Abstract ZnO-based gas sensors have been exploited for the selective detection of acetone and capronaldehyde in the vapour of consomme´soup. The sensitivity to acetone is much improved by the addition (5 wt.%) of two acidic oxides, MoO 3 and WO 3, the highest sensitivity being attained at 500 and 550 °C, respectively. These sensors show fairly good selectivity to acetone over other important flavour components, methylpyrazine, dimethyldisulfide and capronaldehyde. The promoting effects are suggested to result from changes in rate and path of the catalytic oxidation of acetone. For the detection of capronaldehyde, Gd 2O 3- and Er 2O 3-ZnO are found to show excellent sensitivities and selectivities at 300 °C.