Radurization of Korean horse mackerel. Part of a coordinated programme on radiation preservation of Asian fish and fishery products

Samples of fresh horse mackerel (Trachrus japonicus) meat, packaged in plastic bags, were irradiated with various doses from 0 to 1.0Mrad and held at either 0,5 or 10 degrees C. Analyses of histamine concentration, total volatile base (TVB), trimethylamine (TMA) content and total bacterial counts of the samples were carried out periodically during storage. The minimum and maximum doses for Korean horse mackerel were decided to be 0.2 and 0.4Mrad respectively. Histamine accumulation in horse mackerel samples stored at ice temperature up to 35 days did not take place appreciably irrespective of irradiation. At 5 and 10 degrees C storage, however, irradiation showed marked effect on suppressing the histamine accumulation in the samples. There were practically no differences on TVB and TMA contents in horse mackerel stored at 0 degree C, whether irradiated or not, until the 28th day of storage when TVB and TMA contents of unirradiated samples increased sharply. At 5 and 10 degrees C storage, TVB and TMA values in irradiated samples were significantly lower than those in unirradiated ones. Total bacterial counts in horse mackerel were also significantly reduced in irradiated samples, especially those stored at 0 degree C. It appears that a good correlation exists in the histamine, TVB and TMA formations in horse mackerel. The histamine content of various fish species marketed in Seoul, with the exception of certain samples collected during summer months, were unalarmingly low. Relatively low histamine contents were also observed in canned fish in Korea. It was observed that irradiation caused reddening of the flesh of horse mackerel. The reddening effect appeared to be dose-dependent, especially at doses above 0.4Mrad. At lower doses, the reddening contributed positively to the overall sensory quality of the fish