EXAMINATION ON THE FRESHNESS OF BOTTOM FISH

Abstract

The AMANO's method for the evaluation of the fish freshness applied by W. WALKIEWICZ's was found to be unapplicable to bottom fish (Table 1) as well as squid. It is considered that this was caused by the high pH value of those muscles which may be ascribed to the small quantity of lactic acid and high trimethylamine oxide content, having the buffering capacity on acid side below pH 6.25, in comparison with the pelagic fish. In order to justify this consideration, the determination of lactic acid and trimethylamine oxide, was carried out. The results are shown in tables 2, 3 and 4. The pH value of the mixed solution of trimethylamine oxide and lactic acid was measured as shown in Table 3 and the effect of addition of trimethylamine oxide and lactic acid on the pH value of histidine solution (958mg%) was observed as indicated in Table 4. The pH value of bottom fish and squid generally is given as above 6.2, which is due to the small quantity of lactic acid and large amount of trimethylamine oxide. Owing to this high value the AMANO's method is not applicable for bottom fish and squid.