1246Tnls note is concerned with a comparison of the effects of iced and frozen storage on production of trimethylamine (TMA) and dimethylamine (DMA) and decreases in extractable protein nitrogen (EPN) in fillets from four gadoid species. Though there is much in the literature on the production of TMA, there is little on that of DMA, and limited information on comparisons concerning DMA and EPN in iced and frozen fish.Materials and methods -Deep-sea Atlantic cod (Gadus morhua), pollock (Pollachius virens), cttsk (Brosme brosme), and hake (Merluccius bilinearis) were obtained from trawlers as they were being discharged on the wharf. They were immediately fi11eted and the opposite fillets from fish of each species were kept in separate piles. The fillets from the first set were individually packaged in heat sealed, laminated plastic pouches, frozen in a aNo J. D.lrs. 1973. Comparison of changes in trimethylamine, dimethylamine, and extractable protein in iced and frozen gadoid fillets. J' Fish.Res. Board Can. 30: 1246-1248.When flllets of Atlantic cod (Gadus morhua), pollock (Pollachius virens), cusk (Brosme brosme), and silver hake (Merluccius bilinearis) were iced and the opposite flllets frozen, large amounts of trimethylamine were rapidly produced in the iced fish but none was formed in the frozen fish within 60 days. Hake produced large, similar amounts of dimethylamine (DMA) in iced and frozen fillets. The other three species produced more DMA in the frozen than in the iced fillets, but always much less than in the hake. In both frozen and iced fish the production of DMA was accompanied by a corresponding decrease in extractable protein nitrogen. Casrnr,r,, C. H., W. E. Nrnr,, aNo J. Da.r,s. 1973, Comparison of changes in trimethylamine' dimethylamine, and extractable protein in iced and frozen gadoid fillets. J. Fish. Res. Board Can. 30: 1246-1248.Lorsque des filets de morue franche (Gadus morhua), goberge (Pollachius wrezs), brosme (Brosme brosme) et merlu argent6 (Merluccius bilinearis) sont p1ac6s dans la glace, et les filets oppos6s sont congel{s, il se produit de fortes quantit6s de trim6thylamine dans le poisson giai6, alors qo'il ne s'eniorme pas dans le poisson congel6, au cours d'une p6riode de moins de 60 jours. Le merlu argent6 produit de fortes quantit6s de dim6thylamine (DMA), les mOmes dans les filets g1ac6s et dans ies filets congel6s. Les trois autres espdces produisent plus de DMA dans les filets congel6s que dans les filets glac6s, mais toujours en quantit6s beaucoup moindres que chez le merlu argent6, La production de DMA, d la fois dans le poisson congeld et dans li poisson g1ac6, s'accompagne d'une diminution correspondante d'azohe prot6ique extractible.

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Dimethyl-β-propiothetin is found in a number of marine plants and may accumulate in fish. The decomposition of this material by cold concentrated alkali, yielding dimethyl sulphide, is believed to be a specific reaction. A versatile reactor system, suitable for the production of such volatile materials, is described. Coupling of this reactor system to a gas–liquid chromatograph employing a flame ionization detector permits rapid and quantitative estimation of the dimethyl-β-propiothetin present in fish tissues through determination of the dimethyl sulphide.

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