Fish odor

Alkaloids vary widely in structure, from the simple to the enormously complex. The odor of rotting fish, for example, is caused largely by methylamine, CH3NH2, a simple relative of ammonia in which one of the NH3 hydrogens has been replaced by an organic CH3 group. In fact, the use of lemon juice to mask fish odors is simply an acid-base reaction of the citric acid in lemons with methylamine base in the fish. 

Odors can have delayed and unexpected effects. Garter snakes, T. sirtalis, were presented with either live earthworm or mosquito fish, Gambusia affinis, in a screen-covered bowl for several days. One day after transferring the snakes individually to a box free of prey odors, they were tested with aqueous extracts of fish and worms on cotton swabs. Snakes exposed to fish odor attacked fish extract less, and those exposed to worm attacked worm odor less. This is interpreted as habituation with a possible switch to other prey. This also demonstrates that in any experiment with chemical cues an odor not experienced for 22 hours may still have an effect (Burghardt, 1992). 

Dead mice are as attractive as live mice, and dead mouse odor is as active as a dead mouse (Shivik and Clark, 1997). Elucidation of the feeding stimuli used by this species will aid in effective trapping for snake control. Fractions of dead mouse odor are being bioassayed. The best known constituents of rotting carcass (e.g. fish) odor, putrescine (1,4-diaminobutane NH2CH2CH2NH2) and cadaver-ine (NH2CH2CH2CH2NH2) were not active. 

Chemical lures, based on feeding stimuli, are now on the market as odor-impregnated artificial bait. They are specific for certain predatoiy fish and are extremely effective (Schisler and Bergesen, 1996). Efforts to imderstand improving of feeding attractants and stimulants for economically soimd mariculture started early (Bardach and Villars, 1974). Another obvious application of fish odors is the use of waterborne male and female pheromones to improve spawning in fish in aquaculture. 

There is also a genetic deficiency in FM03 in humans leading to Fish Odor syndrome, which results from the inability of the afflicted individuals to metabolism trimethylamine, which has a strong fishy smell, to the N-oxide, which has no smell. 

If an amine is insoluble, reaction with an acid produces a water-soluble salt. Since ammonium salts are water soluble, many drugs containing amines are prepared as ammonium salts. After working with fish in the kitchen, a convenient way to rid one s hands of fish odor is to rub a freshly cut lemon over the hands. The citric acid found in the lemon reacts with the amines found on the fish a salt forms which can be easily rinsed away with water. 

A fisherman can rid his hands of the fish odor by rubbing with the juice from lemons. Why does this work ... 

Properties Colorless to pale yellow liquid. Both l and dl forms are available. dZ-Form fish odor. Bp 173-176C. Freely soluble in water, alcohol, ether. Z-Form refr index 1.4480-1.4495 (26C), distillation range approximately 114C at 100 mm Hg. Combustible. 

Five forms of FMO are found in humans (and several experimental animals). Important physiological substrates have not been established, although some possibilities have been proposed (Ziegler, 1993). An interesting polymorphism involves defects in FMO 3, giving rise to deficient metabolism of trimethylamine and a resulting fish-odor syndrome (Al-Waiz et al., 1987). In contrast to P450, FMOs appear not to be inducible or readily inhibited. 

To illustrate the use of an emission factor, let us turn to the fish-canning industry. From AP-42, section 9.13.1-7 and Table 3, entitled Uncontrolled Emission Factors for Fish Canning and Byproduct Manufacture, emission factors are shown for particulate emissions, trimethylamine (fish odor), and hydrogen sulfide (rotten egg odor). Emissions from the fish scrap cookers for both fresh fish and stale fish are shown. Notice that the particulate emissions are negligible for the cookers. Trimethylamine (fish odor) has an emission factor of 0.3 Ib-tiimethylamine/ton of fresh fish cooked. If we are cooking 5 tons of fresh flsh/hr, then the uncontrolled fish odor emission to the atmosphere is 0.3 Ib-trimethylamine/ton of fresh fish cooked X 5 tons of fresh fish/hr = 1.5 Ib-trimethylamine/ hr. Since the chemical responsible for typical fish odor is trimethylamine, 1.5 Ib/hr will certainly be noticed by residents noses downwind of the plant. 

Classification Sat. aliphatic amine Empirical C4H11N Formula CH3CH2CH(CH3)NH2 Properties Colorless liq. ammonia-like or fish odor sol. in water, many org. soivs. incl. ethanol, acetone, ether, chloroform m.w. 73.14 sp.gr. 0.724 (20 C) m.p. -104 C b.p. 63 C flash pt. (CC) -9C... 

Eugene, M. (1998) [Diagnosis of fish odor syndrome by urine nuclear magnetic resonance proton spectrometry]. Ann Dermatol Venereol 125, 210-212. 

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