Practical experience with 'electronic nose' systems for monitoring the quality of dairy products

The present paper reports some practical experience acquired by testing fiv e sensor technologies and four instruments over approximately one year with Swiss Emmental cheese samples of different stage of ripening. Up to now, t he metal-oxide semiconductor (MOS) technology has given the best discrimina tion between the measured samples. However, sensors of th is type seem to b e damaged by short-chain fatty acids released from Swiss Emmental cheese. O rganic conducting polymer sensors showed a poor sensitivity to volatile com ponents 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-spectro metry system was difficult due to the low sensitivity of this instrument fo r the volatile compounds of cheese. Metal-oxide semiconductor field effect transistor sensors did not give good discrimination between the samples. Ho wever, their combination with MOS sensors seems to produce a favourable sys tem for application in cheese evaluation. Further studies with other types of cheese and other dairy products are still necessary to define reliable a nd practical applications of this analytical tool in the dairy industry.