Canning
Overview
 

Canning is a method of preserving food
Food preservation
Food preservation is the process of treating and handling food to stop or slow down spoilage and thus allow for longer storage....

 in which the food contents are processed and sealed in an airtight container. Canning provides a typical shelf life ranging from one to five years, although under specific circumstances a freeze-dried canned product, such as canned, dried lentils, can last as long as 30 years in an edible state. The process was first developed as a French military discovery by Nicolas Appert
Nicolas Appert
Nicolas Appert , was the French inventor of airtight food preservation. Appert, known as the "father of canning", was a confectioner.-Biography:...

 in 1810.
Encyclopedia

Canning is a method of preserving food
Food preservation
Food preservation is the process of treating and handling food to stop or slow down spoilage and thus allow for longer storage....

 in which the food contents are processed and sealed in an airtight container. Canning provides a typical shelf life ranging from one to five years, although under specific circumstances a freeze-dried canned product, such as canned, dried lentils, can last as long as 30 years in an edible state. The process was first developed as a French military discovery by Nicolas Appert
Nicolas Appert
Nicolas Appert , was the French inventor of airtight food preservation. Appert, known as the "father of canning", was a confectioner.-Biography:...

 in 1810. The packaging prevents microorganism
Microorganism
A microorganism or microbe is a microscopic organism that comprises either a single cell , cell clusters, or no cell at all...

s from entering and proliferating inside.

To prevent the food from being spoiled before and during containment, a number of methods are used: pasteurisation, boiling (and other applications of high temperature over a period of time), refrigeration, freezing, drying, vacuum treatment, antimicrobial agents that are natural to the recipe of the foods being preserved, a sufficient dose of ionizing radiation, submersion in a strong saline solution, acid, base, osmotically extreme (for example very sugary) or other microbe-challenging environments.

Other than sterilization
Sterilization (microbiology)
Sterilization is a term referring to any process that eliminates or kills all forms of microbial life, including transmissible agents present on a surface, contained in a fluid, in medication, or in a compound such as biological culture media...

, no method is perfectly dependable as a preservative. For example, the microorganism 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...

(which causes 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...

), can only be eliminated at temperatures above the boiling point.

From a public safety point of view, foods with low acidity (a pH
PH
In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...

 more than 4.6) need sterilization under high temperature (116-130 °C). To achieve temperatures above the boiling point requires the use of a pressure canner
Pressure cooking
Pressure cooking is a method of cooking in a sealed vessel that does not permit air or liquids to escape below a preset pressure. Because the boiling point of water increases as the pressure increases, the pressure built up inside the cooker allows the liquid in the pot to rise to a higher...

. Foods that must be pressure canned include most 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, 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...

, seafood
Seafood
Seafood is any form of marine life regarded as food by humans. Seafoods include fish, molluscs , crustaceans , echinoderms . Edible sea plants, such as some seaweeds and microalgae, are also seafood, and are widely eaten around the world, especially in Asia...

, poultry
Poultry
Poultry are domesticated birds kept by humans for the purpose of producing eggs, meat, and/or feathers. These most typically are members of the superorder Galloanserae , especially the order Galliformes and the family Anatidae , commonly known as "waterfowl"...

, and dairy
Dairy
A dairy is a business enterprise established for the harvesting of animal milk—mostly from cows or goats, but also from buffalo, sheep, horses or camels —for human consumption. A dairy is typically located on a dedicated dairy farm or section of a multi-purpose farm that is concerned...

 products. The only foods that may be safely canned in an ordinary boiling water bath are highly 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...

ic ones with a pH below 4.6, such as fruit
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, pickled
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...

 vegetables, or other foods to which acidic additives have been added.

History and development of canning

During the first years of the Napoleonic Wars
Napoleonic Wars
The Napoleonic Wars were a series of wars declared against Napoleon's French Empire by opposing coalitions that ran from 1803 to 1815. As a continuation of the wars sparked by the French Revolution of 1789, they revolutionised European armies and played out on an unprecedented scale, mainly due to...

