Development of ornithine biosensor and application to estimation of prawn freshness

The ornithine biosensor based on the immobilized enzymes (ornithine carbamyl transferase, nucleoside phosphorylase and xanthine oxidase) consisted of an oxygen electrode, flow cell, peristaltic pump, recorder and buffer tank. The optimum conditions for the sensor were as follows: pH 8.2, temperature 32°C, flow rate 0.2 ml/min, sample volume 50 μl and transfer solution 0.1 M Tris-HCI buffer solution. A good correlation was obtained between ornithine contents in kuruma prawn muscle which were determined by the biosensor and those by high performance liquid chromatography (HPLC). From these results, the freshness of prawn can be estimated by the determination of ornithine with the proposed sensor system.