Home      Discussion      Topics      Dictionary      Almanac
Signup       Login
Food preservation

Food preservation

Overview


Food preservation is the process of treating and handling food
Food
Food is any substance consumed to provide nutritional support for the body. It is usually of plant or animal origin, and contains essential nutrients, such as carbohydrates, fats, proteins, vitamins, or minerals...

 to stop or slow down spoilage
Food spoilage
Spoilage is the process in which food deteriorates to the point in which it is not edible to humans or its quality of edibility becomes reduced. Various external forces are responsible for the spoilage of food. Food that is capable of spoiling is referred to as perishable food.-Reasons:Harvested...

 (loss of quality, edibility or nutritional value) and thus allow for longer storage
Food storage
Food storage is both a traditional domestic skill and is important industrially. Food is stored by almost every human society and by many animals...

.

Preservation usually involves preventing the growth of bacteria, yeast
Yeast
Yeasts are eukaryotic micro-organisms classified in the kingdom Fungi, with 1,500 species currently described estimated to be only 1% of all fungal species. Most reproduce asexually by mitosis, and many do so by an asymmetric division process called budding...

s, fungi
Fungus
A fungus is a member of a large group of eukaryotic organisms that includes microorganisms such as yeasts and molds , as well as the more familiar mushrooms. These organisms are classified as a kingdom, Fungi, which is separate from plants, animals, and bacteria...

, and other micro-organisms
Microorganism
A microorganism or microbe is a microscopic organism that comprises either a single cell , cell clusters, or no cell at all...

 (although some methods work by introducing benign bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

, or fungi to the food), as well as retarding the oxidation
Redox
Redox reactions describe all chemical reactions in which atoms have their oxidation state changed....

 of fat
Fat
Fats consist of a wide group of compounds that are generally soluble in organic solvents and generally insoluble in water. Chemically, fats are triglycerides, triesters of glycerol and any of several fatty acids. Fats may be either solid or liquid at room temperature, depending on their structure...

s which cause rancidity
Rancidification
Rancidification is the chemical decomposition of fats, oils and other lipids . When these processes occur in food, undesirable odors and flavors can result. In some cases, however, the flavors can be desirable . In processed meats, these flavors are collectively known as "warmed over flavor"...

.
Discussion
Ask a question about 'Food preservation'
Start a new discussion about 'Food preservation'
Answer questions from other users
Full Discussion Forum
 
Unanswered Questions
Recent Discussions
Encyclopedia


Food preservation is the process of treating and handling food
Food
Food is any substance consumed to provide nutritional support for the body. It is usually of plant or animal origin, and contains essential nutrients, such as carbohydrates, fats, proteins, vitamins, or minerals...

 to stop or slow down spoilage
Food spoilage
Spoilage is the process in which food deteriorates to the point in which it is not edible to humans or its quality of edibility becomes reduced. Various external forces are responsible for the spoilage of food. Food that is capable of spoiling is referred to as perishable food.-Reasons:Harvested...

 (loss of quality, edibility or nutritional value) and thus allow for longer storage
Food storage
Food storage is both a traditional domestic skill and is important industrially. Food is stored by almost every human society and by many animals...

.

Preservation usually involves preventing the growth of bacteria, yeast
Yeast
Yeasts are eukaryotic micro-organisms classified in the kingdom Fungi, with 1,500 species currently described estimated to be only 1% of all fungal species. Most reproduce asexually by mitosis, and many do so by an asymmetric division process called budding...

s, fungi
Fungus
A fungus is a member of a large group of eukaryotic organisms that includes microorganisms such as yeasts and molds , as well as the more familiar mushrooms. These organisms are classified as a kingdom, Fungi, which is separate from plants, animals, and bacteria...

, and other micro-organisms
Microorganism
A microorganism or microbe is a microscopic organism that comprises either a single cell , cell clusters, or no cell at all...

 (although some methods work by introducing benign bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

, or fungi to the food), as well as retarding the oxidation
Redox
Redox reactions describe all chemical reactions in which atoms have their oxidation state changed....

 of fat
Fat
Fats consist of a wide group of compounds that are generally soluble in organic solvents and generally insoluble in water. Chemically, fats are triglycerides, triesters of glycerol and any of several fatty acids. Fats may be either solid or liquid at room temperature, depending on their structure...

s which cause rancidity
Rancidification
Rancidification is the chemical decomposition of fats, oils and other lipids . When these processes occur in food, undesirable odors and flavors can result. In some cases, however, the flavors can be desirable . In processed meats, these flavors are collectively known as "warmed over flavor"...

. Food preservation can also include processes which inhibit visual deterioration that can occur during food preparation; such as the enzymatic browning
Enzymatic browning
Browning is the process of becoming brown, especially referring to food. Browning foods may be desirable, as in caramelization, or undesirable, as in an apple turning brown after being cut...

 reaction in apples after they are cut.

Many processes designed to preserve food will involve a number of food preservation methods. Preserving fruit, by turning it into jam, for example, involves boiling (to reduce the fruit’s moisture content and to kill bacteria, yeasts, etc.), sugaring (to prevent their re-growth) and sealing within an airtight jar (to prevent recontamination). There are many traditional methods of preserving food that limit the energy inputs
Waste hierarchy
The waste hierarchy refers to the 3 Rs of reduce, reuse, recycle, or and [ which classify waste management strategies according to their desirability. The Rs are meant to be a hierarchy, in order of importance...

 and reduce carbon footprint.

Maintaining or creating nutritional value, texture
Texture
Texture may refer to:* Textures , album of Brian Eno* Textures , a metal band from the Netherlands* Texture , theoretical topological defect in the structure of spacetime...

 and flavour is an important aspect of food preservation, although, historically, some methods drastically altered the character of the food being preserved. In many cases these changes have now come to be seen as desirable qualities – cheese, yoghurt and pickled onions being common examples.

Preservation processes


Preservation processes include:
  • Heating to kill or denature micro-organisms (e.g., boiling)
  • Oxidation (e.g., use of sulfur dioxide)
  • Ozonation (e.g., use of ozone [O3] or ozonated water to kill undesired microbes)
  • Toxic inhibition (e.g., smoking, use of carbon dioxide, vinegar, alcohol etc.)
  • Dehydration (drying)
  • Osmotic inhibition (e.g., use of syrups)
  • Low temperature inactivation (e.g., freezing)
  • Ultra high water pressure (e.g. a type of “cold” pasteurization; intense water pressure kills microbes which cause food deterioration and affect food safety
    Food safety
    Food safety is a scientific discipline describing handling, preparation, and storage of food in ways that prevent foodborne illness. This includes a number of routines that should be followed to avoid potentially severe health hazards....