, the French government offered a hefty cash award of 12,000 francs to any inventor who could devise a cheap and effective method of preserving large amounts of food. The larger armies of the period required increased, regular supplies of quality food. Limited food availability was among the factors limiting military campaigns to the summer and autumn months. In 1809, a French confectioner and brewer, Nicolas Appert
Nicolas Appert
Nicolas Appert , was the French inventor of airtight food preservation. Appert, known as the "father of canning", was a confectioner.-Biography:...

, observed that food cooked inside a jar did not spoil unless the seals leaked, and developed a method of sealing food in glass jars. The reason for lack of spoilage was unknown at the time, since it would be another 50 years before Louis Pasteur
Louis Pasteur
Louis Pasteur was a French chemist and microbiologist born in Dole. He is remembered for his remarkable breakthroughs in the causes and preventions of diseases. His discoveries reduced mortality from puerperal fever, and he created the first vaccine for rabies and anthrax. His experiments...

 demonstrated the role of microbes in food spoilage. However, glass containers presented challenges for transportation.
Glass jars were largely replaced in commercial canneries with cylindrical tin
Tin can
A tin can, tin , steel can, or a can, is a sealed container for the distribution or storage of goods, composed of thin metal. Many cans require opening by cutting the "end" open; others have removable covers. Cans hold diverse contents: foods, beverages, oil, chemicals, etc."Tin" cans are made...

 or wrought-iron canisters (later shortened to "cans") following the work of Peter Durand
Peter Durand
Peter Durand was a British merchant who is widely credited with receiving the first patent for the idea of preserving food using tin cans. The patent was granted on August 25, 1810 by King George III of England....

 (1810). Cans are cheaper and quicker to make, and much less fragile than glass jars. Glass jars have remained popular for some high-value products and in home canning
Home canning
Home canning or bottling, also known colloquially as putting up or processing, is the process of preserving foods, in particular, fruits, vegetables, and meats, by packing them into glass jars and then heating the jars to kill the organisms that would create spoilage.- North America :In North...

. Can opener
Can opener
A can opener is a device used to open metal cans. Although preservation of food using tin cans had been practiced since at least 1772 in the Netherlands, the first can openers were patented only in 1855 in England and in 1858 in the United States. Those openers were basically variations of a...

s were not invented for another thirty years — at first, soldiers had to cut the cans open with bayonet
Bayonet
A bayonet is a knife, dagger, sword, or spike-shaped weapon designed to fit in, on, over or underneath the muzzle of a rifle, musket or similar weapon, effectively turning the gun into a spear...

s or smash them open with rocks. The French Army began experimenting with issuing canned foods to its soldiers, but the slow process of canning foods and the even slower development and transport stages prevented the army from shipping large amounts across the French Empire
First French Empire
The First French Empire , also known as the Greater French Empire or Napoleonic Empire, was the empire of Napoleon I of France...

, and the war ended before the process was perfected. Unfortunately for Appert, the factory which he had built with his prize money was razed in 1814 by Allied
Six Days Campaign
The Six Days Campaign was a final series of victories by the forces of Napoleon Bonaparte as the Sixth Coalition closed in on Paris....

 soldiers invading France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...

.
Following the end of the Napoleonic Wars
Napoleonic Wars
The Napoleonic Wars were a series of wars declared against Napoleon's French Empire by opposing coalitions that ran from 1803 to 1815. As a continuation of the wars sparked by the French Revolution of 1789, they revolutionised European armies and played out on an unprecedented scale, mainly due to...

, the canning process was gradually employed in other European countries and in the US. Based on Appert's methods of food preservation, Peter Durand patented a process in the United Kingdom
United 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...

 in 1810. He did not develop the process, selling his patent in 1811 to Bryan Donkin
Bryan Donkin
Bryan Donkin was an English engineer and industrialist. Of his six sons, John, Bryan, and Thomas also became engineers.-Early life:Born in Sandoe, Northumberland, his father was a surveyor and land agent...

 and John Hall, who were in business as Donkin Hall and Gamble, of Bermondsey. Bryan Donkin developed the process of packaging food in sealed airtight cans, made of tinned wrought iron. Initially, the canning process was slow and labour-intensive, as each large can had to be hand-made, and took up to six hours to cook, making canned food too expensive for ordinary people. The main market for the food at this stage was the British Army
British Army
The British Army is the land warfare branch of Her Majesty's Armed Forces in the United Kingdom. It came into being with the unification of the Kingdom of England and Scotland into the Kingdom of Great Britain in 1707. The new British Army incorporated Regiments that had already existed in England...

 and Royal Navy
Royal Navy
The Royal Navy is the naval warfare service branch of the British Armed Forces. Founded in the 16th century, it is the oldest service branch and is known as the Senior Service...

