Characterization of volatile compounds contributing to naturally occurring fruity fermented flavor in peanuts

Published research has indicated that ethyl 2-methylpropanoate, ethyl 2-methybutanaote, ethyl 3-methylbutanoate, hexanoic acid, butanoic acid, and 3-methylbutanoic acid are responsible for fruity fermented (FF) off-flavor; however, these compounds were identified in samples that were artificially created by curing immature peanuts at a constant high temperature. The objective of this study was to characterize the volatile compounds contributing to naturally occurring FF off-flavor. Volatile compounds of naturally occurring FF and no-FF samples were characterized using solvent-assisted flavor evaporation (SAFE), solid phase microextraction (SPME), gas chromatography-olfactometry (GC-O), and gas chromatography-mass spectrometry (GC-MS). Aroma extract dilution analysis (AEDA) identified 12 potent aroma active compounds, none of which were the previously identified esters, with no consistent differences among the aroma active compounds in no-FF and FF samples. Hexanoic acid alone was identified in the naturally occurring FF sample using the SAFE GC-MS methodology, whereas two of the three previously identified esters were identified in natural and artificially created samples. The same two esters were confirmed by SPME GC-MS in natural and artificially created samples. This study demonstrated the need for caution in the direct application of data from artificially created samples until those compounds are verified in natural samples. However, these results suggest that a laboratory method using SPME-GC techniques could be developed and correlated on an ester concentration versus FF intensity basis to provide an alternative to sensory analysis for detection of FF off-flavor in peanut lots.     

Linking peanut allergenicity to the processes of maturation,curing, and roasting

The processes of peanut maturation, curing, and roasting are known to have an important role in peanut flavors. One of these processes (i.e., roasting) has been found to have an effect on allergenicity. To determine if the other processes (i.e., maturation and curing) affect allergenicity, mature and immature roasted peanuts and peanuts cured at different temperatures (35-77 degrees C) were, respectively, tested for IgE binding and advanced glycation end adducts (AGEs). Peanuts with and without stress proteins, which are associated with peanut maturation and curing, were also tested. Results showed that mature roasted peanuts exhibited a higher IgE binding and AGEs level than immature roasted peanuts. Curing temperatures between 35 and 60 degrees C gave no difference in the profiles. However, a higher curing temperature (i.e., 77 degrees C) exhibited a profile of higher levels of AGEs and IgE binding. These levels were higher in peanuts with stress proteins than without stress proteins. Roasting increased stress protein level and IgE binding. From these results, the processes of maturation and curing, in conjunction with roasting, may be associated with allergenicity, suggesting that these processes may lead to changes in the allergenic properties of peanuts.     

Changes in key aroma compounds of Criollo cocoa beans during roasting

Application of a comparative aroma extraction dilution analysis on unroasted and roasted Criollo cocoa beans revealed 42 aroma compounds in the flavor dilution (FD) factor range of 1-4096 for the unroasted and 4-8192 for the roasted cocoa beans. While the same compounds were present in the unroasted and roasted cocoa beans, respectively, these clearly differed in their intensity. For example, 2- and 3-methylbutanoic acid (rancid) and acetic acid (sour) showed the highest FD factors in the unroasted beans, while 3-methylbutanal (malty), 4-hydroxy-2,5-dimethyl-3(2H)-furanone (caramel-like), and 2- and 3-methylbutanoic acid (sweaty) were detected with the highest FD factors in the roasted seeds. Quantitation of 30 odorants by means of stable isotope dilution assays followed by a calculation of odor activity values (ratio of the concentration/odor threshold) revealed concentrations above the odor threshold for 22 compounds in the unroasted and 27 compounds in the roasted cocoa beans, respectively. In particular, a strong increase in the concentrations of the Strecker aldehydes 3-methylbutanal and phenylacetaldehyde as well as 4-hydroxy-2,5-dimethyl-3(2H)-furanone was measured, suggesting that these odorants should contribute most to the changes in the overall aroma after roasting. Various compounds contributing to the aroma of roasted cocoa beans, such as 3-methylbutanoic acid, ethyl 2-methylbutanoate, and 2-phenylethanol, were already present in unroasted, fermented cocoa beans and were not increased during roasting.     

