Characterisation of the aroma of green mexican coffee and identification of mouldy/earthy defect

Erworben im Rahmen der Schweizer Nationallizenzen (http://www.nationallizenzen.ch)The aromas of a reference green Mexican coffee (Arabica) and of a coffee from the same origin, but having a pronounced earthy/mouldy off-taint, were characterised. From comparison of the two aroma profiles, the compounds causing the defect were detected by gas chromatography olfactometry, isolated and concentrated by preparative bi-dimensional gas chromatography, and characterised by gas chromatography mass spectrometry. Six compounds participated in the off-flavour. Geosmin, 2-methylisoborneol, 2,4,6-trichloroanisole were found to be the main culprits, while three methoxy pyrazines (2-methoxy-3-isopropyl/-3-sec-butyl/-3-isobutyl pyrazine) contributed to a lesser extent to the earthy/ green undertone. The occurrence of the off-flavour could tentatively be linked to post-harvest drying

Reath-by-breath analysis of banana aroma by proton-transfer-reaction mass-spectrometry

We report on the in vivo breath-by-breath analysis of volatiles released in the mouth during eating of ripe and unripe banana. The air exhaled through the nose, nosespace (NS), is directly introduced into a proton transfer reaction mass spectrometer and the time-intensity profiles of a series of volatiles are monitored on-line. These include isopentyl and isobutyl acetate, two characteristic odour compounds of ripe banana, and 2E-hexenal and hexanal, compounds typical of unripe banana. Comparing the NS with the headspace (HS) profile, two differences are outlined. First, NS concentrations of some compounds are increased, compared to the HS, while others are decreased. This indicates that the in-mouth situation has characteristics of its own?mastication, mixing/dilution with saliva, temperature and pH - which modify the aroma relative to an HS aroma. Second, we discuss the temporal evolution of the NS. While 2E-hexenal and hexanal steadily increase in the NS during mastication of unripe banana, no such evolution is observed in volatile organic compounds (VOCs) while eating ripe banana. Furthermore, ripe banana shows high VOC concentrations in the swallow breath in contrast to unripe banana

Identification of new odorants in Indian Cress (Tropaeolum majus L.), Structure-activity study on synthesized homologues

This paper reports on the analysis of Indian cress absolute (Tropaeolum majus L.). Indian cress is an edible cress species that belongs to the Brassicale order. Its absolute, obtained by extraction of the plant with a non-polar solvent (concrete) followed by treatment with ethanol, has never been studied. It was analyzed by GC-MS and GC-O in order to characterize its main volatile compounds and key odorants. This research made it possible to identify two new volatile compounds: N-benzyl O-ethyl thiocarbamate and O,S-diethyl thiocarbonate. To the best of our knowledge, both compounds were reported in cress extract for the first time. These molecules being of organoleptic interest, 27 homologues were further synthesized and evaluated. Among those new volatiles, N-phenyl thiocarbamates were shown to be particularly interesting for their savory and meaty odors