Retronasal Odor Research Articles

Quantification and sensory studies of character impact odorants of different soybean lecithins.

Fifty-four potent odorants in standardized, hydrolyzed, and deoiled and hydrolyzed soybean lecithins were quantified by high-resolution gas chromatography/mass spectrometry (HRGC/MS). The characterization of their aroma impact was performed by calculation of nasal (n) and retronasal (r) odor activity values (OAVs). For this, the nasal and retronasal recognition thresholds of 18 odor-active compounds were determined in vegetable oil. The following compounds showed the highest nOAVs: 2,3-diethyl-5-methylpyrazine, methylpropanal, acetic acid, pentanoic acid, 2-ethyl-3,5-dimethylpyrazine, pentylpyridine, (Z)-1,5-octadien-3-one, 2-methylbutanal, and beta-damascenone. In addition to the compounds above, 1-octen-3-one, 1-nonen-3-one, and 3-methyl-2,4-nonandione showed potent rOAVs. The results of quantification and OAV calculation were confirmed by a model mixture of 25 impact odorants, which yielded a highly similar sensory profile to that of the original soybean lecithin. The sensory importance of pyrazines and free acids increased through enzymatic hydrolysis and decreased by the process of deoiling. The impact of unsaturated ketones on the lecithin aroma was not changed by either process.

Identification of character impact odorants of different soybean lecithins.

The potent odorants of standardized, enzymatically hydrolyzed, and deoiled soybean lecithins were characterized systematically by combined gas chromatography/mass spectrometry and olfactometry. Sixty-one odorants were identified; 53 of these odor-active compounds have not previously been reported as odorants of soybean lecithin flavor. By aroma extract dilution analysis and modified combined hedonic and response measurement the following odorants showed the highest flavor dilution factors and CHARM values: (E,E)-2, 4-decadienal (deep-fried), (E)-beta-damascenone (apple-like), 2, 3-diethyl-5-methylpyrazine (roasty, earthy), (E)-2-nonenal (cardboard-like), trans-4,5-epoxy-(E)-2-decenal (metallic), 1-nonen-3-one (mushroom-like), 2-ethyl-3,5-dimethylpyrazine (roasty, earthy), and 1-octen-3-one (mushroom-like). Enzymatic hydrolysis intensified especially the roasty sensation of 2, 3-diethyl-5-methylpyrazine, whereas deoiling effected a general significant decrease in olfactory perception on the nitrogen-containing compounds. In addition, sensory profiles of nasal and retronasal lecithin odor were performed.

Odorants of Virgin Olive Oils with Different Flavor Profiles

The potent odorants of virgin olive oils from Italy (I), Spain (S), and Morocco (M) were screened by aroma extract dilution analyses and gas chromatography olfactometry of headspace samples. After quantification, odor activity values (OAVs) were calculated by dividing the concentrations of the odorants in the oil samples by their nasally and retronasally determined odor threshold values in sunflower oil. On the basis of the nasal thresholds, the following compounds showed high OAVs in the oils given in parentheses: acetaldehyde (I, S, M), acetic acid (I, S), propanal (I), 1-penten-3-one (I), (E,Z)-2,4-decadienal (I, M), trans-4,5-epoxy-(E)-2-decenal (I, S, M), (Z)-3-hexenal (I, M), (E)-2-hexenal (I), (Z)-3-hexenyl acetate (I), 4-methoxy-2-methyl-2-butanethiol (S), ethyl 2- and 3-methylbutyrate (S, M), 2- and 3-methylbutanal (S), ethyl cyclohexylcarboxylate (M), and ethyl isobutyrate (M). Higher OAVs were additionally found for hexanal (I) and (Z)-2-nonenal (I, M) when retronasal odor thresholds were used as the basis. The potent odorants were dissolved in a refined plant oil in the concentrations found in the three olive oil samples. The flavor profiles of the models obtained were very close to those of the real samples, indicating that the different notes in the flavor profiles of these oils could be reproduced, e.g., green, fruity, black currantlike. Models missing one or several compounds with the same odor quality gave an insight into the importance of the odorants contributing to the flavor profiles of the oil samples. Keywords: Aroma extract dilution analysis; flavor analysis; flavor differences; flavor imitation; flavor profile analysis; isotope dilution asssay; sensory study; virgin olive oil

Orthonasal and retronasal odorant identification based upon vapor phase input from common substances.

Subjects were trained to identify by assigned number common substances presented as vapor phase stimuli via an orthonasal or a retronasal route. Following training, odorant identification learning was evaluated by measuring ability to correctly identify to a criterion. Those who met the criterion were then tested first with the stimuli presented to the nares that differed in location from the nares used in training, and second to the nares that corresponded in location to the nares used in training. It was found that, under conditions of natural retronasal breathing, orthonasally trained subjects made correct identifications on approximately 80% of the trials upon retronasal testing, but for the following orthonasal testing identifications were significantly more frequent, approaching 100% correct. After subsequent retronasal training, the same subjects' orthonasal identifications remained significantly higher, although identifications improved to approximately 92% correct on retronasal trials. Other subjects were instructed in a breathing technique designed to enhance retronasal stimulation. After orthonasal training, retronasal testing of these subjects still gave significantly fewer correct identifications than orthonasal testing, notwithstanding the modified retronasal breathing, but after subsequent retronasal training correct identifications by these subjects no longer differed significantly between orthonasal and retronasal testing. Efficacy of modified retronasal breathing was confirmed in two subsequent experiments. The observed substantial positive transfers between retronasal and orthonasal odorant identification training and testing loci demonstrate that these odorant pathways do not subserve completely independent olfactory systems, while the less accurate identifications via the retronasal route, unless instruction in retronasal breathing was given, suggest a difference in the efficiency with which odorants are normally delivered to the olfactory mucosa.

Evaluation of Key Odorants of the Neutral Volatiles of Emmentaler Cheese by the Calculation of Odour Activity Values

Thirteen compounds which had been screened by aroma extract dilution analysis (AEDA) as potent odorants of Emmentaler were quantified by isotope dilution assays in two samples of this cheese. Their odour activity values (OAVs) were calculated by dividing the concentrations of the odorants in the cheese samples by the nasal and retronasal odour thresholds in an oil. The highest OAVs (range 150 to 660) were found for methional, 4-hydroxy-2,5-dimethyl-3(2H)-furanone and 5-ethyl-4-hydroxy-2-methyl-3 (2H)-furanone. For this reason they were suggested as belonging to the key odorants of Emmentaler cheese. In addition diacetyl, 3-methylbutanal and three esters with much lower OAVs (range 10 to 20) might play a role in the flavour of this type of cheese. The remaining five compounds with OAVs of 4 and smaller are of minor importance.

The effects of mouth movements, swallowing, and spitting on retronasal odor perception

Although attempts have been made to compare sensations produced by orthonasal and retronasal olfactory stimulation, previous studies have failed to address the dynamic nature of retronasal perception. In this study we demonstrate the importance of oral movements in influencing the perceived retronasal olfactory intensity. For orally-presented solutions of artificial orange and rum extract solutions, average magnitude estimates of eight subjects were significantly increased by various mouth movements (including spitting and swallowing) over a no mouth movement condition. These findings demonstrate that retronasal odor perception is a highly dynamic process, and suggest the hypothesis that mouth movements play a role in retronasal odor perception analogous to that played by sniffing in orthonasal perception. In addition, these data suggest that some disorders of deglutition may have associated chemosensory consequences.

Deglutition.

Deglutition.