Cod is a marine fish of Codiformes, Codidae and Cod.[3]The body of cod is extended, slightly flattened, and the tail tapers back, with a general body length of 25-40 cm;The head is large, the mouth is large, the upper jaw is slightly longer than the lower jaw, and the lower jaw has a chin whisker;The body is covered with small round scales, and the lateral line scales are not obvious;Three dorsal fins and two anal fins;The back and upper side are grayish brown, with many irregular brown and yellow stripes;The ventral surface is gray white, and all fins are gray.[4]
Cod is mainly distributed in the Yellow Sea, the Bohai Sea and the northern part of the East China Sea in China, as well as in the Pacific Ocean, the Atlantic Ocean and the northern cold waters.[5]Cod lives in cold water areas in summer and autumn, and migrates to coastal mud bottom waters with a depth of 50-80 meters in winter,[6]They usually form schools of fish for long-distance migration and predation,[7]It is a bottom cold water fish group.Cod mainly feeds on small fish, crustaceans, molluscs, etc.[8]Cod has strong fecundity and can produce 3-4 million eggs at a time,[9]The egg laying period is the first ten days of January to March;[10]The service life can reach 7 years.[11]
Cod is salty and slightly cold in nature;It is recorded in the Common Medicinal Animals in China that "nourishing and strengthening the body, harmonizing and strengthening the spleen." It has the effect of dietotherapy to assist the recovery of stomach qi discomfort, edema, etc.Cod is low in fat, high in protein and has few spines. It is a nutritious food suitable for all ages.In addition to edible meat, cod liver can be used to make cod liver oil, pancreas can make insulin, and cod liver oil can inhibit tuberculosis.Patients with gout and skin diseases should be careful to eat cod.[12]Norway is one of the most favorite countries to eat cod, which is regarded as a "national treasure".In Portugal, the "Cod Culture Festival" is held every year, and restaurants specializing in cod can be seen everywhere in the city.[13]
Cod, yesCodiformesCodidaeCodMarine fish and animals.The body of cod is extended, slightly flat on the side, and the tail tapers back, with a general body length of 25-40 cm;The head is large, the mouth is large, the upper jaw is slightly longer than the lower jaw, and the lower jaw has a chin whisker;The body is covered with small round scales, and the lateral line scales are not obvious;Three dorsal fins and two anal fins;The back and upper side are grayish brown, with many irregular brown and yellow stripes;The ventral surface is gray white, and all fins are gray.[3-4]
Habitat environment
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Cod lives in cold water areas in summer and autumn, and is a social fish. Most of them live in cold sea with water temperature of 0~16 ℃. Adult fish mainly live in the water layer of 175-225 meters, and juvenile fish live in 80-100 meters. In winter, they migrate to coastal mud bottom waters with water depth of 50-80 meters for wintering.[2][6]
Growth habit
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The adult and young cod have the habit of vertical movement day and night, the adult fish have the habit of swimming from deep water to shallow water spawning hole, and the young fish have the habit ofCluster distributionThe habit of.They feed on invertebrates and small fishes, such as krill, mysis shrimp, smelt, and hairscale fish.They live in the cold water area of the Yellow Sea in summer and autumn, and migrate to the coastal mud bottom area with a water depth of 50~80m in winter.They usually form schools of fish for long-distance migration and predation,It is a bottom cold water fish group.Cod mainly feeds on small fish, crustaceans, molluscs, etc.[2][7-8]
Distribution range
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Cod is widely distributed in the world's oceans, as well as in the Pacific Ocean, the Atlantic Ocean and the northern cold waters;It is native to the cold waters of the North Atlantic from northern Europe to Canada and the eastern United States.At present, the main producing countries areIceland、Canada、Russia、NorwayAnd JapaneseHokkaido。Cod is mainly distributed in ChinaYellow Sea、the bohai seaas well asThe East China SeaIn the north and other sea areas, the main fishing grounds are in the north of the Yellow Sea, east southeast of Shandong Gaojiao, the south of the ocean and the Dongnanhai area. It is one of the marine economic fish species produced in the northern coast.[2][5]
