P. X. Étiévant

Just Noticeable Differences in Component Concentrations Modify the Odor Quality of a Blending Mixture

The odors we perceive are mainly the result of mixtures of odorants that, however, are commonly perceived as single undivided entities; nevertheless, the processes involved remain poorly explored. It has been recently reported that perceptual blending based on configural olfactory processing can cause odorant mixtures to give rise to an emergent odor not present in the components. The present study examined whether specific component proportions are required to elicit an emergent odor. Starting from the composition of a ternary target mixture in which an emergent pineapple odor was perceived, 4 concentration levels of each component were chosen to elicit just noticeable differences (JNDs). Each combination of levels was used to design sample mixtures. Fifteen subjects evaluated the intensity, typicality, and pleasantness of each sample mixture against the target mixture in a paired-comparison protocol. Statistical modeling showed that a variation of less than 1 JND in one of the components was sufficient to induce a significant decrease in pineapple odor typicality in the ternary mixture. This finding confirms previous findings on perceptual blending in simple odorant mixtures and underscores the human ability to discriminate between odor percepts induced by mixtures including very similar odorant proportions.

Detection of powerful odorants in heated milk by use of extract dilution sniffing analysis

The odour impact compounds of raw, pasteurized and UHT bovine milk were investigated using vacuum extraction and extract dilution sniffing analysis using CharmAnalysis™. Fifteen odour peaks with Charm values between 10 and 3443 were detected. Of these peaks, twelve were identified as hexanal, ethyl butanoate, 2-heptanone, heptanal, dimethyl sulphone, l-octen-3-ol, ethyl hexanoate, 2-nonanone, nonanal, benzothiazole, 2-undecanone, indole and one as a mixture of 2-tridecanone and δ-decalactone. Dimethyl sulphone, indole and one unknown compound (retention index 1154) were the only ones detected as odour impact compounds in all three types of milk. Ethyl butanoate and ethyl hexanoate were found as powerful odorants only in raw milk. A further predominant odorant for this milk was dimethyl sulphone, which was the most important odorant in pasteurized milk. 2-Hexanone and 2-nonanone were identified as the most intense volatile flavour compounds of UHT milk. The powerful odorants described can be used as indicators of the aroma quality of heated milk.

Sunflower volatiles involved in honeybee discrimination among genotypes and flowering stages

In order to define the part of olfactory cues in the selective behavior of honeybees, observation on their foraging behavior was carried out on various sunflower genotypes in parallel with chemical analysis of aromatic extracts of the genotypes. Foragers show a preference for the early stages of flowering and, when they are given a choice between couples of parental lines of two commercial hybrids, Marianne and Mirasol, they are randomly distributed on Mirasol parents, but they prefer the female line of Marianne. The comparison of relative proportions of compounds among aromagrams obtained from head space trapping from the two couples of genotypes, reveals (1) a phenological stage effect for 17 compounds among 144 indexed compounds for Marianne lines and for 18 among 136 indexed compounds of Mirasol lines; most of these compounds exhibit higher relative proportions in the early flowering stages, which is related to plant attractiveness towards honeybees; (2) a sex effect for 33 compounds among 144 for Marianne lines and for 14 compounds among 136 for Mirasol lines; further semiquantitative analyses reveal a sex effect for only eight compounds of 134 for Marianne lines and 20 compounds of 250 for Mirasol lines, which represents less than 10% of the indexed compounds. These discriminatory compounds were partly identified by coupled GC-MS. Possible relations between such phenological and genotypical volatile fluctuations and forager attraction are discussed.

Powerful odorants in bovine, ovine, caprine and water buffalo milk determined by means of gas chromatography–olfactometry

The main compounds responsible for the aroma of bovine, ovine, caprine and water buffalo freshly secreted milk have been identified by means of a gas chromatography–olfactometry technique. Of the fourteen odour-active volatile compounds detected, eight were present in all milks studied. Ethylbutanoate and ethylhexanoate (fruit-like aroma), among the neutral odorants, were the major contributors to the odour of bovine, ovine and caprine milk. The aroma of water buffalo milk was less dependent on ethylhexanoate and was also due to l-octen-3-ol (aroma of raw mushrooms), nonanal (freshly cut grass), indole (stable, animals) and an unidentified constituent, characterized by a retention index of 828, with a typical odour of warm milk and/or smoked cheese. Other aroma components were specific for some types of milk, contributing to the complexity and richness of flavour.

Sensory and instrumental characterisation of commercial tomato varieties

Ten tomato varieties, i.e. Cencara, Daniella, Elena, Ibiza, Lemon Boy, Lucy, Melody, Perfecto, Raf and Rondello, were studied over two consecutive years by GC and GC-sniffing for their differences in flavour composition. Precautions were taken to avoid differences due to the growth conditions and stage of matu-rity. The aroma profiles obtained from dilutions of the extracts confirm the importance of most compounds previously reported as being key flavour compounds in tomatoes. Moreover, they outline a greater number of other key compounds which had not been identified or reported as such in the literature. Among them, 2-methoxyphenol, eugenol, decanal and geranylacetone were identified. Among 39 compounds quantified, 27 were found to permit discrimination between varieties both in 1992 and 1993. Six varieties were characterised in both years by specific flavour compositions. The differences between varieties is due to particular relative amounts of volatile compounds arising from the metabolism of aliphatic amino acids and carotenoids. Volatile compounds arising from each metabolic processes were found to be highly correlated with each other.

