COMPARISON OF THREE METHODS OF FORMALDEHYDE DETERMINATION ON FROZEN SOLE, POLLOCK, HADDOCK AND COD FILLETS

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Abstract
The Merchoquant test strip and a rapid, enzymatic method were evaluated for the quantitation of formaldehyde (HCHO) in neutralized perchloric acid (HClO4) extracts of fish muscle. Compared with the standard colorimetric Cochin and Axelrod (1959) modification of the Nash reagent method (1953), the nonglutathione dependent formaldehyde dehydrogenase (EC 1.2.1.46) method based on that of Yasuhara et al. (1982) for creatine was faster and less affected by interferences. The enzyme method resulted in lower HCHO values than did the modified Nash method for the gadoid pollock, haddock and cod samples while the semi-quantitative Merchoquant test strip resulted in positive readings for only one cod sample. Seventy-nine HClO4 fish extracts analyzed by the enzyme and modified Nash procedures showed a species dependent correlation between the two methods, with slopes of 0.847, 0.321, 0.436, 0.519 for sole, pollock, haddock and cod, respectively. The HCHO content of the samples ranged between 0.4 and 75 .mu.moles%. Standard addition evaluation of the accuracy of the formaldehyde dehydrogenase method compared with the modified Nash procedure on three samples also resulted in species dependent slopes. Nongadoid sole samples showed the greatest deviation while cod was the only species where the modified Nash method resulted in HCHO values lower than those attained with the enzyme method. The detection limit of the formaldehyde dehydrogenase method was 0.3 .mu.moles%.

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