Trimethylamine oxide, fish

Metabolism of trimethylamine oxide in fish muscle involves an enzyme-catalyzed oxidation-reduction reaction. The enzyme responsible for the conversion of trimethylamine oxide to trimethylamine is known as trimethylamine-W-oxide reductase. This enzyme acts on nicotinamide adenine dinucleotide (NADH) and TMAO to produce NAD+, trimethylamine and water (Fig. 13.13.1). TMAO acts as the oxidizing agent and is reduced, while NADH undergoes oxidation as the reducing agent. 

Aside from the complications imposed by the oil in fish and the need to keep the catch cold, there is also a compound in fish called trimethylamine oxide (TMAD), which is converted to trimethylamine (TMA). Trimethylamine oxide is essentially an odorless compound which is ccxiverted by bacteria in and on the fish to the fishy tasting and smelling compound, trimethylamine. Retarding this conversion is one of the prime objectives of adequate cold storage of fishery products (3) (8). 

Another chemical method for measuring freshness, that is more rapid, continuous, and less destructive than other methods is the detection of volatile trimethylamine (TMA), dimethylamine (DMA), monomethylamine (MMA), and ammonia 14,15). Trimethylamine oxide (TMAO) is a decomposition product of proteins as well as present in excretions of fish 16). Spoilage bacteria can reduce TMAO to TMA plus small amounts of DMA, MMA, and ammonia. Tissue TMA levels have be correlated with the pungent odor associated with spoiled seafood as well as total bacterial counts 14). Researchers incorporated a test strip... 

Beside BAs, low-molecular-weight alkylamines, commonly used as indicators of food quality, can also be present in fish muscle. Tri- and dimethylamine (TMA and DMA) are produced by bacterial reduction of the osmoregulatory substance trimethylamine oxide (TMAO) in fresh marine fish and by enzymatic reduction in frozen storage of gadoid fish (cod, cusk, hake, pollack), with concurrent formation of formaldehyde. 

Trimethylamine oxide (TMO) is one of the compounds retained by elasmobranchs to assist their osmotic balance (reviewed by Love, 1970). This compound is also used by eels when they are transferred from fresh water to salt. The fish were not fed, but TMO levels increased for about 24 h. The compound is probably synthesized from choline via trimethylamine, and synthesis of the enzymes responsible for the system appears to begin immediately after transfer to the sea water (Daikoku and Sakaguchi, 1990). 

Kelly, R.H., and P.H. Yancey (1999). High contents of trimethylamine oxide correlating with depth in deep-sea teleost fishes, skates, and decapod crustaceans. Biol. Bull. 196 18-25. 

Raymond, J.A. (1998). Trimethylamine oxide and urea synthesis in rainbow smelt and some other northern fishes. Physiol. Zool. 71 515-523. 

Raymond, J.A., and A.L. DeVries (1998). Elevated concentrations and synthetic pathways of trimethylamine oxide and urea in some teleost fishes of McMurdo Sound, Antarctica. Fish. Physiol. Biochem. 18 387-398. 

Trimethylamine oxide demethylase, present in the muscles of many gadoid fishes, affects the functional properties of hsh proteins indirectly by catalyzing the formation of formaldehyde ... 

Trimethylamine and other amines have often been variously associated with the aromas of fish (2, 19, 41). Much of the trimethylamine found in fresh fish arises from the microbial reduction of trimethylamine oxide (42-44) which is found abundantly in only marine fish (45-47). On the other hand, dimethylamine is an abundant product of an endogenous enzymic action on trimethylamine oxide in marine fish muscle, and it is readily produced even under high-sub-freezing conditions in marine fish (48). Both trimethylamine and dimethylamine... 

Trimethylamine oxide demethylase (TMAOase) is one of the indigenons enzymes in fish exhibiting the adverse effect on fish quality. TMAOase converts trimethylamine oxide (TMAO) stoichiometrically to dimethylamine (DMA) and formaldehyde (FA) with 1 1 molar ratio (Benjaknl et al, 2004). 

Rehbein, H. 1988. Relevance of trimethylamine oxide demethylase activity and haemoglobin content to formaldehyde production and texture deterioration in frozen stored minced fish muscle. Journal of the Science of Food and Agriculture 43 261-277. 

Formaldehyde is directly emitted into the air from vehicles. It is released in trace amounts from pressed wood products such as particleboard and plywood paneling, from old sick bnildings, and from cotton and cotton-polyester fabrics with selected crosslink finishes. Formation of formaldehyde has been observed in some frozen gadoid fish due to enzymic decomposition of the additive trimethylamine oxide (Rehbein 1985). Its concentration can build up during frozen storage of fish (Leblanc and Leblanc 1988 Reece 1985). It occurs in the upper atmosphere, cloud, and fog it also forms in photochemical smog processes. 

