Fish – basic information

The chemical composition of fish muscles in terms of quantity and quality is different. It is influenced by many factors, such as species, age, feeding place and type of food, as well as the time and manner of fishing and many factors related to transport, preparation for marketing, etc. 

Muscle fish, occurring in the domestic trade, contain on average 

– water-50-85%, 

– protein-10-25%, 

– fat-0.2-54%, 

– mineral salts – 0.5-5.6%, 

– carbohydrates-0.1-0.4%, 

– vitamins A, B and D. 

Fish proteins are characterized by a very high bioavailability in the human body – about 97%. 

Fish fats have a low melting point and high bioavailability, which is about 92%. They are primarily a source of vitamins A, B and D. 

Fat content in fish muscles is a criterion for dividing fish into three groups 

1) fatty fish containing more than 5% fat (including cesta, halibut, salmon, trout, mackerel, sprat, herring, eel, sardine), 

2) medium-fatty fish, containing 1-5% fat (including barbell, redfish, crucian carp, bream, tench, roach, trout, whitefish, mumps), 

3) lean fish containing up to 1% fat (including cod, hake, perch, zander, pike). 

The content of vitamins in mg / 100g of edible fish parts is e.g. 

– cod-vitamin d (in liver fat) -100; vitamins A- 1000; vitamin B1 -80; Vitamin B2 – 100; vitamin PP-1500; 

– broker – vitamin D (in liver fat) – 750; vitamins A- 1000. 

Due to its nutritional value, such as nutrient properties, absorption by the body and caloricity, fish should be consumed in larger quantities than currently in Poland. 

Fish belong to products of short durability, they are easily spoiled, therefore cooling or freezing is necessary to prolong their durability. 


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Commodity characteristics of selected fish species. 

The herring families include herring, sprat, sardine, sardinella; Herring and sprat have the greatest economic importance. 

Herring from the Baltic Sea reaches a different length, usually 20 cm, and in the North Sea – 35 cm. Herring in Poland is a commonly processed raw material, subjected to salting, smoking and marinating. Compared with North Sea herring, Baltic herring is of lower quality. 

Sardine – a species far sea, warm water, 20-25 cm long; is a raw material for canning in olive oil. 

The salmonid family includes salmon, sea trout, brown trout, rainbow trout, whitefish, whitefish. Meat from this family is very much appreciated because it is extremely tasty. 

Salmon weight is up to 15kg, and body length varies from 75 to 150cm. In trade, salmon is most often offered in a fresh, chilled or frozen state, mainly as a luxury gastronomic raw material, as well as for processing (smoked, canned). 

Carp ropes include ropes, carp, barbel, crucian carp, bream, pig and others. They are freshwater fish; most species are valued for utility reasons. Among the fish of this family, carp is the most popular fish traditionally eaten on the eve of Christmas. He lives both in wild water areas and is also bred; these species differ from each other. Carp is valued for its tasty and medium-fat meat. Preparations 

of this fish are produced sporadically. 

The representative of the eel family is eel. The length of males reaches 51 cm, and females up to 2 m; the average body weight is 0.5-1.0 kg. The eel has white and very greasy tasty meat. 

Cod, hake and other fish belong to the cod. There are both Baltic and deep-sea species; they have an important utility meaning due to the white, lean and tasty meat. 

To okonowatych, include zander and perch. They are freshwater fish with tasty white and lean meat. 

The most important representative of a mackerel family is a broker. It reaches up to 60 cm and body weight up to 1.6 kg. It belongs to oily fish, with very tasty meat. It is a valuable raw material used in processing. 

Depending on the method of preparing the fish raw material for marketing, the fish is divided into fresh and frozen, fish and other products. 

Fresh fish are caught fish and killed, fit for consumption that have not been fixed or have been fixed by cooling; ice pouring is most often used. 

Dreamed fish are those that have been stripped of life due to strangulation, and killed fish are fish without life in a mechanical way. 

Fresh fish should be chilled to a temperature of +5 to -1 C in the depth of the body. 

Frozen fish are those whose temperature in the depth of the body is not higher than -8 degrees C, frozen by fast method, i.e. the fish body temperature decrease to -9 degrees C occurred in no more than 2 hours. 

Selling fresh and frozen fish requires stores to be equipped with adequate refrigeration equipment in order to preserve the so-called cold chain. 

Fish products. 

Salted, smoked and marinated fish. 

Salted fish are fish or parts thereof fixed by the action of sodium chloride (table salt). 

