sometimes also sugar to this liquid. When the can is filled and closed the sterilizing is best completed by placing it in a strong boiler, which is then closed and heated by steam under a pressure of two or three atmospheres or even higher, namely, from 30 to 45 pounds and over per square inch. By heating under pressure in this way the development of any pressure in the can due to the production of steam is counterbalanced by the pressure without the can, so that a swelling or cracking of the can cannot take place. If the cans are heated in an open bath of water or brine it is customary to leave a small perforation in the top of the can through which the combined gas of the interior of the can may escape, and this vent is closed by a small drop of solder applied before or at the time of taking the cans from the bath. The canning of vegetables may also be done in a small way in the household and the principle on which this process is based is exactly the same as that set forth. The vegetables must be properly prepared, placed in the cans, and heated a sufficient length of time to destroy germs and spores, and the vent in the can stopped with solder. For family purposes the use of closed boilers for heating is not practical on account of the expense of securing such apparatus. All kinds of vegetables which are eaten in a cooked state can be preserved by the canning process. This cannot be applied, however, to those forms of vegetables which are eaten raw, such as lettuce, radishes, etc.
The principal forms of canned vegetables are described below:
Canned Beans.—Fresh, green beans used for canning purposes are generally preserved in the pod and not shelled, as is the case with the pea. The raw material should be selected with the same care as that which attends the selection of other vegetable products intended for preserving purposes. If the pods are small they may be placed whole in the can. Sometimes they are cut into small lengths in order to fit better in the package. As in the case of peas, the interstices between the particles of beans are filled by the addition of a sufficient quantity of brine of the proper strength to fill the can to the top. The process of sterilization is the same as that for other vegetable substances. Cooked beans are also preserved by canning and are often improperly called baked beans.
Composition of Typical Samples of Canned Beans.—The composition of typical samples of canned beans is shown in the following table:
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| | | | Starch | | |
Substance. | Water. | Fat. | Fiber. | AND | Protein. | Ash. | Salt.
| | | | Sugar. | | |
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| Percent. | Percent. | Percent. | Percent. | Percent. | Percent. | Percent.
String beans, | 94.33 | .06 | .51 | 3.03 | .92 | 1.16 | .80
Unstringed beans, | 93.91 | .07 | .58 | 2.91 | 1.14 | 1.40 | .92
Lima beans, | 79.68 | .30 | 1.16 | 13.24 | 4.00 | 1.62 | .77
Canned baked beans, | 67.19 | 3.18 | 2.46 | 17.88 | 7.14 | 2.15 | 1.03
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