High resolution gas chromatography/selective odorant measurement by multisensor array (HRGC/SOMSA): A useful approach to standardise multisensor arrays for use in the detection of key food odorants

The typical odour of foods can be represented by a small part of its volatile ingredients. In order to control food quality the monitoring of these key food odorants is indispensable. In the case of butter the odour can be simulated by composing diacetyl, butanoic acid and δ-decalactone in appropriate composition. A sensory panel consisting of five persons evaluated a strong similarity of the recombinant to natural butter. The off-odour of aged (rancid) butter is caused by an increased concentration of butanoic acid. In the experimental setup different kinds of sensors were attached besides a flame ionisation detector (FID) at the port of a gas chromatograph (GC). The involved sensors were different types of metal oxide semiconductors and a surface acoustic wave (SAW) device coated with poly(isobutylene). In different GC runs recombinants of fresh and rancid butter were analysed recording the FID signal and the signals of the different sensors. The quantities were 0.35 ng diacetyl, 3.7 ng butanoic acid (rancid: 37 ng) and 4.9 ng δ-decalactone in each GC run. The SAW sensor and a ZnO sensor at the port of the GC respond with high signals to butanoic acid and δ-decalactone. Both sensors are insensitive to diacetyl. The differing relative sensitivities allow discrimination of butanoic acid and δ-decalactone without GC-separation. The palladium doped ZnO sensor was sensitive to diacetyl. In contrast, the diacetyl peak of the FID was difficult to distinguish from the base-line. Using the HRGC/SOMSA, the characterisation of sensors can be done by replacing natural foodstuff samples with the described recombinants.