    )
  • Combinations of these methods

Drying




Drying is one of the most ancient food preservation techniques, which reduces water activity
Water activity
Water activity or aw was developed to account for the intensity with which water associates with various non-aqueous constituents and solids. Simply stated, it is a measure of the energy status of the water in a system...

 sufficiently to prevent or delay bacterial growth.

Refrigeration



Refrigeration
Refrigeration
Refrigeration is a process in which work is done to move heat from one location to another. This work is traditionally done by mechanical work, but can also be done by magnetism, laser or other means...

 preserves food by slowing down the growth and reproduction of micro-organisms and the action of enzymes which cause food to rot. The introduction of commercial and domestic refrigerators drastically improved the diets of many in the Western world
Western world
The Western world, also known as the West and the Occident , is a term referring to the countries of Western Europe , the countries of the Americas, as well all countries of Northern and Central Europe, Australia and New Zealand...

 by allowing foods such as fresh fruit, salads and dairy products to be stored safely for longer periods, particularly during warm weather.

Freezing


Freezing
Freezing
Freezing or solidification is a phase change in which a liquid turns into a solid when its temperature is lowered below its freezing point. The reverse process is melting....

 is also one of the most commonly used processes commercially and domestically for preserving a very wide range of food including prepared food stuffs which would not have required freezing in their unprepared state. For example, potato waffles are stored in the freezer, but potatoes themselves require only a cool dark place to ensure many months' storage. Cold stores provide large volume, long-term storage for strategic food stocks held in case of national emergency in many countries.

Vacuum packing



Vacuum-packing stores food in a vacuum environment, usually in an air-tight bag or bottle. The 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...

 environment strips bacteria of oxygen needed for survival, slowing spoiling. Vacuum-packing is commonly used for storing nuts
Nut (fruit)
A nut is a hard-shelled fruit of some plants having an indehiscent seed. While a wide variety of dried seeds and fruits are called nuts in English, only a certain number of them are considered by biologists to be true nuts...

 to reduce loss of flavor from oxidation.

Salt


Salting or curing draws moisture from the meat through a process of osmosis. Meat is cured
Curing (food preservation)
Curing refers to various food preservation and flavoring processes, especially of meat or fish, by the addition of a combination of salt, nitrates, nitrite or sugar. Many curing processes also involve smoking, the process of flavoring, or cooking...

 with salt or sugar, or a combination of the two. Nitrates and nitrites are also often used to cure meat and contribute the characteristic pink color, as well as inhibition of 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...

.

Sugar



Sugar is used to preserve fruits, either in syrup with fruit such as apple
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...

s, pear
Pear
The pear is any of several tree species of genus Pyrus and also the name of the pomaceous fruit of these trees. Several species of pear are valued by humans for their edible fruit, but the fruit of other species is small, hard, and astringent....

s, peach
Peach
The peach tree is a deciduous tree growing to tall and 6 in. in diameter, belonging to the subfamily Prunoideae of the family Rosaceae. It bears an edible juicy fruit called a peach...

es, apricot
Apricot
The apricot, Prunus armeniaca, is a species of Prunus, classified with the plum in the subgenus Prunus. The native range is somewhat uncertain due to its extensive prehistoric cultivation.- Description :...

s, plum
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...

s or in crystallized form where the preserved material is cooked in sugar to the point of crystallisation and the resultant product is then stored dry. This method is used for the skins of citrus
Citrus
Citrus is a common term and genus of flowering plants in the rue family, Rutaceae. Citrus is believed to have originated in the part of Southeast Asia bordered by Northeastern India, Myanmar and the Yunnan province of China...

 fruit (candied peel), angelica
Angelica
Angelica is a genus of about 60 species of tall biennial and perennial herbs in the family Apiaceae, native to temperate and subarctic regions of the Northern Hemisphere, reaching as far North as Iceland and Lapland...

 and ginger
Ginger
Ginger is the rhizome of the plant Zingiber officinale, consumed as a delicacy, medicine, or spice. It lends its name to its genus and family . Other notable members of this plant family are turmeric, cardamom, and galangal....

. A modification of this process produces glacé fruit such as glacé cherries
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....

 where the fruit is preserved in sugar but is then extracted from the syrup and sold, the preservation being maintained by the sugar content of the fruit and the superficial coating of syrup. The use of sugar is often combined with alcohol for preservation of luxury products such as fruit in brandy
Brandy
Brandy is a spirit produced by distilling wine. Brandy generally contains 35%–60% alcohol by volume and is typically taken as an after-dinner drink...

 or other spirits. These should not be confused with fruit flavored spirits such as cherry brandy or Sloe gin
Sloe gin
Sloe gin is a red liqueur flavoured with sloe berries, which are a small fruit relative of the plum. Sloe gin has an alcohol content between 15 and 30 percent by volume. The traditional way of making sloe gin is to infuse gin with the berries. Sugar is required to ensure the sloe juices are...

.

Smoking



Smoking is used to lengthen the 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...

 of perishable food items. This effect is achieved by exposing the food to smoke
Smoke
Smoke is a collection of airborne solid and liquid particulates and gases emitted when a material undergoes combustion or pyrolysis, together with the quantity of air that is entrained or otherwise mixed into the mass. It is commonly an unwanted by-product of fires , but may also be used for pest...

 from burning plant materials such as wood
Wood
Wood is a hard, fibrous tissue found in many trees. It has been used for hundreds of thousands of years for both fuel and as a construction material. It is an organic material, a natural composite of cellulose fibers embedded in a matrix of lignin which resists compression...

. Most commonly subjected to this method of food preservation are meats and fish
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...

 that have undergone curing. Fruits and vegetables like paprika
Paprika
Paprika is a spice made from the grinding of dried fruits of Capsicum annuum . In many European languages, the word paprika refers to bell peppers themselves. The seasoning is used in many cuisines to add color and flavor to dishes. Paprika can range from mild to hot...

, cheeses, spices, and ingredients for making beverages such as malt
Malt
Malt is germinated cereal grains that have been dried in a process known as "malting". The grains are made to germinate by soaking in water, and are then halted from germinating further by drying with hot air...

 and tea
Tea
Tea is an aromatic beverage prepared by adding cured leaves of the Camellia sinensis plant to hot water. The term also refers to the plant itself. After water, tea is the most widely consumed beverage in the world...

 leaves are also smoked, but mainly for cooking
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...

 or flavoring them. It is one of the oldest food preservation methods, which probably arose after the development of cooking
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...

 with fire
Fire
Fire is the rapid oxidation of a material in the chemical process of combustion, releasing heat, light, and various reaction products. Slower oxidative processes like rusting or digestion are not included by this definition....

.

Artificial food additives



Preservative food additives can be antimicrobial; which inhibit the growth of bacteria or fungi, including 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...

