Amperometric determination of fish freshness by a hypoxanthine biosensor

The traditional determination of fish freshness is to detect total volatile basic nitrogen, microbial load or hypoxanthine. These methods are complex and expensive. A hypoxanthine biosensor was constructed by using immobilised xanthine oxidase and a platinum electrode. The enzyme was immobilised on a silk membrane. The electrode detected the hydrogen peroxide released during the enzymatic reaction. A linear range from 0.05 to 100 x 10(-6) M of hypoxanthine was observed. When the method was applied to fish samples, the results obtained agreed well with those obtained by the conventional total volatile basic nitrogen and microbial load. This biosensor provides a reliable, simple, rapid and economical method for the measurement of fish freshness.