Food preservation 10834 225933511 2008-07-16T02:20:21Z CarsracBot 6929011 robot Adding: [[simple:Food preservation]] [[Image:Konservering.jpg|thumb|200px|Various preserved foods]] [[Image:Waste not want not WWI poster.jpg|thumb|200px|Canadian World War I poster encouraging people to preserve food for the winter.]] '''Food preservation''' is the process of treating and handling [[food]] in a way that preserves its value as food. The main effort is to stop or greatly slow down spoilage to prevent [[foodborne illness]] (e.g. salting, cooling, cooking). However some methods utilise benign bacteria, yeasts or fungi to add specific qualities and to preserve food (e.g. cheese, wine). While maintaining or creating [[nutrition]]al value, texture and [[flavour]] is important in preserving its value as food; this is a culturally dependent determinant as what qualifies as food fit for humans in one culture may not qualify in another culture. Preservation usually involves preventing the growth of [[bacterium|bacteria]], [[fungus|fungi]] and other [[microorganism|micro-organisms]], as well as retarding the [[redox|oxidation]] of [[fat]]s which cause [[Rancidification|rancidity]]. It also includes processes to inhibit natural ageing and discolouration that can occur during food preparation such as the [[enzymatic browning]] reaction in apples which causes browning when apples are cut. Some preservation methods require the food to be sealed after treatment to prevent re-contamination with microbes; others, such as drying, allow food to be stored without any special containment for long periods. Common methods of applying these processes include [[drying (food)|drying]], [[spray drying]], [[freeze drying]], [[freezing]],[[vacuum-packing]], [[canning]], preserving in syrup, sugar crystallisation, [[food irradiation]], adding [[preservative]]s or inert [[gas]]es such as carbon dioxide. Other methods that not only help to preserve food, but also add flavour, include [[pickling]], [[salting (food)|salting]], [[smoking (food)|smoking]], preserving in [[syrup]] or [[ethanol|alcohol]], [[sugar]] crystallisation and curing. == Preservation processes == {| width="350" border="1" cellpadding="3" cellspacing="0" align="right" style="margin: 0em 0em 1em 1em;" ! Method ! Effect on microbial growth or survival |- | [[Refrigeration]] | Low temperature to retard growth |- | [[Freezing]] | Low temperature and reduction of water activity to prevent microbial growth |- | [[Drying (food)|Drying]], [[curing (food preservation)|curing]] and conserving | Reduction in [[water activity]] sufficient to delay or prevent microbial growth |- | [[Vacuum]] and [[oxygen]] free [[modified atmosphere]] packaging | Low [[oxygen]] tension inhibits strict [[aerobe]]s and delay growth of facultative [[Anaerobic organism|anaerobe]]s |- | Carbon dioxide enriched modified atmosphere packaging | Specific inhibition of some micro-organisms by carbon dioxide |- | Addition of [[weak acid]]s | Reduction of the intracellular [[pH]] of micro-organisms |- | [[Lactic acid|Lactic]] [[fermentation (food)|fermentation]] | Reduction of pH value ''in situ'' by microbial action and sometimes additional inhibition by the lactic and [[acetic acid]]s formed and by other microbial products. (e.g. ethanol, [[bacteriocin]]s) |- | [[Sugar]] preservation | Cooking in high sucrose concentration creating too high osmotic pressure for most microbial survival. |- | [[Ethanol]] preservation | Steeping or cooking in [[Ethanol]] produces toxic inhibition of microbes. Can be combined with sugar preservation |- | [[Emulsion|Emulsification]] | Compartmentalisation and [[nutrient limitation]] within the [[aqueous]] droplets in water-in-oil emulsion foods |- | Addition of preservatives such as [[nitrite]] or [[sulphite]] ions | Inhibition of specific groups of micro-organisms |- | [[Pasteurization]] and [[appertization]] | Delivery of [[heat]] sufficient to inactivate target micro-organisms to the desired extent |- | [[Food irradiation]] ([[Radurization]], [[radicidation]] and [[radappertization]]) | Delivery of [[ionising radiation]] |- | Application of high hydrostatic pressure (Pascalization) | Pressure-inactivation of vegetative bacteria, yeasts and moulds |- | [[Pulsed Electric Field Processing|Pulsed electric field processing]] (PEF