Food cans are cans for the long-term storage of perishable substances, such as B. Food. The term "preserve" (from the Latin conserva ) originally meant a medicine preserved with honey or sugar . (See also: Preservation .) The can, which is sealed with technical means, protects its contents from dirt, microorganisms and atmospheric oxygen during storage and transport .
Compared to canning jars , they are lighter and not breakable.
They are made of sheet metal, e.g. B. tinplate or aluminum , and are sealed after filling by soldering or flanging . Once opened, they cannot be closed tightly again.
In 1795, Napoleon Bonaparte , after being appointed commanding general of the French Home Army, offered a price of 12,000 gold francs for a method of preserving food and feeding soldiers without looting.
The idea of heating food in airtight containers and thus preserving it came to the Parisian confectioner and confectioner Nicolas Appert . He used glass bottles. This method was tested by the French Navy and Appert was paid the money in 1810, for “The art of all animal and vegetable substances, namely all kinds of meat, poultry, venison, fish, vegetables, cakes - Arzney plants, fruits, soups, juices; Furthermore, to keep beer, coffee, tea etc. in full freshness, palatability and peculiar flavor for several years. ”In 1810, the British merchant Peter Durand came up with the idea of implementing the Appert method with tin canisters, and thus invented the tin can. This invention was patented on August 25, 1810 . Durand himself did not deal with the production, this was first done by the British Bryan Donkin and John Hall, who opened a canning factory in 1813 and supplied it to the British Army.
Since the 1930s, beverage cans , which have since become more and more specialized , mainly used for beer and soft drinks , emerged as special types of cans in the USA .
The Norwegian Can Museum, founded in Stavanger in 1982, deals with the history of the canning industry, especially the Norwegian one .
Tinplate and aluminum sheet in particular are used as material for food cans. Tinplate is a thin sheet of steel with a thickness of up to 0.49 millimeters , the surface of which has been coated with tin by a hot-dip process or electrolytically in order to protect the steel from corrosion . Around 70 percent of the tinplate produced is used in the food sector for the manufacture of food cans and beverage cans. Recently, chromated (electrolytically chrome-plated) sheet steel has also been used for this purpose.
Three-part cans consist of the tubular body (the "frame"), which is welded or flanged (and possibly also soldered) along the longitudinal seam, and the two lids. Two-part cans consist of the deep-drawn (and possibly also ironed) can body and the lid.
Early food cans were sealed with lead by soldering . Under unfavorable circumstances, this could lead to lead poisoning after consuming the food stored in the can. The Arctic expedition of the British Sir John Franklin from 1845 to 1848, whose members suffered from severe lead poisoning after three years of canned food , is best known . Also in the Arctic, canned food with excessively high concentrations of lead could be identified as the cause of death of 17 Norwegian seal hunters in the tragedy in Svenskhuset on Spitzbergen in 1872/1873 .
Today's tin cans are hermetically sealed by flanging after they have been filled . For this, can sealing machines are used, some of which have 20 sealing stations.
After sealing, the cans are pasteurized or sterilized in an autoclave to make them durable.
Today's cans are usually provided with a plastic coating on the inside . The paints used are plastics based on polyester , epoxy resins or organosols . Epoxy systems are currently the subject of criticism because they release small amounts of substances such as bisphenol A ( bisphenol A problem ) into the contents of the canned food. Before the introduction of the plastic coating, the contents had to be transferred to other vessels, since after the access of air, the metal on the inside of the can reacted with the possibly acidic contents of the can when it was opened.
A possible external coating or (offset) printing or embossing is applied to the starting material (sheet metal or sheet metal strip) for larger quantities before the actual can production. In the case of deep-drawn cans, the pressure is applied in a distorted form, so that the desired image results after the deformation.
Small numbers of promotional tins can be subsequently embossed or printed with pad printing. The laser labeling of sealed tin cans is new.
Even microwaveable cans are now available. For this purpose, a process was developed with which a metal can body can be connected to a plastic lid . Through the plastic lid as a permeable window for electromagnetic microwaves , the energy enters the can and heats the contents there.
For some products (peanuts, cat food, etc.), PE lids are added to seal them for short-term storage (after removing the tear-off plate) .
Typical by heating canned preserved foods are fruits such as peaches , pears and pineapples , vegetables , especially legumes such as cooked lentils and beans , fish such as sardines , mackerel and herring and corned beef , sausage , duration bread and ready meals with or without meat . In addition, feed such as dog and cat food are packaged in tins.
If the food, such as vegetables, is freshly processed and bottled directly, a tin can allows the aroma and approximately half of the vitamins to be preserved for several years. However, they do not reach the minimum shelf life of five years, as most of the vitamins are broken down within three years.
In a bulge of the lid ( cambering ) of the content may be spoiled, because of insufficient sterilization during manufacture. In particular, spore-forming bacteria, which are difficult to suppress, can cause life-threatening poisoning ( botulism ). The Swedish specialty Surstromming, however, is always offered in bombs.
