Fish preservation is the method of increasing the

shelf life Shelf life is the length of time that a commodity may be stored without becoming unfit for use, consumption, or sale. In other words, it might refer to whether a commodity should no longer be on a pantry shelf (unfit for use), or no longer on a ...

fish Fish are aquatic, craniate, gill-bearing 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. Approximately 95% of ...

and other

fish products Fish and fish products are consumed as food all over the world. With other seafoods, they provides the world's prime source of high-quality protein; 14–16 percent of the animal protein consumed worldwide. Over one billion people rely on fish a ...

by applying the principles of different branches of science in order to keep the fish, after it has landed, in a condition wholesome and fit for human consumption. Ancient methods of preserving fish included

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 consider ...

, salting,

pickling Pickling is the process of preserving or extending the shelf life of food by either anaerobic fermentation in brine or immersion in vinegar. The pickling procedure typically affects the food's texture and flavor. The resulting food is cal ...

and smoking. All of these techniques are still used today but the more modern techniques of

freezing Freezing is a phase transition where a liquid turns into a solid when its temperature is lowered below its freezing point. In accordance with the internationally established definition, freezing means the solidification phase change of a liquid ...

and canning have taken on a large importance. Fish curing includes and of curing

, salting, smoking, and

, or by

combinations In mathematics, a combination is a selection of items from a set that has distinct members, such that the order of selection does not matter (unlike permutations). For example, given three fruits, say an apple, an orange and a pear, there are th ...

of these processes have been employed since ancient times. On sailing vessels fish were usually salted down immediately to prevent spoilage; the swifter boats of today commonly bring in unsalted fish. Modern

and canning methods have largely supplanted older methods of preservation. Fish to be cured are usually first cleaned, scaled, and eviscerated. Fish are salted by packing them between layers of

salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quant ...

or by

immersion Immersion may refer to: The arts * "Immersion", a 2012 story by Aliette de Bodard * ''Immersion'', a French comic book series by Léo Quievreux#Immersion, Léo Quievreux * Immersion (album), ''Immersion'' (album), the third album by Australian gro ...

in brine. The fish most extensively salted are

cod Cod is the common name for the demersal fish genus '' Gadus'', belonging to the family Gadidae. Cod is also used as part of the common name for a number of other fish species, and one species that belongs to genus ''Gadus'' is commonly not call ...

, herring, mackerel, and

haddock The haddock (''Melanogrammus aeglefinus'') is a saltwater ray-finned fish from the family Gadidae, the true cods. It is the only species in the monotypic genus ''Melanogrammus''. It is found in the North Atlantic Ocean and associated seas wher ...

. Smoking preserves fish by drying, by deposition of creosote ingredients, and, when the fish are near the source of heat, by heat penetration. Herring and haddock (finnan haddie) are commonly smoked.

Kippers A kipper is a whole herring, a small, oily fish, that has been split in a butterfly fashion from tail to head along the dorsal ridge, gutted, salted or pickled, and cold-smoked over smouldering wood chips (typically oak). In the United Kin ...

are split herring, and bloaters are whole herring, salted and smoked.

Sardines "Sardine" and "pilchard" are common names for various species of small, oily forage fish in the herring family Clupeidae. The term "sardine" was first used in English during the early 15th century, a folk etymology says it comes from the Ital ...

pilchards "Sardine" and "pilchard" are common names for various species of small, oily forage fish in the herring family Clupeidae. The term "sardine" was first used in English during the early 15th century, a folk etymology says it comes from the Ital ...

, and

anchovies An anchovy is a small, common forage fish of the family Engraulidae. Most species are found in marine waters, but several will enter brackish water, and some in South America are restricted to fresh water. More than 140 species are placed in 1 ...

are small fish of the herring family, often salted and smoked and then preserved in

oil An oil is any nonpolar chemical substance that is composed primarily of hydrocarbons and is hydrophobic (does not mix with water) & lipophilic (mixes with other oils). Oils are usually flammable and surface active. Most oils are unsaturated ...

. Fish are dried under controlled conditions of

temperature Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measurement, measured with a thermometer. Thermometers are calibrated in various Conversion of units of temperature, temp ...

humidity Humidity is the concentration of water vapor present in the air. Water vapor, the gaseous state of water, is generally invisible to the human eye. Humidity indicates the likelihood for precipitation, dew, or fog to be present. Humidity dep ...

, and air velocity. Since the dried product is relatively unappetizing and rehydrating slow, other preservation methods are common.