. By 1817 Donkin recorded that he had sold £3000 worth of canned meat in six months. In 1824 Sir William Edward Parry
William Edward Parry
Sir William Edward Parry was an English rear-admiral and Arctic explorer, who in 1827 attempted one of the earliest expeditions to the North Pole...

 took canned beef and pea soup with him on his voyage to the Arctic in HMS Fury, during his search for a northwestern passage to India. In 1829, Admiral Sir James Ross
James Clark Ross
Sir James Clark Ross , was a British naval officer and explorer. He explored the Arctic with his uncle Sir John Ross and Sir William Parry, and later led his own expedition to Antarctica.-Arctic explorer:...

 also took canned food to the Arctic, as did Sir John Franklin in 1845. Some of his stores were found by the search expedition led by Captain (later Admiral Sir) Leopold McLintock in 1857. One of these cans was opened in 1939, and was edible and nutritious, though it was not analysed for contamination by the lead solder used in its manufacture.

Throughout the mid-19th century, canned food became a status symbol amongst middle-class households in Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

, becoming something of a frivolous novelty
Novelties
A novelty item is a small manufactured adornment, especially a personal adornment.- Novelty item :This term covers a range of small manufactured goods, such as*antiques*collectables*chocolates*esoterica*executive toys*gadgets*tools and implements...

. Early methods of manufacture employed poisonous lead
Lead
Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...

 solder
Solder
Solder is a fusible metal alloy used to join together metal workpieces and having a melting point below that of the workpiece.Soft solder is what is most often thought of when solder or soldering are mentioned and it typically has a melting range of . It is commonly used in electronics and...

 for sealing the cans, which may have worsened the disastrous outcome of the 1845 Franklin expedition
Franklin's lost expedition
Franklin's lost expedition was a doomed British voyage of Arctic exploration led by Captain Sir John Franklin that departed England in 1845. A Royal Navy officer and experienced explorer, Franklin had served on three previous Arctic expeditions, the latter two as commanding officer...

 to chart and navigate the Northwest Passage
Northwest Passage
The Northwest Passage is a sea route through the Arctic Ocean, along the northern coast of North America via waterways amidst the Canadian Arctic Archipelago, connecting the Atlantic and Pacific Oceans...

.

Increasing mechanisation of the canning process, coupled with a huge increase in urban populations across Europe, resulted in a rising demand for canned food. A number of inventions and improvements followed, and by the 1860s smaller machine-made steel cans were possible, and the time to cook food in sealed cans had been reduced from around six hours to thirty minutes. Canned food also began to spread beyond Europe — Robert Ayars established the first American canning factory in New York City
New York City
New York is the most populous city in the United States and the center of the New York Metropolitan Area, one of the most populous metropolitan areas in the world. New York exerts a significant impact upon global commerce, finance, media, art, fashion, research, technology, education, and...

 in 1812, using improved tin-plated wrought-iron cans for preserving oyster
Oyster
The word oyster is used as a common name for a number of distinct groups of bivalve molluscs which live in marine or brackish habitats. The valves are highly calcified....

s, 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, fruit
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 and 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. Demand for canned food greatly increased during wars. Large-scale wars in the nineteenth century, such as the Crimean War
Crimean War
The Crimean War was a conflict fought between the Russian Empire and an alliance of the French Empire, the British Empire, the Ottoman Empire, and the Kingdom of Sardinia. The war was part of a long-running contest between the major European powers for influence over territories of the declining...

, American Civil War
American Civil War
The American Civil War was a civil war fought in the United States of America. In response to the election of Abraham Lincoln as President of the United States, 11 southern slave states declared their secession from the United States and formed the Confederate States of America ; the other 25...

