What is the objection to excessive use of spiced foods?
Name some substitutes for pickles. Why is an excessive or continuous use of pickles objectionable in diet?
LESSON CLXXI
CANNED VEGETABLES
MICROORGANISMS IN THE SPORE FORM.—Many microorganisms are destroyed by heating them for a few minutes to boiling temperature. However, some microorganisms have a peculiar power of retaining life under most adverse conditions. When subjected to extreme heat or cold, intense drying, or when there is lack of food, certain microorganisms assume a spore form, i.e. they cease growing and reproducing, and are able to undergo conditions which would readily kill microorganisms in the active form. Some microorganisms in the spore form are able to resist the temperature of boiling water for an hour or longer. Then as soon as the adverse conditions mentioned above are removed, the microorganisms assume active form and begin to grow and reproduce. In the growing state, their destruction is not so difficult.
Some of the microorganisms in certain foods, especially vegetables and fruits grown in a dry season, are capable of spore formation. When microorganisms in spore form do exist in foods that are to be canned, or the microorganisms change into spore form during the canning process, the microorganisms may not be destroyed by the time the ordinary process of canning is completed. If such is the case, when the canned foods are cooled and the conditions are favorable for growth, the microorganisms assume active form, begin to grow, and cause the decomposition of food. Twenty-four hours is sufficient time for the microorganisms to change from the spore to the active form. Hence the canned foods must be heated again, if they are to be preserved. For foods difficult to process (for the reason given above) processing should be carried on for three successive days. This is called intermittent processing.
Destruction of microorganisms in the spore form can be accomplished in a short time by subjecting them to very intense heat. In canning factories this is done by processing at a temperature higher than that of boiling water. In the home this may be accomplished by processing in the pressure cooker. According to one authority processing intermittently, i.e. on three successive days, does not insure satisfactory processing of materials containing spores.
SINGLE PERIOD AND INTERMITTENT PROCESSING.—The acid of tomatoes and fruits aids in the destruction of microorganisms. Hence intermittent processing is unnecessary for these. Processing tomatoes and fruits in a hot water bath for one period has proved very satisfactory and certain.
There is some question, however, regarding the safety of canning all vegetables by one period of processing in the water bath at 212 degrees F., especially in regions where botulism is known to occur and where Foods cannot be stored in a cool place. In Farmers' Bulletin 1211, "Home Canning of Fruits and Vegetables," revised August, 1922, one period of processing in the water bath at 212 degrees F. is not advised in climates where the storage conditions are trying for the following vegetables: corn, beans, asparagus, okra, spinach and other greens, and peas (especially if at all mature). For processing these vegetables, a higher temperature than that obtained in the boiling water bath is recommended. Processing at a high temperature (from 228 degrees F. to 250 degrees F.) can be accomplished conveniently by means of a pressure cooker. This is especially recommended for vegetable canning in high altitudes and in localities where botulism has occurred.
It is thought that in some places the above mentioned vegetables may be processed intermittently with safety. For vegetables difficult to can, pint jars only are recommended for both intermittent and single period processing in the water bath. Heat penetrates more rapidly to the center of the small jars than to the center of the large jars.