Practical Experience with 'Electronic Nose' Systems for Monitoring the Quality of Dairy Products

The present paper reports some practical experience acquired by testing five sensor technologies and four instruments over approximately one year with Swiss Emmental cheese samples of different stage of ripening. Up to now, the metal-oxide semiconductor (MOS) technology has given the best discrimination between the measured samples. However, sensors of this type seem to be damaged by short-chain fatty acids released from Swiss Emmental cheese. Organic conducting polymer sensors showed a poor sensitivity to volatile components of cheese, the main problem being a rapid drift of the sensors. The response of quartz microbalance sensors was too weak to detect differences between cheese samples. Discrimination using a newly designed mass-spectrometry system was difficult due to the low sensitivity of this instrument for the volatile compounds of cheese. Metal-oxide semiconductor field effect transistor sensors did not give good discrimination between the samples. However, their combination with MOS sensors seems to produce a favourable system for application in cheese evaluation. Further studies with other types of cheese and other dairy products are still necessary to define reliable and practical applications of this analytical tool in the dairy industry