A sensitive xanthine oxidase electrode with silk net for estimating fish freshness

An enzyme biosensor was constructed using a plate platinum electrode and immobilized xanthine oxidase (XOD). Only a very small quantity of enzyme was chemically immobilized on a special silk net. Hydrogen peroxide released during the enzymatic reaction was detected by the electrode at +0.65 V (vs. Ag/AgCl). The electrode was very sensitive to hypoxanthine and its detection limit was 1×10–⁷ mol/L. When it was applied to the determination of fish freshness, the results agreed well with those obtained by traditional methods-determination of total volatile basic nitrogen (TVB-N) and microbial count. A range for estimating the freshness of river fish was suggested.