The main nitrogenous end products of protein metabolism are amino acids, ammonia, uric acid, and urea. Much has been written concerning the excretion of these substances by various animals and the relationship this bears to their evolution, habitat, and mode of reproduction. The excretion of guanine by spiders and trimethylamine oxide by marine teleosts are important exceptions. Guanine deposited in fish scales and pterines in butterfly pigments might also be regarded as excretory products if one were also to consider as such the keratin of mammalian hair. 

The fishy OF is primarily due to the generation of Irimethylamine via bacterial action [130,131]. Trimethylamine is formed from trimethylamine oxide, which is a natural constituent of fish muscle. This reduction is accomplished through bacterial enzymes and involves a coupled oxidation of lactic acid to acetic acid and CO2 [ 132], The latter stages of fish spoilage involve the production of various nitrogen- and sulfin-containing compounds. These componnds prodnce pntrid, sulfury notes in the fish. 

Stansby, M.E., Speculations on fishy odors and flavors. Food TechnoL, 16, p. 28,1962. Watson, D.W., Studies on fish spoilage the bacterial reduction of trimethylamine oxide, J. Fish Res. Bd. (Canada), 4, p. 252, 1939. 

Fig. 13.3. Cod fish quality change during storage (according to Ludorff, 1973). Sensory evaluation in total 15 points are given, 5 for visual appearance and 10 for odor, taste and texture Q-value electric resistance of the fish tissue as recorded by a fish tester Q40 quality class S, Q = 30-40 A, Q = 20-30 B, Q20 C and worse TMAO-N trimethylamine oxide-N TVB-N total volatile base-N VRS volatile reducing substances, TMA-N trimethylamine-N...

Secondary and tertiary amines are formed from precursors other than amino acids. Dimethylamine results from degradation of choline (which is present in some phospholipids), some alkaloids (e.g. in beer it is produced from gramine (see 10-198) present in germinating barley grains and also in non-enzymatic browning reactions from methylamine and formaldehyde or by decarboxylation of sarcosine. Trimethylamine, together with dimethylamine, methylamine and ammonia, is an odorous compound of fish and other aquatic animals. It is formed by reduction of the sensory indifferent trimethylamine oxide (trimethylaminoxide, 8-143) in tissues post mortem. 

The characteristic essential flavour-active components of fish and other aquatic animals are amines and other nitrogenous compounds. Trimethylamine arises by reduction of sensorially indifferent trimethylamine oxide (acting in the regulation of osmotic pressure in cells) in the tissue post mortem. The amount of trimethylamine oxide, as well as the amount of a number of simultaneously produced biogenic amines, depends primarily on the species, type and time of storage. Its content in fresh water fish is about 5 mg/kg, and in seafood is 40-120 mg/kg. Other important compounds are dimethylamine and ammonia. 

Some eggs may have an unusual or unacceptable odour or taste, although their appearance is normal. The cause may be age (they are past their best ), high storage temperatures, or poor storage conditions, resulting in fishy or other undesirable flavours. The fishy off-flavour, more common in brown-shelled eggs, is caused by the presence of trimethylamine that is produced by microbial decomposition of choline when hens are fed excessive amounts of fishmeals or fish oils and rapeseed and mustard meals. In the case of oilseed meals, trimethylamine arises from sinapine, an ester of choline with sinapic acid. In most breeds of hens, trimethylamine is enzymatically oxidised to odourless trimethylamine oxide, which is excreted from the body. 

Flebard, C. E., G. J. Flick, and R. E. Martin. 1982. Occurrence and significance of trimethylamine oxide and its derivatives in fish and shellfish. In Chemistry and Biochemistry of Marine Food Products, eds. R. E. Martin, G. J. Flick, C. E. Flerbard, and D. R. Ward, pp. 149-304. Westport, Connecticut AVI Publishing Company. 

Oehlenschlalager, J. 1997. Suitability of ammonia-N, dimethylamine-N, trimethyl-amine-N, trimethylamine oxide-N and total volatile basic nitrogen as freshness indicators in seafood. In Methods to Determine the Freshness of Fish in Research and Industry. Nantes Conference, November 12-14. 

Trimethylamine oxide, (CH3)jN+0, an onium salt found in marine but never in fresh-water fishes. Rich sources are eephalo-pods and crustaceans, the muscle of the lobster containing about 0 3 per cent. The oxide is soluble, non-toxic and almost neutral, and is an important excretory form of nitrogen. Among the elasmobranchs it serves in the maintenance of fluid equilibrium, and is responsible for 20-25 per cent, of the total osmotic pressure of the blood. It is rapidly decomposed by post-mortem autolytic and bacterial changes, and the liberated trimethylamine, (CH3)jN, characterises the odour and taste of stale marine fish. 

Most marine fishes contain trimethylamine oxide (TMAO) this colorless, odorless, and flavorless compound is degraded to trimethylamine, which gives a fishy odor and causes consumer rejection. This compound is not present in land animals and freshwater species (except for Nile perch and tila-pia from Lake Victoria). TMAO reductase catalyzes the reaction and is found in several fish species (in the red muscle of scombroid fishes and in the white and red muscle of gadoids) and in certain microorganisms Enterobacteriaceae, She-tvanella putrefaciens). 

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