Reproductive mode
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Cod and cod have strong fecundity and are generally 4-5 years old.The spawning period is from December to April of the next year, and the peak period is from January to February. Three to four million eggs can be produced at a time. The diameter of the eggs is 0.98-1.05mm, and the spawning period is the first ten days of January to March. The fertilized eggs hatch out in 12-17 days at 6-7 ℃.[2][9-10]
Morphological characteristics: dorsal fin 11~15, 15~23, 18~21;Hip fin 20-24, 19-22;Pectoral fin i-17-i;Pelvic fin 6;Caudal fin 60[1]。
The body is long and slightly flat;The tail handle is prominent.The head is large.The kiss protrudes slightly.The eyes are small and lateral.The eye spacing is wide and flat, slightly convex.Large mouth, slightly lower.Lips are thick.There is a chin whisker in the center of the mandible.The upper jaw is slightly longer than the lower jaw.The posterior end of the upper jaw reaches below the eye.There are several rows of fine canines in the front of the two jaws and the vomer bone.The gill hole is large.The operculum is interconnected and separated from the isthmus. The head and body are covered with small round scales.One side line, complete.3 dorsal fins, obviously separated, all composed of fins;The first dorsal fin starts from the upper back of the pectoral fin base;The second dorsal fin is slightly posterior to the first dorsal fin;The third dorsal fin is located above the second anal fin.There are 2 hip fins, the first and second hip fins are opposite to the second and third dorsal fins respectively.Lateral median pectoral fin.In the sublingual position of the pelvic fin, the left and right fins are far apart, and the second fin is prominent and filiform.The caudal fin is truncate at the rear end, or slightly concave.The head and back of the body are dark olive, scattered with many irregular cloud like spots. The upper part of the side is purple gray, with dark spots. The lower part of the side is yellow brown, and the abdomen is silver white.Each fin is yellowish white or reddish, and dorsal fin and caudal fin have white edges[1]。
geographical distribution: It is distributed in the North Pacific Ocean, from the Korean Peninsula (Yellow Sea) to Incheon, South Korea, southeast to Alaska, Bering Strait to Chukchi Sea, and east to the southern coast of Victoria Island.It is produced in the Yellow Sea, Tumen River basin and Heilongjiang estuary in China[1]。
Ecological habits: It is a cold water near bottom fish that lives in deeper waters and also enters estuaries, brackish water and nearby river basins.Mainly prey on small fish and crustaceans[1]。
economic significance : It is an important fishing target in the northwest Pacific Ocean and one of the economic food fishes[1]。
Pacific cod
Scientific name：Gadus macrocephalusTilesius (Codidae) Local name: cod, haddock, bighead fish, bighead fishy, Ming Tai fish
morphological character: dorsal fin 12-14, 16-19, 18-20; hip fin 19-22, 18-20;Pectoral fins 18-19;Pelvic fin ii-4;Tail fin 41~44[1]
The body is long and slightly flat.The tail tapers back.The tail handle is thin and flat on the side.Big head.The tip of the snout is blunt and slightly protruding.The eyes are equal in size and side up.The mouth is large and slightly inclined.The lip is thick, and there are small velvety protuberances at the lower edge of the lower lip.There is a chin whisker below the mandibular symphysis.The lower jaw is shorter than the upper jaw.There are canines in both jaw and vomer, and the external jaw teeth are longer and larger.The gill hole is large.The operculum is interconnected and separated from the isthmus.The external gill rakes are developed, and the internal gill rakes are all small protrusions.Gill harrow 3+17-19.Operculum strips 7.Pseudobranchial.The head and body are covered with oval small round scales.One side line, complete.There are 3 dorsal fins, which are obviously separated, and all are composed of fins. The first dorsal fin starts from the upper back of the pectoral fin base;The second dorsal fin is slightly posterior to the first dorsal fin;The third dorsal fin is located on two hip fins above the second hip fin, and the first and second hip fins are opposite to the second and third dorsal fins respectively.Lateral median pectoral fin.At the throat position of the pelvic fin, the left and right fins are far apart, and the second fin is prominent and slightly filiform.The caudal fin is shallow concave at the rear end.The head and the back of the body are light brown green, scattered with many dark brown spots, and the ventral side is light white.Each fin is bluish brown, and the color of pelvic fin and anal fin is lighter[1]。
