CONCENTRATION OF CARBON-MONOXIDE IN COMMERCIAL FISH FLESH AND IN FISHFLESH EXPOSED TO CARBON-MONOXIDE GAS FOR COLOR FIXING

A survey of the concentration of carbon monoxide (GO) in flesh from a variety of fish was conducted to see whether fish which had been expos ed to CO gas could be detected. CO in fish flesh was obtained by head- space gas chromatography and determined after conversion of CO to meth ane with a methanizer. Concentrations of CO ranged from 3 to 12 mu g/k g fish flesh, showing a narrow range in each species of fish except ti lapia (Tilapia mossambica). CO was high in the red-flesh fish and low in the white-flesh fish. CO in sliced tilapia (a species of white-fles h fish), however, ranged from 7 to 957 mu g/kg. In tilapia, a high con centration of CO was observed in a sample in which the blood-colored p arts of the slice were bright red, whereas the CO concentration was lo w in a sample in which the blood-colored parts were dark brown. The CO concentration in sliced tilapia containing 8 mu g CO/kg increased to 234 mu g/kg when the slice was exposed to CO gas. The blood-colored pa rts of the slice became bright red after the exposure. CO in the homog enate prepared from the GO-exposed sample decreased to less than 50 mu g/kg within 4 days on storage in a refrigerator (5 degrees C). The co ncentration of CO in the control increased slightly during this period . Among 19 commercial samples of tilapia, CO slightly increased in 5 s amples containing about 10 mu g CO/kg and decreased in 14 samples cont aining more than 50 mu g CO/kg when the homogenate was kept at 5 degre es C for 2 days. The blood-colored parts of the former group containin g lower concentrations of CO were dark brown and those of the latter g roup containing higher concentrations of CO were bright red. The latte r group Of tilapia was suspected to have been exposed to CO gas.