, and Franco-Prussian War
Franco-Prussian War
The Franco-Prussian War or Franco-German War, often referred to in France as the 1870 War was a conflict between the Second French Empire and the Kingdom of Prussia. Prussia was aided by the North German Confederation, of which it was a member, and the South German states of Baden, Württemberg and...

 introduced increasing numbers of working-class men to canned food, and allowed canning companies to expand their businesses to meet military demands for non-perishable food, allowing companies to manufacture in bulk and sell to wider civilian markets after wars ended. Urban populations in Victorian
Victorian era
The Victorian era of British history was the period of Queen Victoria's reign from 20 June 1837 until her death on 22 January 1901. It was a long period of peace, prosperity, refined sensibilities and national self-confidence...

 Britain
United Kingdom of Great Britain and Ireland
The United Kingdom of Great Britain and Ireland was the formal name of the United Kingdom during the period when what is now the Republic of Ireland formed a part of it....

 demanded ever-increasing quantities of cheap, varied, quality food that they could keep at home without having to go shopping daily. In response, companies such as Nestlé
Nestlé
Nestlé S.A. is the world's largest food and nutrition company. Founded and headquartered in Vevey, Switzerland, Nestlé originated in a 1905 merger of the Anglo-Swiss Milk Company, established in 1867 by brothers George Page and Charles Page, and Farine Lactée Henri Nestlé, founded in 1866 by Henri...

, Heinz
H. J. Heinz Company
The H. J. Heinz Company , commonly known as Heinz and famous for its "57 Varieties" slogan and its ketchup, is an American food company with world headquarters in Pittsburgh, Pennsylvania.Perhaps best known for its ketchup, the H.J...

, and others emerged to provide quality canned food for sale to working class
Working class
Working class is a term used in the social sciences and in ordinary conversation to describe those employed in lower tier jobs , often extending to those in unemployment or otherwise possessing below-average incomes...

 city-dwellers. In particular, Crosse and Blackwell took over the concern of Donkin Hall and Gamble. The late 19th century saw the range of canned food available to urban populations greatly increase, as canners competed with each other using novel foodstuffs, highly decorated printed labels, and lower prices.

Demand for canned food skyrocketed during World War I
World War I
World War I , which was predominantly called the World War or the Great War from its occurrence until 1939, and the First World War or World War I thereafter, was a major war centred in Europe that began on 28 July 1914 and lasted until 11 November 1918...

, as military commanders sought vast quantities of cheap, high-calorie
Calorie
The calorie is a pre-SI metric unit of energy. It was first defined by Nicolas Clément in 1824 as a unit of heat, entering French and English dictionaries between 1841 and 1867. In most fields its use is archaic, having been replaced by the SI unit of energy, the joule...

 food to feed their millions of soldiers, which could be transported safely, survive trench
Trench warfare
Trench warfare is a form of occupied fighting lines, consisting largely of trenches, in which troops are largely immune to the enemy's small arms fire and are substantially sheltered from artillery...

 conditions, and not spoil in transport. Throughout the war, soldiers generally subsisted on low-quality canned foodstuffs, such as the British "Bully Beef" (cheap corned beef
Corned beef
Corned beef is a type of salt-cured beef products present in many beef-eating cultures. The English term is used interchangeably in modernity to refer to three distinct types of cured beef:...

), pork and beans
Pork and beans
Pork and beans is a culinary dish that uses pork and beans as its main ingredients. Numerous variations exist from Fabada Asturiana to Olla podrida to American canned pork and beans.-American canned pork and beans:...

 and Maconochies Irish Stew, but by 1916 widespread boredom with cheap canned food amongst soldiers resulted in militaries purchasing better-quality food to improve morale, and the complete meals in a can began to appear. In 1917 the French Army
French Army
The French Army, officially the Armée de Terre , is the land-based and largest component of the French Armed Forces.As of 2010, the army employs 123,100 regulars, 18,350 part-time reservists and 7,700 Legionnaires. All soldiers are professionals, following the suspension of conscription, voted in...

 began issuing canned French cuisine
French cuisine
French cuisine is a style of food preparation originating from France that has developed from centuries of social change. In the Middle Ages, Guillaume Tirel , a court chef, authored Le Viandier, one of the earliest recipe collections of Medieval France...

, such as coq au vin
Coq au vin
Coq au vin is a French braise of chicken cooked with wine, lardons, mushrooms, and optionally garlic.While the wine is typically Burgundy, many regions of France have variants of coq au vin using the local wine, such as coq au vin jaune , coq au Riesling , coq au pourpre , coq au Champagne, and so...

