Home canning
Encyclopedia
Fruit
In broad terms, a fruit is a structure of a plant that contains its seeds.The term has different meanings dependent on context. In non-technical usage, such as food preparation, fruit normally means the fleshy seed-associated structures of certain plants that are sweet and edible in the raw state,...
s, vegetable
Vegetable
The noun vegetable usually means an edible plant or part of a plant other than a sweet fruit or seed. This typically means the leaf, stem, or root of a plant....
s, and meat
Meat
Meat is animal flesh that is used as food. Most often, this means the skeletal muscle and associated fat and other tissues, but it may also describe other edible tissues such as organs and offal...
s, by packing them into glass jars and then heating the jars to kill the organisms that would create spoilage.
North America
In North America, home canning is usually done in Mason jarMason jar
A Mason jar is a glass jar used in canning to preserve food. They were invented and patented by John Landis Mason, a Philadelphia tinsmith in 1858. They are also called Ball jars, after Ball Corp., a popular and early manufacturer of the jars; fruit jars because they are often used to store...
s, which have thicker walls than single-use commercial glass jars. Unless the food being preserved has a high acid
Acid
An acid is a substance which reacts with a base. Commonly, acids can be identified as tasting sour, reacting with metals such as calcium, and bases like sodium carbonate. Aqueous acids have a pH of less than 7, where an acid of lower pH is typically stronger, and turn blue litmus paper red...
(pH <4.6), salt or sugar content (resulting in water availability <0.85), such as pickles
Pickling
Pickling, also known as brining or corning is the process of preserving food by anaerobic fermentation in brine to produce lactic acid, or marinating and storing it in an acid solution, usually vinegar . The resulting food is called a pickle. This procedure gives the food a salty or sour taste...
or jellies, the filled jars are also processed under pressure
Pressure
Pressure is the force per unit area applied in a direction perpendicular to the surface of an object. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure.- Definition :...
in a canner, a specialized type of pressure cooker. Ordinary pressure cookers are not recommended for canning as their smaller size and the reduced thickness of the cooker wall will not allow for the correct building up and reducing time of pressure, which is factored into the overall processing time and therefore will not destroy all the harmful microorganisms. The goal in using a pressure canner is to achieve a "botulinum cook" of 121°C for 3 minutes, throughout the entire volume of canned product. Canners often incorporate racks to hold Mason jars, and pressure canners are capable of achieving the elevated temperatures needed to prevent spoilage.
The most common configuration is a Mason jar
Mason jar
A Mason jar is a glass jar used in canning to preserve food. They were invented and patented by John Landis Mason, a Philadelphia tinsmith in 1858. They are also called Ball jars, after Ball Corp., a popular and early manufacturer of the jars; fruit jars because they are often used to store...
with a flat lid and screw ring. The lid is generally made of plated or painted steel
Steel
Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...
, with an elastomeric
Elastomer
An elastomer is a polymer with the property of viscoelasticity , generally having notably low Young's modulus and high yield strain compared with other materials. The term, which is derived from elastic polymer, is often used interchangeably with the term rubber, although the latter is preferred...
washer or gasket
Gasket
thumb|sright|250px|Some seals and gaskets1. [[o-ring]]2. fiber [[Washer |washer]]3. paper gaskets4. [[cylinder head]] [[head gasket|gasket]]...
bonded to the underside of the rim. The lid also incorporates a slightly dimpled shape, which acts as an indicator of the vacuum (or lack thereof) inside a sealed jar. A newer reusable lid is now available that uses a flat plastic disk with a reusable rubber gasket. The brand name for this type of lid is Tattler. The ring threads onto the top of the jar over the lid to hold it in place while the jar cools after processing; the ring can be removed once a vacuum has been established in the jar. Jars are commonly in either pint or quart capacities, with two opening diameters, known as "standard" and "wide mouth".
When a jar has cooled and is properly sealed, pressing the dimple on the lid will not make any sound. An improperly sealed jar will allow the dimple to move up and down, sometimes making a popping noise. Lack of this noise does not necessarily indicate that the food in the jar is properly preserved. Typically, during the cooling process, a properly sealed lid will pop once as the pressure inside the jar is reduced enough that atmospheric pressure pushes the lid inward.
