Characterization of the key aroma compounds in dried fruits of the West African peppertree Xylopia aethiopica (Dunal) A. Rich (Annonaceae) using aroma extract dilution analysis.

Application of aroma extract dilution analysis on an extract of the dried fruits of the West African peppertree Xylopia aethiopica obtained by extraction with diethyl ether followed by sublimation in vacuo revealed 28 odor-active compounds in the flavor dilution (FD) factor range of 4-8192, all of which could be identified. The highest FD factor was found for linalol (floral), followed by (E)-beta-ocimene (flowery), alpha-farnesene (sweet, flowery), beta-pinene (terpeny), alpha-pinene (pine needle-like), myrtenol (flowery), and beta-phellandrene (terpeny). Vanillin (vanilla-like) and 3-ethylphenol (smoky, phenolic) showing somewhat lower FD factors (FD = 128) were detected for the first time as constituents of the dried fruit.     

Characterization of the key aroma compounds in the beverage prepared from Darjeeling black tea: quantitative differences between tea leaves and infusion

By application of the aroma extract dilution analysis on the volatile fraction isolated from a black tea infusion (Darjeeling Gold Selection), vanillin (vanilla-like), 4-hydroxy-2,5-dimethyl-3(2H)-furanone (caramel), 2-phenylethanol (flowery), and (E,E,Z)-2,4,6-nonatrienal (oat-flake-like) were identified with the highest flavor dilution (FD) factors among the 24 odor-active compounds detected in the FD factor range of 4-128. Quantitative measurements performed by means of stable isotope dilution assays and a calculation of odor activity values (OAVs; ratio of concentration to odor threshold in water) revealed, in particular, the previously unknown tea constituent (E,E,Z)-2,4,6-nonatrienal as a key odorant in the infusion and confirmed the important role of linalool and geraniol for the tea aroma. An aroma recombinate performed by the 18 odorants for which OAVs > 1 were determined in their "natural" concentrations matched the overall aroma of the tea beverage. In the black tea leaves, a total of 42 odorants were identified, most of which were identical with those in the beverage prepared thereof. However, quantitative measurements indicated that, in particular, geraniol, but also eight further odorants were significantly increased in the infusion as compared to their concentration in the leaves.     

Studies on the aroma of five fresh tomato cultivars and the precursors of cis- and trans-4,5-epoxy-(E)-2-decenals and methional

Three tasty (BR-139, FA-624, and FA-612) and two less tasty (R-144 and R-175) fresh greenhouse tomato cultivars, which significantly differ in their flavor profiles, were screened for potent odorants using aroma extract dilution analysis (AEDA). On the basis of AEDA results, 19 volatiles were selected for quantification in those 5 cultivars using gas chromatography-mass spectrometry (GC-MS). Compounds such as 1-penten-3-one, ( E, E)- and ( E, Z)-2,4-decadienal, and 4-hydroxy-2,5-dimethyl-3(2 H)-furanone (Furaneol) had higher odor units in the more preferred cultivars, whereas methional, phenylacetaldehyde, 2-phenylethanol, or 2-isobutylthiazole had higher odor units in the less preferred cultivars. Simulation of the odor of the selected tomato cultivars by preparation of aroma models and comparison with the corresponding real samples confirmed that all important fresh tomato odorants were identified, that their concentrations were determined correctly in all five cultivars, and that differences in concentration, especially of the compounds mentioned above, make it possible to distinguish between them and are responsible for the differential preference. To help elucidate formation pathways of key odorants, labeled precursors were added to tomatoes. Biogenesis of cis- and trans-4,5-epoxy-( E)-2-decenals from linoleic acid and methional from methionine was confirmed.     

Aroma constituents and alkylamides of red and green huajiao (Zanthoxylum bungeanum and Zanthoxylum schinifolium)

Huajiao denotes the fruits of various species of Zanthoxylum in the plant family Rutaceare used for cooking. The two most commercially popular species are bungeanum (red huajiao) and schinifolium (green huajiao). Fresh huajiao has a very high content of essential oil, up to 11%, which is described as having fresh, spicy, floral, cooling, and green aroma notes. A comprehensive analysis of the essential oils by GC-MS using advanced peak deconvolution and data processing software, revealed many overlapping components. A total of 120 aroma compounds for each species has been found. In the essential oils, linalyl acetate (15%), linalool (13%), and limonene (12%) are the major components of red huajiao, whereas linalool (29%), limonene (14%), and sabinene (13%) are the major components of green huajiao. For estimation of the aroma contribution of individual components, a new concept, "aroma character impact value" (ACI), is introduced as the percentage of the ratio of the concentration of an aroma component to its odor threshold value. Despite the differences in major components, both species have six common compounds of top aroma character impact: linalool, alpha-terpineol, myrcene, 1,8-cineole, limonene, and geraniol. The tingling sensation of huajiao is caused mainly by the alkylamide hydroxy-alpha-sanshool. The tingling compound decomposes easily under hydrolytic conditions or under UV light.     