geographical distribution: It is distributed in the North Pacific waters, including Bering Strait, Korean Peninsula, China, Japan, the Gulf of Alaska, and south to the coast of Los Angeles.Made in Bohai Sea and Yellow Sea in China[1]。
Ecological habits: It is a cold water near bottom fish.They like to live in groups and usually inhabit the sea area with water depth of 15-250 m.It feeds on small fishes, crustaceans and molluscs such as small yellow croaker and Pacific herring.The individual is large, and the maximum body length can reach 80cm[1]。
economic significance : The meat is delicious and has high economic value. It is one of the important economic fishes in the North Pacific Ocean[1]。
theragra chalcogramma
Scientific name：Theragra chalcogramma(Codidae)
Place name:Ming Tai fish, cod
morphological character:Dorsal fins 13~14, 18~19, 21;Gluteal fin 22-23, 21-23;Pectoral fins 19-20;Pelvic fin 6;Caudal fin 42[1]
The body is slender, fusiform, slightly thick in the front, tapering back, and slightly flat on the side.The head is medium and large.The kiss protrudes slightly.The big side of the eye is superior.The eye spacing is wide and flat, slightly convex.Big mouth.The upper jaw is slightly longer than the lower jaw.The posterior end of the maxilla reaches below the anterior edge of the pupil.There is a short dentate chin whisker in the center of the mandible.There are several rows of fine canines in the front of the two jaws and the vomer bone.The maxillary and mandibular exodontic teeth were longer.There are villous teeth in the hypopharyngeal bone.The tongue is blunt in width and free in front.The gill hole is large.The operculum is interconnected and separated from the isthmus.The outer gill rakes are slender, and the inner gill rakes are blunt protuberant. The number of gill rakes is 6+26.The head and body are covered with small round scales.One side line, complete.3 dorsal fins, obviously separated, all composed of fins;The first dorsal fin is high, starting from the upper back of the pectoral fin base;The second dorsal fin is slightly posterior to the first dorsal fin;The third dorsal fin is located above the second anal fin.There are 2 hip fins, the first and second hip fins are opposite to the second and third dorsal fins respectively.Lateral median pectoral fin.At the throat position of the pelvic fin, the left and right fins are far apart, and the second fin is prominent and filiform.The caudal fin is shallow concave at the rear end.Olive color on the head and back of the body, with 2-5 dark longitudinal stripes, and yellow longitudinal stripes between the longitudinal stripes.The ventral side is white.Olive dorsal fin.The pectoral fins are dark black.The pelvic and anal fins are gray.Tail fin light olive[1]。
Geographic distribution:It is distributed in the North Pacific waters, including the Okhotsk Sea, Bering Sea, Korean Peninsula, Japan, and the coast of Alaska in the United States.Made in the east of the Yellow Sea in China[1]。
Ecological habits:It is a cold water near bottom fish.They often gather at the water temperature close to 0 ℃, live in deep waters, and sometimes move on the water surface.They mainly prey on small fish and crustaceans.The maximum body length can reach 80cm[1]。
Economic significance:It is one of the important fishing objects in the North Pacific and has economic value[1]。
morphological character:Dorsal fin Ⅱ - 9~10, 93~104;Hip fin 90-105;Pectoral fins 15-16;Ventral fin 7;Tail fin 1[1]。
