DEVELOPMENT OF SCREEN-PRINTED ENZYME ELECTRODES FOR THE ESTIMATION OFFISH QUALITY

Enzyme electrodes for the determination of biogenic amines have been d eveloped using monoamine oxidase (MAO) from Aspergillus niger and putr escine oxidase (PO) from Micrococcus rubens. Determination is based on the electrochemical oxidation of enzymatically produced H2O2 at scree n-printed platinum electrodes. The enzymes are immobilized on silanize d electrodes by cross-linking with glutaraldehyde. Compositions of the immobilization mixtures are optimized with respect to stability, sens itivity and selectivity of the sensors. The electrodes using MAO as th e biochemical component respond to several amines including histamine, an important amine in the determination of fish freshness. The PO ele ctrodes show a significant response not only to putrescine and its hom ologue cadaverine but also to tyramine, an electrochemically active am ine. The optimal buffer for both types of amine oxidase electrodes is Clark and Lubs (C+L) buffer pH 8.5. Simultaneous determination of the substrates of both enzymes can be accomplished by immobilizing PO and MAO onto different working electrodes of the same sensor. The sensors have been used to monitor the freshness of mackerel and codfish in sto rage. As expected, sensor signals increase with storage time of the fi sh, indicating the production of biogenic amines. During storage of ma ckerel, mainly histamine is produced, which leads to an increase in th e signals obtained with the MAO electrodes. On the other hand, the put refaction process of codfish during storage is detected mainly by the PO electrodes. All results are confirmed by comparison with HPLC data.