, or antioxidant
Antioxidant
An antioxidant is a molecule capable of inhibiting the oxidation of other molecules. Oxidation is a chemical reaction that transfers electrons or hydrogen from a substance to an oxidizing agent. Oxidation reactions can produce free radicals. In turn, these radicals can start chain reactions. When...

; such as oxygen absorber
Oxygen absorber
An oxygen absorber is a small packet of material used to prolong the shelf life of food. They are used in food packaging to prevent food colour change, to stop oils in foods from becoming rancid, and also retard the growth of oxygen-using aerobic microorganisms such as fungi.Oxygen supports the...

s, which inhibit the oxidation of food constituents. Common antimicrobial preservatives include calcium propionate
Calcium propionate
Calcium propanoate or calcium propionate has the formula Ca2. It is the calcium salt of propanoic acid.-Uses:As a food additive, it is listed as E number 282 in the Codex Alimentarius. Calcium propanoate is used as a preservative in a wide variety of products, including but not limited to bread,...

, 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...

, sodium nitrite
Sodium nitrite
Sodium nitrite is the inorganic compound with the chemical formula NaNO2. It is a white to slight yellowish crystalline powder that is very soluble in water and is hygroscopic...

, sulfite
Sulfite
Sulfites are compounds that contain the sulfite ion SO. The sulfite ion is the conjugate base of bisulfite. Although the acid itself is elusive, its salts are widely used.-Structure:...

s (sulfur dioxide
Sulfur dioxide
Sulfur dioxide is the chemical compound with the formula . It is released by volcanoes and in various industrial processes. Since coal and petroleum often contain sulfur compounds, their combustion generates sulfur dioxide unless the sulfur compounds are removed before burning the fuel...

, sodium bisulfite
Sodium bisulfite
Sodium bisulfite is a chemical compound with the chemical formula NaHSO3. Sodium bisulfite is a food additive with E number E222. This salt of bisulfite can be prepared by bubbling sulfur dioxide in a solution of sodium carbonate in water...

, potassium hydrogen sulfite, etc.) and disodium EDTA
EDTA
Ethylenediaminetetraacetic acid, widely abbreviated as EDTA , is a polyamino carboxylic acid and a colourless, water-soluble solid. Its conjugate base is named ethylenediaminetetraacetate. It is widely used to dissolve limescale. Its usefulness arises because of its role as a hexadentate ligand...

. Antioxidant
Antioxidant
An antioxidant is a molecule capable of inhibiting the oxidation of other molecules. Oxidation is a chemical reaction that transfers electrons or hydrogen from a substance to an oxidizing agent. Oxidation reactions can produce free radicals. In turn, these radicals can start chain reactions. When...

s include BHA
Butylated hydroxyanisole
Butylated hydroxyanisole is an antioxidant consisting of a mixture of two isomeric organic compounds, 2-tert-butyl-4-hydroxyanisole and 3-tert-butyl-4-hydroxyanisole. It is prepared from 4-methoxyphenol and isobutylene. It is a waxy solid used as a food additive with the E number E320...

 and BHT
Butylated hydroxytoluene
Butylated hydroxytoluene , also known as butylhydroxytoluene, is a lipophilic organic compound that is primarily used as an antioxidant food additive as well as an antioxidant additive in cosmetics, pharmaceuticals, jet fuels, rubber, petroleum products, electrical transformer oil, and embalming...

. Other preservatives include formaldehyde
Formaldehyde
Formaldehyde is an organic compound with the formula CH2O. It is the simplest aldehyde, hence its systematic name methanal.Formaldehyde is a colorless gas with a characteristic pungent odor. It is an important precursor to many other chemical compounds, especially for polymers...

 (usually in solution), glutaraldehyde
Glutaraldehyde
Glutaraldehyde is an organic compound with the formula CH22. A pungent colorless oily liquid, glutaraldehyde is used to disinfect medical and dental equipment...

 (kills insects), ethanol
Ethanol
Ethanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatile, flammable, colorless liquid. It is a psychoactive drug and one of the oldest recreational drugs. Best known as the type of alcohol found in alcoholic beverages, it is also used in thermometers, as a...

 and methylchloroisothiazolinone
Methylchloroisothiazolinone
Methylchloroisothiazolinone is a preservative with antibacterial and antifungal effects within the group of isothiazolinones. It is effective against gram-positive and gram-negative bacteria, yeast, and fungi....

.

Pickling



Pickling is a method of preserving food in an edible anti-microbial liquid. Pickling can be broadly categorized as chemical pickling for example,
In chemical pickling, the food is placed in an edible liquid that inhibits or kills bacteria and other micro-organisms. Typical pickling agents include brine
Brine
Brine is water, saturated or nearly saturated with salt .Brine is used to preserve vegetables, fruit, fish, and meat, in a process known as brining . Brine is also commonly used to age Halloumi and Feta cheeses, or for pickling foodstuffs, as a means of preserving them...

 (high in 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...

), vinegar
Vinegar
Vinegar is a liquid substance consisting mainly of acetic acid and water, the acetic acid being produced through the fermentation of ethanol by acetic acid bacteria. Commercial vinegar is produced either by fast or slow fermentation processes. Slow methods generally are used with traditional...

, alcohol
Ethanol
Ethanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatile, flammable, colorless liquid. It is a psychoactive drug and one of the oldest recreational drugs. Best known as the type of alcohol found in alcoholic beverages, it is also used in thermometers, as a...

, and vegetable oil, especially olive oil
Olive oil
Olive oil is an oil obtained from the olive , a traditional tree crop of the Mediterranean Basin. It is commonly used in cooking, cosmetics, pharmaceuticals, and soaps and as a fuel for traditional oil lamps...

 but also many other oils. Many chemical pickling processes also involve heating or boiling so that the food being preserved becomes saturated with the pickling agent. Common chemically pickled foods include cucumbers, pepper
Capsicum
Capsicum is a genus of flowering plants in the nightshade family, Solanaceae. Its species are native to the Americas where they have been cultivated for thousands of years, but they are now also cultivated worldwide, used as spices, vegetables, and medicines - and have become are a key element in...

s, 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:...

, herring
Herring
Herring is an oily fish of the genus Clupea, found in the shallow, temperate waters of the North Pacific and the North Atlantic oceans, including the Baltic Sea. Three species of Clupea are recognized. The main taxa, the Atlantic herring and the Pacific herring may each be divided into subspecies...

, and eggs
Pickled egg
Pickled eggs are hard boiled eggs preserved by pickling.After the eggs are hard boiled the shell is removed and they are submerged in a solution of vinegar, salt, spices, and other seasonings. Recipes vary from the traditional brine solution used for pickles to other solutions which can impart a...