, while the Italian Army
Italian Army
The Italian Army is the ground defence force of the Italian Armed Forces. It is all-volunteer force of active-duty personnel, numbering 108,355 in 2010. Its best-known combat vehicles are the Dardo infantry fighting vehicle, the Centauro tank destroyer and the Ariete tank, and among its aircraft...

 experimented with canned ravioli
Ravioli
Ravioli are a traditional type of Italian filled pasta. They are composed of a filling sealed between two layers of thin egg pasta dough and are served either in broth or with a pasta sauce. The word ravioli is reminiscent of the Italian verb riavvolgere , though the two words are not...

 and spaghetti bolognese
Bolognese sauce
Bolognese sauce is a meat-based sauce for pasta originating in Bologna, Italy. It is traditionally used to dress tagliatelle and is one of the two sauces used to prepare "lasagne alla Bolognese"...

. Shortages of canned food in the British Army
British Army
The British Army is the land warfare branch of Her Majesty's Armed Forces in the United Kingdom. It came into being with the unification of the Kingdom of England and Scotland into the Kingdom of Great Britain in 1707. The new British Army incorporated Regiments that had already existed in England...

 in 1917 led to the government issuing cigarette
Cigarette
A cigarette is a small roll of finely cut tobacco leaves wrapped in a cylinder of thin paper for smoking. The cigarette is ignited at one end and allowed to smoulder; its smoke is inhaled from the other end, which is held in or to the mouth and in some cases a cigarette holder may be used as well...

s and amphetamine
Amphetamine
Amphetamine or amfetamine is a psychostimulant drug of the phenethylamine class which produces increased wakefulness and focus in association with decreased fatigue and appetite.Brand names of medications that contain, or metabolize into, amphetamine include Adderall, Dexedrine, Dextrostat,...

s to soldiers to suppress their appetites. After the war, companies that had supplied military canned food improved the quality of their goods for civilian sale.

Today, tin-coated 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...

 is the material most commonly used. Laminate vacuum pouches
Aseptic processing
Aseptic processing is the process by which a sterile product is packaged in a sterile container in a way that maintains sterility...

 are also used for canning, such as used in MREs and Capri Sun
Capri Sun
Capri Sun is a brand of juice concentrate drink owned by the German Company WILD and sold in silver pouches. It was developed by Rudolf Wild in 1966 in Germany, where Capri Sonne has been a registered trademark since 1952. Capri Sun has been distributed in the United States since 1981. Kraft Foods...

 drinks.

Double seams

Invented in 1888 by Max Ams, modern double seams
Can seamer
A Can seamer is a machine used to seal the lid to the can body such as in paint or food cans. The lid should be of metal while the body can be of metal , paper or plastic....

 provide an airtight seal
Hermetic seal
A hermetic seal is the quality of being airtight. In common usage, the term often implies being impervious to air or gas. When used technically, it is stated in conjunction with a specific test method and conditions of usage.-Etymology :...

 to the tin can
Tin can
A tin can, tin , steel can, or a can, is a sealed container for the distribution or storage of goods, composed of thin metal. Many cans require opening by cutting the "end" open; others have removable covers. Cans hold diverse contents: foods, beverages, oil, chemicals, etc."Tin" cans are made...

. This airtight nature is crucial to keeping bacteria out of the can and keeping its contents sealed inside. Thus, double seamed cans are also known as Sanitary Cans. Developed in 1900 in Europe, this sort of can was made of the traditional cylindrical body made with tin plate. The two ends (lids
Lid (container)
A lid, also known as a cap, is part of a container, and serves as the cover or seal, usually one that completely closes the object.-History:...

) were attached using what is now called a double seam. A can thus sealed is impervious to the contamination by creating two tight continuous folds between the can’s cylindrical body and the lids. This eliminated the need for solder
Solder
Solder is a fusible metal alloy used to join together metal workpieces and having a melting point below that of the workpiece.Soft solder is what is most often thought of when solder or soldering are mentioned and it typically has a melting range of . It is commonly used in electronics and...

 and allowed improvements in manufacturing speed, reducing cost.

