Andrea Buettner

Physiological and analytical studies on flavor perception dynamics as induced by the eating and swallowing process

The transfer of odorants from the oral to the nasal cavity was studied during food consumption by observation of the swallowing process using videofluoroscopic and real-time MRI (magnetic resonance imaging)-methodologies. Together with the application of the SOOM (spit-off odorant measurement)-technique, the exact timing of odorant transfer to the nose as well as the phenomenon of odorant adsorption to oral mucosa were investigated thus revealing a new understanding of flavor perception as it is caused during the eating process.

Influence of mastication on the concentrations of aroma volatiles — some aspects of flavour release and flavour perception

Abstract General aspects of flavour perception are discussed with regard to the relationships between odour concentration and odour intensity and effects on odour thresholds occurring in mixtures of odourants. Factors modifying flavour release during eating are emphasised, such as the influence of human physiology, the structure and the concentration of the odourants or the duration of mastication. Recent investigations performed by our group in terms of COST action 96 “Interaction of food matrix with small ligands influencing flavour and texture” concerning this topic are summarised.

Real-time breath gas analysis for pharmacokinetics: monitoring exhaled breath by on-line proton-transfer-reaction mass spectrometry after ingestion of eucalyptol-containing capsules

Eucalyptol (1,8-cineole) is a common active agent in non-prescription pharmaceutical products that is employed to clear the airways during mucus blockages. Following ingestion of a eucalyptol-containing capsule, the capsule dissolves in the gut and transfers eucalyptol into the blood, which is subsequently expelled via the lungs, thus exposing this decongesting and inflammation-abating compound to the airways. The breath gas concentrations of eucalyptol in 11 healthy adult volunteers were monitored at regular intervals after capsule ingestion using on-line proton-transfer-reaction mass spectrometry (PTR-MS). Eucalyptol appeared in exhaled breath gas at varying times following ingestion, with its onset ranging from 1 h and 6 min to 4 h and 48 min (mean ± SD: 2.1 ± 0.5 h). Maximum concentrations also varied greatly, with peak eucalyptol levels between 106 and 1589 ppb(v) (mean ± SD: 489 ± 319 ppb(v)). These variations were not only inter-subject, but also intra-subject, i.e. repeated tests with the same participant yielded different onset times and a broad range of concentration maxima. A considerable contribution to these variations from infrequent sampling and analysis is discussed. This study characterized the temporal transfer of eucalyptol via the blood into the airways by examining exhaled breath and thereby demonstrated the suitability of on-line breath gas analyses, particularly PTR-MS, for certain pharmacokinetic investigations.

The Influence of Molecular Structure on Odor Qualities and Odor Detection Thresholds of Volatile Alkylated Phenols

The relationship between chemical structure and odor characteristics of aroma compounds is interesting in terms of establishing a fundamental understanding and, in the long term, a perspective for the prediction of odor qualities and intensities of unknown compounds; on the other hand, such studies provide a useful tool to analytically elucidate compounds that are exceptionally potent odor contributors to a specific smell. In this respect, a broad knowledge of compounds with regard to their odor threshold and smell specificities compiled in a comprehensive odor library would drastically simplify the chemoanalytical process in identifying aromas and smells. Whereas numerous odor-active substance classes have been investigated intensively, such relationships and fundamental data have hitherto not been established for volatile phenols. In this study, a homologous series and isomers of 30 volatile phenols, including monoalkylated phenols and di- and trimethylphenols, were evaluated by determining their aroma attributes and their odor detection thresholds in air. The investigation demonstrates that the odor qualities, among them leather-like, horse stable-like, and medicinal, as well as the respective threshold values clearly depend on the arrangement of the alkyl substituents at the phenol ring. In particular, phenols with monoalkyl groups in the meta-position were found with very low odor detection thresholds of <1 ng/L air. A comparison of some selected phenols and their corresponding toluenes, which were found to be almost odorless, showed in addition that the phenolic hydroxyl group is obviously an important factor for the odor characteristic of this substance class.

GABA(A) receptor modulation by terpenoids from Sideritis extracts.

Scope GABAA receptors are modulated by Sideritis extracts. The aim of this study was to identify single substances from Sideritis extracts responsible for GABAA receptor modulation. Methods and results Single volatile substances identified by GC have been tested in two expression systems, Xenopus oocytes and human embryonic kidney cells. Some of these substances, especially carvacrol, were highly potent on GABAA receptors composed of α1β2 and α1β2γ2 subunits. All effects measured were independent from the presence of the γ2 subunit. As Sideritis extracts contain a high amount of terpenes, 13 terpenes with similar structure elements were tested in the same way. Following a prescreening on α1β2 GABAA receptors, a high-throughput method was used for identification of the most effective terpenoid substances on GABA-affinity of α1β2γ2 receptors expressed in transfected cell lines. Isopulegol, pinocarveol, verbenol, and myrtenol were the most potent modifiers of GABAA receptor function. Conclusion Comparing the chemical structures, the action of terpenes on GABAA receptors is most probably due to the presence of hydroxyl groups and a bicyclic character of the substances tested. We propose an allosteric modulation independent from the γ2 subunit and similar to the action of alcohols and anesthetics.