Characterization of the key aroma compounds in rape honey by means of the molecular sensory science concept

By application of aroma extract dilution analysis (AEDA) on the volatile fraction isolated by solvent extraction and solvent-assisted flavor evaporation (SAFE) from unifloral rape honey harvested in July 2009, 28 odor-active areas could be detected within a flavor dilution factor (FD) range of 4-2048. The highest FD factors were found for (E)-β-damascenone (cooked apple-like), phenylacetic acid (honey-like), 4-methoxybenzaldehyde (aniseed-like), 3-phenylpropanoic acid (flowery, waxy), and 2-methoxy-4-vinylphenol (clove-like). Twenty-three odorants were then quantitated by application of stable isotope dilution assays, and their odor activity values (OAV, ratio of concentration to odor threshold) were calculated on the basis of newly determined odor thresholds in an aqueous fructose-glucose solution. The highest OAVs were calculated for (E)-β-damascenone, 3-phenylpropanoic acid, phenylacetic acid, dimethyl trisulfide, and phenylacetaldehyde. Quantitative measurements on a rape honey produced in 2011 confirmed the results. A model mixture containing the 12 odorants showing an OAV ≥ 1 at the same concentrations as they occurred in the rape honey was able to mimick the aroma impression of the original honey. The characterization of the key odorants in rape flowers from the same field suggested 3-phenylpropanoic acid, phenylacetic acid, and three further odorants to be transferred via the bees into the honey.     

Aroma evaluation of an aquatic herb, Changpo (Acorus calamus Var. angustatus Bess), by AEDA and SPME

This study was conducted to determine the volatile flavor composition of fresh changpo (Acorus calamus var. angustatus Bess) leaves quantitatively and qualitatively by use of two internal standards and to determine which volatile compounds are primarily responsible for the aroma of this aquatic herb. The headspace composition of fresh changpo leaves was also analyzed by a solid-phase microextraction method. Aroma extract dilution analysis (AEDA) and sniffing test by gas chromatography-olfactometry were used for the detection of aroma-active compounds of this herb. According to the instrumental analyses of the changpo oil, octanoic acid (49.13%), alpha-cedrene (16.71%), alpha-phellandrene (4.46%), and gamma-elemene (3.75%) were the most abundant compounds. n-Butylidene dihydrophthalide (8.61%), trans,trans-farnesyl acetate (7.29%), and trans-2-dodecenal (7%) were the main components of changpo headspace. cis-beta-Farnesene was evaluated as the key aroma compound of this herb from results of AEDA and sniffing test.     

Characterization of the odor-active volatiles in citrus Hyuganatsu (Citrus tamurana Hort. ex Tanaka)

The volatile components of Hyuganatsu (Citrus tamurana Hort. ex Tanaka) peel oil, isolated by cold-pressing, were investigated by chemical and sensory analyses. According to chemical analysis by GC and GC-MS, limonene (84.0%) was the most abundant compound, followed by gamma-terpinene (6.9%), myrcene (2.2%), alpha-pinene (1.2%), and linalool (1.0%). Monoterpene hydrocarbons were predominant in Hyuganatsu peel oil. The odor-active volatiles in Hyuganatsu flavor were studied by GC-olfactometry and omission tests. The characteristic flavor was present in the oxygenated fraction. Flavor dilution (FD) factors of the volatile flavor components of the Hyuganatsu cold-pressed oil were determined by aroma extraction dilution analysis (AEDA). Furthermore, relative flavor activity was investigated by means of FD factor and weight percent. Ten kinds of odor compounds having Hyuganatsu-like aroma were detected by AEDA: limonene, linalool, octanol, neral, neryl acetate, tridecanal, trans-carveol, cis-nerolidol, trans,trans-farnesyl acetate, and trans,trans-farnesol. Linalool and octanol were regarded as the most odor-active or key compounds of Hyuganatsu aroma. Diluted solutions of linalool and octanol of approximately 2 ppm gave a fresh and fruity aroma note similar to Hyuganatsu flavor.     

