POSTMORTEM CHANGES IN QUALITY INDICES OF ICE-STORED FLOUNDER (PARALICHTHYS PATAGONICUS)

Abstract

The characteristics of flounder (Paralichthys patagonicus) were evaluated during a 12-day period of storage in ice by monitoring the biochemical, microbiological and sensory parameters. The adenosine-5′-triphosphate and adenosine-5′-diphosphate were not detected, and the initial content of adenosine-5′-monophosphate (AMP) rapidly decreased to zero. Inosine-5′-monophosphate (IMP) but not adenosine (Ado) was present in muscle extracts. The AMP deaminase activity was found in the muscle. Conversely, the Ado deaminase activity was not detected. A 55% decrease in IMP concentration occurred during the first 2 days of storage. The inosine content was barely detectable (<0.1 μmol/g), probably because of the high nucleoside phosphorylase activity in the muscle. Hypoxanthine significantly (P < 0.01) increased up to the seventh day and then remained approximately constant. The muscle pH fluctuated between 6.6 and 7.0. The iced flounder was microbiologically acceptable for up to 7 days with aerobic plate counts reaching <107 cfu/g. The sensory score, determined by the Quality Index Method, linearly increased (r2 = 0.96) with the keeping time. All the parameters, including the K-value, indicated that the shelf life of iced flounder was 7 days.