Safe Canning Methods
Preserving food by canning can be fun and economical, but only if done correctly. There are three safe methods of canning food at home – water bath, atmospheric steam, and pressure canning. Water bath canning and atmospheric steam canning can only be safely used for high acid foods i.e. pickled vegetables, acidic tomatoes, and similar. Pressure canning can be used for high or low acid foods such as green beans, peas, and meats. Each method has its own specific process that should be followed.
Low-acid foods lack the acidity needed to inhibit the growth of bacteria and harmful spores that can survive the temperature of boiling water (212°F). One of the deadliest bacteria is Clostridium botulinum, which produces spores that generate a toxin that causes food poisoning. These spores can survive boiling water, but are killed when subjected to heat and pressure in a pressure canner. The temperature in a pressure canner can reach 240°F or more.
High-acid foods, include most fruits and some tomatoes. When canning tomatoes lemon juice, citric acid, or vinegar (labeled 5% acidity) must be added to increase the products acidity. Increasing the acidity level, will make it safe to process these foods, using either a water bath or atmospheric steam processing method.
Other foods which are high in acidity are fermented foods, i.e. sauerkraut, and pickled vegetables. Jams and jellies are high-acid foods, too, unless low-acid vegetables, such as peppers, have been added. If low-acid food has been added to the high-acid food, then in most cases these will need to be processed in a pressure canner.
Low-acid foods should be processed in a pressure canner.
Examples of Low-Acid Foods Are:
• Most Vegetables – asparagus, beets, carrots, green beans, peas, peppers, pumpkin, etc.
• Meats – beef, poultry, seafood, and wild game
• Combination Foods – sauces, soups, stews
High-acid foods can be processed in either a water bath, atmospheric steam, or pressure canner.
Examples of High-Acid Foods Are:
• Most fruits – apples and applesauce, apricots, berries, cherries, fruit only jams and jellies, fruit only pie fillings, etc.
• Acidified and fermented foods – chutney, pickled vegetables, pickles (cucumbers), relishes, salsa, sauerkraut, and acidified tomatoes Mason jars are recommended for home canning. These jars with appropriate lids are more likely to seal and less likely to break during processing than when attempting to re-use commercial single-use jars.
Canning jars come in different sizes the most common being pints and quarts. If processing times are not specific for the size of jar you are using, then use the recommended processing time for the next larger size of jar. Mason jars and the lid ring can be used again for canning, but will require a new unused lid.
Thoroughly read and understand an up to date canning guide, such as the one from the Missouri Extension office before starting.
The majority of the time, when good quality produce and correct canning methods are used, the result will be safe high quality canned food. Sometimes there are canning failures. These failures can be faulty sealing or food spoilage and are usually a result of inadequate processing times or
inconsistent temperature, during processing to destroy microorganisms. If the food from the jar looks bad or smells bad – throw it out.
Do not taste it! It may contain organisms that are harmful.