, as well mixed vegetables such as piccalilli
Piccalilli
Piccalilli is a British relish of chopped pickled vegetables and spices; regional recipes vary considerably. A more finely chopped variety "sandwich piccalilli" is also available from major British supermarkets.-Etymology:...

.

In fermentation pickling, the food itself produces the preservation agent, typically by a process that produces lactic acid
Lactic acid
Lactic acid, also known as milk acid, is a chemical compound that plays a role in various biochemical processes and was first isolated in 1780 by the Swedish chemist Carl Wilhelm Scheele. Lactic acid is a carboxylic acid with the chemical formula C3H6O3...

. Fermented pickles include sauerkraut
Sauerkraut
Sauerkraut , directly translated from German: "sour cabbage", is finely shredded cabbage that has been fermented by various lactic acid bacteria, including Leuconostoc, Lactobacillus, and Pediococcus. It has a long shelf-life and a distinctive sour flavor, both of which result from the lactic acid...

, nukazuke
Nukazuke
are a type of Japanesepickle, made by fermenting vegetables in rice bran . Almost any edible vegetable may be pickled through this technique,though traditional varieties include eggplant, Japanese radish ,...

, kimchi
Kimchi
Kimchi , also spelled gimchi, kimchee, or kim chee, is a traditional fermented Korean dish made of vegetables with varied seasonings. There are hundreds of varieties of kimchi made with a main vegetable ingredient such as napa cabbage, radish, green onions or cucumber. It is the most common...

, surströmming
Surströmming
Surströmming herring") is a northern Swedish dish consisting of fermented Baltic herring. Surströmming is sold in cans, which often bulge during shipping and storage, due to the continued fermentation. When opened, the contents release a strong and sometimes overwhelming odor, which explains why...

, and curtido
Curtido
Curtido is a type of cabbage relish, lightly fermented. It is typical of Mexican and Central American cuisine. In Salvadoran cuisine it is usually made with pickled cabbage, onions, carrots, and sometimes lemon juice and resembles sauerkraut, kimchi, or cole slaw. It is commonly served alongside...

. Some pickled cucumbers are also fermented.

In commercial pickles, a preservative like sodium benzoate
Sodium benzoate
Sodium benzoate has the chemical formula NaC6H5CO2; it is a widely used food preservative, with E number E211. It is the sodium salt of benzoic acid and exists in this form when dissolved in water. It can be produced by reacting sodium hydroxide with benzoic acid.-Uses:Sodium benzoate is a...

 or EDTA
EDTA
Ethylenediaminetetraacetic acid, widely abbreviated as EDTA , is a polyamino carboxylic acid and a colourless, water-soluble solid. Its conjugate base is named ethylenediaminetetraacetate. It is widely used to dissolve limescale. Its usefulness arises because of its role as a hexadentate ligand...

 may also be added to enhance 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...

.

Lye


Sodium hydroxide (lye
Lye
Lye is a corrosive alkaline substance, commonly sodium hydroxide or historically potassium hydroxide . Previously, lye was among the many different alkalis leached from hardwood ashes...

) makes food too alkaline for bacterial growth. Lye will saponify
Saponification
Saponification is a process that produces soap, usually from fats and lye. In technical terms, saponification involves base hydrolysis of triglycerides, which are esters of fatty acids, to form the sodium salt of a carboxylate. In addition to soap, such traditional saponification processes...

 fats in the food, which will change its flavor and texture. Lutefisk
Lutefisk
Lutefisk or Lutfisk is a traditional dish of the Nordic countries and parts of the Midwest United States. It is made from aged stockfish or dried/salted whitefish and lye . It is gelatinous in texture, and has an extremely strong, pungent odor...

 uses lye in its preparation, as do some olive recipes. Modern recipes for century egg
Century egg
Century egg or pidan , also known as preserved egg, hundred-year egg, thousand-year egg, thousand-year-old egg, and millennium egg, is a Chinese cuisine ingredient made by preserving duck, chicken or quail eggs in a mixture of clay, ash, salt, lime, and rice hulls for several weeks to several...

s also call for lye. Masa harina and hominy
Hominy
Hominy or nixtamal is dried maize kernels which have been treated with an alkali in a process called nixtamalization.The English term hominy is derived from the Powhatan language word for maize. Many other Native American cultures also made hominy and integrated it into their diet...

 use agricultural lime
Agricultural lime
Agricultural lime, also called aglime, agricultural limestone, garden lime or liming, is a soil additive made from pulverized limestone or chalk. The primary active component is calcium carbonate...

 in their preparation and this is often misheard as 'lye'.

Canning and bottling




Canning
Canning
Canning is a method of preserving food 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...

 involves cooking food, sealing it in sterile cans or jars, and boiling
Boiling
Boiling is the rapid vaporization of a liquid, which occurs when a liquid is heated to its boiling point, the temperature at which the vapor pressure of the liquid is equal to the pressure exerted on the liquid by the surrounding environmental pressure. While below the boiling point a liquid...

 the containers to kill or weaken any remaining bacteria as a form of 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...

. It was invented 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:...

. Foods have varying degrees of natural protection against spoilage and may require that the final step occur in a pressure cooker. High-acid fruits like strawberries require no preservatives to can and only a short boiling cycle, whereas marginal fruits such as tomato
Tomato
The word "tomato" may refer to the plant or the edible, typically red, fruit which it bears. Originating in South America, the tomato was spread around the world following the Spanish colonization of the Americas, and its many varieties are now widely grown, often in greenhouses in cooler...

es require longer boiling and addition of other acidic elements. Low acid foods, such as vegetables and meats require pressure canning. Food preserved by canning or bottling is at immediate risk of spoilage once the can or bottle has been opened.

Lack of quality control in the canning process may allow ingress of water or micro-organisms. Most such failures are rapidly detected as decomposition within the can causes gas production and the can will swell or burst. However, there have been examples of poor manufacture (underprocessing) and poor hygiene
Hygiene
Hygiene refers to the set of practices perceived by a community to be associated with the preservation of health and healthy living. While in modern medical sciences there is a set of standards of hygiene recommended for different situations, what is considered hygienic or not can vary between...

 allowing contamination of canned food by the obligate anaerobe
Anaerobic organism
An anaerobic organism or anaerobe is any organism that does not require oxygen for growth. It could possibly react negatively and may even die if oxygen is present...

 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 produces an acute toxin within the food, leading to severe illness or death. This organism produces no gas or obvious taste and remains undetected by taste or smell. Its toxin is denatured by cooking, though. Cooked mushrooms, handled poorly and then canned, can support the growth of Staphylococcus aureus
Staphylococcus aureus
Staphylococcus aureus is a facultative anaerobic Gram-positive coccal bacterium. It is frequently found as part of the normal skin flora on the skin and nasal passages. It is estimated that 20% of the human population are long-term carriers of S. aureus. S. aureus is the most common species of...