History

In the past, fishing vessels were restricted in range by the simple consideration that the catch must be returned to port before it spoils and becomes worthless. The development of

refrigeration The term refrigeration refers to the process of removing heat from an enclosed space or substance for the purpose of lowering the temperature.International Dictionary of Refrigeration, http://dictionary.iifiir.org/search.phpASHRAE Terminology, ht ...

and freezing technologies transformed the

commercial fishing Commercial fishing is the activity of catching fish and other seafood for commercial profit, mostly from wild fisheries. It provides a large quantity of food to many countries around the world, but those who practice it as an industry must often ...

industry: fishing vessels could be larger, spending more time away from port and therefore accessing fish stocks at a much greater distance. Refrigeration and freezing also allow the catch to be distributed to markets further inland, reaching customers who previously would have had access only to dried or salted sea fish. Canning, developed during the 19th century, has also had a significant impact on fishing by allowing seasonal catches of fish that are possibly far from large centres of population to be exploited. For example:

canned sardines Sardines ("pilchards") are a nutrient-rich, small, oily fish widely consumed by humans and as forage fish by larger fish species, seabirds and marine mammals. Sardines are a source of omega-3 fatty acids. Sardines are often served in cans, but c ...

. Preservation techniques are needed to prevent fish spoilage and lengthen

. They are designed to inhibit the activity of spoilage

bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of prokaryotic microorganisms. Typically a few micrometr ...

and the metabolic changes that result in the loss of fish quality. Spoilage bacteria are the specific bacteria that produce the unpleasant odours and flavours associated with spoiled fish. Fish normally host many bacteria that are not spoilage bacteria, and most of the bacteria present on spoiled fish played no role in the spoilage. To flourish, bacteria need the right temperature, sufficient water and oxygen, and surroundings that are not too acidic. Preservation techniques work by interrupting one or more of these needs. Preservation techniques can be classified as follows.FAO
Preservation techniques
Fisheries and aquaculture department, Rome. Updated 27 May 2005. Retrieved 14 March 2011.

Control of temperature

If the temperature is decreased, the metabolic activity in the fish from microbial or autolytic processes can be reduced or stopped. This is achieved by

where the temperature is dropped to about 0 °C, or

where the temperature is dropped below -18 °C. On fishing vessels, the fish are refrigerated mechanically by circulating cold air or by packing the fish in boxes with ice.

Forage fish Forage fish, also called prey fish or bait fish, are small pelagic fish which are preyed on by larger predators for food. Predators include other larger fish, seabirds and marine mammals. Typical ocean forage fish feed near the base of the foo ...

, which are often caught in large numbers, are usually chilled with refrigerated or chilled seawater. Once chilled or frozen, the fish need further cooling to maintain the low temperature. There are key issues with fish cold store design and management, such as how large and energy efficient they are, and the way they are insulated and palletized. An effective method of preserving the freshness of fish is to chill with ice by distributing ice uniformly around the fish. It is a safe cooling method that keeps the fish moist and in an easily stored form suitable for transport. It has become widely used since the development of mechanical

, which makes ice easy and cheap to produce. Ice is produced in various shapes; crushed ice and ice flakes, plates, tubes and blocks are commonly used to cool fish.FAO
Handling of fish and fish products
Fisheries and aquaculture department, Rome. Updated 27 May 2005. Retrieved 22 July 2012. Particularly effective is

slurry ice Slurry ice is a phase changing refrigerant made up of millions of ice "micro-crystals" (typically 0.1 to 1 mm in diameter) formed and suspended within a solution of water and a freezing point depressant. Some compounds used in the field are sa ...

, made from microcrystals of ice formed and suspended within a solution of water and a freezing point depressant, such as common salt. A more recent development is

pumpable ice technology Pumpable ice technology (PIT) uses thin liquids, with the cooling capacity of ice. Pumpable ice is typically a slurry of ice crystals or particles ranging from 5 micrometers to 1 cm in diameter and transported in brine, seawater, food liqui ...

. Pumpable ice flows like water, and because it is homogeneous, it cools fish faster than freshwater solid ice methods and eliminates freeze burns. It complies with

HACCP Hazard analysis and critical control points, or HACCP (), is a systematic preventive approach to food safety from biological, chemical, and physical hazards in production processes that can cause the finished product to be unsafe and designs mea ...

and

ISO ISO is the most common abbreviation for the International Organization for Standardization. ISO or Iso may also refer to: Business and finance * Iso (supermarket), a chain of Danish supermarkets incorporated into the SuperBest chain in 2007 * Iso ...

food safety and public health standards, and uses less energy than conventional freshwater solid ice technologies. File:Fish Packed in Ice.jpg, Fish packed in ice File:sunwell fish packing pumpable slurry ice.JPG, Fish chilling with

