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Home canning of foods is a good way to preserve the bounty from a backyard garden as well as to save money. Almost any food can be preserved by canning, but the type of food and the particular recipe used necessarily dictates the method by which it must be processed. Canning in the home kitchen is generally done either with a pressure canner or a boiling water bath, sometimes called open kettle canning. Each method has its advantages and drawbacks. Knowing these is important before undertaking any canning project as using the wrong method can be potentially dangerous and result in severe food poisoning.
Open kettle canning has many advantages over pressure canning. It can be done in almost any pot large enough to hold the jars, provided that some method is available to hold the jars above the bottom of the pot, preventing the jars from cracking or bursting during processing. A special kind of large stock pot, often an enameled steel, covered pot with a rack for holding jars, is the most common, and pots of this type are relatively inexpensive. Some home canners use a regular stock pot with a heat diffuser or pizza disc to hold the jars off the bottom of the pot. For these reasons, open kettle canning is less expensive and a little more suitable to improvising in terms of equipment than pressure canning.
Many of the most common foods that are canned at home are suitable for open kettle canning. Tomatoes, pickles, jams and jellies are all suitable for this method. The reason for this is that high acid foods rely on the acidity of the food at least as much as the canning process to keep down bacterial growth, making the preserved food safe to eat.
The temperature at which open kettle canning is done prevents certain foods from being safely processed this way, and this is the main drawback to this method. Foods that are not high in acidity must be processed in a pressure canner to guarantee safety. This also limits flexibility in recipe alteration. Recipes for pressure canners are more easily altered without fear of compromising safety as the pressure canning process kills bacteria in the food. Recipes for open kettle canning cannot be altered without increasing the risk of food-borne illnesses because of the possibility of altering the acid content of the food, which is the main mechanism for keeping down the growth of potentially dangerous bacteria in this type of canning.
Open kettle canning involves placing hot foods in jars, placing the seals and allowing them to seal as they cool without processing in a boiling water bath, and is not a recommended method. A boiling water bath is not the same as open kettle canning.