treatment) | Short bursts of electricity for microbial inactivation |} Preservation processes include: * Heating to kill or denature organisms (e.g. boiling) * Oxidation (e.g use of sulphur dioxide) * 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. fresherized, a kind of “cold” pasteurization, the pressure kills naturally occurring pathogens, which cause food deterioration and affect [[food safety]].) * Many combinations of these methods * [[Chelation]] == Drying == {{Main|Drying (food)}} One of the oldest methods of food preservation is by drying, which reduces [[water activity]] sufficiently to delay or prevent [[Bacterium|bacterial]] growth.{{Fact|date=May 2008}} Most types of meat can be dried. This is especially valuable in the case of pork, since it is difficult to keep without preservation. Many fruits can also be dried; for example, the process is often applied to apples, pears, bananas, mangoes, papaya, apricot, and coconut. [[Zante currant]]s, [[Sultana (grape)|sultanas]] and [[raisin]]s are all forms of dried grapes. Drying is also the normal means of preservation for cereal grains such as wheat, maize, oats, barley, rice, millet and rye. == Smoking == {{Main|Smoking (food)}} Meat, fish and some other foods may be both preserved and flavoured through the use of smoke, typically in a smoke-house. The combination of heat to dry the food without cooking it, and the addition of the aromatic hydrocarbons from the smoke preserves the food. == Freezing == {{Main|Frozen food}} Freezing is also one of the most commonly used processes commercially and domestically for preserving a very wide range of food stuffs 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 == {{Main|Vacuum packing}} Vacuum-packing stores food in a vacuum environment, usually in an air-tight bag or bottle. The [[vacuum]] environment strips bacteria of oxygen needed for survival, preventing the food from spoiling. Vacuum-packing is commonly used for storing [[nut (fruit)|nuts]]. == Salt == {{Main|Curing (food preservation)}} Salting or curing draws moisture from the meat through a process of osmosis. Meat is [[curing|cured]] with salt or sugar, or a combination of the two. Nitrates and nitrites are also often used to cure meat. == Sugar == Sugar is used to preserve fruits, either in syrup with fruit such as [[apple]]s, [[pear]]s, [[peach]]es, [[apricot]]s, [[plum]]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]] fruit (candied peel), [[angelica]] and [[ginger]]. A modification of this process produces [[glacé fruit]] such as glacé [[cherry|cherries]] 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]] or other spirits. These should not be confused with fruit flavored spirits such as [[Cherry Brandy]] or [[Sloe gin]]. == Pickling == {{Main|Pickling}} Pickling is a method of preserving food in an edible [[anti-microbial]] liquid. Pickling can be broadly categorized as chemical pickling (for example, [[brining]]) and [[fermentation]] pickling (for example, making [[sauerkraut]]). In chemical pickling, the food is placed it in an edible liquid that inhibits or kills bacteria and other micro-organisms. Typical pickling agents include [[brine]] (high in [[edible salt|salt]]), [[vinegar]], [[ethanol|alcohol]], and [[vegetable oil]], especially [[olive oil]] 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]], [[capsicum|pepper]]s, [[corned beef]], [[herring]], and [[Pickled egg|eggs]], as well mixed vegetables such as [[piccalilli]], [[chow-chow]], [[giardiniera]], and [[achar]]. In fermentation pickling, the food itself produces the preservation agent, typically by a process that produces [[lactic acid]]. Fermented pickles include [[sauerkraut]], [[nukazuke]], [[kimchi]], [[surströmming]], and [[curtido]]. Some chemically [[pickled cucumber]]s are also fermented. In commercial pickles, a preservative like [[sodium benzoate]] or [[EDTA]] may also be added to enhance [[shelf life]]. == Lye == [[Sodium hydroxide]] ([[lye]]) makes food too [[alkaline]] for bacterial growth. Lye will [[saponification|saponify]] fats in the food, which will change its flavor and texture. [[Lutefisk]] and [[hominy]] use lye in their preparation, as do some olive recipes. Modern recipes for [[century egg]]s also call for lye. == Canning and bottling == [[Image:PreservedFood1.jpg|thumb|right|225px|Preserved food]] {{Main|Canning}} :''See also [[Home canning]]'' [[Canning]] involves cooking [[fruit]]s or [[vegetable]]s, sealing them in sterile cans or jars, and [[boiling]] the containers to kill or weaken any remaining bacteria as a form of [[pasteurization]]. Various 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 [[strawberry|strawberries]] require no preservatives to can and only a short boiling cycle, whereas marginal fruits such as [[tomato]]es require longer boiling and addition of other acidic elements. Many vegetables 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 and poor [[hygiene]] allowing contamination of canned food by the obligate , ''[[Clostridium botulinum]]'' 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. Food contaminated in this way has included [[Edible mushroom|Mushrooms]], [[Corned beef]] and [[Tuna]]. == Jellying == {{Main|Aspic}} :''see also [[Fruit preserves]] Food may be preserved by cooking in a material that solidifies to form a gel. Such materials include [[gelatine]], [[agar]], [[maize]] flour and [[arrowroot]] flour. Some foods naturally form a [[protein]] gel when cooked such as [[Eel|eels and elvers]], and [[Sipuncula|sipunculid]] worms which are a delicacy in the town of [[Xiamen]] in Fujian province of the [[People's Republic of China]]. [[Jellied eels]] are a delicacy in the East End of [[London]] where they are eaten with mashed potatoes. Potted meats in [[aspic]], (a gel made from gelatine and clarified meat broth) were a common way of serving meat off-cuts in the UK until the [[1950]]s. Many jugged meats are also jellied. Fruit preserved by jellying is known as [[jelly]], [[marmalade]], or [[fruit preserves]]. In this case, the jellying agent is usually [[pectin]], either added during cooking or arising naturally from the fruit. Most preserved fruit is also sugared. == Jugging == {{Main|Jugging}} Meat can be preserved by jugging, the process of [[stewing]] the meat (commonly [[game (food)|game]] or [[fish]]) in a covered [[earthenware]] jug or [[casserole]]. The animal to be jugged is usually cut into pieces, placed into a tightly-sealed jug with brine or [[gravy]], 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 == {{Main|Food irradiation}} Irradiation of food<ref>anon., Food Irradation - A technique for preserving and improving the safety of food, WHO, Geneva, 1991</ref> is the exposure of food to [[ionizing radiation]]; either high-energy [[electron]]s or [[X-ray]]s from accelerators, or by [[gamma ray]]s (emitted from radioactive sources as [[Cobalt]]-60 or [[Caesium]]-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]]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]], but it may use the radiation emitted from radioactive nuclides produced in nuclear reactors. Ionizing radiation is hazardous to life; 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. <ref>[http://www.consumersinternational.org/homepage.asp Consumers International - Home<!-- Bot generated title -->]</ref> National and international expert bodies have declared food irradiation as 'wholesome'; UN-organizations as WHO and FAO are endorsing to utilize food irradiation. International legislature on whether food may be irradiated or not varies worldwide from no regulation to full banning.<ref>[http://nucleus.iaea.org/NUCLEUS/nucleus/Content/Applications/FICdb/FoodIrradiationClearances.jsp?module=cif NUCLEUS - Food Irradiation Clearances<!-- Bot generated title -->]</ref> It is estimated that about 500,000 tons of food items are irradiated per year world-wide in over 40 countries. These are mainly [[spice]]s and [[condiment]]s with an increasing segment of fresh fruit irradiated for fruit fly quarantine<ref>[http://www.mindfully.org/Food/Irradiation-Position-ADA.htm Food irradiation - Position of ADA J Am Diet Assoc. 2000;100:246-253<!