, frequently collapse from outside atmospheric pressure as they cool off, showing that the exhaustion was complete; even more so than needed.