On the effectiveness of EDTA in prolonging the shelf life of fresh fish

Abstract

The purpose of this investigation was to ascertain whether EDTA might be useful in prolonging the keeping quality of fresh fish. The criteria of quality used were: the total bacterial count, the content of volatile basic nitrogen and trimethylamine, the degree of dephosphorylation of the nucleotides, the level of the hypoxanthine, and the organoleptic properties. The material consisted of rainbow trout (Salmo irideus) and Baltic herring (Clupea harengus var. membranus). The results showed that EDTA had a markedly favorable effect on the keeping quality of fish. Although the effect on the total bacterial count was only slight, a chemical and organoleptical comparison with control material revealed that spoilage in the EDTA-treated samples was definitely slower. In the case of fillets of rainbow trout, judged by the organoleptical method, the controls became unacceptable after storage for 18–20 days at +4°C, whereas after the same storage time the EDTA-treated samples were still free of off-odors and had a fair taste. Similarly, the values of volatile basic nitrogen, trimethylamine, and hypoxanthine increased at a slower rate, and the dephosphorylation of nucleotides proceeded less rapidly in the EDTA-treated fillets than in the controls. In the case of fillets of Baltic herring, sensory evaluation brought out the positive effect of the EDTA treatment. A corresponding difference was noted in the volatile basic nitrogen and trimethylamine values, and a slight difference in the hypoxanthine values. In this fish, the dephosphorylation of the nucleotides was rapid, and between the samples subjected to EDTA treatment and the control material there appeared only a small difference. With regard to the round Baltic herring, again, the differences between the two categories were less conspicuous; the chief difference was noted in the volatile basic nitrogen, but in the sensory evaluation the difference was not fully consistent.