. File:Fish cooling by Pumpable Ice.jpg, Fish cooling by pumpable ice File:Zhuhai-fishing-port-Loading-ice-0707.jpg, Loading blocks of factory-made ice from a truck to an "ice depot" boat File:Ice house, Pittenweem - geograph.org.uk - 602960.jpg, Ice manufactured in this ice house is delivered down the Archimedes screw into the ice hold on the boat,

Pittenweem Pittenweem ( ) is a fishing village and civil parish in Fife, on the east coast of Scotland. At the 2001 census, it had a population of 1,747. Etymology The name derives from Pictish and Scottish Gaelic. "Pit-" represents Pictish ''pett'' 'pl ...

Control of water activity

The

water activity Water activity (''aw'') is the partial vapor pressure of water in a solution divided by the standard state partial vapor pressure of water. In the field of food science, the standard state is most often defined as pure water at the same tempe ...

, a_w, in a fish is defined as the ratio of the

water vapour (99.9839 °C) , - , Boiling point , , - , specific gas constant , 461.5 J/( kg·K) , - , Heat of vaporization , 2.27 MJ/kg , - , Heat capacity , 1.864 kJ/(kg·K) Water vapor, water vapour or aqueous vapor is the gaseous pha ...

pressure in the flesh of the fish to the vapour pressure of pure water at the same temperature and pressure. It ranges between 0 and 1, and is a parameter that measures how available the water is in the flesh of the fish. Available water is necessary for the microbial and enzymatic reactions involved in spoilage. There are a number of techniques that have been or are used to tie up the available water or remove it by reducing the a_w. Traditionally, techniques such as

, salting and smoking have been used, and have been used for thousands of years. These techniques can be very simple, for example, by using solar drying. In more recent times, freeze-drying, water-binding humectants, and fully automated equipment with temperature and humidity control have been added. Often a combination of these techniques is used. File:COLLECTIE TROPENMUSEUM Vrouwen tijdens het drogen van vis TMnr 20018454.jpg, Women drying fish in Indonesia, 1971 File:BD Mohanganj 6.jpg, Dry fish market at Mohanganj File:Stockfisch in Iceland 2005.JPG, Drying stockfish in Iceland File:Fish-Drying Barn.jpg, Fish barn with fish drying in the sun –

Van Gogh Vincent Willem van Gogh (; 30 March 185329 July 1890) was a Dutch Post-Impressionist painter who posthumously became one of the most famous and influential figures in Western art history. In a decade, he created about 2,100 artworks, inc ...

1882. File:Carlb-nfld-codflakes.jpg, Platforms, called

fish flake A fish flake is a platform built on poles and spread with boughs for drying cod on the foreshores of fishing villages and small coastal towns in Newfoundland and Nordic countries. Spelling variations for fish flake in Newfoundland include ', ...

s, where cod dry in the sun before being packed in salt File:Usines de Salaison I Neapolis.JPG, Remains of Roman fish-salting plant at Neapolis File:Tunisie Néapolis musée 8.jpg, Reconstruction of the Roman fish-salting plant at Neapolis File:Malpe(24-1-08).JPG, Drying salted fish at Malpe Harbour File:Salt fish dip 070826-292 mank.jpg, Salt fish dip at Jakarta File:Port Eynon - The Salt House - geograph.org.uk - 868752.jpg, Ruins of the Port Eynon Salt House – seawater was boiled to extract salt for preserving fish

Physical control of microbial loads

Heat or ionizing irradiation can be used to kill the

that cause decomposition. Heat is applied by cooking, blanching or microwave heating in a manner that pasteurizes or sterilizes fish products. Cooking or pasteurizing does not completely inactivate microorganisms and may need to be followed with refrigeration to preserve fish products and increase their shelf life. Sterilised products are stable at ambient temperatures up to 40 °C, but to ensure they remain sterilized they need packaging in metal cans or retortable pouches before the heat treatment.

Chemical control of microbial loads

Microbial growth and proliferation can be inhibited by a technique called biopreservation. Biopreservation is achieved by adding

antimicrobial An antimicrobial is an agent that kills microorganisms or stops their growth. Antimicrobial medicines can be grouped according to the microorganisms they act primarily against. For example, antibiotics are used against bacteria, and antifungals ar ...

s or by increasing the

acidity In computer science, ACID ( atomicity, consistency, isolation, durability) is a set of properties of database transactions intended to guarantee data validity despite errors, power failures, and other mishaps. In the context of databases, a ...

of the fish muscle. Most bacteria stop multiplying when the pH is less than 4.5. Acidity is increased by fermentation,

marination Marinating is the process of soaking foods in a seasoned, often acidic, liquid before cooking. The origin of the word alludes to the use of brine (''aqua marina'' or sea water) in the pickling process, which led to the technique of adding flav ...

or by directly adding acids (acetic, citric, lactic) to fish products.

