Lean fish

Zabik et al. (1996) determined 26 different PAHs in the flesh of raw trout from Lakes Michigan and Superior. The total concentration of 15 PAHs found in the samples ranged from 1.2 to 2.2 ng per g in lean fish to 5.2 to 7.6 ng per g in fat trout. 

This period is also marked by the deposition of energy substrates - mostly triacyl-glycerols in fatty fish and liver glycogen in lean fish. The rate of accumulation is much lower than that of protein production (O Boyle and Beamish, 1977), a fact explicable from the life strategy of the fish they must attain maximum size and weight as soon as possible before becoming sexually mature, so as to be able to escape predators, to search effectively for food and to evolve optimum reproductive power. Fecundity is directly proportional to... 

Muravskaya, 1978 Diana and Mackay, 1979 Shatunovsky, 1980). However, in all starved fish it is the lipid that is mobilized first, except possibly in the eel. In fatty fish, much lipid is used from the flesh, while in lean fish it is used from the liver. In both types of fish, muscle protein is mobilized only when the lipid resources fall below a critical level. Black and Love (1986) showed that energy substrates are mobilized in a definite sequence, white muscle protein, for example, being metabolized at an earlier stage than red muscle protein, while, on refeeding, the latter is replenished before the former. 

Fish, including finfish and shellfish, has contributed less than half as much zinc in recent years as in 1909-13. This decrease occurred despite increases in consumption. A comparison of contributions now and at the beginning of the century indicates that more zinc is currently provided by fresh and frozen lean fish. 

In contrast to salmon, cod is a lean fish as its lipid content amounts to less Consequently, the concentration of octadienone (no. 10) in boiled cod is... 

Lean fish Cassava Cheese Egg yolk Cereals Milk... 

Lipids constitute below 1% of the weight of fruits, vegetables, and lean fish 3.5% of milk 6% of beef 32% of egg yolk and 85% of butter. The lipids contained in the food raw materials in low quantities serve mainly as components of protein-phospholipid membranes and perform metabolic functions. In fatty commodities the majority of the lipids are stored as depot fat in the form of triacylglycerols. The lipids of numerous food fishes, such as orange roughy, mullets, codfish, and sharks,... 

Among the fishermen s wives, west coast cohort members ate significantly more lean fish species than the east coast cohort members. There were no statistically significant differences between the east and west coast fishermen s wives in the total number of fatty fish meals eaten/month or in the amount of fatty fish consumed on a monthly basis. 

From his data on four kinds of fish, Dyer (21,22) suggested that fatty fishes are more stable in frozen storage than lean fishes. However, more recent data indicate that species differences may sometimes be more important than fat content (2,43,44). For example, the pattern of ice crystal formation differs between Alaska pollack and yellowtail muscles (34) and this may influence stability. 

Lipids occurring in plant and animal materials consist of structural lipids, which build the cell membranes, and depot fats. The cell and organelle membranes of animal organisms are made of phospholipids and non-esterified cholesterol, whereas in plants they consist of phospholipids and glycolipids. The latter are also found in the central nervous systems of some animals. If a muscle tissue like that in lean fish contains only 0.3% w/w of lipids, they consist almost entirely (90%) of phospholipids. Galactoglycerols and phospholipids serve as important factors in nutrient and antioxidant delivery systems (Herslof, 2000). 

Humans eat fish of more than 1000 fish species approximately 350 of these species are regarded as commercially valuable. The term fish products applies to all marine and freshwater animals, including finfish (i.e., scale fish or bony fish, and sharks and rays) and shellfish (i.e., the crustaceans [e.g., prawns, shrimps, lobsters, Antarctic krill], and mollusks [e.g., squid, oysters, abalone]). The only exceptions are aquatic mammals and frogs (EC Directive 91/493/EEC). Overall, the number of species from aquatic environments consumed by humans is consequently much higher. The marine and freshwater fish consumed by humans are mainly wild-caught. On the other hand, cultured fish contribute about 12% to the world fish catch, but these are mainly freshwater fish. Edible parts of fish include fillets (mainly the muscle tissue called the fish meat, with or without skin), carcasses (e.g., canned), and by-products of some fish species, mainly gonads (roe) and livers (of lean fish). 

Fish skin contains more lipid than the muscle tissue. The lipid content in the skin of lean fish (e.g., cod, blue whiting) averages 0.2 to 3.9% w/w. The lipid content... 

Because phospholipids are typically the other main lipid class found in fish flesh, the leaner the fish and the higher the proportion that phospholipids contribute to total lipids. For this reason, phospholipids comprise almost 90% of total lipids of lean fish such as cod, with TAG contributing as little as about 1%. Due to anatomical and physiological reasons, the amount of structural lipids (phospholipids) varies between 0.3 and 0.5 per 100 g w/w of fish muscle and does not usually exceed 1% w/w. This is most likely the minimum level of phospholipids essential for the cell and organelle membranes, of which they are a major component. Phospholipids are the major lipid class in most Australian fish, and in mollusks and crustaceans, all of which are typically lean (Table 12.3). In contrast to finfish, which tend to store lipid as TAG, an increase in the lipid content of shellfish is usually due to an accumulation of polar lipids (Nichols et al., 1998). This is similar to the case in Antarctic krill Euphausia superba D.), the phospholipids of which serve as storage lipids along with TAG. 

A comparison of FA composition in lean fish flesh from various areas shows similar amounts of total PUFA but variable proportions of individual (n-3) PUFA in them. The pattern of variation seems clear freshwater fish contain less (n-3) PUFA than marine fish and the content of (n-3) PUFA increases with increasing latitude (Dunstan et al., 1999), which can be explained by adjustment of the membrane function to environmental constraints. The (n-3)/(n-6) ratios in the same fish species (barra-mundi) from salt and fresh water were 1.66 + 0.57 and 0.66 + 0.15, respectively, and... 

Phospholipids, as structural lipids, are rich in LC PUFA. Various organs of a species show similar FA compositions to each other (Watanabe et al., 1995). The FA profile of phospholipids can be used for identification (taxonomic) purposes (Grahl-Nielsen and Mjaavatten, 1995 Joensen and Grahl-Nielsen, 2001). However, the PUFA compositions of the total phospholipids of various species of fish and shellfish are not strikingly different (Ackman, 1994), but the differences that do occur involve the (n-3) PUFA, particularly DHA. The lipids of lean fish and shellfish have the most PUFA. Cephalopods (e.g., octopus, squid) contained the highest average proportion of DHA when compared to other taxonomic or dietary groups from Antarctic, temperate, and tropical zones (Dunstan et al., 1999). 

The extent of lipid oxidation in frozen lean fish is usually high, due to their high PUFA contents and because the membrane lipids are the first to be oxidized (Hultin,... 

However, if lean fish is stored frozen at an appropriate temperature (e.g., -28°C, but not higher than -18°C), lipid oxidation may not be perceivable until after 1 year of storage, due to the low contribution of lipids to muscle rancidity. This effect produces a flavor described as cardboardy and is related to the presence of CM-d-heptenal (Hardy et al., 1979). In shellfish, regardless of the absence of direct sensory signals of rancidity, lipid oxidation is evidenced for example, a 70% decrease in DHA and EPA content after 6 months in prawns at -18°C (see references in Sikorski and Kolakowska, 1990). Lipid oxidation in frozen whole krill and in products obtained through controlled autoproteolysis is clearly inhibited, most probably by carotenoids and products of proteolysis and phospholipid hydrolysis. No (n-3) PUFA losses were found in whole kriU stored for 3 months at -18°C, nor in krill precipitate stored for 8 months (Kolakowska et al., 1994). 

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