
Food preservation includes processes that make
food
Food is any substance consumed by an organism for Nutrient, nutritional support. Food is usually of plant, animal, or Fungus, fungal origin and contains essential nutrients such as carbohydrates, fats, protein (nutrient), proteins, vitamins, ...
more resistant to
microorganism
A microorganism, or microbe, is an organism of microscopic scale, microscopic size, which may exist in its unicellular organism, single-celled form or as a Colony (biology)#Microbial colonies, colony of cells. The possible existence of unseen ...
growth and slow the
oxidation
Redox ( , , reduction–oxidation or oxidation–reduction) is a type of chemical reaction in which the oxidation states of the reactants change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is ...
of
fat
In nutrition science, nutrition, biology, and chemistry, fat usually means any ester of fatty acids, or a mixture of such chemical compound, compounds, most commonly those that occur in living beings or in food.
The term often refers specif ...
s. This slows down the
decomposition
Decomposition is the process by which dead organic substances are broken down into simpler organic or inorganic matter such as carbon dioxide, water, simple sugars and mineral salts. The process is a part of the nutrient cycle and is ess ...
and
rancidification
Rancidification is the process of complete or incomplete autoxidation or hydrolysis of fats and oils when exposed to air, light, moisture, or bacterial action, producing short-chain aldehydes, ketones and free fatty acids.
When these processes ...
process. Food preservation may also include processes that inhibit visual deterioration, such as the
enzymatic browning reaction in apples after they are cut during food preparation. By preserving
food
Food is any substance consumed by an organism for Nutrient, nutritional support. Food is usually of plant, animal, or Fungus, fungal origin and contains essential nutrients such as carbohydrates, fats, protein (nutrient), proteins, vitamins, ...
,
food waste
The causes of food going uneaten are numerous and occur throughout the food system, during food production, production, food processing, processing, Food distribution, distribution, Grocery store, retail and food service sales, and Social clas ...
can be reduced, which is an important way to decrease production costs and increase the efficiency of
food systems, improve
food security
Food security is the state of having reliable access to a sufficient quantity of affordable, healthy Human food, food. The availability of food for people of any class, gender, ethnicity, or religion is another element of food protection. Simila ...
and
nutrition
Nutrition is the biochemistry, biochemical and physiology, physiological process by which an organism uses food and water to support its life. The intake of these substances provides organisms with nutrients (divided into Macronutrient, macro- ...
and contribute towards
environmental sustainability
Sustainability is a social goal for people to co-exist on Earth over a long period of time. Definitions of this term are disputed and have varied with literature, context, and time. Sustainability usually has three dimensions (or pillars): env ...
. For instance, it can reduce the
environmental impact of food production.
Many processes designed to preserve food involve more than one food preservation method. Preserving fruit by turning it into jam, for example, involves boiling (to reduce the fruit's moisture content and to kill bacteria, etc.), sugaring (to prevent their re-growth) and sealing within an airtight jar (to prevent recontamination).
Different food preservation methods have different impacts on the quality of the food and food systems. Some traditional methods of preserving food have been shown to have a lower
energy input and
carbon footprint compared to modern methods.
Some methods of food preservation are also known to create
carcinogen
A carcinogen () is any agent that promotes the development of cancer. Carcinogens can include synthetic chemicals, naturally occurring substances, physical agents such as ionizing and non-ionizing radiation, and biologic agents such as viruse ...
s.
Traditional techniques
Some techniques of food preservation pre-date the
dawn of agriculture. Others were discovered more recently.
Boiling
Boiling liquids can kill any existing microbes. Milk and water are often boiled to kill any harmful microbes that may be present in them.
Burial
Burial of food can preserve it due to a variety of factors: lack of light, lack of oxygen, cool temperatures, pH level, or
desiccants 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) such as sand, or soil that is frozen.
Many
root vegetables
Root vegetables are underground plant parts eaten by humans or animals as food. In agricultural and culinary terminology, the term applies to true roots, such as taproots and tuberous root, root tubers, as well as non-roots such as bulbs, corms, ...
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 (not to be confused with a
root cellar). Cabbage was traditionally buried during autumn in northern US farms for preservation. Some methods keep it crispy while other methods produce
sauerkraut. A similar process is used in the traditional production of
kimchi.
Sometimes meat is buried under conditions that 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, or, in areas of
permafrost
Permafrost () is soil or underwater sediment which continuously remains below for two years or more; the oldest permafrost has been continuously frozen for around 700,000 years. Whilst the shallowest permafrost has a vertical extent of below ...
, a freezer.
In
Odisha, India, it is practical to store rice by burying it underground. This method helps to store for three to six months during the dry season.
Butter and similar substances have been preserved as
bog butter in Irish
peat bogs
A bog or bogland is a wetland that accumulates peat as a deposit of dead plant materials often mosses, typically sphagnum moss. It is one of the four main types of wetlands. Other names for bogs include mire, mosses, quagmire, and mus ...
for centuries.
Century eggs are traditionally 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.
