means, is able to command at all seasons of the year and in all locations an abundant supply of wholesome, fresh, succulent vegetable materials.
Principles and Process of Canning.—The sterilization of succulent vegetables depends upon the same principles as that of meat, already described. The decay of these vegetable substances is due to the action of certain ferments, either organic or inorganic, which act as agents in securing the oxidation and decay of the organic material. If the action of these organisms can be prevented or inhibited the food material will remain for a certain length of time, not yet definitely determined, in an excellent, almost perfect state of preservation and without losing, notably, any of its nutritive or palatable properties.
It is not the purpose of this manual to describe the technique of canning, further than to illustrate the principles thereof in their relations to wholesome and nutritive food.
Selection of Materials.—It is of the highest importance in the canning industry, both for the reputation of the manufacturer and the health and comfort of the consumer, that the vegetables selected for canning be fresh, free from disease, and prepared in such a way that all adhering dirt or other foreign substances be excluded. The process of preparation for canning should begin as soon as possible after the harvesting of the vegetables, since a delay, especially at the high temperature which usually prevails at the time of canning, produces rapid deterioration, both as respects the quality of the vegetable and its flavor. After the proper cleaning and preparation of the fresh vegetables they are next subjected to the process of canning. It is then the vegetables are heated to a temperature of, or above, that of boiling water for a sufficient length of time to thoroughly destroy all the living germs and spores contained therein. The degree of temperature and the length of time of heating depend upon the nature of the vegetable substance, the size of its particles and of the package and the relative difficulty of preservation. Where only living organisms are present the proper temperature is that which will destroy the life of the germ. It is well known that spores from which fermentative germs may be developed are more resistant to the action of heat than the germ itself. When, therefore, spores of this kind are present, the temperature of heating must be higher and the time more prolonged, or, in lieu of this, the food should be heated on two or three consecutive days during which time any spores which may have been present will have developed into organisms and been killed. Some forms of vegetable materials are sterilized much more readily than others. For instance, the kernels of green Indian corn are of such a character and degree of hardness as to resist, with a considerable degree of success, the influence of heat on the life of the germs which they contain. In such cases it is customary to previously cook the vegetable substance before placing it in the cans. The cans should contain enough water to fill the interstices between the particles of vegetable matter. It is the practice in many instances to add a little salt and