Powders, such as milk powder , are also packaged in cans. In this case, before sealing, a vacuum is created in the can and then nitrogen is filled in as a protective atmosphere to prevent the contents from spoiling, as pasteurization is not possible with powdered products.
A distinction is made in the preservation of foodstuffs or luxury foods:
- Fully canned food with an unlimited shelf life of at least two years
- Semi- preserved foods (preserves) that have been made durable to a limited extent by chemical additives
- Three-quarter tins that can be kept for up to twelve months (at max. 20 ° C)
Tin cans were initially broken open with an ax , hammer and chisel or a large knife. The handy can opener was invented by Robert Yeates in 1855 .
Today tins are often offered with a tear-off lid (ring pull). Such covers have a metal tab that is riveted to the cover. It is opened along a scratch line.
The production takes place in several steps. First, a cover is punched out of a metal sheet. Then the geometry of the lid edge is formed in the roller and the sealing compound (compound) is introduced into the gumming machine. After the compound has dried, the first production stage (shell) is ready. It is a fully functional lid with no opening mechanism.
In the last production step, the tab is punched and shaped from narrow metal coils. A bubble is drawn from the mirror of the shell and shaped into a cylinder in several steps. At the same time, the cover area is provided with beads . The prefabricated flap is finally placed on the cylinder and the cylinder is leveled so that a rivet results. Typical production speeds are between 300 and 500 strokes per minute. In this way, 2000 lids per minute can be produced on multi-lane systems with up to 4 tools. At first, tear-open lids were mainly made of aluminum, but steel has been the standard here since the 1980s.
- Improvised cooker from a tin can, see hobo cooker
- A corded phone is made up of cans or paper or plastic cups
- For the environmental balance of cans, see beverage can
- Merda d'artista , conceptual art with feces in cans
- Canstruction , art with cans.
- M. Appert: The art of preserving of all kinds of animal and vegetable substances for several years . Black, Parry, and Kingsbury, London 1812.
- The Repertory of Arts, Manufactures, and Agriculture. Second Series 112; Sept 1811: Specification of the patent granted to Peter Durand, of Hoxton-square, in the County of Middlesex, Merchant; for a Method of preserving Animal Food, Vegetable Food, and other perishable Articles, a long time from perishing or becoming useless . Communicated to him by a person residing abroad. London, August 25, 1810.
- ND Cowell: More light on the dawn of canning. In: Food Technology. 2007; No. 5, pp. 40-45.
- M. Appert: Le livre de tous ménages, ou l'art de conserver, pendant plusieurs années, toutes les substances animales et végétales . Barrois L'Ainé, Paris 1831.
- K. Gierschner et al .: Specific modifications of cell wall hydrocolloids in a new technique for processing high quality canned vegetables. In: Deutsche Lebensmittel-Rundschau . 1995; 91, pp. 103-109.
- R. Garciaa, J. Adriana: Nicolas Appert: Inventor and manufacturer. In: Food Reviews International. 2009; 25, pp. 115-125.
- H. Sielaff: Technology of canning production. 1st edition. Behr's Verlag, Hamburg 1996, ISBN 3-86022-283-X .
- G. Hartwig, H. von der Linden, HP Skrobisch: Thermal preservation in the food industry. 2nd Edition. Behr's Verlag, Hamburg 2014, ISBN 978-3-95468-038-2 .
- H. Keim, R. Franke: Expertise meat technology. 13th edition. Deutscher Fachverlag, Frankfurt am Main 2007, ISBN 978-3-87150-899-8 , pp. 379-391.
- Canned bread is still edible after 50 years. on: welt.de , July 2, 2002.
- Udo Pollmer : It's the tin can's birthday. Contribution to Deutschlandradio Kultur on August 29, 2010. *
- Specialist trade information about the shelf life of canned food
- ↑ Willem F. Daems: dosage forms. In: Lexikon des Mittelalters I, Sp. 1094-1096, here: Sp. 1095
- ↑ Hanno Ballhausen, Ute Kleinelümern: The most important inventions of mankind. Ingenious ideas that changed the world . Chronik Verlag, Gütersloh / Munich 2008, p. 128.
- ↑ Article on the website of the Weck company
- ↑ Specification of the patent granted to Peter Durand (via Google Books )
- ↑ Owen Beattie, John Geiger: The icy sleep. The fate of the Franklin expedition . vgs, Cologne 1990, ISBN 3-8025-2182-X , p. 154 .
- ↑ Packaging Europe . Volume 2.2, 2007, p. 7.
- ↑ Nutrition and diet: Vegetables and fruit in winter: frozen or canned ( page no longer available , search in web archives ) Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice. , know everything, hr-online.de, January 23, 2013, accessed on January 27, 2013.