The body is slender, slightly flattened in the front, tapering back and flattened in the side.The head is large, sharp and flat in the front, and slightly flat in the rear.Ridges and ridges are developed.The tip of the snout is long and prominent.The nasal fossa is located near the front of the eyes.Eyes are oval in length, located in the middle and upper part of the head, with small mouth and lower position.The upper jaw is longer than the eye diameter and extends from the middle lower part of the nasal fossa to the front upper part of the posterior edge of the eye.There are villous teeth in the upper and lower jaw, and the tooth group is banded.The chin has 1 whisker.The operculum is interconnected with the isthmus below the posterior edge of the eye, and there is a free membrane at the posterior edge.The gill rake is protuberant and has small spines.The number of gill rakes is 1-2+6-8.The head and body are covered with weak pectin scales, the scales are wide and pentagonal, and the pectin spines are thin and sharp, with different sizes and irregular arrangement.The throat and chest scales are regular and nearly radial.One side line, complete.2 dorsal fins, separated;The first dorsal fin starts from the upper back of the pectoral fin base and is high. The second stiff spine is the longest and not prominent, which is filiform and can extend to the front of the second dorsal fin;The second dorsal fin starts slightly in front of and above the anus.The anal fin is more developed than the second dorsal fin.The pectoral fin is longer, lateral middle, and the third and fourth fins are the longest, not reaching the anus.The ventral fin starts from below the rear end of the pectoral fin base, and the first fin is slightly prominent and filiform.The caudal fin is thin and sharp.The dorsal side of the body is light blue gray, scattered with many obvious insect like or cloud like irregular patches, and there are often 1 or 2 longitudinal dark brown black stripes slightly below the body side, and there is often 1 longitudinal small black spot below the first dorsal fin base.The lower side of the body is silver or light blue white.Each fin is dark gray.The first dorsal fin is grayish black after the second spine.The pelvic fins often have small black spots.White mouth.Dark gill cavity and fins[1]。
geographical distribution: It is distributed in the northwest Pacific Ocean, including China, the Korean Peninsula and Japan.Made in the Yellow Sea and East China Sea[1]。
Ecological habits:It is a deep-sea fish.It mainly inhabits muddy and sandy bottom waters.Polychaetes and crustaceans as staple food in the South China Sea[1]。
Economic significance:Meat is edible and of low economic value[1]。
Key values
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Medicinal value
Cod is salty in taste and slightly cold in nature;It is recorded in the Common Medicinal Animals in China that "nourishing and strengthening the body, harmonizing and strengthening the spleen." It has the effect of dietotherapy to assist the recovery of stomach qi discomfort, edema, etc.[12]
nutritive value
Codfish
The meat of cod is white, fine, fresh, tender, thick, and less spiny. It tastes delicious and is not greasy. It is the main food fish in many countries in the world.Cod is low in fat and spines. It is a nutritious food suitable for all ages.Cod is rich in nutrients, such as protein, vitamin A, vitamin D, calcium, magnesium, selenium and other nutrients.[2][12]
The protein content of cod is higher than that of salmon, crucian carp, pomfret and hairtail;The fat content is 7 times lower than hairtail and 17 times lower than salmon.Cod fat contains globulin, albumin, etc., as well as various amino acids necessary for children's development. Its ratio is very similar to children's requirements, and it is very easy to be digested and absorbed by human body.Cod liver is large and high in oil content (20-40% oil content). In addition to all DHA and EPA in common fish oil, it is also rich in vitamin A, D, E and other vitamins necessary for human body. It is a high-quality raw material for extracting cod liver oil.The proportion of these nutrients in cod liver oil is the best proportion of the daily requirement of human body.In addition, cod meat is rich in magnesium, which is conducive to preventing hypertension, myocardial infarction and other cardiovascular diseases, and has a good protective effect on the cardiovascular system.Therefore, cod is known as "gold in the sea" and "dietitian on the table" in Europe[2]。
Cod also has certain health care effects.Fish can promote blood circulation and remove blood stasis;The swim bladder can replenish blood and stop bleeding;Fish bone can cure beriberi;Cod liver oil can astringe sore, clear away heat and diminish inflammation, inhibit tubercle bacillus, and eliminate bacteria existing in infectious trauma. The ointment made of cod liver oil can quickly liquefy gangrenous tissue;Cod pancreas contains a large amount of insulin, which can extract 12000IU insulin from 1kg pancreas and has a good hypoglycemic effect[2]。