Canning
Canning
Canning is a method of food preservation in which food is processed and sealed in an airtight container (jars like Mason jars, and steel and tin cans). Canning provides a shelf life that typically ranges from one to five years, although under ...
involves cooking food, sealing it in sterilized cans or jars, and
boiling
Boiling or ebullition is the rapid phase transition from liquid to gas or vapor, vapour; the reverse of boiling is condensation. Boiling occurs when a liquid is heated to its boiling point, so that the vapour pressure of the liquid is equal to ...
the containers to kill or weaken any remaining bacteria as a form of
sterilization. It was invented by the French confectioner
Nicolas Appert. By 1806, this process was used by the French Navy to preserve meat, fruit, vegetables, and even milk. Although Appert had discovered a new way of preservation, it was not understood until 1864 when
Louis Pasteur
Louis Pasteur (, ; 27 December 1822 – 28 September 1895) was a French chemist, pharmacist, and microbiologist renowned for his discoveries of the principles of vaccination, Fermentation, microbial fermentation, and pasteurization, the la ...
found the relationship between microorganisms, food spoilage, and illness.
Foods have varying degrees of natural protection against spoilage and may require that the final step occurs in a
pressure cooker. High-acid fruits like
strawberries require no preservatives to can and only a short boiling cycle, whereas marginal vegetables such as
carrots require longer boiling and the 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 cause gas production and the can will swell or burst. However, there have been examples of poor manufacture (underprocessing) and poor
hygiene
Hygiene is a set of practices performed to preserve health.
According to the World Health Organization (WHO), "Hygiene refers to conditions and practices that help to maintain health and prevent the spread of diseases." Personal hygiene refer ...
allowing contamination of canned food by the obligate
anaerobe ''
Clostridium botulinum
''Clostridium botulinum'' is a Gram-positive bacteria, gram-positive, Bacillus (shape), rod-shaped, Anaerobic organism, anaerobic, endospore, spore-forming, Motility, motile bacterium with the ability to produce botulinum toxin, which is a neurot ...
'', 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, however. Cooked
mushroom
A mushroom or toadstool is the fleshy, spore-bearing Sporocarp (fungi), fruiting body of a fungus, typically produced above ground on soil or another food source. ''Toadstool'' generally refers to a poisonous mushroom.
The standard for the n ...
s, when handled poorly and then canned, can support the growth of ''
Staphylococcus aureus
''Staphylococcus aureus'' is a Gram-positive spherically shaped bacterium, a member of the Bacillota, and is a usual member of the microbiota of the body, frequently found in the upper respiratory tract and on the skin. It is often posi ...
'', which produces a toxin that is not destroyed by canning or subsequent reheating.
Confit
Meat can be preserved by salting it, cooking it at or near in some kind of fat (such as
lard or
tallow), and then storing it immersed in the fat. These preparations were popular in Europe before refrigerators became ubiquitous. They are still popular in France, where the term originates.
[Bruce Aidells (2012): ]
The Great Meat Cookbook
', page 429. Houghton Mifflin Harcourt; 632 pages. [Susan Jung (2012):]
Truc: confit, a fat-fabulous way to preserve meat
. ''Post Magazine'', online article, posted on 2012-11-03, accessed 2019-02-21. The preparation will keep longer if stored in a cold cellar or buried in cold ground.
Cooling
Cooling
Cooling is removal of heat, usually resulting in a lower temperature and/or Phase transition, phase change. Temperature lowering achieved by any other means may also be called cooling.
The Heat transfer, transfer of Internal energy, thermal energ ...
preserves food by slowing down the growth and reproduction of microorganisms and the action of enzymes that causes the food to rot. The introduction of commercial and domestic refrigerators drastically improved the diets of many in the
Western world
The Western world, also known as the West, primarily refers to various nations and state (polity), states in Western Europe, Northern America, and Australasia; with some debate as to whether those in Eastern Europe and Latin America also const ...
by allowing food such as fresh fruit, salads and dairy products to be stored safely for longer periods, particularly during warm weather.
Before the era of mechanical refrigeration, cooling for food storage occurred in the forms of
root cellars and
iceboxes. Rural people often did their own
ice cutting, whereas town and city dwellers often relied on the
ice trade. Today, root cellaring remains popular among people who value various goals, including
local food
Local food is food that is produced within a short distance of where it is consumed, often accompanied by a social structure and supply chain different from the large-scale supermarket Food system, system.
Local food (or locavore) movements ...
,
heirloom crops, traditional home
cooking techniques,
family farming,
frugality,
self-sufficiency
Self-sustainability and self-sufficiency are overlapping states of being in which a person, being, or system needs little or no help from, or interaction with others. Self-sufficiency entails the self being enough (to fulfill needs), and a sel ...
,
organic farming
Organic farming, also known as organic agriculture or ecological farming or biological farming,Labelling, article 30 o''Regulation (EU) 2018/848 of the European Parliament and of the Council of 30 May 2024 on organic production and labelling of ...
, and others.
Curing

The earliest form of curing was dehydration or
drying, used as early as 12,000BC.
