Jacques P. Roozen

Combined gas chromatography and sniffing port analysis of volatile compounds of mineral water packed in polyethylene laminated packages

Abstract Commercial mineral waters packed in polyethylene-lined aluminium/cardboard packages were incubated at 40°C and sensorially evaluated for intensities of the descriptors: synthetic, musty, sickly, metallic, astringent and dry. Tasting of these samples with the use of nose clips diminishes the intensities of the descriptors significantly, except for dry. Volatile compounds of this mineral water were analysed by sniffing the effluent of a gas chromatographic column, which provided similar descriptors as above. The components detected by sniffing were tentatively identified by combined gas chromatography and mass spectrometry as being mainly aromatic hydrocarbons and carbonyls. Semiquantitative analysis showed that the concentrations of the compounds which migrated into the mineral water ranged between 10 and 15 ppb. Storage at elevated temperatures seems to involve flavour deterioration, because no taint was observed in mineral water samples, which were incubated at 20°C.

Volatile composition of white bread using enzyme active soya flour as improver

Abstract Soya flour is often used in the baking industry as a bread improver. This study deals with the influence of addition of enzyme active soya flour on the volatile composition of bread. These volatiles have been isolated by a dynamic headspace technique, analysed by gas chromatography and identified by combined gas chromatography/mass spectrometry. The chromatograms of bread with and without soya flour have been compared and the major differences quantified. Addition of enzyme active soya flour increases the concentrations of hexanal, 1-hexanol, 1-penten-3-ol, 1-pentanol and 2-heptanone, while 2-heptenal and 1-octen-3-ol have only been detected in bread containing soya.

Modeling panel detection frequencies by queuing system theory: An application in gas chromatography olfactometry

In continuous vigilance tasks, the number of coincident panel responses to stimuli provides an index of stimulus detectability. To determine whether this number is due to chance, panel noise levels have been approximated by the maximum coincidence level obtained in stimulus-free conditions. This study proposes an alternative method by which to assess noise levels, derived from queuing system theory (QST). Instead of critical coincidence levels, QST modeling estimates the duration of coinciding responses in the absence of stimuli. The proposed method has the advantage over previous approaches that it yields more reliable noise estimates and allows for statistical testing. The method was applied in an olfactory detection experiment using 16 panelists in stimulus-present and stimulus-free conditions. We propose that QST may be used as an alternative to signal detection theory for analyzing data from continuous vigilance tasks.