Use of an electronic nose for the early detection and differentiation between spoilage fungi

Six spoilage fungi (four Eurotium species, a Penicillium sp. and Wallemia sebi) were grown as spore lawn surface cultures at 0.95 water activity and 25 degrees C. Prior to and during visible growth (24 and 48, and 72 h), single cultures were enclosed in polyethylene bags, the head space was sampled with an electronic nose unit, consisting of 14 polymer sensors, and the data analysed. There was good replication between volatile patterns of the same species and using principal component, discriminant function and cluster analyses it was possible to differentiate between the agar blanks, three Eurotium spp., the Penicillium sp. and W. sebi during microscopic growth for the first time. This suggests that there is potential for the early detection of the activity of spoilage fungi in general, as well as possible differentiation between related xerophilic spoilage fungi, by detection of the patterns of volatile odours produced using an electronic nose system.