The electronic nose applied to dairy products: a review

The state-of-the-art and current trends in the development of “aroma” analysis with electronic noses are reviewed with special reference to applications to dairy-products. Some of the reported problems with electronic noses have recently been reduced, e.g. the correction/reduction of signal drift, the influence of humidity and temperature. New promising and reproducible sensor manufacturing techniques are being implemented, e.g. electro-spray for QMB sensor production. The development of more selective and sensitive sensors, especially of QMB and conducting polymer (CP) type, should improve their applicability. Interesting novel sampling techniques, such as SPME or SBSE, offer more possibilities for the analysis of semi-volatile compounds which are generally more odoriferous. However, standard calibration procedures and reference materials are not yet available. Although they are normally less powerful than human noses, electronic noses offer some significant advantages in the analysis of volatiles, for example, in instrumental classifications based on hedonic or sensory analyses and in potentially automated on-line monitoring of volatiles. Several groups have explored the application of different electronic noses in the investigation of various aspects of dairy products. The present review includes as examples the evaluation of Swiss and Cheddar cheese aroma, the assessment of the ripening of Pecorino Toscano cheese (ewe’s), the detection of mould in Parmesan cheese, the classification of milk by trademark, by fat level and by preservation process, the classification and the quantification of off-flavours in milk, the evaluation of Maillard reactions during heating processes in block-milk, as well as the identification of single strains of disinfectant–resistant bacteria in mixed cultures in milk.