, which produces a toxin that is not destroyed by canning or subsequent reheating.

Jellying



Food may be preserved by cooking in a material that solidifies to form a gel. Such materials include gelatine, agar
Agar
Agar or agar-agar is a gelatinous substance derived from a polysaccharide that accumulates in the cell walls of agarophyte red algae. Throughout history into modern times, agar has been chiefly used as an ingredient in desserts throughout Asia and also as a solid substrate to contain culture medium...

, maize
Maize
Maize known in many English-speaking countries as corn or mielie/mealie, is a grain domesticated by indigenous peoples in Mesoamerica in prehistoric times. The leafy stalk produces ears which contain seeds called kernels. Though technically a grain, maize kernels are used in cooking as a vegetable...

 flour and arrowroot
Arrowroot
Arrowroot, or obedience plant , Bermuda arrowroot, araru, ararao, is a large perennial herb found in rainforest habitats...

 flour. Some foods naturally form a protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...

 gel when cooked such as eels and elvers
Eel
Eels are an order of fish, which consists of four suborders, 20 families, 111 genera and approximately 800 species. Most eels are predators...

, and sipunculid
Sipuncula
The Sipuncula or Sipunculida is a group containing 144-320 species of bilaterally symmetrical, unsegmented marine worms...

 worms which are a delicacy in the town of Xiamen
Xiamen
Xiamen , also known as Amoy , is a major city on the southeast coast of the People's Republic of China. It is administered as a sub-provincial city of Fujian province with an area of and population of 3.53 million...

 in Fujian province of the People's Republic of China
People's Republic of China
China , officially the People's Republic of China , is the most populous country in the world, with over 1.3 billion citizens. Located in East Asia, the country covers approximately 9.6 million square kilometres...

. Jellied eels
Jellied eels
Jellied eels is a traditional English dish that originated in the 18th century, primarily in London's East End. The dish consists of chopped eels boiled in a spiced stock that is allowed to cool and set, forming a jelly...

 are a delicacy in the East End of London
London
London is the capital city of :England and the :United Kingdom, the largest metropolitan area in the United Kingdom, and the largest urban zone in the European Union by most measures. Located on the River Thames, London has been a major settlement for two millennia, its history going back to its...

 where they are eaten with mashed potatoes. Potted meats in aspic
Aspic
Aspic is a dish in which ingredients are set into a gelatin made from a meat stock or consommé. Non-savory dishes, often made with commercial gelatin mixes without stock or consommé, are usually called gelatin salads....

, (a gel made from gelatine and clarified meat broth) were a common way of serving meat off-cuts in the UK until the 1950s. Many jugged meats are also jellied.

Potting


A traditional British way of preserving meat (particularly shrimp
Potted shrimps
Potted shrimps are a traditional Lancastrian dish made with brown shrimp flavoured with mace. The dish consists of brown shrimp in mace-flavoured butter, which has set in a small pot. Cayenne pepper and nutmeg may also be included. It is traditionally eaten with bread...

) is by setting it in a pot and sealing it with a layer of fat. Also common is potted chicken liver; compare pâté
Pâté
Pâté is a mixture of ground meat and fat minced into a spreadable paste. Common additions include vegetables, herbs, spices, and either wine or cognac, armagnac or brandy...

.

Jugging



Meat can be preserved by jugging, the process of stewing the meat (commonly game
Game (food)
Game is any animal hunted for food or not normally domesticated. Game animals are also hunted for sport.The type and range of animals hunted for food varies in different parts of the world. This will be influenced by climate, animal diversity, local taste and locally accepted view about what can or...

 or fish
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...

) in a covered earthenware
Earthenware
Earthenware is a common ceramic material, which is used extensively for pottery tableware and decorative objects.-Types of earthenware:Although body formulations vary between countries and even between individual makers, a generic composition is 25% ball clay, 28% kaolin, 32% quartz, and 15%...

 jug or casserole
Casserole
A casserole, from the French for "saucepan", is a large, deep dish used both in the oven and as a serving vessel. The word casserole is also used for the food cooked and served in such a vessel, with the cookware itself called a casserole dish or casserole pan...

. The animal to be jugged is usually cut into pieces, placed into a tightly-sealed jug with brine or gravy
Gravy
Gravy is a sauce made often from the juices that run naturally from meat or vegetables during cooking. In North America the term can refer to a wider variety of sauces and gravy is often thicker than in Britain...

, and stewed. Red wine and/or the animal's own blood is sometimes added to the cooking liquid. Jugging was a popular method of preserving meat up until the middle of the 20th century.

Irradiation



Irradiation of food is the exposure of food to ionizing radiation
Ionizing radiation
Ionizing radiation is radiation composed of particles that individually have sufficient energy to remove an electron from an atom or molecule. This ionization produces free radicals, which are atoms or molecules containing unpaired electrons...

; either high-energy electron
Electron
The electron is a subatomic particle with a negative elementary electric charge. It has no known components or substructure; in other words, it is generally thought to be an elementary particle. An electron has a mass that is approximately 1/1836 that of the proton...

s or X-ray
X-ray
X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma...

s from accelerators, or by gamma ray
Gamma ray
Gamma radiation, also known as gamma rays or hyphenated as gamma-rays and denoted as γ, is electromagnetic radiation of high frequency . Gamma rays are usually naturally produced on Earth by decay of high energy states in atomic nuclei...

s (emitted from radioactive sources as Cobalt
Cobalt
Cobalt is a chemical element with symbol Co and atomic number 27. It is found naturally only in chemically combined form. The free element, produced by reductive smelting, is a hard, lustrous, silver-gray metal....

-60 or Caesium
Caesium
Caesium or cesium is the chemical element with the symbol Cs and atomic number 55. It is a soft, silvery-gold alkali metal with a melting point of 28 °C , which makes it one of only five elemental metals that are liquid at room temperature...

-137). The treatment has a range of effects, including killing bacteria, molds and insect pests, reducing the ripening and spoiling of fruits, and at higher doses inducing sterility. The technology may be compared to pasteurization; it is sometimes called 'cold pasteurization', as the product is not heated. Irradiation is not effective against viruses or prion
Prion
A prion is an infectious agent composed of protein in a misfolded form. This is in contrast to all other known infectious agents which must contain nucleic acids . The word prion, coined in 1982 by Stanley B. Prusiner, is a portmanteau derived from the words protein and infection...

s, it cannot eliminate toxins already formed by microorganisms, and is only useful for food of high initial quality.