economic value
The cod meat can be processed into feed and fish meal,The liver can be used to make cod liver oil, the pancreas can make insulin, and cod liver oil can inhibit tuberculosis.Patients with gout and skin diseases should be careful to eat cod.[12]
Fish meal is a kind of high protein feed that uses fish with low economic value and poor freshness and leftovers from aquatic product processing as raw materials after degreasing, dehydration and crushing.The fishmeal producing countries in the world mainly include New Zealand, Peru, Denmark, Chile, Norway, Japan and other countries. The export volume of Peru and Chile accounts for about 70% of the total trade volume.The output of fishmeal in China is not very high. The main producing areas are Zhejiang and Shandong, followed by Hebei, Tianjin, Fujian, Guangxi and other provinces and cities. Shandong is mainly concentrated in Qingdao.At the end of the 20th century, China imported about 700000 tons of fish meal every year, about 80% from Peru, 10% from Chile, and a small amount from Japan, the United States and some Southeast Asian countries[2]。
Collagen extracted from fish skin
Fish skin is an important raw material for food industry, chemical production and medicine. In recent years, the value of fish skin has been gradually valued by many countries. Making full use of fish skin resources and developing new products of fish skin have become an important aspect of the comprehensive utilization of leftovers from fish products[2]。
Production of hydrolyzed protein
The crude protein content of fish processing leftovers is high. It is reported that the crude protein content of green scale fish leftovers can reach 58.7%, which is 76% of the crude protein of fish meat, and the crude protein content of roasted eel leftovers is 22.6%.In order to make full use of the protein resources in the leftovers of fish processing, many domestic researchers have explored the production of fish hydrolytic protein from leftovers.Zhang Luxia et al. extracted fish bone protein by hydrolyzing cod fillet with complex protease using cod fillet as raw material, and prepared Maillard reaction products using the obtained soluble protein.The results showed that the yield of soluble substances obtained from the enzymatic hydrolysis of cod excreta was 24.14%. The Maillard reaction product of cod excreta protein had significant free radical scavenging ability and iron reducing ability. It was a nutritional flavor food additive with strong antioxidant activity[2]。
Fish oil extraction
In the process of fish processing, a large number of processing wastes are generated.The content of visceral fat is high, accounting for about 20% of the total mass.Dyeber J and others proved through experiments that fish oil is rich in unsaturated fatty acids, especially eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA[2]。
Fish bone processing
Fish bones are rich in calcium and phosphorus, and the proportion is reasonable.Fish bones contain high-quality active calcium that can promote human growth and development and a variety of essential trace elements.Fish bone powder is a kind of natural calcium supplement product, which is made from the leftover fish bone after high temperature, saponification, degreasing, deodorization, degumming, drying, crushing and other processes.Studies on biological utilization and clinical trial show that fishbone powder has good calcium absorption and retention rate, and is a high-quality natural calcium agent with high utilization rate[2]。
Xue Changhu et al. studied the effect of hydrochloric acid, lactic acid and acetic acid on the extraction of bone calcium from fish bone meal at different concentrations and temperatures with cod steak as raw material;The active calcium powder prepared from fish bones contains 38.27% calcium, 17.73% phosphorus, and the Ca/P ratio is about 2:1. However, trace elements such as Cu, Mn, Mg, Fe, Zn, and Se have some losses after the activation of fish bones.Huo Jiancong et al. explored the preparation method of cod bone calcium powder with the fish bones produced in the processing of cod as raw materials, and studied the biological efficacy of cod bone calcium tablets with Wistar rats as models.The results showed that the optimal technological parameters for preparing cod bone calcium tablet were: 1 mol/L NaOH solution, 30 h immersion, 60% ethanol, 15 h immersion, 4% polyvinyl pyrrolidone ethanol solution as adhesive, and the ratio of filler to milk powder was 1:2.In addition, animal experiments show that 2 g/(kg · d) and 5 g/(kg · d) of cod bone calcium tablets can significantly increase the content of blood calcium, blood phosphorus and bone calcium in rats, which can promote bone growth, increase bone density and prevent osteoporosis[2]。
