Determination of K-value using freshness testing paper and freshness prediction of the finfishes stored at some different temperatures by the kinetic parameters

Abstract

SUMMARY: A freshness index for fish muscle (K-value) was measured for six species of fish using freshness testing paper (FTP) and column chromatography. The correlation coefficient between these K-values determined by both methods was 0.917, although K-values of reddish muscle of big-eyed tuna, flying fish and common horse mackerel were evaluated lower by FTP than by column chromatography. The changes of K-values which were determined at regular intervals by FTP indicated that the decrease in freshness of amberjack and big-eyed tuna muscles was due to a first-order reaction. The kinetic parameters for the freshness-lowering, activation energy and frequency factor were obtained from Arrnhenius’ plots of K-values at the storage temperatures between –1 and +20°C, and then it was clarified that the quality of amberjack and big-eyed tuna with the different history of storage temperature should be predictable on the basis of these kinetic parameters.