Characterization of (E,E,Z)-2,4,6-nonatrienal as a character impact aroma compound of oat flakes

To identify the compounds evoking the characteristic cereal-like, sweet aroma of oat flakes, an aroma extract dilution analysis (AEDA) was applied to a distillate prepared by solvent extraction/vacuum distillation from commercial oat flakes. Among the nine aroma-active compounds detected by gas chromatography-olfactometry and AEDA in the flavor dilution (FD) factor range of 4-1024, eight odorants, for example, (E)-beta-damascenone, (Z)-3-hexenal, and butanoic acid, showed only low FD factors. However, one odorant eliciting the typical cereal, sweet aroma of the flakes was detected with the highest FD factor of 1024. By mass spectrometry and nuclear magnetic resonance measurements followed by a synthesis, (E,E,Z)-2,4,6-nonatrienal, exhibiting an intense oat flake-like odor at the extremely low odor threshold of 0.0002 ng/L in air, was identified as the key odorant of the flakes. By means of a newly developed stable isotope dilution analysis using synthesized, carbon-13-labeled nonatrienal as the internal standard, a concentration of 13 mug of (E,E,Z)-2,4,6-nonatrienal per kilogram of the flakes was measured. Model studies suggested linolenic acid as the precursor of nonatrienal in oats.     

Characterization of the key aroma compounds in apricots (Prunus armeniaca) by application of the molecular sensory science concept

An aroma extract dilution analysis applied on an aroma distillate prepared from fresh apricots revealed (R)-gamma-decalactone, (E)-beta-damascenone, delta-decalactone, and (R/S)-linalool with the highest flavor dilution (FD) factors among the 26 odor-active compounds identified. On the basis of quantitative measurements performed by application of stable isotope dilution assays, followed by a calculation of odor activity values (OAVs), beta-ionone, (Z)-1,5-octadien-3-one, gamma-decalactone, (E,Z)-2,6-nonadienal, linalool, and acetaldehyde appeared with OAVs >100, whereas in particular certain lactones, often associated with an apricot aroma note, such as gamma-undecalactone, gamma-nonalactone, and delta-decalactone, showed very low OAVs (<5). An aroma recombinate prepared by mixing the 18 most important odorants in concentrations as they occurred in the fresh fruits showed an overall aroma very similar to that of apricots. Omission experiments indicated that previously unknown constituents of apricots, such as (E,Z)-2,6-nonadienal or (Z)-1,5-octadien-3-one, are key contributors to the apricot aroma.     

Antimicrobial and bactericidal activities of esters of 2-endo-hydroxy-1,8-cineole as new aroma chemicals

Fourteen kinds of alkyl esters of 2-endo-hydroxy-1,8-cineole were synthesized, with yields of 57.8-98.0%. Each ester had a characteristic and unique odor. Especially, the tert-butyl acetate of 2-endo-hydroxy-1,8-cineole had the most interesting odor of all the synthetic esters. The antimicrobial and bactericidal activities of these synthetic esters against test bacteria (Staphylococcus aureus, Escherichia coli, and Pseudomonas fluorescens) were examined using the broth dilution method. As a result, the tert-butyl acetate of 2-endo-hydroxy-1,8-cineole showed the highest antimicrobial and bactericidal activities against all kinds of the test bacteria.     

Determination of key aroma compounds in the crumb of a three-stage sourdough rye bread by stable isotope dilution assays and sensory studies

An investigation of the volatile fraction of a freshly prepared sourdough rye bread crumb by means of the aroma extract dilution analysis (AEDA), followed by identification experiments, revealed 22 flavor compounds in the flavor dilution (FD) factor range of 128 to 2048. Quantitations performed by stable isotope dilution assays (SIDA) and a calculation of odor activity values (OAV; ratio of concentration to odor threshold) revealed the following as contributors to the overall crumb flavor: 3-methylbutanal (malty), (E)-2-nonenal (green, fatty), (E,E)-2,4-decadienal (fatty, waxy), hexanal (green), acetic acid (sour, pungent), phenylacetaldehyde (honey-like), methional (boiled potato-like), vanillin (vanilla-like), 2,3-butandione (buttery), 3-hydroxy-4,5-dimethyl-2(5H)-furanone (spicy), and 2- and 3-methylbutanoic acid (sweaty). Using either citrate buffer, starch, or deodorized crumb as model matrixes, the typical malty and sour rye bread crumb flavor was reproduced by adding a mixture of 20 reference odorants in the "natural" concentrations as quantitatively determined in the fresh crumb.     

