food, medicinal preparations, animal feeds, and industrial products obtained from the processing of fish. (Also included in this category are products obtained from marine mammals, marine invertebrates, and algae.) The value of fish (which make up about 90 percent of the catch) as a food product primarily lies in its high content of complete proteins, containing all the vitally essential amino acids. Fish also contain other important nutrients, such as fats, vitamins, and minerals. Fish flesh, including the muscles and the small bones found in them, the ligaments, fatty tissue, and blood vessels, is the most nutritional part of the fish. The flesh generally constitutes 35–69 percent of the fish’s total weight. Other edible parts are the developed gonads (roe and milt) and, frequently, the liver.
The chemical composition of the flesh of various types of fish varies greatly (see Table 1). On the basis of fat content, fish is divided into three categories: lean (with a fat content no higher than 2 percent), medium-fatty (containing 2–5 percent fat), and fatty (with a fat content greater than 5 percent). The content of nitrogen compounds in fish ordinarily is 16–20 percent.
Dead fish, as a result of the action of their own enzymes and microorganisms, undergo physical and chemical changes that lead to spoilage. A slime appears on the surface of the body, and the muscles lose their flexibility and elasticity. Fermentative decomposition of the proteins, fats, and other substances occurs (autolysis), and bacterial decomposition commences (rotting). The change in the chemical composition of the tissues as a result of rotting is easily detected: the flesh becomes soft and turns a dull greenish color, cavities and gas bubbles form in the flesh, and the flesh separates from the bones. Fish in a stage of bacterial decomposition is not suitable for use and cannot be used as raw material.
|Table 1. Chemical composition and caloric value of the flesh of certain fishes|
|Water (%)||Fat (%)||Protein (%)||Minerals (%)||Caloric value (kilocaloriesper 100g)1|
|11 kilocalorie = 4.19 kilojoules|
To prevent spoilage, fish and other seafoods are frozen, salted, or smoked. Most frozen fish products are obtained from cleaned fish in the form of carcasses or sections. Filet is produced from large ocean fish (cod, haddock, bluefish, and dentex). Cod liver and whale blubber are used as raw materials in the production of medicinal preparations (medicinal fats and vitamin preparations). Fish meal, fish glue, guanine, and pearl essence are among the products used for animal feed or industrial purposes. These fish products are made from wastes obtained in dressing the fish (heads, fins, scales, innards), as well as from fish unsuitable for use as food.
Food fishes are evaluated to determine their food suitability. The freshness of the products is established, and any agents of food poisoning are eliminated. Parasites are detected, as are fish whose organs and tissues are toxic and thus dangerous for human health. Veterinary experts conduct the examinations, using organoleptic, physicochemical, microscopic, and microbiological research methods. Pathologicoanatomical methods are used to examine the integuments, eyes, gills, muscle tissue, and internal organs. In the evaluation of fish products specific rules and standards are observed. Quality certificates are issued for good-quality fish products processed for sale by enterprises of the fish industry and by refrigeration plants. Local meat dairy and food inspection stations also tag products that are acceptable for sale in markets.
REFERENCESRukovodstvo po veterinarno-sanitarnoi ekspertize i gigiene pererabotki zhivotnykhproduktov, 2nd ed. Edited by I. V. Shur. Moscow, 1965.
Bykov, V. P. Tekhnologiia rybnykhproduktov. Moscow, 1971.
V. N. RUSAKOV