Water Bath Canning Vs. Pressure Canning

There are two basic methods of canning which are used to preserve different types of food. Water bath canning involves heating canning jars in water and then allowing them to cool to form a seal on their own. Pressure canning utilizes a pressure cooker to achieve higher temperatures throughout this process.

Canning is a way to preserve many types of foods for long periods of time. The food to be preserved is heated to destroy bacteria and then vacuum sealed inside glass mason jars. Certain types of food can harbor different types of bacteria. Foods with a pH of less than 4.6 can be canned using the basic water bath method; however, all other foods must be canned using the pressure canning method. This is because Clostridium Botulinum – the bacteria that produces botulism – produces spores that can survive boiling water temperatures in low-acidity environments. This makes items like meats and vegetables dangerous to can unless a temperature of 240°F can first be reached. The water bath method can only reach 212°F, so the pressure canning method must be used to can anything except fruits and pickled items. Certain foods such as tomatoes must have an acid such as lemon juice added to them in order to safely can them.

The two methods are very similar and can both be performed by the amateur. Since water bath canning is the easiest, it is the recommended method to start with. Remember that water bath canning is only for foods with a pH of 4.6 or less. Fruit and pickled items are best for this method. To begin, sterilize everything – especially the jars. Make sure all the jar seals are clean and in good working order. The jars should be free of cracks and chips as this can cause them to shatter when heated. The food to be canned should be placed into the jars based on a canning recipe. The rim of the jars should then be wiped clean and the gasket lid placed on top. The jars are then arranged on a rack which stretches across the bottom of a large pot. the pot is filled so that each jar is covered with one to two inches of water. After this has been done, the water and cans are all brought to a vigorous boil for a few minutes. After boiling, the bath is allowed to cool before the cans are removed. Any can lids which have not formed vacuum seals are bad and should be discarded. The threaded rings of the cans can then be tightened down to make the seals more durable for storage.

Pressure canning is essentially the same as water bath canning except that the boiling is done in a pressure cooker. This allows pressure to increase the boiling temperature of the water from 212°F to over 240°F, killing
Clostridium Botulinum spores. However, since this requires a pressure cooker, batch size is typically smaller. It is advisable that whenever possible, acids should be added to foods so that the water bath method can be used. In pressure canning, the same recipes are followed to introduce the food into clean and crack-free jars. The jars are then loaded into a pressure cooker which is then filled with enough water to cover the jars. The cooker is sealed and heated until the contents have reached a safe temperature. The recipe and type of food will determine how long the food should be held at this temperature, but ten minutes is enough to be safe. Once again, let the cooker cool before removing the lid. Remove the cans and check for a proper seal before installing the threaded seal retaining rings.

With these two methods, virtually anything can be safely canned and stored for many years. Canning is an excellent way to prepare for natural disasters or simply to preserve summer fruit for mid-winter cakes and pies.