The radiation process is unrelated to nuclear energy
Nuclear power
Nuclear power is the use of sustained nuclear fission to generate heat and electricity. Nuclear power plants provide about 6% of the world's energy and 13–14% of the world's electricity, with the U.S., France, and Japan together accounting for about 50% of nuclear generated electricity...

, but it may use the radiation emitted from radioactive nuclides produced in nuclear reactors. Ionizing radiation is hazardous to life (hence its usefulness in sterilisation); for this reason irradiation facilities have a heavily shielded irradiation room where the process takes place. Radiation safety procedures ensure that neither the workers in such facility nor the environment receive any radiation dose from the facility. Irradiated food does not become radioactive, and national and international expert bodies have declared food irradiation as wholesome. However, the wholesomeness of consuming such food is disputed by opponents and consumer organizations. National and international expert bodies have declared food irradiation as 'wholesome'; UN-organizations as WHO and FAO are endorsing to use food irradiation. International legislation on whether food may be irradiated or not varies worldwide from no regulation to full banning. Irradiation may allow lower quality or contaminated foodstuffs to be rendered marketable.

It is estimated that about 500,000 tons of food items are irradiated per year worldwide in over 40 countries. These are mainly spice
Spice
A spice is a dried seed, fruit, root, bark, or vegetative substance used in nutritionally insignificant quantities as a food additive for flavor, color, or as a preservative that kills harmful bacteria or prevents their growth. It may be used to flavour a dish or to hide other flavours...

s and condiment
Condiment
A condiment is an edible substance, such as sauce or seasoning, added to food to impart a particular flavor, enhance its flavor, or in some cultures, to complement the dish. Many condiments are available packaged in single-serving sachets , like mustard or ketchup, particularly when supplied with...

s with an increasing segment of fresh fruit irradiated for fruit fly quarantine.

Pulsed electric field processing


Pulsed electric field (PEF) processing is a method for processing cells by means of brief pulses of a strong electric field. PEF holds potential as a type of low temperature alternative pasteurization process for sterilizing food products. In PEF processing, a substance is placed between two electrodes, then the pulsed electric field is applied. The electric field enlarges the pores of the cell membranes which kills the cells and releases their contents. PEF for food processing is a developing technology still being researched. There have been limited industrial applications of PEF processing for the pasteurization of fruit juices.

Modified atmosphere


Modifying atmosphere is a way to preserve food by operating on the atmosphere around it. Salad crops which are notoriously difficult to preserve are now being packaged in sealed bags with an atmosphere modified to reduce the oxygen (O2) concentration and increase the carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...

 (CO2) concentration. There is concern that although salad vegetables retain their appearance and texture in such conditions, this method of preservation may not retain nutrients, especially 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.
Grains may be preserved using carbon dioxide by one of two methods; either using a block of dry ice
Dry ice
Dry ice, sometimes referred to as "Cardice" or as "card ice" , is the solid form of carbon dioxide. It is used primarily as a cooling agent. Its advantages include lower temperature than that of water ice and not leaving any residue...

  placed in the bottom and the can is filled with grain or the container can be purged from the bottom by gaseous carbon dioxide from a cylinder or bulk supply vessel.

Carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...

 prevents insects, and depending on concentration, 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...

, and oxidation from damaging the grain. Grain stored in this way can remain edible for five years.

Nitrogen
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...

 gas (N2) at concentrations of 98% or higher is also used effectively to kill insects in grain through hypoxia
Hypoxia (medical)
Hypoxia, or hypoxiation, is a pathological condition in which the body as a whole or a region of the body is deprived of adequate oxygen supply. Variations in arterial oxygen concentrations can be part of the normal physiology, for example, during strenuous physical exercise...

. However, carbon dioxide has an advantage in this respect as it kills organisms through hypercarbia and depending on concentration hypoxia and, requiring concentrations of above 35%, or so. This makes carbon dioxide preferable for fumigation in situations where a hermetic 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 :...

 cannot be maintained.

High pressure food preservation



High pressure food preservation refers to high pressure
High pressure
High pressure in science and engineering is studying the effects of high pressure on materials and the design and construction of devices, such as a diamond anvil cell, which can create high pressure...

 used for food preservation. "Pressed inside a vessel exerting 70000 pound per square inches (482.6 MPa) or more, food can be processed so that it retains its fresh appearance, flavour, texture and nutrients while disabling harmful microorganisms and slowing spoilage." By 2001, adequate commercial equipment was developed so that by 2005 the process was being used for products ranging from orange juice
Orange juice
Orange juice is a popular beverage made from oranges. It is made by extraction from the fresh fruit, by desiccation and subsequent reconstitution of dried juice, or by concentration of the juice and the subsequent addition of water to the concentrate...

 to guacamole
Guacamole
Guacamole , is an avocado-based dip that originated in Mexico. It is traditionally made by mashing ripe avocados with a molcajete with sea salt. Some recipes call for limited tomato, spicy Asian spices such as white onion, lime juice, and/or additional seasonings.-History:Guacamole was made by...

 to deli meats and widely sold.

Burial in the ground


Burial of food can preserve it due to a variety of factors: lack of light, lack of oxygen, cool temperatures, pH level, or desiccant
Desiccant
A desiccant is a hygroscopic substance that induces or sustains a state of dryness in its local vicinity in a moderately well-sealed container....

s in the soil. Burial may be combined with other methods such as salting or fermentation. Most foods can be preserved in soil that is very dry and salty (thus a desiccant
Desiccant
A desiccant is a hygroscopic substance that induces or sustains a state of dryness in its local vicinity in a moderately well-sealed container....

), or soil that is frozen.

Many root vegetables are very resistant to spoilage and require no other preservation than storage in cool dark conditions, for example by burial in the ground, such as in a storage clamp
Storage clamp
A storage clamp is used in the agricultural industry for temporary storage of root crops such as potato, turnip, rutabaga, mangelwurzel, sugar beet etc....

. Century egg
Century egg
Century egg or pidan , also known as preserved egg, hundred-year egg, thousand-year egg, thousand-year-old egg, and millennium egg, is a Chinese cuisine ingredient made by preserving duck, chicken or quail eggs in a mixture of clay, ash, salt, lime, and rice hulls for several weeks to several...

s are created by placing eggs in alkaline mud (or other alkaline substance) resulting in their "inorganic" fermentation through raised pH instead of spoiling. The fermentation preserves them and breaks down some of the complex, less flavorful proteins and fats into simpler more flavorful ones. Cabbage
Cabbage
Cabbage is a popular cultivar of the species Brassica oleracea Linne of the Family Brassicaceae and is a leafy green vegetable...

 was traditionally buried in the fall in northern farms in the USA for preservation. Some methods keep it crispy while other methods produce sauerkraut
Sauerkraut
Sauerkraut , directly translated from German: "sour cabbage", is finely shredded cabbage that has been fermented by various lactic acid bacteria, including Leuconostoc, Lactobacillus, and Pediococcus. It has a long shelf-life and a distinctive sour flavor, both of which result from the lactic acid...