Sunflower aroma detection by the honeybee : study by coupling gas chromatography and electroantennography

Combined electrophysiological recordings (EAG) and gas chromatographic separation were performed in order to investigate which volatile chemical components of a sunflower extract could be detected by honeybee workers and thus are likely to trigger the foraging behavior. A direct coupling device allowed for the stimulation of the antennal receptors with individual constituents of a polar fraction of the flower aroma shown to be attractive to bees. More than 100 compounds were separated from the extract. Twenty-four compounds elicited clear EAG responses. These compounds were identified by mass spectrometry (electronic impact and chemical ionisation). Both short- and long-chain aliphatic alcohols, one short-chain aliphatic aldehyde, one acid, two esters, and terpenic compounds were found to stimulate the antennal receptors. Six compounds identified in previous behavioral experiments were found to exhibit EAG activity. The chemicals screened by this method may be used for recognition of the plant odor and the selective behavior of honeybees.

Enantiomeric ratios of pantolactone, solerone, 4-carboethoxy-4-hydroxy-butyrolactone and of sotolon, a flavour impact compound of flor-sherry and botrytized wines

ZusammenfassungDie Synthese der Enantiomeren des Sotolons (2), einer Aromaleitsubstanz für Flor-Sherryund Botrytis-Weine, wird aufgezeigt und das chromatographische Verhalten der Enantiomeren (R)-2 und (S)-2 an permethyliertemβ-Cyclodextrin bestimmt. Mittels enantioselektiver multidimensionaler Gaschromatographie (Säulenkombination: DB 1701/Permethyl-β-Cyclodextrin) werden die Enantiomerenverhältnisse der chiralenγ-Lactone Pantolacton (1), Sotolon (2), Soleron (3) und 4-Carbethoxy-4-hydroxybutyrolactone (4) in Flor-Sherry- und Botrytis-Weinen ermittelt. Während für die Lactone1 und4 hohe Enantiomerenüberschüsse zugunsten der (4R)-konfigurierten Spiegelbildisomere nachgewiesen werden, können aus dem für Soleron (3) bzw. Sotolon (2) ermittelten Enantiomerenverhältnissen keine Rückschlüsse auf die Authentizität dieser Verbindungen abgeleitet werden.SummaryThe enantiomers of sotolon (2), a flavour impact compound of flor-sherry and botrytized wines, were synthesized to determine the Chromatographic behaviour of the enantiomers (R)-2 and (S)-2 on permethylatedβ-cyclodextrin as the chiral stationary phase. Using enantioselective multidimensional gas chromatography (column combination: DB 1701/permethyl-β-cyclodextrin) the enantiomeric ratios of the chiralγ-lactones pantolactone (1), sotolon (2), solerone (3) and 4-carboethoxy-4-hydroxy butyrolactone (4) in flor-sherry and botrytized wines were evaluated. High enantiomeric excess in favour of the (4R)-configurated mirror images was detected for lactones1 and4. The measured enantiomeric ratios of sotolon (2) and solerone (3) were too low and unspecific to be useful in authenticity control of2 and3.

The volatile constituents of strawberry jam

Zusammenfassung153 flüchtige Verbindungen wurden in einem Dichlormethanextrakt aus Erdbeermarmelade bestimmt. Die Identifizierung der Aromastoffe erfolgte mittels HRGC-MS und Vergleich der spektroskopischen und chromatographischen Daten mit Referenzverbindungen. Die Hauptkomponenten des Aromas von Erdbeermarmelade stellen Mesifuran, 1-(2-Furanyl)-2-hydroxyethanon sowie verschiedene Säuren, Alkohole und Ester dar. Das Aroma von Erdbeermarmelade zeichnet sich im Vergleich zum Aroma der Frucht durch einen erhöhten Gehalt an Furfural und 2-Acetylfuran aus. Während ca. zwei Drittel der flüchtigen Bestandteile von Erdbeermarmelade aus der Frucht stammen, sind 1-(2-Furanyl)-2-hydroxyethanon und drei unbekannte „Nerolidol-oxide“ charakteristische Aromakomponenten der Marmelade. Maillard-Reaktionsprodukte wie 5-Hydroxymethyl-2-furaldehyd und 2,3-Dihydro-3,5-dihydroxy-6-me-thyl-4H-pyran-4-on kommen in Marmelade in nur relativ geringen Konzentrationen vor.SummaryOne hundred and fifty-three volatile compounds were characterized in the dichloromethane extract of strawberry jam. Their identification was carried out mainly by HRGC-MS and compared with reference compounds. The major constituents responsible for the aroma of strawberry jam are mesifurane, 1-(2-furanyl)-2-hydroxyethanone, as well as a number of acids, alcohols and esters. The aroma of strawberry jam is characterized by a high concentration of furfural and 2-acetyl furan, as compared with the aroma of the intact fruit. While about two-thirds of strawberry jam volatiles seem to originate from the fruit, 1-(2-furanyl)-2-hydroxyethanone and three unknown “nerolidol oxides” are characteristic constituents of the jam. Maillard reaction products such as 5-hydroxymethyl-2-furaldehyde and 2,3-dihydro-3,5-dihydroxy-6-methyl-4H-pyran-4-one occur in unexpectedly, relatively low amounts in the jam.

Comparison of wine discrimination with orthonasal and retronasal profilings. Application to Burgundy Pinot Noir wines

Two sensory spaces, corresponding to the same wine sample profiled by nose (BN) and profiled by mouth (BM), were compared. The similarity between the two maps of product differences were measured by multivariate analysis, showing a good agreement and comparable product discrimination by the panel in the two modes, slightly in favor of BN discrimination. The superiority of one particular mode was not established from the comparison of individual performances BN versus BM, but differences between panelists and between descriptor use were found. Two-way canonical variate analysis of BN minus BM scores was also performed: the results revealed that panelists had higher influence than products in the differences observed between the two modes.