Identification of the Airborne Aggregation Pheromone of the Common Bed Bug, <Emphasis Type="Italic">Cimex lectularius</Emphasis>

Adults and juveniles of the common bed bug, Cimex lectularius L. (Hemiptera: Cimicidae), return to and aggregate in harborages after foraging for hosts. We tested the hypothesis that the aggregation is mediated, in part, by an airborne aggregation pheromone. Volatiles from experimental C. lectularius harborages were captured on Porapak Q, fractionated by liquid chromatography, and bioassayed in dual-choice, still-air olfactometer experiments. Of 14 compounds with >100 pg abundance in gas chromatography-mass spectrometry analyses of two bioactive fractions, 10 compounds [nonanal, decanal, (E)-2-hexenal, (E)-2-octenal, (2E,4E)-octadienal, benzaldehyde, (+)- and (-)-limonene, sulcatone, benzyl alcohol] proved to be essential components of the C. lectularius airborne aggregation pheromone.     

Investigation on microstructure and nonanal sensing properties of hierarchical Sb2WO6 microspheres

Various metal oxides with unique microstructures have been hopeful in fabricating gas sensors applications. This paper reports the room-temperature sensing properties of hierarchical Sb₂WO₆ (antimony tungstate) microspheres for nonanal, which is a dominant aromatic aldehyde compound in cooked rice. The hierarchical Sb₂WO₆ microspheres were obtained by pH control (from pH 1 to 5) through a one-step hydrothermal reaction. The experiment indicated that the optimal response of the Sb₂WO₆ (pH = 4) gas sensor to 30 ppm nonanal reached 62 at room temperature, which was about 8 times that of Sb₂WO₆ (pH = 1). The improved sensing performance resulted from the finer microstructure and larger specific surface area of Sb₂WO₆ with a pH value of 4, providing abundant adsorption sites for nonanal molecules. Meanwhile, the practicability of cooked rice stored for various periods was verified through gas detection, and the results indicated that the sensor might recognize the deterioration of cooked rice and ready-to-eat rice. Therefore, the as-prepared sensor can be used in electronic nose systems to detect cooked rice and ready-to-eat rice deterioration and improve rice cooking methods.     

Analysis,occurrence and potential sensory significance of aliphatic aldehydes in white wines

An analytical method was developed for C8–C11 aliphatic aldehydes in wine consisting of solid phase extraction (SPE) followed by multidimensional gas chromatography/mass spectrometry (MDGC/MS). The method achieves low detection limits (<30 ng L⁻¹), minimises problems of blank contamination and shows high repeatability (RSD% < 5%), but strong matrix effects were noticed during validation. These matrix effects were attributed to strong interactions between aliphatic aldehydes and other matrix elements. Three fractions were differentiated: free extractable aldehydes, aldehydes bound in hydrophilic complexes (extractable in the presence of acetaldehyde) and aldehydes bound in hydrophobic complexes (extractable in the presence of heptanal). The distribution of the three aldehyde species in wine samples was estimated using a surrogate (3,5,5-trimethylhexanal) and an internal standard (methyl phenylacetate) in double determinations (directly and after incubation with 1000 mg L⁻¹ acetaldehyde). These components had a clear additive sensory effect in mixtures and odour thresholds in wine were very low. This caused that although they were present at very low levels, in 2 out of 24 white wine samples were clearly above threshold, and in six more were at levels close to threshold. These results suggest that these components are active contributors to the citrus fruit notes of some white wines.     

Quantification of Nonanal and Oleic Acid Formed During the Ozonolysis of Vegetable Oil Free Fatty Acids or Fatty Acid Methyl Esters

The ozonolysis of unsaturated lipids is a process that has been used to generate aldehydes, acids, alcohols, and other biobased chemical intermediates. Reported here is a method that can be used to measure the formation of nonanal and oleic acid during the ozonolysis of unsaturated vegetable oil fatty acids or their methyl esters to indicate the extent of the ozonolysis reaction. Derivatization was performed using boron trifluoride in methanol solution to transform nonanal and oleic acid into nonanal dimethyl acetal and oleic acid methyl ester, respectively. Undecanal and 10‐heptadecenoic acid were used as internal standards and separation was performed using gas chromatography coupled with a flame ionization detector. The method was validated by performing a standard addition procedure in which nonanal or oleic acid standards were spiked into samples collected during the ozonolysis of oleic acid or canola oil fatty acid methyl ester (FAME). Linear regression results indicated that the measured nonanal and oleic acid are in good agreement with the actual amounts of nonanal and oleic acid added to the sample with at least 98 % recovery. The application of the method was demonstrated by the successful measurement of nonanal and oleic acid formed throughout the ozonolysis process for high oleic canola oil FAME.