. A similar process is used in the traditional production of kimchi
Kimchi
Kimchi , also spelled gimchi, kimchee, or kim chee, is a traditional fermented Korean dish made of vegetables with varied seasonings. There are hundreds of varieties of kimchi made with a main vegetable ingredient such as napa cabbage, radish, green onions or cucumber. It is the most common...

. Sometimes meat is buried under conditions which cause preservation. If buried on hot coals or ashes, the heat can kill pathogens, the dry ash can desiccate, and the earth can block oxygen and further contamination. If buried where the earth is very cold, the earth acts like a refrigerator.

Controlled use of micro-organism



Some foods, such as many cheese
Cheese
Cheese is a generic term for a diverse group of milk-based food products. Cheese is produced throughout the world in wide-ranging flavors, textures, and forms....

s, wine
Wine
Wine is an alcoholic beverage, made of fermented fruit juice, usually from grapes. The natural chemical balance of grapes lets them ferment without the addition of sugars, acids, enzymes, or other nutrients. Grape wine is produced by fermenting crushed grapes using various types of yeast. Yeast...

s, and beer
Beer
Beer is the world's most widely consumed andprobably oldest alcoholic beverage; it is the third most popular drink overall, after water and tea. It is produced by the brewing and fermentation of sugars, mainly derived from malted cereal grains, most commonly malted barley and malted wheat...

s will keep for a long time because their production uses specific micro-organisms that combat spoilage from other less benign organisms. These micro-organisms keep pathogens in check by creating an environment toxic for themselves and other micro-organisms by producing acid or alcohol. Starter micro-organisms, salt, hops, controlled (usually cool) temperatures, controlled (usually low) levels of oxygen and/or other methods are used to create the specific controlled conditions that will support the desirable organisms that produce food fit for human consumption.

Biopreservation



Biopreservation
Biopreservation
Biopreservation is the use of natural or controlled microbiota or antimicrobials as a way of preserving food and extending its shelf life. Beneficial bacteria or the fermentation products produced by these bacteria are used in biopreservation to control spoilage and render pathogens inactive in food...

 is the use of natural or controlled microbiota
Microbiota (disambiguation)
Microbiota is a genus of coniferous plants in the family Cupressaceae.Microbiota also refers to microflora and microfauna in an ecosystem . Also, can be used to refer to life outside a host such as life found in a soil sample....

 or antimicrobial
Antimicrobial
An anti-microbial is a substance that kills or inhibits the growth of microorganisms such as bacteria, fungi, or protozoans. Antimicrobial drugs either kill microbes or prevent the growth of microbes...

s as a way of preserving food and extending 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...

. Beneficial bacteria or the fermentation
Fermentation
Fermentation may refer to:* Fermentation , the use of fermentation in food preparation* Fermentation , a metabolic process whereby electrons released from nutrients are ultimately transferred to molecules obtained from the breakdown of those same nutrients* Fermentation , the process of...

 products produced by these bacteria are used in biopreservation to control spoilage and render pathogen
Pathogen
A pathogen gignomai "I give birth to") or infectious agent — colloquially, a germ — is a microbe or microorganism such as a virus, bacterium, prion, or fungus that causes disease in its animal or plant host...

s inactive in food. It is a benign ecological approach which is gaining increasing attention.

Of special interest are lactic acid bacteria
Lactic acid bacteria
The lactic acid bacteria comprise a clade of Gram-positive, low-GC, acid-tolerant, generally non-sporulating, non-respiring rod or cocci that are associated by their common metabolic and physiological characteristics. These bacteria, usually found in decomposing plants and lactic products, produce...

 (LAB). Lactic acid bacteria have antagonistic properties which make them particularly useful as biopreservatives. When LABs compete for nutrients, their metabolite
Metabolite
Metabolites are the intermediates and products of metabolism. The term metabolite is usually restricted to small molecules. A primary metabolite is directly involved in normal growth, development, and reproduction. Alcohol is an example of a primary metabolite produced in large-scale by industrial...

s often include active antimicrobials such as lactic and acetic acid, hydrogen peroxide, and peptide
Peptide
Peptides are short polymers of amino acid monomers linked by peptide bonds. They are distinguished from proteins on the basis of size, typically containing less than 50 monomer units. The shortest peptides are dipeptides, consisting of two amino acids joined by a single peptide bond...

 bacteriocin
Bacteriocin
Bacteriocins are proteinaceous toxins produced by bacteria to inhibit the growth of similar or closely related bacterial strain. They are typically considered to be narrow spectrum antibiotics, though this has been debated...

s. Some LABs produce the antimicrobial nisin
Nisin
Nisin is a polycyclic antibacterial peptide with 34 amino acid residues used as a food preservative. It contains the uncommon amino acids lanthionine , methyllanthionine , didehydroalanine and didehydroaminobutyric acid . These unusual amino acids are introduced by posttranslational modification...

 which is a particularly effective preservative.

These days LAB bacteriocins are used as an integral part of hurdle technology
Hurdle technology
Hurdle technology is a method of ensuring that pathogens in food products can be eliminated or controlled. This means the food products will be safe for consumption, and their shelf life will be extended. Hurdle technology usually works by combining more than one approach. These approaches can be...

. Using them in combination with other preservative techniques can effectively control spoilage bacteria and other pathogens, and can inhibiting the activities of a wide spectrum of organisms, including inherently resistant Gram-negative bacteria.

Hurdle technology


Hurdle technology
Hurdle technology
Hurdle technology is a method of ensuring that pathogens in food products can be eliminated or controlled. This means the food products will be safe for consumption, and their shelf life will be extended. Hurdle technology usually works by combining more than one approach. These approaches can be...

 is a method of ensuring that pathogen
Pathogen
A pathogen gignomai "I give birth to") or infectious agent — colloquially, a germ — is a microbe or microorganism such as a virus, bacterium, prion, or fungus that causes disease in its animal or plant host...

s in food products can be eliminated or controlled by combining more than one approach. These approaches can be thought of as "hurdles" the pathogen has to overcome if it is to remain active in the food. The right combination of hurdles can ensure all pathogens are eliminated or rendered harmless in the final product.

Hurdle technology has been defined by Leistner (2000) as an intelligent combination of hurdles which secures the microbial safety and stability as well as the organoleptic
Organoleptic
Organoleptic is an adjective used to refer to the aspects of food or other substances as experienced by the senses, including taste, sight, smell, and touch.-USDA uses:...

 and nutritional quality and the economic viability of food products. The organoleptic quality of the food refers to its sensory properties, that is its look, taste, smell and texture.