Double seaming uses rollers to shape the can, lid and the final double seam. To make a sanitary can and lid suitable for double seaming, manufacture begins with a sheet of coated tin plate. To create the can body, rectangles are cut and curled around a die, and welded together creating a cylinder with a side seam.

Rollers are then used to flare out one or both ends of the cylinder to create a quarter circle flange around the circumference. Precision is required to ensure that the welded sides are perfectly aligned, as any misalignment will cause inconsistent flange shape, compromising its integrity.

A circle is then cut from the sheet using a die cutter. The circle is shaped in a stamping press to create a downward countersink to fit snugly in to the can body. The result can be compared to an upside down and very flat top hat
Top hat
A top hat, beaver hat, high hat silk hat, cylinder hat, chimney pot hat or stove pipe hat is a tall, flat-crowned, broad-brimmed hat, predominantly worn from the latter part of the 18th to the middle of the 20th century...

. The outer edge is then curled down and around about 140 degrees using rollers to create the end curl.

The result is a steel tube with a flanged edge, and a countersunk steel disc with a curled edge. A rubber
Rubber
Natural rubber, also called India rubber or caoutchouc, is an elastomer that was originally derived from latex, a milky colloid produced by some plants. The plants would be ‘tapped’, that is, an incision made into the bark of the tree and the sticky, milk colored latex sap collected and refined...

 compound is put inside the curl.

Seaming

The body and end are brought together in a seamer and held in place by the base plate and chuck, respectively. The base plate provides a sure footing for the can body during the seaming operation and the chuck fits snugly in to the end (lid). The result is the countersink of the end sits inside the top of the can body just below the flange. The end curl protrudes slightly beyond the flange.

First operation

Once brought together in the seamer, the seaming head presses a first operation roller against the end curl. The end curl is pressed against the flange curling it in toward the body and under the flange. The flange is also bent downward, and the end and body are now loosely joined together. The first operation roller is then retracted. At this point five thicknesses of steel exist in the seam. From the outside in they are:
  • End
  • Flange
  • End Curl
  • Body
  • Countersink

Second operation

The seaming head then engages the second operation roller against the partly formed seam. The second operation presses all five steel components together tightly to form the final seal. The five layers in the final seam are then called; a) End, b) Body Hook, c) Cover Hook, d) Body, e) Countersink. All sanitary cans require a filling medium within the seam because otherwise the metal-to-metal contact will not maintain a hermetic seal. In most cases, a rubberized compound is placed inside the end curl radius, forming the critical seal between the end and the body.

Probably the most important innovation since the introduction of double seams is the welded side seam. Prior to the welded side seam, the can body was folded and/or soldered together, leaving a relatively thick side seam. The thick side seam required that the side seam end juncture at the end curl to have more metal to curl around before closing in behind the Body Hook or flange, with a greater opportunity for error.

Seamer setup and quality assurance

Many different parts during the seaming process are critical in ensuring that a can is airtight and vacuum sealed. The dangers of a can that is not hermetically sealed are contamination by foreign objects (bacteria or fungicide sprays), or that the can could leak or spoil.

One important part is the seamer setup. This process is usually performed by an experienced technician. Amongst the parts that need setup are seamer rolls and chucks which have to be set in their exact position (using a feeler gauge or a clearance gauge). The lifter pressure and position, roll and chuck designs, tooling wear, and bearing wear all contribute to a good double seam.

Incorrect setups can be non-intuitive. For example, due to the springback effect, a seam can appear loose, when in reality it was closed too tight and has opened up like a spring. For this reason, experienced operators and good seamer setup are critical to ensure that double seams are properly closed.

Quality control usually involves taking full cans from the line - one per seamer head, at least once or twice per shift, and performing a teardown operation (wrinkle
Wrinkle
A wrinkle is a fold, ridge or crease in the skin. Skin wrinkles typically appear as a result of aging processes such as glycation or, temporarily, as the result of prolonged immersion in water. Wrinkling in the skin is caused by habitual facial expressions, aging, sun damage, smoking, poor...

/tightness), mechanical tests (external thickness, seamer length/height and countersink) as well as cutting the seam open with a twin blade saw and measuring with a double seam inspection system. The combination of these measurements will determine the seam's quality.