Smoking
Smoking is a practice in which a substance is combusted, and the resulting smoke is typically inhaled to be tasted and absorbed into the bloodstream of a person. Most commonly, the substance used is the dried leaves of the tobacco plant, whi ...
and
salting techniques improve on the drying process and add antimicrobial agents that aid in preservation. Smoke deposits a number of pyrolysis products onto the food, including the
phenol
Phenol (also known as carbolic acid, phenolic acid, or benzenol) is an aromatic organic compound with the molecular formula . It is a white crystalline solid that is volatile and can catch fire.
The molecule consists of a phenyl group () ...
s
syringol
Syringol is the organic compound with the formula HO(CH3O)2C6H3. The molecule is a phenol, with methoxy groups in the flanking (2 and 6) positions. It is the symmetrically dimethylated derivative of pyrogallol. It is a colorless solid, alth ...
,
guaiacol and
catechol.
[Msagati, T. (2012). "The Chemistry of Food Additives and Preservatives"] Salt accelerates the drying process using
osmosis
Osmosis (, ) is the spontaneous net movement or diffusion of solvent molecules through a selectively permeable membrane, selectively-permeable membrane from a region of high water potential (region of lower solute concentration) to a region of ...
and also inhibits the growth of several common strains of bacteria. More recently
nitrites have been used to cure meat, contributing a characteristic pink colour.
In 2015, the
International Agency for Research on Cancer
The International Agency for Research on Cancer (IARC; ) is an intergovernmental agency forming part of the World Health Organization of the United Nations.
Its role is to conduct and coordinate research into the causes of cancer. It also cance ...
of the
World Health Organization
The World Health Organization (WHO) is a list of specialized agencies of the United Nations, specialized agency of the United Nations which coordinates responses to international public health issues and emergencies. It is headquartered in Gen ...
classified
processed meat—i.e., meat that has undergone salting, curing, and smoking—as "carcinogenic to humans".
Fermentation
Some foods, such as many
cheese
Cheese is a type of dairy product produced in a range of flavors, textures, and forms by coagulation of the milk protein casein. It comprises proteins and fat from milk (usually the milk of cows, buffalo, goats or sheep). During prod ...
s,
wine
Wine is an alcoholic drink made from Fermentation in winemaking, fermented fruit. Yeast in winemaking, Yeast consumes the sugar in the fruit and converts it to ethanol and carbon dioxide, releasing heat in the process. Wine is most often made f ...
s, and
beer
Beer is an alcoholic beverage produced by the brewing and fermentation of starches from cereal grain—most commonly malted barley, although wheat, maize (corn), rice, and oats are also used. The grain is mashed to convert starch in the ...
s, are prepared by fermentation. This involves cultivating specific
microorganisms
A microorganism, or microbe, is an organism of microscopic size, which may exist in its single-celled form or as a colony of cells. The possible existence of unseen microbial life was suspected from antiquity, with an early attestation in ...
to combat spoilage from other, less benign organisms. These microorganisms keep pathogens in check by producing acid or alcohol, which eventually creates an environment toxic for themselves and other microorganisms.
Methods of fermentation include, but are not limited to, starter microorganisms, salt, hops, controlled (usually cool) temperatures and controlled (usually low) levels of oxygen. These methods are used to create the specific controlled conditions that will support the desirable organisms that produce food fit for human consumption. Fermentation is the microbial conversion of starch and sugars into alcohol. Not only can fermentation produce alcohol, but it can also be a valuable preservation technique. Fermentation can also make foods more nutritious and palatable.
Water was also turned into alcoholic beverages through fermentation. When water is used to make beer, the boiling during the brewing process may kill bacteria that could make people sick. The barley and other ingredients also infuse the drink with nutrients, and the microorganisms can also produce vitamins as they ferment.
However, the common belief that premodern people avoided drinking ordinary water is a myth. While people avoided drinking dirty or polluted water, they also avoided using it for the production of beer and wine. Water was visually inspected, smelled, tasted, filtered, and boiled if necessary. It was used for drinking as well as for diluting wine, cooking, and many other processes.
Freezing
Freezing
Freezing is a phase transition in which a liquid turns into a solid when its temperature is lowered below its freezing point.
For most substances, the melting and freezing points are the same temperature; however, certain substances possess dif ...
is also one of the most commonly used processes, both commercially and domestically, for preserving a very wide range of foods, including prepared foods that 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.
Heating
Heating to temperatures which are sufficient to kill microorganisms inside the food is a method used with
perpetual stews.
Jellying
Food may be preserved by cooking in a material that solidifies to form a gel. Such materials include
gelatin
Gelatin or gelatine () is a translucent, colorless, flavorless food ingredient, commonly derived from collagen taken from animal body parts. It is brittle when dry and rubbery when moist. It may also be referred to as hydrolyzed collagen, coll ...
,
agar
Agar ( or ), or agar-agar, is a jelly-like substance consisting of polysaccharides obtained from the cell walls of some species of red algae, primarily from " ogonori" and " tengusa". As found in nature, agar is a mixture of two components, t ...
