An alternative way to improve the sensitivity of electronic olfactometers

Systems so-called 'electronic noses' encountered many problems when they came out from research laboratories to plants. After improving many steps in the systems, one of the remaining problems is the limited range of the signal-to-noise ratio which does not enable to maintain an efficient search in the library patterns of the products database. This can be solved by the classical way, which consists in increasing the sensitivity of the sensing element itself, or by an alternative way which is increasing the amount of volatile compounds reaching the sensitive element. After providing some background information about the measurement of food aroma, we will review the main methods that can be found in electronic olfactometers for managing the effluent transfer. In this study, we have only compared the usable transfer methods, independently of the kind of sensors used. Five transfer methods were compared versus the fully static original method. Advantages and drawbacks were studied for each method. The main parameters were: efficiency, importance of transients (kinetic information), automation and sensor recovery time (level of pollution). Obviously, no method was perfect, but each have a lot of pros and cons. This work indicates that the transfer technique considerably influences the system performance. We have also proposed a novel approach based on the headspace kinetic information for improving the classification of samples which are relatively close in terms of flavour-or which contains major compounds of weak flavour impact but present at relatively high concentrations, This method. still under development, seems to be promising in terms of efficiency (sensitivity) and transient analysis. (C) 1999 Elsevier Science S.A. All rights reserved.