Comparison and integration of different electronic noses for freshness evaluation of cod-fish fillets

For the instrumental analysis of fish freshness, several different methods have been proposed based on different principles (such as mechanical, electrical, and optical). Although, it is well-known that the headspace composition changes greatly during the spoilage process, the difficulties in sampling and measuring the headspaces with traditional analytical chemistry techniques makes the practical implementation of this principle not viable. Recently, the advent of sensor array technology has given the possibility to reconsider the headspace variation for instrumental applications. In this paper the use of measurements of two electronic noses, based on different sensor technologies and sampling methodologies, to detect freshness of cod-fish fillets is illustrated and discussed. Over a period of 17 storage days, the two sensor systems have shown different resolution, while the combination of them achieves the best performances allowing an almost complete evaluation of the freshness of samples. Trimethylamine (TMA) and total volatile basic nitrogen, measured with conventional techniques, show a non-monotonic behaviour, that induces the possibility of large errors in freshness estimation, as shown by the electronic noses.