Characterization of odorants in human urine using a combined chemo-analytical and human-sensory approach: a potential diagnostic strategy

The volatile and odorous profile of human urine may be a rich source for physiological information and could increase our understanding of metabolization and excretion processes of low-molecular weight compounds originating from, for example, dietary or endogenous sources. However, the diagnostic potential of the urinary volatile fraction is not yet fully understood, probably due to the limited application of modern analytical tools in urine volatile analysis. Accordingly, the aim of this study was to evaluate a combined chemo-analytical and human-sensory approach for characterization of the human urine odorant composition. We used one- and two-dimensional high resolution gas chromatography–olfactometry/mass spectrometry to identify commonly occurring and potent odorants in human urine. The studies were carried out on both native urine and on urine that had been treated by glucuronidase assays, with analysis of the liberated odor-active compounds using the same techniques. Based on retention indices, odor qualities and intensities, and mass spectra compared to references, a total of 14 odorants were detected in the majority of the untreated urine samples, and 24 odorants in the glucuronidase-treated samples. A major part of the identified substances are reported here for the first time. Our results show that chemosensory approaches are a useful strategy for the characterization of the odorant profile of human urine.

Volatile release and structural stability of β-lactoglobulin primary and multilayer emulsions under simulated oral conditions.

The relationship between emulsion structure and the release of volatile organic compounds (VOCs) was investigated using a model mouth system under oral conditions (tongue mastication, artificial saliva, pH and salt). The VOCs were monitored on-line by proton transfer reaction mass spectrometry (PTR-MS). Two types of emulsion system were compared: primary and multilayer oil-in-water (P-O/W, M-O/W) emulsions consisting of soy oil coated by β-lactoglobulin and pectin layers. The P-O/W emulsions showed intensive flocculation at pH 5 and above 200 mM NaCl where the electrostatic repulsive charge was at a minimum. Bridging and depletion flocculation were mostly observed for P-O/W emulsions containing artificial saliva with 1 wt% mucin. The VOC release was found to increase when the emulsion droplets flocculated, thus changing the oil volume phase distribution. The adsorbed pectin layer stabilised the emulsion structure under conditions of short-time oral processing, and hindered the release of hydrophobic VOCs.

Odor-Active Compounds in Cardboard

The odor-active compounds of cardboard were identified by aroma extract dilution analysis and HRGC-MS analysis. In total, 36 compounds were detected with medium to high intensities during HRGC-olfactometry. The highest odor intensities were evaluated for vanillin, (E)-non-2-enal, (R/S)-gamma-nonalactone, 2-methoxyphenol, (R/S)-delta-decalactone, p-anisaldehyde, 3-propylphenol, and a woody-smelling unknown compound. Most of the identified compounds were described as odor-active cardboard constituents for the first time. Sensory experiments demonstrated that extensive release of odor-active compounds occurred upon moistening of the cardboard. Accordingly, data indicated that the odorants are present in cardboard in relatively high amounts. In a further sensory study, a transfer of the released odor to food was demonstrated in a model experiment showing that cardboards with high odor potential can cause unwanted flavor changes in foods.

Time-dependent aroma changes in breast milk after oral intake of a pharmacological preparation containing 1,8-cineole

BACKGROUND & AIMS This study investigates time-dependent aroma changes in human milk after intake of an odorant-containing pharmaceutical preparation by correlating sensory evaluation with quantitative results. METHODS Human milk donors ingested 100 mg of encapsulated 1,8-cineole. 21 milk samples from 12 participants underwent sensory analysis, of which 14 samples were quantified by stable isotope dilution assay (SIDA) analysis. Furthermore, several consecutive breast milk and exhaled breath gas samples from one volunteer after intake of 1,8-cineole were analysed by proton-transfer-reaction mass spectrometry (PTR-MS) and sensory evaluation on three separate days. RESULTS The emergence of the characteristic eucalyptus-like odour of 1,8-cineole in exhaled breath after capsule ingestion coincided with its transfer into milk; its presence in breath was therefore used to indicate the time at which milk should be expressed for gathering samples. Odorant transfer could not be confirmed by sensory analysis in 7 of the 21 milk samples, most likely due to disadvantageous timing of milk expression. The other 14 samples exhibited a distinct eucalyptus-like odour. Quantitative results matched these observations with <20 μg/kg 1,8-cineole in the odourless samples and 70 to an estimated 2090 μg/kg 1,8-cineole in the other samples. CONCLUSIONS Transfer of 1,8-cineole into human milk after oral intake is time dependent and exhibits large inter and intra-individual differences.

Sensory and molecular characterisation of human milk odour profiles after maternal fish oil supplementation during pregnancy and breastfeeding

The odourant profile of human milk has been proposed to be modulated by the composition of the maternal diet via the transference of specific food aromas to the milk, such that neonates are exposed to these aromas and are prepared for latter acceptance of specific diets. For that reason the aim of the present study was to investigate whether specific fish oil odour constituents translate into human milk. To achieve this goal, human sensory analyses and qualitative and quantitative instrumental determination of fish oil odourants were performed on the fish oil, as well as on human milk obtained from mothers after long-term fish oil supplementation in comparison to a control group. Sensory and analytical data showed that no statistically significant modification occurred from fish oil intervention.