Use of a Statistical Process Control
Statistical process control
Statistical process control is the application of statistical methods to the monitoring and control of a process to ensure that it operates at its full potential to produce conforming product. Under SPC, a process behaves predictably to produce as much conforming product as possible with the least...

 (SPC) software in conjunction with a manual double-seam monitor, computerized double seam scanner, or even a fully automatic double seam inspection system makes the laborious process of double seam inspection faster and much more accurate. Statistically tracking the performance of each head or seaming station of the can seamer
Can seamer
A Can seamer is a machine used to seal the lid to the can body such as in paint or food cans. The lid should be of metal while the body can be of metal , paper or plastic....

 allows for better prediction of can seamer issues, and may be used to plan maintenance when convenient, rather than to simply react after bad or unsafe cans have been produced.

Nutrition value

Canning is a way of processing food to extend its shelf life
Shelf life
Shelf life is the length of time that food, drink, medicine, chemicals, and many other perishable items are given before they are considered unsuitable for sale, use, or consumption...

. The idea is to make food available and edible long after the processing time. A 1997 study found that canned fruits and vegetables provide as much dietary fiber
Dietary fiber
Dietary fiber, dietary fibre, or sometimes roughage is the indigestible portion of plant foods having two main components:* soluble fiber that is readily fermented in the colon into gases and physiologically active byproducts, and* insoluble fiber that is metabolically inert, absorbing water as it...

 and vitamin
Vitamin
A vitamin is an organic compound required as a nutrient in tiny amounts by an organism. In other words, an organic chemical compound is called a vitamin when it cannot be synthesized in sufficient quantities by an organism, and must be obtained from the diet. Thus, the term is conditional both on...

s as the same corresponding fresh or frozen foods, and in some cases, even more. The heating process during canning appears to make dietary fiber more soluble, and therefore more readily fermented in the colon into gases and physiologically active byproducts. Canned tomatoes have a higher available lycopene
Lycopene
Lycopene is a bright red carotene and carotenoid pigment and phytochemical found in tomatoes and other red fruits and vegetables, such as red carrots, watermelons and papayas...

 content.

Potential hazards

To improve food safety for those who eat canned food, governments have enacted laws requiring alphanumeric codes being put on food cans during manufacture indicating information relevant to health, such as the date of canning, etc.

Migration of can components

In canning toxicology, migration is the movement of substances from the can itself into the contents. Potential toxic substances that can migrate are lead, causing lead poisoning
Lead poisoning
Lead poisoning is a medical condition caused by increased levels of the heavy metal lead in the body. Lead interferes with a variety of body processes and is toxic to many organs and tissues including the heart, bones, intestines, kidneys, and reproductive and nervous systems...

, or bisphenol A
Bisphenol A
Bisphenol A is an organic compound with two phenol functional groups. It is used to make polycarbonate plastic and epoxy resins, along with other applications....

, a potential endocrine disruptor
Endocrine disruptor
Endocrine disruptors are chemicals that interfere with endocrine in animals, including humans. These disruptions can cause cancerous tumors, birth defects, and other developmental disorders...

 that is an ingredient in the epoxy commonly used to coat the inner surface of cans.

Salt content

Canned food can be a major source of dietary salt (sodium chloride). Too much salt increases the risk of health problems, including high blood pressure
Hypertension
Hypertension or high blood pressure is a cardiac chronic medical condition in which the systemic arterial blood pressure is elevated. What that means is that the heart is having to work harder than it should to pump the blood around the body. Blood pressure involves two measurements, systolic and...

. Therefore, health authorities have recommended limitations of dietary sodium. Many canned products are available in low-salt and no-salt alternatives.

Botulism

Foodborne 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...

results from contaminated foodstuffs in which C. botulinum spores have been allowed to germinate and produce botulism toxin, and this typically occurs in canned
Home canning
Home canning or bottling, also known colloquially as putting up or processing, is the process of preserving foods, in particular, fruits, vegetables, and meats, by packing them into glass jars and then heating the jars to kill the organisms that would create spoilage.- North America :In North...

 non-acidic food substances. C. botulinum prefers low oxygen environments, and can therefore grow in canned foods. Botulism is a rare but serious paralytic illness, leading to paralysis that typically starts with the muscles of the face and then spreads towards the limbs. In severe forms, it leads to paralysis of the breathing muscles and causes respiratory failure
Respiratory failure
The term respiratory failure, in medicine, is used to describe inadequate gas exchange by the respiratory system, with the result that arterial oxygen and/or carbon dioxide levels cannot be maintained within their normal ranges. A drop in blood oxygenation is known as hypoxemia; a rise in arterial...

