GLOSSARY

alum  a compound that was widely used in home canning to keep pickles, cucumbers, and some other fresh foods crisp. It’s rarely used anymore, but you may see it in some heirloom recipes.

boiling water canning  see water bath canning

citric acid solution  a solution used in canning to prevent darkening of foods such as potatoes, apples, pears, and peaches. Can be made from citric acid powder or by using vitamin C tablets.

dial-gauge pressure canner  this pressure canner uses a dial to indicate when the proper pressure has been reached within the pressure canner.

high-acid foods  foods with enough acid to make them safe for water bath canning. This includes foods with a pH of 4.6 or lower.

jam  smooth, spreadable fruit product made with pureed or crushed fruit.

jelly  a clear, spreadable fruit product made from only the juice of the fruit.

low-acid foods  foods that lack the acid content to be safely canned in a water bath canner. These include foods with a pH of 4.6 or higher.

pectin  a naturally occurring compound that is present in the skin and pulp of many fruits, especially apples. It is used to thicken the liquid in jams and jellies.

pH  the measurement of the amount of acid in foods.

preserves  a spreadable fruit product made with whole or mostly whole fruit. It is thicker than jams.

pressure canning  the process of canning using both heat and pressure. Essentially, food is packed into jars and steamed within the canner. It is always used for canning low-acid foods, but can also be used to can high-acid foods.

processing time  the length of time a food must be processed in a water bath canner or pressure canner. In a water bath canner, that time starts from the moment the water returns to a boil. In a pressure canner, it begins from the time the canner has reached the proper pressure.

psi  pounds per square inch. It is used in pressure canning to indicate the proper pressure for processing each food.

water bath canning  the process of canning using boiling water. It can be used only for high-acid foods.

weighted-gauge pressure canner  most older models of pressure canners and some newer models are weighted-gauge canners, with a weight attached to the vent of the canner that jiggles and rattles when the proper pressure is reached and maintained.