Glycosidically bound volatiles and flavor precursors in Laurus nobilis L

Glycosidically bound volatile compounds in different parts (leaves and buds) of Laurus nobilis L. were investigated. After isolation of extracts obtained by Amberlite XAD-2 adsorption and methanol elution, glycosides were analyzed after enzymatic hydrolysis by GC-MS or directly after trifluoroacetyl (TFA) derivatization by GC-MS in EI and NCI mode. In the leaves most of the glycosidically bound volatiles occur as beta-D-glucopyranosides. Among the disaccharides, primeverosides are predominant; smaller amounts of alpha-L-arabinofuranosyl-beta-D-glucopyranosides, rutinosides, and vicianocides could also be identified. Major aglycons comprised benzyl alcohol, some linalool-diols, 2-hydroxy-1,8-cineole and its derivatives such as 2,3-dehydro-1,8-cineole, sobrerols, and menthadien-8-ols. Among the identified nor-carotenoids, 3-oxo-alpha-ionol, the corresponding 7,8-dihydro derivative, and vomifoliol are predominant in leaves. 3-Hydroxy-beta-damascone and 3-hydroxy-7,8-didehydro-beta-ionol, precursors of the sensorially active damascenone, were identified only in the buds.     

Changes in the aroma compounds of sake during aging

Changes in the aroma of sake during aging were investigated by aroma extract dilution analysis (AEDA) and quantitative analysis using the stir bar sorptive extraction method. In AEDA, more odor zones were detected in aged sake than in fresh sake. The dilution factors of aldehydes, polysulfides, and some esters were greater in the aged sake, and their increase during aging was confirmed through a quantitative analysis of sake stored for 0-35 years. Among these compounds, 3-methylbutanal, methional, and dimethyltrisulfide (DMTS) were present in aged sake at concentrations exceeding their odor thresholds, and the highest odor active value was observed for DMTS. Sensory tests showed that supplementation with DMTS contributed to both the total odor intensity and the sulfury odor of aged sake aroma.     

Evolution and occurrence of 1,8-cineole (eucalyptol) in Australian wine

A new method has been developed for the quantitation of 1,8-cineole in red and white wines using headspace solid-phase microextraction (SPME) combined with stable isotope dilution analysis (SIDA) and gas chromatography-mass spectrometry (GC-MS). An extensive survey of Australian wines (44 white and 146 red) highlighted that only red wines contained significant amounts of 1,8-cineole (up to 20 μg/L). Hydrolytic studies with limonene and α-terpineol, putative precursors to 1,8-cineole, showed a very low conversion into 1,8-cineole (< 0.6%) over a 2 year period, which does not account for the difference between white and red wines. 1,8-Cineole was chemically stable in model wine solution over 2 years, and absorption from a Shiraz wine by bottle closures was most evident for a synthetic closure only (14% absorption after 1 year). Two commercial ferments at two different locations were monitored daily to investigate the evolution of 1,8-cineole throughout fermentation. Both ferments showed daily increases in 1,8-cineole concentration while in contact with grape solids, but this accumulation ceased immediately after pressing. This observation is consistent with the extraction of 1,8-cineole into the ferment from the solid portions of the grape berries.     

Aroma content of fresh basil (Ocimum basilicum L.) leaves is affected by light reflected from colored mulches

Sweet basil (Ocimum basilicum L.) is an herb that is used to add a distinct aroma and flavor to food. Volatile compounds emitted from fully expanded fresh leaves grown in drip-irrigated plots that were covered with six colors of mulch were compared. The colors reflected a range of photosynthetic photon flux, far-red, red, and blue light from the soil surface to developing leaves. Our objective was to determine whether reflection from the different colors could influence concentrations of volatile compounds emitted from the fresh leaves. Volatile compounds were isolated by headspace sampling and quantified by gas chromatography. Twenty-six compounds were identified, of which the terpenoids linalool and 1,8-cineole comprised more than 50% of the total yield. Concentrations of volatile compounds from leaves that developed over green, blue, yellow, white, and red mulches followed the same patterns as they did for air-dried leaves of the same cultivar. However, the concentration of volatile compounds from fresh leaves was about 50-fold higher than those found in the previous study of air-dried leaves.     

