Microorganisms, some of which are harmful, found in the soil, water and air around us. Some bacteria thrive in conditions common in low-acid preserved food and produce toxins that must be destroyed by heating to 240F (116C) for a specified length of time. For this reason, low-acid foods must be processed in a pressure canner.

See screw band.

To submerge a food in boiling water or steam for a short period of time, done to loosen the skin or peel or to inactivate enzymes. Blanching is immediately followed by rapidly cooling the food in ice water.

To heat a liquid until bubbles break the surface. At sea level, this happens at 212F (100C). At elevations above 1,000 feet (305 m), the boiling point is reached at a lower temperature. A boil is achieved only when the liquid is continuously rolling or actively bubbling. See also boil gently or simmer or boil, full rolling.

To cook food gently just below the boiling point (180F to 200F/82C to 93C). Bubbles rise from the pot bottom, only slightly disturbing the surface of the food.

A rapid boil, usually foaming or spurting, that cannot be stirred down, achieved at a temperature of 220F (104C). This stage is essential for attaining a gel when making cooked jams or jellies.

The temperature at which liquid reaches a boil (212F/100C at sea level).

A large, deep saucepan equipped with a lid and a rack to lift jars off direct heat. The pot must be deep enough to fully surround and immerse jars in water by 1 to 2 inches and allow for the water to boil rapidly with the lid on. If you don't have a rack designed for preserving, use a cake cooling rack or extra bands tied together to cover the bottom of the pot.

The fresh preserving method used to process high-acid foods. Heat is transferred to the food product by the boiling water, which completely surrounds the jar and two-piece closure. A temperature of 212F (100C) is reached and must be maintained for the time specified by the recipe. This method is adequate to destroy molds, yeasts and some bacteria, as well as to inactivate enzymes. The boiling water method must not be used to process low-acid foods.

Food poisoning caused by the ingestion of the toxin produced by spores of the bacterium Clostridium botulinum. Botulism can be fatal. The spores are usually present in the dust, wind and soil clinging to raw food. They belong to a species of bacteria that cannot grow in the presence of air, and they do not normally thrive in high-acid foods. The spores can survive and grow in any tightly sealed jar of low-acid food that has not been processed correctly. Using the correct processing temperature and time to preserve low-acid foods will destroy toxin-producing spores.

A spice bag, or a square of cheesecloth tied into a bag, that is filled with whole herbs and spices and is used to flavor broth, soup, pickling liquid and other foods. This method allows for easy removal of the herbs and spices after cooking.

A salt-water solution used in pickling or when preserving foods. Although salt and water are the main ingredients, sugar and spices are sometimes added.

See fermented pickles.

The unfavorable color change caused when the cut surface of some fruits and vegetables is exposed to the oxygen in the air. The reaction is called oxidation.

A non-metallic utensil used in fresh preserving to remove or free air bubbles trapped inside the jar. To ensure appropriate headspace, air bubbles should be removed before the two-piece closure is applied.