Freshness-Lowering Rates of Cod and Sea Bream Viewed from Changes in Bacterial Count, Total Volatile Base- and Trimethylamine-Nitrogen, and ATP Related Compounds

Abstract

It has been known experientially that the rate of freshness-lowering of fish varies markedly between species: that of cod being quite rapid and that of sea bream slow. These fish species were stored in ice and changes in bacterial count, TVB-N, TMA-N, ATP related compounds and K value of their muscle were examined in relation to their freshness-lowering rates and initial spoilage. Determination of ATP related compounds was performed using an autoanalyzer by a concave gradient method. The results obtained are as follows; Using AG 1×4, Cl− type, 200–400 mesh, ATP related compounds were automatically separated in about 70 min. The time from death to the onset of initial spoilage differed considerably between cod and sea bream. IMP in cod muscle dropped remarkably within two days of ice storage, whereas that of sea bream persisted to some extent even after 16 days. Consequently, with regard to K value, there was also a striking difference between cod and sea bream. The rate of IMP decomposition in Japanese red bream muscle was changed little by mixing it with an aqueous extract of Alaska pollack muscle, or the muscle itself. Changes in ATP related compounds in the muscles and the K values coincided with the freshness-lowering of fish. It was concluded that the K value could be used as one means of evaluating the freshness of fish. © 1974, The Japanese Society of Fisheries Science. All rights reserved.