Lactic acid bacteria Lactobacillales are an order of gram-positive, low-GC, acid-tolerant, generally nonsporulating, nonrespiring, either rod-shaped ( bacilli) or spherical ( cocci) bacteria that share common metabolic and physiological characteristics. These bact ...

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), di ...

which further enhances preservation. Other preservatives include nitrites, sulphites,

sorbate Sorbic acid, or 2,4-hexadienoic acid, is a natural organic compound used as a food preservative. It has the chemical formula and the structure . It is a colourless solid that is slightly soluble in water and sublimes readily. It was first isol ...

benzoate Benzoic acid is a white (or colorless) solid organic compound with the formula , whose structure consists of a benzene ring () with a carboxyl () substituent. It is the simplest aromatic carboxylic acid. The name is derived from gum benzoin, wh ...

s and essential oils.

Control of the oxygen reduction potential

Spoilage bacteria and

lipid oxidation Lipid peroxidation is the chain of reactions of oxidative degradation of lipids. It is the process in which free radicals "steal" electrons from the lipids in cell membranes, resulting in cell damage. This process proceeds by a free radical chain ...

usually need oxygen, so reducing the oxygen around fish can increase shelf life. This is done by controlling or modifying the atmosphere around the fish, or by vacuum packaging. Controlled or modified atmospheres have specific combinations of oxygen, carbon dioxide and nitrogen, and the method is often combined with refrigeration for more effective fish preservation.

Combined techniques

Two or more of these techniques are often combined. This can improve preservation and reduce unwanted side effects such as the denaturation of nutrients by severe heat treatments. Common combinations are salting/drying, salting/marinating, salting/smoking, drying/smoking, pasteurization/refrigeration and controlled atmosphere/refrigeration. Other process combinations are currently being developed along the multiple hurdle theory.Leistner L and Gould GW (2002
''Hurdle technologies: combination treatments for food stability, safety, and quality''
Springer. . File:Making fish paste Cambodia.jpg, Making fish paste in Cambodia See: *

Haddock The haddock (''Melanogrammus aeglefinus'') is a saltwater ray-finned fish from the family Gadidae, the true cods. It is the only species in the monotypic genus ''Melanogrammus''. It is found in the North Atlantic Ocean and associated seas wher ...

: Arbroath Smokie (lightly smoked). * Herring:

kipper A kipper is a whole herring, a small, oily fish, that has been split in a butterfly fashion from tail to head along the dorsal ridge, gutted, salted or pickled, and cold-smoked over smouldering wood chips (typically oak). In the United Ki ...

(salted and smoked), surströmming (fermented), rollmops (pickled), soused (salted). *

Salmon Salmon () is the common name for several commercially important species of euryhaline ray-finned fish from the family Salmonidae, which are native to tributaries of the North Atlantic (genus ''Salmo'') and North Pacific (genus '' Oncorhy ...

smoked salmon Smoked salmon is a preparation of salmon, typically a fillet that has been cured and hot or cold smoked. Due to its moderately high price, smoked salmon is considered a delicacy. Although the term lox is sometimes applied to smoked salmon, t ...

, cured salmon, and

gravlax Gravlax () or graved salmon is a Nordic dish consisting of salmon that is cured using a mix of salt and sugar, and either dill or sprucetwigs placed on top, and may occasionally be cold- smoked afterwards. Gravlax is usually served as an app ...

(fermented). *

Cod Cod is the common name for the demersal fish genus '' Gadus'', belonging to the family Gadidae. Cod is also used as part of the common name for a number of other fish species, and one species that belongs to genus ''Gadus'' is commonly not call ...

: stockfish (air dried),

lutefisk ''Lutefisk'' ( Norwegian, in Northern and parts of Central Norway, in Southern Norway; sv, lutfisk ; fi, lipeäkala ; literally " lye fish") is dried whitefish (normally cod, but ling and burbot are also used). It is made from aged sto ...

(soaked in

lye A lye is a metal hydroxide traditionally obtained by leaching wood ashes, or a strong alkali which is highly soluble in water producing caustic basic solutions. "Lye" most commonly refers to sodium hydroxide (NaOH), but historically has been u ...

References

{{seafood Preservation Food preservation Fish processing Smoked fish