,
maize
Maize (; ''Zea mays''), also known as corn in North American English, is a tall stout grass that produces cereal grain. It was domesticated by indigenous peoples in southern Mexico about 9,000 years ago from wild teosinte. Native American ...
flour, and
arrowroot
Arrowroot is a starch obtained from the rhizomes (rootstock) of several tropical plants, traditionally ''Maranta arundinacea'', but also Florida arrowroot from ''Zamia integrifolia'', and tapioca from cassava (''Manihot esculenta''), which is of ...
flour.
Some animal flesh forms a protein gel when cooked.
Eels and elvers, and
sipunculid worms, are a delicacy in
Xiamen
Xiamen,), also known as Amoy ( ; from the Zhangzhou Hokkien pronunciation, zh, c=, s=, t=, p=, poj=Ē͘-mûi, historically romanized as Amoy, is a sub-provincial city in southeastern Fujian, People's Republic of China, beside the Taiwan Stra ...
, China, as are
jellied eels in the
East End of London, where they are eaten with mashed potatoes.
British cuisine
British cuisine consists of the cooking traditions and practices associated with the United Kingdom, including the regional cuisines of English cuisine, England, Scottish cuisine, Scotland, Welsh cuisine, Wales, and Northern Irish cuisine, Nort ...
has a rich tradition of
potted meats. Meat off-cuts were, until the 1950s, preserved in
aspic
Aspic () or meat jelly is a savoury gelatin made with a meat stock (food), stock or broth, set in a mold to encase other ingredients. These often include pieces of meat, seafood, vegetable, or eggs. Aspic is also sometimes referred to as ''aspic ...
, a gel made from gelatin and clarified meat broth. Another form of preservation is setting the cooked food in a container and covering it with a layer of fat. Potted chicken liver can be prepared in this way, and so can
potted shrimps, to be served on toast.
Calf's foot jelly used to be prepared for invalids.
Jellying is one of the steps in producing traditional
pâté
Pâté ( , , ) is a forcemeat. Originally, the dish was cooked in a pastry case; in more recent times it is more usually cooked without pastry in a terrine. Various ingredients are used, which may include meat from pork, poultry, fish or bee ...
s. Many
jugged meats (see below) are also jellied.
Another type of jellying is
fruit preserves, which are preparations of cooked fruits, vegetables and sugar, often stored in glass jam jars and
Mason jar
A Mason jar, also known as a canning jar, preserves jar or fruit jar, is a glass jar used in home canning to food preservation, preserve food. It was named after American tinsmith John Landis Mason, who patented it in 1858. The jar's mouth has a ...
s. Many varieties of fruit preserves are made globally, including sweet fruit preserves, such as those made from strawberry or apricot, and savory preserves, such as those made from tomatoes or squash. The ingredients used and how they are prepared determine the type of preserves;
jams,
jellies, and
marmalades are all examples of different styles of fruit preserves that vary based upon the fruit used. In English, the word ''preserves'', in plural form, is used to describe all types of jams and jellies.
Jugging
Meat can be preserved by jugging. Jugging is the process of
stewing the meat (commonly
game
A game is a structured type of play usually undertaken for entertainment or fun, and sometimes used as an educational tool. Many games are also considered to be work (such as professional players of spectator sports or video games) or art ...
or
fish
A fish (: fish or fishes) is an aquatic animal, aquatic, Anamniotes, anamniotic, gill-bearing vertebrate animal with swimming fish fin, fins and craniate, a hard skull, but lacking limb (anatomy), limbs with digit (anatomy), digits. Fish can ...
) in a covered
earthenware
Earthenware is glazed or unglazed Vitrification#Ceramics, nonvitreous pottery that has normally been fired below . Basic earthenware, often called terracotta, absorbs liquids such as water. However, earthenware can be made impervious to liquids ...
jug or
casserole
A casserole (French language, French: diminutive of , from Provençal dialect, Provençal , meaning 'saucepan') is a kind of large, deep cookware and bakeware, pan or bowl used for cooking a variety of dishes in the oven; it is also a categor ...
. The animal to be jugged is usually cut into pieces, placed into a tightly sealed jug with brine or
gravy
Gravy is a sauce made from the juices of meats and vegetables that run naturally during cooking and often thickened with thickeners for added texture. The gravy may be further coloured and flavoured with gravy salt (a mix of salt and caramel food ...
, 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.
''Kangina''
In rural
Afghanistan
Afghanistan, officially the Islamic Emirate of Afghanistan, is a landlocked country located at the crossroads of Central Asia and South Asia. It is bordered by Pakistan to the Durand Line, east and south, Iran to the Afghanistan–Iran borde ...
, grapes are preserved in disc-shaped vessels made of mud and straw, called ''
kangina''. The vessels, which can preserve fresh grapes for up to 6 months, passively control their internal environments to restrict gas exchange and water loss, prolonging the lives of late-harvested grapes stored within them.
Lye
Sodium hydroxide
Sodium hydroxide, also known as lye and caustic soda, is an inorganic compound with the formula . It is a white solid ionic compound consisting of sodium cations and hydroxide anions .
Sodium hydroxide is a highly corrosive base (chemistry), ...
