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Curing (food preservation)

Curing (food preservation)

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Curing refers to various 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....

 and flavor
Seasoning is the process of imparting flavor to, or improving the flavor of, food.- General meaning :Seasonings include herbs and spices, which are themselves frequently referred to as "seasonings"...

ing processes, especially of 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...

 or fish
Fish (food)
Fish is a food consumed by many species, including humans. The word "fish" refers to both the animal and to the food prepared from it. Fish has been an important source of protein for humans throughout recorded history.-Terminology:...

, by the addition of a combination of salt
Edible salt
Salt, also known as table salt, or rock salt, is a mineral that is composed primarily of sodium chloride , a chemical compound belonging to the larger class of ionic salts. It is essential for animal life in small quantities, but is harmful to animals and plants in excess...

, nitrate
The nitrate ion is a polyatomic ion with the molecular formula NO and a molecular mass of 62.0049 g/mol. It is the conjugate base of nitric acid, consisting of one central nitrogen atom surrounded by three identically-bonded oxygen atoms in a trigonal planar arrangement. The nitrate ion carries a...

s, nitrite
The nitrite ion has the chemical formula NO2−. The anion is symmetric with equal N-O bond lengths and a O-N-O bond angle of ca. 120°. On protonation the unstable weak acid nitrous acid is produced. Nitrite can be oxidised or reduced, with product somewhat dependent on the oxidizing/reducing agent...

 or sugar
Sugar is a class of edible crystalline carbohydrates, mainly sucrose, lactose, and fructose, characterized by a sweet flavor.Sucrose in its refined form primarily comes from sugar cane and sugar beet...

. Many curing processes also involve smoking, the process of flavoring, or cooking
Cooking is the process of preparing food by use of heat. Cooking techniques and ingredients vary widely across the world, reflecting unique environmental, economic, and cultural traditions. Cooks themselves also vary widely in skill and training...

. The use of food dehydration
Drying (food)
Drying is a method of food preservation that works by removing water from the food, which inhibits the growth of microorganisms and hinders quality decay. Drying food using sun and wind to prevent spoilage has been practised since ancient times, and was the earliest form of food curing...

 was the earliest form of food curing.


Food curing dates back to ancient times, both in the form of smoked meat
Smoked meat
Smoked meat is a method of preparing red meat which originates in prehistory. Its purpose is to preserve these protein-rich foods, which would otherwise spoil quickly, for long periods. There are two mechanisms for this preservation: dehydration and the antibacterial properties of absorbed smoke...

 and as salt-cured meat
Salt-cured meat
Salt-cured meat or salted meat, for example bacon and kippered herring, is meat or fish preserved or cured with salt. Salting, either with dry salt or brine, was the only widely available method of preserving meat until the 19th century...

. The Plains Indians
Plains Indians
The Plains Indians are the Indigenous peoples who live on the plains and rolling hills of the Great Plains of North America. Their colorful equestrian culture and resistance to White domination have made the Plains Indians an archetype in literature and art for American Indians everywhere.Plains...

 used to hang their meat at the top of their teepees to increase the amount of smoke coming into contact with the food. It was discovered in the 1800s that salt mixed with nitrites (saltpeter
Sodium nitrate
Sodium nitrate is the chemical compound with the formula NaNO3. This salt, also known as Chile saltpeter or Peru saltpeter to distinguish it from ordinary saltpeter, potassium nitrate, is a white solid which is very soluble in water...

) would color meats red, rather than grey, and consumers at that time then strongly preferred the red-colored meat.


Table salt (sodium chloride
Sodium chloride
Sodium chloride, also known as salt, common salt, table salt or halite, is an inorganic compound with the formula NaCl. Sodium chloride is the salt most responsible for the salinity of the ocean and of the extracellular fluid of many multicellular organisms...

) is the primary ingredient used in meat curing. Removal of water and addition of salt to meat creates a solute
A solvent is a liquid, solid, or gas that dissolves another solid, liquid, or gaseous solute, resulting in a solution that is soluble in a certain volume of solvent at a specified temperature...

-rich environment where osmotic pressure
Osmotic pressure
Osmotic pressure is the pressure which needs to be applied to a solution to prevent the inward flow of water across a semipermeable membrane....

 draws water out of microorganisms, retarding their growth. Doing this requires a concentration of salt of nearly 20%. In addition, salt causes the soluble meat proteins to come to the surface of the meat particles within sausages. These proteins coagulate when the sausage is heated, helping to hold the sausage together. Finally, salt slows the oxidation process, effectively preventing the meat from going rancid.