Deodorization method
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Cause of fishy smell
Codfish
There are many reasons for fishy smell, which can be summarized as follows: fish are polluted by volatile organic compounds from outside, such as phenols, petroleum hydrocarbons, etc., and enter the body through its gills and skin, causing muscle odor;Metabolites from certain organisms in the diet or environment, such as eugenol and 2-methylisobarnol produced by actinomycetes and cyanobacteria, enter the fish body through some channels and accumulate to produce odor;Improper handling and storage of fresh fish may lead to the action of microorganisms and enzymes or automatic oxidation, resulting in the corruption of fresh materials[2]。
method
It mainly includes chemical deodorization, physical deodorization and biological deodorization.Chemical deodorization methods include acid-base salt method, antioxidant method, etc.Physical methods include embedding method, adsorption method, masking method, organic solvent extraction method and microcapsule method[2]。
Acid-base salt method
The chemical reaction between the odor components in the aquatic products and the acid and alkali produces the odor free substances, and the role of salt is generally believed to be mainly to promote the release of the odor components in the aquatic products, so as to achieve deodorization.At the same time, organic acids can dissolve and extract pigments, fats and odorous substances and partially eliminate them.In addition, organic acids can also kill bacteria, eliminate histamine, and reduce the pH value of fish, which is conducive to inhibiting the growth of microorganisms during processing and storage[2]。
Antioxidant method
The tea polyphenols, flavonoids and terpenes in tea have the functions of deodorization and odor absorption. In addition, the catechins in tea can eliminate methyl mercaptan compounds and combine with amino acids, which has a certain role in inactivating enzymes and killing bacteria[2]。
Embedding method
It uses some cage molecules (such as β - CD) to embed volatile substances with low molecular weight to remove odor.But generally, the dosage is large, and the effect is difficult to control[2]。
Adsorption method
Materials with highly developed pore structure and huge surface area, such as activated carbon, glass fiber, phenolic formaldehyde resin and polysaccharide gel, are used to adsorb fishy substances to achieve the purpose of eliminating fishy smell.But the latter are not practical, and activated carbon is the most common method[2]。
Cover up method
Use the special flavor of spice or some flavor presenting substances to cover up those undesirable odors[2]。
Organic solvent extraction
The principle of dissolving and extracting odorous ingredients with organic solvents is used to achieve the effect of deodorization.Common extractants include ethanol and ether, which can remove part of fat while removing fishy smell.And the deodorization effect increases with the increase of extraction times[2]。
Microcapsule technology
Use glue materials as wall materials to wrap fishy substances in a small closed capsule to achieve the effect of deodorization[2]。
Biological deodorization
Through the metabolism of microorganisms, some macromolecular fishy substances participate in the anabolism and transform into fishy substances, or the molecular structure changes under the action of microbial enzymes and transform into fishy substances to achieve the goal of eliminating fishy substances.Much research in this field focuses on the use of yeast and lactic acid bacteria to ferment to remove fishy smell. Data show that yeast powder has obvious effect on removing fishy smell of aquatic products, but the amount of yeast and treatment conditions should be controlled to avoid excessive fermentation and bad fermentation smell of the solution[2]。