(
lye) makes food too
alkaline
In chemistry, an alkali (; from the Arabic word , ) is a basic salt of an alkali metal or an alkaline earth metal. An alkali can also be defined as a base that dissolves in water. A solution of a soluble base has a pH greater than 7.0. The ...
for bacterial growth. Lye will
saponify fats in the food, which will change its flavor and texture.
Lutefisk uses lye in its preparation, as do some olive recipes. Modern recipes for
century eggs also call for lye.
Pickling
Pickling is a method of preserving food in an edible, antimicrobial liquid. Pickling can be broadly classified into two categories: chemical pickling and fermentation pickling.
In chemical pickling, the food is placed in an edible liquid that inhibits or kills bacteria and other microorganisms. Typical pickling agents include
brine (high in salt),
vinegar,
alcohol
Alcohol may refer to:
Common uses
* Alcohol (chemistry), a class of compounds
* Ethanol, one of several alcohols, commonly known as alcohol in everyday life
** Alcohol (drug), intoxicant found in alcoholic beverages
** Alcoholic beverage, an alco ...
, and
vegetable oil
Vegetable oils, or vegetable fats, are oils extracted from seeds or from other parts of edible plants. Like animal fats, vegetable fats are ''mixtures'' of triglycerides. Soybean oil, grape seed oil, and cocoa butter are examples of seed ...
. 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,
peppers,
corned beef,
herring, and
eggs, as well as mixed vegetables such as
piccalilli.
In fermentation pickling, bacteria in the liquid produce
organic acids as preservation agents, typically by a process that produces
lactic acid
Lactic acid is an organic acid. It has the molecular formula C3H6O3. It is white in the solid state and it is miscible with water. When in the dissolved state, it forms a colorless solution. Production includes both artificial synthesis as wel ...
through the presence of
lactobacillales. Fermented pickles include
sauerkraut,
nukazuke,
kimchi, and
surströmming.
Sugaring
The earliest cultures have used
sugar
Sugar is the generic name for sweet-tasting, soluble carbohydrates, many of which are used in food. Simple sugars, also called monosaccharides, include glucose
Glucose is a sugar with the Chemical formula#Molecular formula, molecul ...
as a preservative, and it was commonplace to store fruit in honey. "Sugar tends to draw water from the microbes (plasmolysis). This process leaves the microbial cells dehydrated, thus killing them. In this way, the food will remain safe from microbial spoilage."
In northern climates without sufficient sun to dry foods,
preserves are made by heating the fruit with sugar.
Sugar is used to preserve fruits, either in an
antimicrobial
An antimicrobial is an agent that kills microorganisms (microbicide) or stops their growth (bacteriostatic agent). Antimicrobial medicines can be grouped according to the microorganisms they are used to treat. For example, antibiotics are used aga ...
syrup with fruit such as apples, pears, peaches, apricots, and plums, or in crystallized form where the preserved material is cooked in sugar to the point of crystallization and the resultant product is then stored dry. The latter method is used for the skins of
citrus
''Citrus'' is a genus of flowering trees and shrubs in the family Rutaceae. Plants in the genus produce citrus fruits, including important crops such as oranges, mandarins, lemons, grapefruits, pomelos, and limes.
''Citrus'' is nativ ...
fruit (candied peel),
angelica
''Angelica'' is a genus of about 90 species of tall Biennial plant, biennial and Perennial plant, perennial herbaceous, herbs in the family Apiaceae, native to temperate and subarctic regions of the Northern Hemisphere, reaching as far north as ...
, and
ginger
Ginger (''Zingiber officinale'') is a flowering plant whose rhizome, ginger root or ginger, is widely used as a spice and a folk medicine. It is an herbaceous perennial that grows annual pseudostems (false stems made of the rolled bases of l ...
.
Modern industrial techniques
Techniques of food preservation were developed in research laboratories for commercial applications.
Aseptic processing
Aseptic processing works by placing sterilized food (typically by heat, see
ultra-high temperature processing) into sterlized packaging material under sterile conditions. The result is a sealed, sterile food product similar to canned food, but depending on the technique used, damage to food quality is typically reduced compared to canned food. A greater variety of packaging materials can be used as well.
Besides UHT, aseptic processing may be used in conjunction with any of the microbe-reduction technologies listed below. With pasteurization and "high pressure pasteurization", the food may not be completely sterilized (instead achieving a specified
log reduction), but the use of sterile packaging and environments is retained.
Pasteurization
Pasteurization is a process for preservation of liquid food. It was originally applied to combat the souring of young local wines. Today, the process is mainly applied to dairy products. In this method, milk is heated at about for 15–30 seconds to kill the bacteria present in it and cooling it quickly to to prevent the remaining bacteria from growing. The milk is then stored in sterilized bottles or pouches in cold places. This method was invented by
Louis Pasteur
Louis Pasteur (, ; 27 December 1822 – 28 September 1895) was a French chemist, pharmacist, and microbiologist renowned for his discoveries of the principles of vaccination, Fermentation, microbial fermentation, and pasteurization, the la ...