-- Bot generated title -->]</ref><ref>C.M. Deeley, M. Gao, R. Hunter, D.A.E. Ehlermann, The development of food irradiation in the Asia Pacific, the Americas and Europe; tutorial presented to the International Meeting on Radiation Processing, Kuala Lumpur, 2006. http://www.doubleia.org/index.php?sectionid=43&parentid=13&contentid=494</ref>. == Modified atmosphere == [[Modified 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 (O<sub>2</sub>) concentration and increase the [[carbon dioxide]] (CO<sub>2</sub>) 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]]s. Grains may be preserved using carbon dioxide. A block of [[dry ice]] is placed in the bottom and the can is filled with grain. The can is then "burped" of excess gas. The [[carbon dioxide]] from the sublimation of the dry ice prevents insects, [[mold]], and [[oxidation]] from damaging the grain. Grain stored in this way can remain edible for five years. [[Nitrogen]] gas (N<sub>2</sub>) at concentrations of 98% or higher is also used effectively to kill insects in grain through [[Hypoxia (medical)|hypoxia]]. However, carbon dioxide has an advantage in this respect as it kills organisms through both hypoxia and hypercarbia, requiring concentrations of only 80%, or so. This makes carbon dioxide preferable for fumigation in situations where an [[hermetic seal]] cannot be maintained. == 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]]s in the soil. Burial may be combined with other methods such as fermentation. Many root vegetables are very resistant to spoilage and require no other preservation other than storage in cool dark conditions, for example by burial in the ground, such as in a [[storage clamp]]. [[Century egg]]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. Most foods can be preserved in soil that is very dry and salty (thus a [[desiccant]]), or soil that is frozen. [[Cabbage]] was traditionally buried in the fall in northern farms in the USA for preservation. Some methods keep it crispy while other methods produce [[sauerkraut]]{{Fact|date=January 2008}}. A similar process is used in the traditional production of [[kimchi]]. 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. Fish (e.g. [[Gravlax]]) has been buried to preserve by fermentation. == Controlled use of micro-organism== {{see also|Fermentation (food)}} Some foods, such as many [[cheese]]s, [[wine]]s, and [[beer]]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. ==High pressure food preservation== {{main|High pressure food preservation}} High pressure food preservation refers to [[high pressure]] used for [[food preservation]]. "Pressed inside a vessel exerting 70,000 pounds per square inch or more, food can be processed so that it retains its fresh appearance, flavour, texture and nutrients while disabling harmful microorganisms and slowing spoilage."<ref name=military> [http://www.military.com/soldiertech/0,14632,Soldiertech_Squeeze,,00.html military.com] article ''KILLING PATHOGENS: High-Pressure Processing Keeps Food Safe'' copyright 2005</ref> By 2001, adequate commercial equipment was developed so that by 2005 the process was being used for products ranging from [[orange juice]] to [[guacamole]] to [[deli meat]]s and widely sold.<ref name=military/> == See also == * [[Food manufacturing]] * [[Food engineering]] * [[Chutney]] * [[Food processing]] * [[Jam]] * [[Marmalade]] * [[Pickling]] * [[Shelf life]] * [[Fresherized]] * [[Gourmet Library and museum]] == Notes == {{reflist}} == References == {{refbegin}} * {{ cite book | title = Food Conservation | first = Astri | last = Riddervold | id = ISBN 9780907325406 }} * {{ cite book | title = Eating for Victory: Food Rationing and the Politics of Domesticity | first = Amy | last = Bentley | id = ISBN 9780252067273 }} * {{ cite book | title = Pickled, Potted, and Canned: How the Art and Science of Food Preserving Changed the World | first = Sue | last = Shephard | id = ISBN 9780743255530 }} {{refend}} == External links == {{commonscat|Food preservation}} * [http://hgic.clemson.edu/factsheets/HGIC3000.htm Preserving foods ~ from the Clemson Extension Home and Garden Information Center] * [http://www.uga.edu/nchfp National Center for Home Food Preservation] * [[BBC News Online]] - [http://news.bbc.co.uk/1/hi/world/americas/3915659.stm US army food... just add urine] [[Category:Food preservation| ]] [[Category:Garde manger]] [[cs:Konzervace potravin]] [[da:Konservering (madvarer)]] [[de:Lebensmittelkonservierung]] [[es:Conserva]] [[fr:Conservation des aliments]] [[he:שימור מזון]] [[nl:Conserveren]] [[ja:保存食]] [[pl:Konserwacja żywności]] [[ru:Консервирование]] [[simple:Food preservation]] [[sr:Конзервирање]] [[fi:Säilöntä]] [[sv:Konservering]] [[th:การถนอมอาหาร]] [[zh:食物保存法]]