Electronic nose systems to study shelf life and cultivar effect on tomato aroma profile

The performance of a quartz microbalance based electronic nose (E-nose) and a mass spectrometry based electronic nose (MSE-nose) for tomato aroma profiling has been evaluated. Solid phase micro-extraction (SPME) headspace sampling combined with gas chromatography (GC) has been used as a reference method. In the first experiment, the changes in tomato aroma profiles of two different cultivars have been monitored during shelf life (Days 1, 8, 12 and 19). The score plot of the principal component analysis (PCA) for the E-nose measurements shows a slight shift along the first principal component corresponding to an increasing number of days of shelf life. However, the tomato aroma profiles measured on Days I and 8 could not be discriminated by the E-nose. In contrast, MSE-nose score plots indicated an evident change in aroma profile with shelf life. The loading plots of the PCA reveals that mainly three discriminant mass to charge ratios (m/z = 93, 43 and 57) are responsible of the observed shelf life effect in both cultivars. These fragments indicate that P-phellandrene, 6-methyl-5-hepten-2-one, 1-nitropentane and 2-methylbutanol undergo important concentration changes during shelf life of tomatoes. In the second experiment, the aroma differences between cultivars were analysed by means of the electronic nose systems. A clear distinction between cultivars based on MSE-nose measurements is obtained; however, based on E-nose measurements it is difficult to discriminate between tomato varieties in two dimensions. (C) 2003 Elsevier B.V. All rights reserved.