, a
French chemist, in 1862.
Vacuum packing
Vacuum-packing stores food in a vacuum environment, usually in an air-tight bag or bottle. The
vacuum
A vacuum (: vacuums or vacua) is space devoid of matter. The word is derived from the Latin adjective (neuter ) meaning "vacant" or "void". An approximation to such vacuum is a region with a gaseous pressure much less than atmospheric pressur ...
environment strips bacteria of oxygen needed for survival. Vacuum-packing is commonly used for storing
nuts to reduce loss of flavor from oxidization. A major drawback to vacuum packaging, at the consumer level, is that vacuum sealing can deform contents and rob certain foods, such as cheese, of its flavor.
Freeze drying
Preservatives
Preservative
food additives can be ''
antimicrobial
An antimicrobial is an agent that kills microorganisms (microbicide) or stops their growth (bacteriostatic agent). Antimicrobial medicines can be grouped according to the microorganisms they are used to treat. For example, antibiotics are used aga ...
'' – which inhibit the growth of
bacteria
Bacteria (; : bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of Prokaryote, prokaryotic microorganisms. Typically a few micr ...
or
fungi
A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified as one ...
, including
mold
A mold () or mould () is one of the structures that certain fungus, fungi can form. The dust-like, colored appearance of molds is due to the formation of Spore#Fungi, spores containing Secondary metabolite#Fungal secondary metabolites, fungal ...
– or ''
antioxidant
Antioxidants are Chemical compound, compounds that inhibit Redox, oxidation, a chemical reaction that can produce Radical (chemistry), free radicals. Autoxidation leads to degradation of organic compounds, including living matter. Antioxidants ...
'', such as
oxygen absorbers, which inhibit the
oxidation
Redox ( , , reduction–oxidation or oxidation–reduction) is a type of chemical reaction in which the oxidation states of the reactants change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is ...
of food constituents. Common antimicrobial preservatives include
nisin
Nisin is a polycyclic antibacterial peptide produced by the bacterium ''Lactococcus lactis'' that is used as a food preservative. It has 34 amino acid residues, including the uncommon amino acids lanthionine (Lan), methyllanthionine (MeLan), dideh ...
,
sorbates,
calcium propionate,
sodium nitrate
Sodium nitrate is the chemical compound with the chemical formula, formula . This alkali metal nitrate salt (chemistry), salt is also known as Chile saltpeter (large deposits of which were historically mined in Chile) to distinguish it from ordi ...
/
nitrite,
sulfites (
sulfur dioxide
Sulfur dioxide (IUPAC-recommended spelling) or sulphur dioxide (traditional Commonwealth English) is the chemical compound with the formula . It is a colorless gas with a pungent smell that is responsible for the odor of burnt matches. It is r ...
,
sodium bisulfite,
potassium hydrogen sulfite, etc.),
EDTA
Ethylenediaminetetraacetic acid (EDTA), also called EDTA acid, is an aminopolycarboxylic acid with the formula . This white, slightly water-soluble solid is widely used to bind to iron (Fe2+/Fe3+) and calcium ions (Ca2+), forming water-solubl ...
,
hinokitiol, and
ε-polylysine.
Antioxidant
Antioxidants are Chemical compound, compounds that inhibit Redox, oxidation, a chemical reaction that can produce Radical (chemistry), free radicals. Autoxidation leads to degradation of organic compounds, including living matter. Antioxidants ...
s include
tocopherols (Vitamin E),
butylated hydroxyanisole (BHA) and
butylated hydroxytoluene (BHT). Other preservatives include
ethanol
Ethanol (also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound with the chemical formula . It is an Alcohol (chemistry), alcohol, with its formula also written as , or EtOH, where Et is the ps ...
.
There is also another approach of impregnating packaging materials (plastic films or other) with antioxidants and antimicrobials.
Irradiation
Irradiation of food is the exposure of food to
ionizing radiation
Ionizing (ionising) radiation, including Radioactive decay, nuclear radiation, consists of subatomic particles or electromagnetic waves that have enough energy per individual photon or particle to ionization, ionize atoms or molecules by detaching ...
. Multiple types of ionizing radiation can be used, including
beta particles (high-energy
electron
The electron (, or in nuclear reactions) is a subatomic particle with a negative one elementary charge, elementary electric charge. It is a fundamental particle that comprises the ordinary matter that makes up the universe, along with up qua ...
s) and
gamma ray
A gamma ray, also known as gamma radiation (symbol ), is a penetrating form of electromagnetic radiation arising from high energy interactions like the radioactive decay of atomic nuclei or astronomical events like solar flares. It consists o ...
s (emitted from radioactive sources such as
cobalt-60 or
cesium-137). Irradiation can kill bacteria, molds, and insect pests, reduce the ripening and spoiling of fruits, and at higher doses induce sterility. The technology may be compared to
pasteurization
In food processing, pasteurization (American and British English spelling differences#-ise, -ize (-isation, -ization), also pasteurisation) is a process of food preservation in which packaged foods (e.g., milk and fruit juices) are treated wi ...