The sugar
Sugar is a class of edible crystalline carbohydrates, mainly sucrose, lactose, and fructose, characterized by a sweet flavor.Sucrose in its refined form primarily comes from sugar cane and sugar beet...

 added to meat for the purpose of curing it comes in many forms, including honey
Honey is a sweet food made by bees using nectar from flowers. The variety produced by honey bees is the one most commonly referred to and is the type of honey collected by beekeepers and consumed by humans...

, corn syrup
Corn syrup
Corn syrup is a food syrup, which is made from the starch of maize and contains varying amounts of maltose and higher oligosaccharides, depending on the grade. Corn syrup is used in foods to soften texture, add volume, prevent crystallization of sugar, and enhance flavor...

 solids, and maple syrup
Maple syrup
Maple syrup is a syrup usually made from the xylem sap of sugar maple, red maple, or black maple trees, although it can also be made from other maple species such as the bigleaf maple. In cold climates, these trees store starch in their trunks and roots before the winter; the starch is then...

. However, with the exception of bacon, it does not contribute much to the flavor, but it does alleviate the harsh flavor of the salt. Sugar also contributes to the growth of beneficial bacteria like Lactobacillus
Lactobacillus is a genus of Gram-positive facultative anaerobic or microaerophilic rod-shaped bacteria. They are a major part of the lactic acid bacteria group, named as such because most of its members convert lactose and other sugars to lactic acid. They are common and usually benign...

by feeding them.

Nitrates and nitrites

Nitrates and nitrites not only help kill bacteria, but also produce a characteristic flavor and give meat a pink or red color. Nitrate (NO3), generally supplied by sodium nitrate
Sodium nitrate
Sodium nitrate is the chemical compound with the formula NaNO3. This salt, also known as Chile saltpeter or Peru saltpeter to distinguish it from ordinary saltpeter, potassium nitrate, is a white solid which is very soluble in water...

 or potassium nitrate
Potassium nitrate
Potassium nitrate is a chemical compound with the formula KNO3. It is an ionic salt of potassium ions K+ and nitrate ions NO3−.It occurs as a mineral niter and is a natural solid source of nitrogen. Its common names include saltpetre , from medieval Latin sal petræ: "stone salt" or possibly "Salt...

, is used as a source for nitrite (NO2). The nitrite further breaks down in the meat into nitric oxide
Nitric oxide
Nitric oxide, also known as nitrogen monoxide, is a diatomic molecule with chemical formula NO. It is a free radical and is an important intermediate in the chemical industry...

 (NO), which then binds to the iron atom in the center of myoglobin's
Myoglobin is an iron- and oxygen-binding protein found in the muscle tissue of vertebrates in general and in almost all mammals. It is related to hemoglobin, which is the iron- and oxygen-binding protein in blood, specifically in the red blood cells. The only time myoglobin is found in the...

A heme or haem is a prosthetic group that consists of an iron atom contained in the center of a large heterocyclic organic ring called a porphyrin. Not all porphyrins contain iron, but a substantial fraction of porphyrin-containing metalloproteins have heme as their prosthetic group; these are...

 group, reducing oxidation and causing a reddish-brown color (nitrosomyoglobin) when raw, and the characteristic cooked-ham pink color (nitrosohemochrome or nitrosyl-heme) when cooked. The addition of ascorbate to cured meat reduces formation of nitrosamine
Nitrosamines are chemical compounds of the chemical structure R1N-N=O, some of which are carcinogenic.-Usages:Nitrosamines are used in manufacture of some cosmetics, pesticides, and in most rubber products. -Occurrences:...

s, but increases the nitrosylation of iron.
The use of nitrates in food preservation is controversial, though, due to the potential for the formation of nitrosamines when the preserved food is cooked at high temperature. The usage of either compound is therefore carefully regulated; for example, in the United States, the concentration of nitrates and nitrites is generally limited to 200 ppm or lower. However, they are considered irreplaceable in the prevention of botulinum poisoning
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...

 from consumption of cured dry sausages by preventing spore germination.

A 2007 study by Columbia University
Columbia University
Columbia University in the City of New York is a private, Ivy League university in Manhattan, New York City. Columbia is the oldest institution of higher learning in the state of New York, the fifth oldest in the United States, and one of the country's nine Colonial Colleges founded before the...

 suggests a link between eating cured meats and chronic obstructive pulmonary disease
Chronic obstructive pulmonary disease
Chronic obstructive pulmonary disease , also known as chronic obstructive lung disease , chronic obstructive airway disease , chronic airflow limitation and chronic obstructive respiratory disease , is the co-occurrence of chronic bronchitis and emphysema, a pair of commonly co-existing diseases...

