This section is from the book "Everywoman's Canning Book", by Mary B. Hughes. Also available from Amazon: Everywomans canning book; the A B C of safe home canning and preserving.
Flat-sour is a term used to denote spoilage that is not detected until the jar is opened. A product which has flat-soured, however slightly, should never be eaten. Just what, specific bacteria cause flat-sour is not known, but it is quite safe to say that home canners whose methods are clean and who use fresh products, and process the required time according to the time tables, are never troubled with flat-sour.
Beets will turn dark if exposed to a strong light, and also if they are allowed to stand in the jars without water for any length of time before they are processed. Jars should be filled and processed immediately.
A cool, dark place is the best for storing home-canned products. A cellar preserve closet is not a necessity. A pantry near the kitchen, where the jars will be convenient when wanted, makes as good a storage place as any. The jars should be protected from the light.
If the jars are placed in the cellar, they must be looked at occasionally, as the molds which attack rubbers in a damp atmosphere cause them to decay, letting the air into the jars and causing spoilage.
Preserving powders are good things to let alone. Housewives are cautioned against buying these so-called preserving powders from agents who go from door to door. Benzoic acid, salicylic acid, boric acid, and formaldehyde are sometimes sold to shorten the time of processing fruits and vegetables.
Under no circumstances should the housewife use any preservative in her canning. Process the full time given in the time tables and preservatives will be unnecessary. Their use is not only very dangerous, but also expensive.
Against following everybody's advice as to canning. Do not look for short cuts. There are none. Follow a reliable guide and remember that in canning there is one best method, which will insure uniform success year after year.
It is generally agreed that fruits and vegetables which are canned in glass are of a finer flavor than those canned in tins, though their nutritive value is no higher. Experts tell us there is nothing about the use of a good tin can which is harmful. For home canning, however, glass jars are to be recommended, as they last from year to year.
When several bushels of tomatoes or peaches are to be canned, to take care of a large surplus, the cost of the container is an important consideration. Cans are much cheaper than jars. A special outfit must be purchased if tin is to be used.
Prices vary so that it is impossible to give a definite answer to this question. The first-year cost is the greatest, since it includes equipment and jars. A conservative estimate shows a saving of seventy per cent on all home-canned products over the market price for the same varieties canned in tin.