Older variations had a ceramic seal inside a one-piece zinc lid. Another method that is no longer recommended, was the use of layer of hot paraffin wax poured directly over the top of the food (especially jams and jellies) to seal it from air, thus reducing growth of aerobic microorganisms like mold
Mold
Molds are fungi that grow in the form of multicellular filaments called hyphae. Molds are not considered to be microbes but microscopic fungi that grow as single cells called yeasts...
.
While it is possible to safely preserve many kinds of foodstuffs, home canning can expose consumers to botulism
Botulism
Botulism also known as botulinus intoxication is a rare but serious paralytic illness caused by botulinum toxin which is metabolic waste produced under anaerobic conditions by the bacterium Clostridium botulinum, and affecting a wide range of mammals, birds and fish...
and other kinds of food poisoning if done incorrectly. The most common source of food borne botulism is home-canned foods prepared in unsafe manner Safety measures must be taken when performing home canning, since ingestion of toxin in food produced by Clostridium botulinum
Clostridium botulinum
Clostridium botulinum is a Gram-positive, rod-shaped bacterium that produces several toxins. The best known are its neurotoxins, subdivided in types A-G, that cause the flaccid muscular paralysis seen in botulism. It is also the main paralytic agent in botox. C. botulinum is an anaerobic...
can cause death. Because of the high risk of illness or death associated with improper canning techniques, the United States Department of Agriculture
United States Department of Agriculture
The United States Department of Agriculture is the United States federal executive department responsible for developing and executing U.S. federal government policy on farming, agriculture, and food...
(USDA) considers it critical that consumers who intend to can at home obtain proper and current information from a reliable source. At the basis of these recommendations is the balance between bringing the food to a high enough temperature for a long enough time that spoilage and disease-producing microorganisms are killed, while not heating the food so much that it loses nutritive value or palatability.
Food safety precautions (Steps for Home Canning)
Thoroughly wash food itemsBoiling process
- Preparation methods and processing times for canning. Differs for each food, for partial list, see the following link http://www.ext.colostate.edu/pubs/foodnut/09348.pdf
- Kills the spore-forming bacteria
Pressuring process
- Usually pressurize foods at 10 pounds per square inch (psi); add 1/2 psi per 1,000 ft. of elevation
- This process will kill the spores and denature the toxin
Prior to consumtion:
- Boil home canned veggies first
- Boil for 10 minutes plus 1 minute per 1,000 ft of elevation
- Home canned fruits – use boiling water bath
Acidic foods are less likely to induce botulinum toxin production because low pH inhibits germination. Tomatoes are an unlikely food vehicle because of the acidity.
- Add acid (vinegar, lemon/lime juice) to lower pH but in acidic foods like tomatoes and fruits, germination may still occur if molds or other bacteria are present.
- Molds or other bacteria can raise the pH.
United Kingdom
In the United KingdomUnited Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
home bottling is done with Kilner jar
Kilner jar
Kilner jar is a rubber-sealed, screw-topped jar used for the storage of food, which was invented by the Kilner family and produced by John Kilner & Co., Yorkshire, England....
s in a similar way to the Mason jars in the USA, and although old-style Kilner jars have a glass lid without a "dimple" more recent varieties do.
Australia
In AustraliaAustralia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
the most popular home canning system is Fowler's Vacola. This system uses glass jars, single use seals, and metal lids. During the canning process the lids are secured by metal tension clips which are removed once a vacuum seal has formed. Fowler's Vacola products are still produced and are available from some hardware stores. Used equipment is frequently sold on online auction sites and in opportunity shops.
External links
- USDA Complete Guide to Home Canning
- How Do I? ...Can, from the National Center for Home Food Preservation
- Preservation: Canning, Freezing & Drying from the South Carolina Cooperative ExtensionCooperative extension serviceThe Cooperative Extension Service, also known as the Extension Service of the USDA, is a non-formal educational program implemented in the United States designed to help people use research-based knowledge to improve their lives. The service is provided by the state's designated land-grant...
at Clemson UniversityClemson UniversityClemson University is an American public, coeducational, land-grant, sea-grant, research university located in Clemson, South Carolina, United States.... - Richard Roller Papers, documents the history of glass manufacturing, with an emphasis on fruit and vegetable canning jars at the Ball State University Archives and Special Collections Research Center
- "Pressing Lids Seals Fruit Jar; Gasket Molds to Rim" Popular Mechanics, December 1943 article right-middle of page