Canning |
Food Prosessing |
Canning -
how to canning, for canning, canning jars, canning food - is a method of
preserving food by first
sealing it in
air-tight jars,
cans or pouches, and then
heating it to a temperature that destroys
contaminating microorganisms that can either be of health or spoilage concern because of the danger posed by several
spore-forming thermo-resistant microorganisms, such as
Clostridium botulinum.Spores of
C.Botulinum(in a concentration of 104/ml)can resist
boiling at 100°C(212°F)for more than 300 minutes; however, as temperature increases the times decrease exponentially, so at 121°C(250°F)for the same concentration just 2.8minutes are required.
From a
public safety point of view,
foods with
low acidity(i.e., pH 4.3)need
sterilization by
canning under conditions of both high temperature(116-130°C)and pressure.
Foods that must be pressure
canned include most
vegetables,
meats,
seafood,
poultry,and
dairy products. The only
foods that may be safely
canned in a boiling water bath (without high pressure) are highly acidic foods with a pH below 4.6,such as fruits, pickled vegetables, or other foods to which acid has been added.
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| Cans / Tins |
During the early Civil Wars, the notable French newspaper Le Monde, prompted by the government, offered a hefty cash award of 12,000 Francs to any inventor who could come up with a cheap and effective method of preserving large amounts of food. The massive armies of the period required regular supplies of quality food, and so preservation became a necessity. In 1809, the French confectioner Nicolas François Appert observed that food cooked inside a
jar did not spoil unless the seals leak, thus developed a method of
sealing food inside
glass jars. The reason why food did not spoil was unknown at the time, since it would take another 50 years before Louis Pasteur would confirm the existence of microbes. However, glass containers presented many challenges for transportation.
Glass jars were replaced with cylindrical tin or wrought-iron canisters (later shortened to "cans") following the work of Peter Durand (1810), which were both cheaper and quicker to make and much more resilient than fragile glass jars. Tin-openers were not to be invented for another 30 years—at first, soldiers had to cut the cans open with bayonets or smash them open with rocks. The French Army began experimenting with issuing tinned foods to its soldiers, but the slow process of tinning foods and the even slower development and transport stages prevented the army from shipping large amounts around the French Empire, and the war ended before the process could be perfected. Unfortunately for Appert, the factory which he had built with his prize money was burned down in 1814 by Allied soldiers invading France. Following the end of the Napoleonic Wars, the canning process was gradually put into practice in other European countries and in the United States. Based on Appert's methods of food preservation, Peter Durand patented a process in the United Kingdom in 1810, developing a process of packaging food in sealed airtight wrought-iron cans. Initially, the canning process was slow and labor-intensive, as each can had to be hand-made and took up to six hours to cook properly, making tinned food too expensive for ordinary people to buy. In 1824 meats and stews produced by the Appert method were carried by Sir William Edward Parry in his voyage to find a northwestern passage to India. Throughout the mid-nineteenth century, tinned food became a status symbol amongst middle-class households in Europe, becoming something of a frivolous novelty. Early methods of manufacture employed poisonous lead solder for sealing the tins, which had disastrous consequences for the 1845 Franklin expedition to the Arctic Ocean.
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| Glass jars |
Increasing mechanization of the
canning process, coupled with a huge increase in urban populations across Europe, resulted in a rising demand for tinned food. A number of inventions and improvements followed, and by the 1860s, the time to cook food in
sealed cans had been reduced from around six hours to only 30 minutes.
Canned food also began to spread beyond Europe-ThomasKensett established the first American
canning factory in New York City in 1812, using improved tin-plated wrought-iron cans for
preserving oysters,
meats,
fruits and
vegetables. Demand for
tinned food greatly increased during wars. Large-scale wars in the nineteenth century, such as the Crimean War, American Civil War, and Franco-Prussian War introduced increasing numbers of working-class men to tinned 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 era Britain demanded ever-increasing quantities of cheap, varied,
good-quality food that they could keep on the shelves at home without having to go to the shops every day for fresh produce. In response, companies such as Nestlé, Heinz, and others emerged to provide shops with
good-quality tinned food for sale to ordinary working class city-dwellers. The late nineteenth century saw the range of tinned food available to urban populations greatly increase, as rival
canning companies competed with each other using novel foodstuffs, highly decorated printed labels, and lower prices.
Demand for tinned food skyrocketed during World War I, as military commanders sought vast quantities of cheap, high-calorie food to feed their millions of soldiers; food which could be transported safely, would survive trench conditions, and which would not spoil in between the factory and the front lines. Throughout the war soldiers generally subsisted on very low-quality tinned foodstuffs, such as the British "Bully Beef" , pork and beans and Maconochies Irish Stew, but by 1916 widespread boredom with cheap tinned food amongst soldiers resulted in militarily purchasing better-quality food, in order to improve low morale, and the first complete meals in a tin began to appear. In 1917 the French Army began issuing tinned French cuisine, such as coq au vin, whilst the Italian Army experimented with tinned ravioli and spaghetti bolognese. Shortages of tinned food in the British Army in 1917 led to the government issuing cigarettes and even amphetamines to soldiers to suppress their appetites. After the war, companies that had supplied tinned food to national militarily improved the quality of their goods for sale on the civilian market.
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| Laminate-vacuum-pouches |
Today,
tin-coated steel is the material most commonly used.
Laminate vacuum pouches are also now used for
canning,such as those found in an
MRE.
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