; it is sometimes called "cold pasteurization", as the product is not heated. Irradiation may allow lower-quality or contaminated foods to be rendered marketable.
National and international expert bodies have declared food irradiation as "wholesome"; organizations of the
United Nations
The United Nations (UN) is the Earth, global intergovernmental organization established by the signing of the Charter of the United Nations, UN Charter on 26 June 1945 with the stated purpose of maintaining international peace and internationa ...
, such as the
World Health Organization
The World Health Organization (WHO) is a list of specialized agencies of the United Nations, specialized agency of the United Nations which coordinates responses to international public health issues and emergencies. It is headquartered in Gen ...
and
Food and Agriculture Organization
The Food and Agriculture Organization of the United Nations; . (FAO) is a specialized agency of the United Nations that leads international efforts to defeat hunger and improve nutrition and food security. Its Latin motto, , translates ...
, endorse food irradiation.
[World Health Organization. Wholesomeness of irradiated food. Geneva, Technical Report Series No. 659, 1981][World Health Organization. High-Dose Irradiation: Wholesomeness of Food Irradiated With Doses Above 10 kGy. Report of a Joint FAO/IAEA/WHO Study Group. Geneva, Switzerland: World Health Organization; 1999. WHO Technical Report Series No. 890] Consumers may have a negative view of irradiated food based on the misconception that such food is radioactive; in fact, irradiated food does not and cannot become radioactive. Activists have also opposed food irradiation for other reasons, for example, arguing that irradiation can be used to sterilize contaminated food without resolving the underlying cause of the contamination. International legislation on whether food may be irradiated or not varies worldwide from no regulation to a full ban.
Approximately 500,000 tons of food items are irradiated per year worldwide in over 40 countries. These are mainly
spice
In the culinary arts, a spice is any seed, fruit, root, Bark (botany), bark, or other plant substance in a form primarily used for flavoring or coloring food. Spices are distinguished from herbs, which are the leaves, flowers, or stems of pl ...
s and
condiment
A condiment is a preparation that is added to food, typically after cooking, to enhance the Flavoring, flavour, to complement the dish or to impart a specific flavor. Such specific flavors generally add sweetness or pungency, or sharp or piquant ...
s, with an increasing segment of fresh fruit irradiated for fruit fly quarantine.
Pulsed electric field electroporation
Pulsed electric field (PEF) electroporation 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. To date, several PEF treated juices are available on the market in Europe. Furthermore, for several years a juice pasteurization application in the US has used PEF. For cell disintegration purposes especially potato processors show great interest in PEF technology as an efficient alternative for their preheaters. Potato applications are already operational in the US and Canada. There are also commercial PEF potato applications in various countries in Europe, as well as in Australia, India, and China.
Modified atmosphere
Modifying atmosphere is a way to preserve food by operating on the atmosphere around it. It is often used to package:
* Fresh fruits and vegetables, especially salds crops, which contain living cells that respire even while refrigerated. Reducing oxygen () concentration and increasing the
carbon dioxide
Carbon dioxide is a chemical compound with the chemical formula . It is made up of molecules that each have one carbon atom covalent bond, covalently double bonded to two oxygen atoms. It is found in a gas state at room temperature and at norma ...
() concentration slows down their respiration, conserves stored energy, and therefore increases shelf life.
High humidity is also used to reduce water loss.
* Red meat, which needs high to reduce oxidation of
myoglobin
Myoglobin (symbol Mb or MB) is an iron- and oxygen-binding protein found in the cardiac and skeletal muscle, skeletal Muscle, muscle tissue of vertebrates in general and in almost all mammals. Myoglobin is distantly related to hemoglobin. Compar ...
and maintain an attractive bright red color of the meat.
* Other meat and fish, which uses higher to reduce oxidation and slow down some microbes.
Nonthermal plasma
This process subjects the surface of food to a "flame" of ionized gas molecules, such as helium or nitrogen. This causes micro-organisms to die off on the surface.
High-pressure food preservation
High pressure
In science and engineering the study of high pressure examines its effects on materials and the design and construction of devices, such as a diamond anvil cell, which can create high pressure. ''High pressure'' usually means pressures of thousan ...
can be used to disable harmful microorganisms and spoilage enzymes while retaining the food's fresh appearance, flavor, texture and nutrients. By 2005, the process was being used for products ranging from
orange juice
Orange juice is a liquid extract of the orange (fruit), orange tree fruit, produced by squeezing or reaming oranges. It comes in several different varieties, including blood orange, navel oranges, valencia orange, clementine, and tangerine. As ...
to
guacamole to
deli meats and widely sold.
Depending on temperature and pressure settings, HP processing can achieve either pasteurization-equivalent
log reduction or go all the way to achieve sterilization of all microbes.
Biopreservation
Biopreservation is the use of natural or controlled
microbiota or
antimicrobial
An antimicrobial is an agent that kills microorganisms (microbicide) or stops their growth (bacteriostatic agent). Antimicrobial medicines can be grouped according to the microorganisms they are used to treat. For example, antibiotics are used aga ...
s as a way of preserving food and extending its
shelf life.