In the domestic trade there are wet salted fish (in brine). Most often salted sledzie, which during this process acquire a characteristic taste and smell. Salting with the addition of spices is also used; herring obtained in this way is called spicy. Due to the development of refrigeration, the importance of salting as a method of fixing is reduced. 

Smoked fish are fish or parts thereof prepared for immediate consumption as a result of smoke. 

There is a distinction between hot smoking, which takes place at a temperature of 120-140 degrees C, and cold smoked at 30 degrees Celsius. Salmon smoke is smoked with cold smoke, which is fixed with smoke and acquires specific sensory characteristics. 

Marinated fish are those obtained from fish or parts thereof which have been treated with a solution of salt and vinegar with spices. 

Due to the way they are prepared, cold, boiled and fried marinades stand out. Cold pickles are obtained by marinating fresh or salted fish, pickled marinades – by marinating boiled or steamed fish, fried marinades are obtained by frying fish and then marinating. 


Canned fish. 

Fish preserves are products in airtight packaging, subjected to thermal sterilization or other processes, causing the destruction of microorganisms to such an extent that their development is impossible, irrespective of the temperature at which these canned food is to be stored; they are suitable for direct consumption. 

The rules for the production of canned fish, as well as the requirements for packaging, marking and storage, are the same as, for example, canned meat. 

Canned fish is a very large assortment group, which results from the variety of raw material, various pre-treatment methods and various types of applied inundation and additives. 

The canned fish in the market are divided depending on how they are prepared, canned in own sauce, in oil, in tomato sauce, fish and vegetable sauce, fish pate and others. 

Fish preserves are fish products fixed mainly by salting and possibly with the use of permitted additives, sealed in airtight packaging, not subjected to sterilization. 

The use of benzoic acid and its sodium salt or sorbic acid or its sodium, potassium or calcium salt may be added in a total amount not exceeding 0.1 g per 100 g of product, calculated on the corresponding acid, in order to prolong the preservation of the preserves. 

Fish preserves are usually packed in metal cans, Twist-Off jars, plastic packaging or other, acceptable by sanitary authorities for use. Canned food should be stored in rooms with a temperature of 0-5 degrees C and relative humidity of up to 80%; without sudden changes in temperature and humidity. 



The caviar is called sturgeon fish roe – black caviar. 

The rats are separated from the connective tissue and then the salt, so that it becomes glassy, ​​swollen and has a desirable taste. 

Caviar contains in its composition about 50% water, 26-33% protein, 16-19% fat and 4-7% mineral salts. 

In more general terms, caviar is also called spawn of other salmonids (red caviar), cod fish (Norwegian caviar). 


Sales counseling. 

Customers who buy fish are most often interested in their freshness and culinary possibilities. You have to be able to answer, among others for questions 

– Which fish will be the best for baking and which is suitable for frying? 

– Which fish are very bony? 

– Which fish are greasy and which are lean? 

You should also inform customers about the high nutritional value of fish, and that they are easily digestible and contain many valuable nutrients. Sea fish provide a large amount of iodine and other minerals. However, fish consumption, despite the high content of nutrients, should not be dominant in the diet, due to the simultaneous accumulation of toxic environmental pollutants such as mercury, lead, cadmium, polychlorinated diphenyls. Consuming so they should not be enough to use valuable nutrients, and do not allow toxic chemicals to enter the system. Especially with small amounts of fish should be given carefully to children. 

Due to the possibility of very rapid spoiling of fresh fish, they are usually stored in a frozen state. You need to pay attention to the need to keep them in this state during the journey home, if they are to be kept in the home freezer. You can also inform that the fish can be baked, and if they are portioned, then also fry in a frozen state. 



Characteristics of commodities and the use of seafood. 

In recent years, there are more and more imported products in the domestic trade, known as seafood, “frutti di mare,” or “seafood.” They are very appreciated because of their sensory properties. 

Seafood is edible sea or freshwater frameless animals, mainly crustaceans and molluscs. 

They deserve attention from sea animals 

– cephalopods (squid), 

– crustaceans (crabs, crawfish, lobsters, shrimps), 

– mussels (oysters). 

Of freshwater animals, crayfish is the most important. 

Land snails and sea animals without shells (calamari, octopus), as well as edible frogs, are prepared in a similar way. A characteristic feature of some crustaceans is that when they are put into boiling water they immediately change the color of the armor. Shellfish change their color to orange-red. Under the influence of elevated temperature, carotenoid pigments, previously associated with protein molecules, are released. 

Meat of edible invertebrates is valued because of its properties (soft and compact). Often, however, it is largely contaminated with microorganisms from the waters in which they live. The dishes prepared from them are impermanent. 


You can read also: Krill oil vs fish oil: which is better for you?


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