. In view of this life-threatening complication, all suspected cases of botulism are treated as medical emergencies
Medical emergency
A medical emergency is an injury or illness that is acute and poses an immediate risk to a person's life or long term health. These emergencies may require assistance from another person, who should ideally be suitably qualified to do so, although some of these emergencies can be dealt with by the...

, and public health
Public health
Public health is "the science and art of preventing disease, prolonging life and promoting health through the organized efforts and informed choices of society, organizations, public and private, communities and individuals" . It is concerned with threats to health based on population health...

 officials are usually involved to prevent further cases from the same source.

Canning and Economic Recession

Canned Goods (and canning supplies) sell particularly well in times of recession due to the tendency of financially stressed individuals to engage in cocooning
Cocooning
Cocooning is the name given to the trend that sees individuals socializing less and retreating into their home more. The term was coined in the 1990s by Faith Popcorn, a trend forecaster and marketing consultant. Popcorn identified cocooning as a commercially significant trend that would lead to,...

, a term used by retail analysts to describe the phenomenon in which people actively avoid straying from their houses.
In February 2009, the recession-laden United States saw an 11.5% rise in sales of canning-related items.

See also

  • Amanda Jones, an American woman author and inventor most noted for inventing a vacuum
    Vacuum
    In everyday usage, vacuum is a volume of space that is essentially empty of matter, such that its gaseous pressure is much less than atmospheric pressure. The word comes from the Latin term for "empty". A perfect vacuum would be one with no particles in it at all, which is impossible to achieve in...

     method of canning called the Jones Process.
  • Canstruction
    Canstruction
    Canstruction is a United States 501 nonprofit organization providing canned food to local food banks in cities holding Canstruction competitions. Canstruction is an international charity competition where architects, engineers, contractors and students they mentor, compete to design and build giant...

     (nonprofit organization)
  • Food industry
    Food industry
    The food production is a complex, global collective of diverse businesses that together supply much of the food energy consumed by the world population...

  • Food preservation
    Food preservation
    Food preservation is the process of treating and handling food to stop or slow down spoilage and thus allow for longer storage....

  • Home canning
    Home canning
    Home canning or bottling, also known colloquially as putting up or processing, is the process of preserving foods, in particular, fruits, vegetables, and meats, by packing them into glass jars and then heating the jars to kill the organisms that would create spoilage.- North America :In North...

  • Pasteurization
    Pasteurization
    Pasteurization is a process of heating a food, usually liquid, to a specific temperature for a definite length of time, and then cooling it immediately. This process slows microbial growth in food...


Famous canned foods

  • Spam
    Spam (food)
    Spam is a canned precooked meat product made by the Hormel Foods Corporation, first introduced in 1937. The labeled ingredients in the classic variety of Spam are chopped pork shoulder meat, with ham meat added, salt, water, modified potato starch as a binder, and sodium nitrite as a preservative...

  • Vienna sausage
    Vienna sausage
    A Vienna sausage is a kind of hot dog...

  • Baked beans
    Baked beans
    Baked beans is a dish containing beans, sometimes baked but, despite the name, usually stewed, in a sauce. Most commercial canned baked beans are made from haricot beans, also known as navy beans – a variety of Phaseolus vulgaris – in a sauce. In Ireland and the United Kingdom, a tomato...

  • Pineapple
    Pineapple
    Pineapple is the common name for a tropical plant and its edible fruit, which is actually a multiple fruit consisting of coalesced berries. It was given the name pineapple due to its resemblance to a pine cone. The pineapple is by far the most economically important plant in the Bromeliaceae...

  • Tomato soup
    Tomato soup
    Tomato soup is a soup made from tomatoes. It may be served hot or cold, and can be made in many styles. It may be smooth in texture, but there are recipes which include chunks of tomato, cream and/or chicken stock. Popular toppings for tomato soup include sour cream, and croutons. Tomato soup is...

  • Tuna fish

External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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