Beneficial bacteria or the
fermentation
Fermentation is a type of anaerobic metabolism which harnesses the redox potential of the reactants to make adenosine triphosphate (ATP) and organic end products. Organic molecules, such as glucose or other sugars, are catabolized and reduce ...
products produced by these bacteria are used in biopreservation to control spoilage and render
pathogen
In biology, a pathogen (, "suffering", "passion" and , "producer of"), in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a Germ theory of d ...
s inactive in food.
[Yousef AE and Carolyn Carlstrom C (2003]
''Food microbiology: a laboratory manual''
Wiley, Page 226. . It is a benign ecological approach which is gaining increasing attention.
[Ananou S, Maqueda M, Martínez-Bueno M and Valdivia E (2007]
"Biopreservation, an ecological approach to improve the safety and shelf-life of foods"
In: A. Méndez-Vilas (Ed.) ''Communicating Current Research and Educational Topics and Trends in Applied Microbiology'', Formatex. .
Lactic acid bacteria (LAB) have antagonistic properties that make them particularly useful as biopreservatives. When LABs compete for nutrients, their
metabolite
In biochemistry, a metabolite is an intermediate or end product of metabolism.
The term is usually used for small molecules. Metabolites have various functions, including fuel, structure, signaling, stimulatory and inhibitory effects on enzymes, c ...
s often include active antimicrobials such as lactic acid, acetic acid, hydrogen peroxide, and
peptide
Peptides are short chains of amino acids linked by peptide bonds. A polypeptide is a longer, continuous, unbranched peptide chain. Polypeptides that have a molecular mass of 10,000 Da or more are called proteins. Chains of fewer than twenty am ...
bacteriocin
Bacteriocins are proteinaceous or peptide, peptidic toxins produced by bacteria to inhibit the growth of similar or closely related bacterial strain(s). They are similar to yeast and paramecium killing factors, and are structurally, functionally ...
s. Some LABs produce the antimicrobial
nisin
Nisin is a polycyclic antibacterial peptide produced by the bacterium ''Lactococcus lactis'' that is used as a food preservative. It has 34 amino acid residues, including the uncommon amino acids lanthionine (Lan), methyllanthionine (MeLan), dideh ...
, which is a particularly effective preservative.
[FAO]
Preservation techniques
Fisheries and aquaculture department, Rome. Updated 27 May 2005. Retrieved 14 March 2011.
LAB bacteriocins are used in the present day as an integral part of
hurdle technology. Using them in combination with other preservative techniques can effectively control spoilage bacteria and other pathogens, and can inhibit the activities of a wide spectrum of organisms, including inherently resistant
Gram-negative bacteria
Gram-negative bacteria are bacteria that, unlike gram-positive bacteria, do not retain the Crystal violet, crystal violet stain used in the Gram staining method of bacterial differentiation. Their defining characteristic is that their cell envelo ...
.
Hurdle technology
Hurdle technology is a method of ensuring that
pathogen
In biology, a pathogen (, "suffering", "passion" and , "producer of"), in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a Germ theory of d ...
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 that secures the
microbial safety and stability as well as the
organoleptic
Organoleptic properties are the aspects of food, water or other substances as apprehended via the senses—including taste, sight, smell, and touch.
In traditional U.S. Department of Agriculture meat and poultry inspections, inspectors p ...
and nutritional quality and the economic viability of
food products.
[Leistner I (2000]
"Basic aspects of food preservation by hurdle technology"
''International Journal of Food Microbiology'', 55:181–186. 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 or
redox potential, and the presence of
preservative
A preservative is a substance or a chemical that is added to products such as food products, beverages, pharmaceutical drugs, paints, biological samples, cosmetics, wood, and many other products to prevent decomposition by microbial growth or ...
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.
[Alasalvar C (2010]
''Seafood Quality, Safety and Health Applications''
John Wiley and Sons, Page 203. .
See also
*
Blast chilling
*
Food engineering
*
Food microbiology
*
Food packaging
*
Food rheology
*
Food science
*
Food spoilage
Food spoilage is the process whereby food becomes unsuitable to ingest by a person; it is a matter of food safety. Bacteria and various fungi are the causes of spoilage, and can create serious consequences for consumers, but there are preventive ...
*
Freeze-drying
*
Fresherized
*
List of dried foods
*
List of pickled foods
*
List of smoked foods
*
Shelf life
Notes
Sources
*
References
*
*
*
Further reading
*
External links
A c. 1894 Gustav Hammer & Co. commercial cooking machinery catalogue.Preserving foods ~ from the Clemson Extension Home and Garden Information CenterNational Center for Home Food Preservation*
BBC News Online
BBC News Online is the website of BBC News, the division of the BBC responsible for newsgathering and production. It is one of the most popular news websites, with 1.2 billion website visits in April 2021, as well as being used by 60% of the U ...
�
US army food... just add urineHome Economics Archive: Tradition, Research, History (HEARTH)An e-book collection of over 1,000 classic books on home economics spanning 1850 to 1950, created by Cornell University'
Mann Library
*
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