Examples of hurdles in a food system are high temperature during processing, low temperature during storage, increasing the acidity, lowering the water activity
Water activity
Water activity or aw was developed to account for the intensity with which water associates with various non-aqueous constituents and solids. Simply stated, it is a measure of the energy status of the water in a system...

 or redox potential, or the presence of preservative
Preservative
A preservative is a naturally occurring or synthetically produced substance that is added to products such as foods, pharmaceuticals, paints, biological samples, wood, etc. to prevent decomposition by microbial growth or by undesirable chemical changes....

s or biopreservatives. According to the type of pathogens and how risky they are, the intensity of the hurdles can be adjusted individually to meet consumer preferences in an economical way, without sacrificing the safety of the product.

Principal hurdles used for food preservation (after Leistner, 1995)
Parameter Symbol Application
High temperature F Heating
Low temperature T Chilling
Refrigeration
Refrigeration is a process in which work is done to move heat from one location to another. This work is traditionally done by mechanical work, but can also be done by magnetism, laser or other means...

, freezing
Frozen food
Freezing food preserves it from the time it is prepared to the time it is eaten. Since early times, farmers, fishermen, and trappers have preserved their game and produce in unheated buildings during the winter season. Freezing food slows down decomposition by turning water to ice, making it...

Reduced water activity
Water activity
Water activity or aw was developed to account for the intensity with which water associates with various non-aqueous constituents and solids. Simply stated, it is a measure of the energy status of the water in a system...

aw Drying
Drying
Drying is a mass transfer process consisting of the removal of water or another solvent by evaporation from a solid, semi-solid or liquid. This process is often used as a final production step before selling or packaging products. To be considered "dried", the final product must be solid, in the...

, curing
Curing (food preservation)
Curing refers to various food preservation and flavoring processes, especially of meat or fish, by the addition of a combination of salt, nitrates, nitrite or sugar. Many curing processes also involve smoking, the process of flavoring, or cooking...

, conserving
Increased acidity 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...

Acid addition or formation
Reduced redox potential Eh Removal of oxygen or addition of ascorbate
Biopreservatives Competitive flora
Flora
Flora is the plant life occurring in a particular region or time, generally the naturally occurring or indigenous—native plant life. The corresponding term for animals is fauna.-Etymology:...

 such as microbial fermentation
Fermentation (food)
Fermentation in food processing typically is the conversion of carbohydrates to alcohols and carbon dioxide or organic acids using yeasts, bacteria, or a combination thereof, under anaerobic conditions. Fermentation in simple terms is the chemical conversion of sugars into ethanol...

Other preservative
Preservative
A preservative is a naturally occurring or synthetically produced substance that is added to products such as foods, pharmaceuticals, paints, biological samples, wood, etc. to prevent decomposition by microbial growth or by undesirable chemical changes....

s
Sorbates, sulfite
Sulfite
Sulfites are compounds that contain the sulfite ion SO. The sulfite ion is the conjugate base of bisulfite. Although the acid itself is elusive, its salts are widely used.-Structure:...

s, nitrite
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...

s


See also


  • Blast chilling
    Blast chilling
    Blast chilling is a method of cooling food quickly to a low temperature that is relatively safe from bacterial growth. Bacteria multiply fastest between +8 °C and +68 °C...

  • Dietary supplement
    Dietary supplement
    A dietary supplement, also known as food supplement or nutritional supplement, is a preparation intended to supplement the diet and provide nutrients, such as vitamins, minerals, fiber, fatty acids, or amino acids, that may be missing or may not be consumed in sufficient quantities in a person's diet...

  • Food and Bioprocess Technology
    Food and Bioprocess Technology
    Food and Bioprocess Technology: An International Journal is a peer reviewed scientific journal published by Springer Science+Business Media. It is available in print and online...

  • Food chemistry
    Food chemistry
    Food chemistry is the study of chemical processes and interactions of all biological and non-biological components of foods. The biological substances include such items as meat, poultry, lettuce, beer, and milk as examples...

  • Food engineering
    Food engineering
    Food engineering is a multidisciplinary field of applied physical sciences which combines science, microbiology, and engineering education for food and related industries. Food engineering includes, but is not limited to, the application of agricultural engineering, mechanical engineering and...

  • Food fortification
    Food fortification
    Food fortification or enrichment is the process of adding micronutrients to food. It can be purely a commercial choice to provide extra nutrients in a food, or sometimes it is a public health policy which aims to reduce numbers of people with dietary deficiencies in a population.Diets that lack...

  • Food manufacturing
  • Food microbiology
    Food microbiology
    Food microbiology is the study of the microorganisms that inhabit, create, or contaminate food. Of major importance is the study of microorganisms causing food spoilage. "Good" bacteria, however, such as probiotics, are becoming increasingly important in food science...

  • Food packaging
    Food packaging
    Food packaging is packaging for food. It requires protection, tampering resistance, and special physical, chemical, or biological needs. It also shows the product that is labeled to show any nutrition information on the food being consumed....

  • Food processing
    Food processing
    Food processing is the set of methods and techniques used to transform raw ingredients into food or to transform food into other forms for consumption by humans or animals either in the home or by the food processing industry...

  • Food rheology
    Food rheology
    Food rheology is the study of the rheological properties of food, that is, the consistency and flow of food under tightly specified conditions. The consistency, degree of fluidity, and other mechanical properties are important in understanding how long food can be stored, how stable it will...

  • Food science
    Food science
    Food science is a study concerned with all technical aspects of foods, beginning with harvesting or slaughtering, and ending with its cooking and consumption, an ideology commonly referred to as "from field to fork"...

  • Food spoilage
    Food spoilage
    Spoilage is the process in which food deteriorates to the point in which it is not edible to humans or its quality of edibility becomes reduced. Various external forces are responsible for the spoilage of food. Food that is capable of spoiling is referred to as perishable food.-Reasons:Harvested...

  • Food technology
    Food technology
    Food technology, is a branch of food science which deals with the actual production processes to make foods.-Early history of food technology:...

  • Fresherized
  • Gourmet Library and museum
  • Nutraceutical
    Nutraceutical
    Nutraceutical, a portmanteau of the words “nutrition” and “pharmaceutical”, is a food or food product that reportedly provides health and medical benefits, including the prevention and treatment of disease. Health Canada defines the term as "a product isolated or purified from foods that is...

  • Nutrification
  • Refrigerate after opening
    Refrigerate after opening
    The term refrigerate after opening is an instruction on commercial preserved food products to cool the container after it has been opened and the contents exposed to open air....



External links