. Nitrites were posited as a possible cause.


Meat can also be preserved by smoking, which is to cook the meat in the presence of smoke. (Thus, the meat is usually near a fire.) Slow-cooking meat while smoking it will also keep it tender. One method of smoking calls for a smokehouse
A smokehouse is a building where meat or fish is cured with smoke. The finished product might be stored in the building, sometimes for a year or more.-History:...

 with damp wood chips or sawdust
Sawdust is a by-product of cutting lumber with a saw, composed of fine particles of wood. It can present a hazard in manufacturing industries, especially in terms of its flammability....

. In North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

, hardwoods such as hickory
Trees in the genus Carya are commonly known as hickory, derived from the Powhatan language of Virginia. The genus includes 17–19 species of deciduous trees with pinnately compound leaves and big nuts...

, mesquite
Mesquite is a leguminous plant of the Prosopis genus found in northern Mexico through the Sonoran Desert and Chihuahuan Deserts, and up into the Southwestern United States as far north as southern Kansas, west to the Colorado Desert in California,and east to the eastern fifth of Texas, where...

 and maple
Acer is a genus of trees or shrubs commonly known as maple.Maples are variously classified in a family of their own, the Aceraceae, or together with the Hippocastanaceae included in the family Sapindaceae. Modern classifications, including the Angiosperm Phylogeny Group system, favour inclusion in...

 are commonly used for smoking, as are fruit woods such as apple
The apple is the pomaceous fruit of the apple tree, species Malus domestica in the rose family . It is one of the most widely cultivated tree fruits, and the most widely known of the many members of genus Malus that are used by humans. Apple grow on small, deciduous trees that blossom in the spring...

, cherry
The cherry is the fruit of many plants of the genus Prunus, and is a fleshy stone fruit. The cherry fruits of commerce are usually obtained from a limited number of species, including especially cultivars of the wild cherry, Prunus avium....

 and plum
A plum or gage is a stone fruit tree in the genus Prunus, subgenus Prunus. The subgenus is distinguished from other subgenera in the shoots having a terminal bud and solitary side buds , the flowers in groups of one to five together on short stems, and the fruit having a groove running down one...

, and even corncob
A corncob is the central core of a maize ear.The corn plant's ear is also considered a "cob" or "pole" but it is not fully a "pole" until the ear is shucked, or removed from the plant material around the ear...


The smoking can be done in combination with other curing methods such as salting and helps seal the outer layer of the food being cured, making it more difficult for bacteria to enter. Slower and warmer smoking methods can be used to dehydrate the meat, further increasing its susceptibility to bacteria, similar to jerky
Jerky can refer to:*Jerky, a type of dried meat*The Jerky Boys, a prank phone call performance groupSee also*Jerk...


There are several types of smoking styles, but hot smoking, smoke roasting (pit barbecuing) and cold smoking are the most common. Smoke roasting and hot smoking actually cooks the food while cold smoking does not, as the food is only exposed to the cooled smoke of the wood before it exits the smoking device. Some foods, such as smoked salmon
Smoked salmon
Smoked salmon is a preparation of salmon, typically a fillet that has been cured and then hot or cold smoked. Due to its moderately high price, smoked salmon is considered a delicacy.-Presentation:...

, can be smoked in a variety of ways.

See also

  • Brining
    In cooking, brining is a process similar to marination in which meat is soaked in brine before cooking.Brining makes cooked meat moister by hydrating the cells of its muscle tissue before cooking, via the process of osmosis, and by allowing the cells to hold on to the water while they are cooked,...

  • Charcuterie
    Charcuterie is the branch of cooking devoted to prepared meat products such as bacon, ham, sausage, terrines, galantines, pâtés, and confit, primarily from pork. Charcuterie is part of the garde manger chef's repertoire...

  • Curing salt
    Curing salt
    Prague powder #1 or pink salt contains 93.75% table salt and 6.25% sodium nitrite. Prague powder #2 contains sodium nitrate in addition to sodium nitrite. Both kinds are used in the preserving and curing of meats, and in sausage making...

  • 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...

  • Salting (food)
    Salting (food)
    Salting is the preservation of food with dry edible salt. It is related to pickling . It is one of the oldest methods of preserving food, and two historically significant salt-cured foods are dried and salted cod and salt-cured meat.Salting is used because most bacteria, fungi and other potentially...

  • Sausage making
    Sausage making
    Sausage making originally developed as a means to preserve and transport meat. Primitive societies learned that dried berries and spices could be added to dried meat. By 600-500 BC there is mention of sausages from China, Rome and Greece. Sausages come in two main types: fresh and cured. Cured...

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