Volatile constituents of wild citrus Mangshanyegan (Citrus nobilis Lauriro) peel oil

Volatiles of a wild mandarin, Mangshanyegan (Citrus nobilis Lauriro), were characterized by GC-MS, and their aroma active compounds were identified by aroma extract dilution analysis (AEDA) and gas chromatography-olfactometry (GC-O). The volatile profile of Mangshanyegan was compared with those of other four citrus species, Kaopan pummelo (Citrus grandis), Eureka lemon (Citrus limon), Huangyanbendizao tangerine (Citrus reticulata), and Seike navel orange (Citrus sinensis). Monoterpene hydrocarbons predominated in Mangshanyegan, in particular d-limonene and β-myrcene, which accounted for 85.75 and 10.89% of total volatiles, respectively. Among the 12 compounds with flavor dilution factors (FD) = 27, 8 oxygenated compounds, including (Z)- and (E)-linalool oxides, were present only in Mangshanyegan. The combined results of GC-O, quantitative analysis, odor activity values (OAVs), and omission tests revealed that β-myrcene and (Z)- and (E)-linalool oxides were the characteristic aroma compounds of Mangshanyegan, contributing to the balsamic and floral notes of its aroma.     

Chemical characterization of commercial Sherry vinegar aroma by headspace solid-phase microextraction and gas chromatography-olfactometry

The sensorial representativeness of the headspace solid-phase microextraction (HS-SPME) aroma extract from commercial Sherry vinegars has been determined by direct gas chromatography-olfactometry (D-GCO). Extracts obtained under optimal conditions were used to characterize the aroma of these vinegars by means of GCO and aroma extract dilution analysis (AEDA). Among the 37 different odorants determined, 13 of them were identified for the first time in Sherry vinegars: 2 pyrazines (3-isopropyl-2-methoxypyrazine, 3-isobutyl-2-methoxypyrazine), 2 sulfur compounds (methanethiol, dimethyl trisulfide), 1 unsaturated ketone (1-octen-3-one), 1 norisoprenoid (β-damascenone), 1 ester (ethyl trans-cinnamate) and 6 aldehydes (2- and 3-methylbutanal, octanal, nonanal, (E)-2-nonenal and (E,E)-2,4-decadienal). The determination of the odor thresholds in a hydroacetic solution together with the quantitative analysis-which was also performed using the simple and fast SPME technique-allowed obtaining the odor activity values (OAV) of the aromatic compounds found. Thus, a first pattern of their sensory importance on commercial Sherry vinegar aroma was provided.     

Impact odorants contributing to the fungus type aroma from grape berries contaminated by powdery mildew (Uncinula necator); incidence of enzymatic activities of the yeast Saccharomyces cerevisiae

Powdery mildew due to the fungus Uncinula necator is an important disease for the vineyard. The development of the fungus at the surface of the berries leads to the occurrence of a very characteristic and sometimes intense mushroom-type odor cited as an important default for grapes quality. Gas chromatography/olfactometry, gas chromatography, and multidimensional gas chromatogaphy/mass spectrometry techniques were used to investigate the most important odorants of grapes diseased by powdery mildew. Among 22 odorants detected, strongly odorant compounds were identified or tentatively identified in purified extracts obtained from grapes diseased by powdery mildew. Aroma extraction dilution analysis (AEDA) analysis revealed that 1-octen-3-one (mushroom odor), (Z)-1,5-octadien-3-one (geranium-leaf odor), and an unidentified odorous zone (fishy-mushroom like odor) were the most potent volatiles of the diseased grapes. In the presence of nonproliferating Saccharomyces cerevisiae yeast cells, and consequently during alcoholic fermentation, the enzymatic reduction of 1-octen-3-one and (Z)-1,5-octadien-3-one to much less odorant compounds, namely 3-octanone and (Z)-5-octen-3-one, was shown. Those results explain to some extent the disappearance of the fungal aroma specific to powdery mildew grapes during alcoholic fermentation.     

Olfactory and quantitative analysis of aroma compounds in elder flower (Sambucus nigra L.) drink processed from five cultivars

Fresh elder flowers (Sambucus nigra L.) were extracted with an aqueous solution containing sucrose, peeled lemon slices, tartaric acid, and sodium benzoate to make elder flower syrup. Aroma compounds emitted from the elder flower syrup were collected by the dynamic headspace technique and analyzed by GC-FID and GC-MS. A total of 59 compounds were identified, 18 of which have not previously been detected in elder flower products. The concentrations of the identified volatiles were measured in five elder cultivars, Allesoe, Donau, Sambu, Sampo, and Samyl, and significant differences were detected among cultivars in the concentration levels of 48 compounds. The odor of the volatiles was evaluated by the GC-sniffing technique. cis-Rose oxide, nerol oxide, hotrienol, and nonanal contributed to the characteristic elder flower odor, whereas linalool, alpha-terpineol, 4-methyl-3-penten-2-one, and (Z)-beta-ocimene contributed with floral notes. Fruity odors were associated with pentanal, heptanal, and beta-damascenone. Fresh and grassy odors were primarily correlated with hexanal, hexanol, and (Z)-3-hexenol.