Characterization of aroma compounds of chinese "Wuliangye" and "Jiannanchun" liquors by aroma extract dilution analysis

Aroma compounds in Chinese "Wuliangye" liquor were identified by gas chromatography-olfactometry (GC-O) after fractionation. A total of 132 odorants were detected by GC-O in Wuliangye liquor on DB-wax and DB-5 columns. Of these, 126 aromas were identified by GC-mass spectrometry (MS). Aroma extract dilution analysis (AEDA) was further employed to identify the most important aroma compounds in "Wuliangye" and "Jiannanchun" liquors. The results showed that esters could be the most important class, especially ethyl esters. Various alcohols, aldehydes, acetals, alkylpyrazines, furan derivatives, lactones, and sulfur-containing and phenolic compounds were also found to be important. On the basis of flavor dilution (FD) values, the most important aroma compounds in Wuliangye and Jiannanchun liquors could be ethyl butanoate, ethyl pentanoate, ethyl hexanoate, ethyl octanoate, butyl hexanoate, ethyl 3-methylbutanoate, hexanoic acid, and 1,1-diethoxy-3-methylbutane (FD > or = 1024). These compounds contributed to fruity, floral, and apple- and pineapple-like aromas with the exception of hexanoic acid, which imparts a sweaty note. Several pyrazines, including 2,5-dimethyl-3-ethylpyrazine, 2-ethyl-6-methylpyrazine, 2,6-dimethylpyrazine, 2,3,5-trimethylpyrazine, and 3,5-dimethyl-2-pentylpyrazine, were identified in these two liquors. Although further quantitative analysis is required, it seems that most of these pyrazine compounds had higher FD values in Wuliangye than in Jiannanchun liquor, thus imparting stronger nutty, baked, and roasted notes in Wuliangye liquor.     

Isolation and characterization of a peanut maturity-associated protein

Using reversed-phase high-performance liquid chromatography (RP-HPLC), the peanut protein profile was shown to be related to the maturity, drying time, and drying procedure of the peanut. Differences were seen between (a) immature and mature seeds for untreated and windrow-dried peanuts, (b) untreated and windrow-dried peanuts for immature and mature seeds, and (c) windrow- and stackpole-dried peanuts. The most pronounced HPLC peak that increased in size as the peanut matured and decreased in size with longer drying times was isolated and identified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and electrospray ionization mass spectrometry to have a molecular weight of 62 500. Since maturity is related to the sensory quality of peanuts, this protein may be a marker for peanuts that will produce a higher quality flavor when roasted.     

Evaluation of key aroma compounds in hand-squeezed grapefruit juice (Citrus paradisi Macfayden) by quantitation and flavor reconstitution experiments

Twenty-five odor-active compounds were quantified in the fresh, hand-squeezed juice of White Marsh seedless grapefruits using stable isotope dilution assays. By calculation of the odor activity values of the odorants (ratio of their concentrations in the juice to their odor thresholds in water) it was shown that the fruity esters ethyl 2-methylpropanoate, ethyl butanoate, and (S)-ethyl 2-methylbutanoate, and the fruity, sweet winelactone, as well as the grassy smelling (Z)-hex-3-enal, and trans-4,5-epoxy-(E)-dec-2-enal with metallic odor, were among the most potent odorants of the fresh grapefruit juice. The typical sulfurous, grapefruit-like odor quality was mainly due to the catty, blackcurrant-like 4-mercapto-4-methylpentan-2-one and the grapefruit-like smelling 1-p-menthene-8-thiol. These findings were confirmed by reconstitution experiments to simulate the aroma of the fresh grapefruit juice.     

Changes in the concentrations of acrylamide, selected odorants, and catechins caused by roasting of green tea

This research aims to optimize roasted green tea (Houjicha) processing by using roasting treatments to achieve acrylamide mitigation without compromising the quality. 2-Ethyl-3,5-dimethylpyrazine and 2-ethyl-3,6-dimethylpyrazine were identified as potent odorants by aroma extract dilution analysis. In preliminary sensory experiments, the desirable Houjicha flavor was produced in products roasted at 160 degrees C for 30 min and at 180 degrees C for 15 min. Under these conditions, potent odorants were formed at levels adequate for contributing to the Houjicha flavor. Acrylamide amounts in tea infusions were 2.0 and 4.0 microg/L by roasting at 160 degrees C for 30 min and at 180 degrees C for 15 min, respectively. Compared to roasting at 180 degrees C, the degradation of tea catechins was suppressed by roasting at 160 degrees C. Hence, roasting at 160 degrees C for is recommended for Houjicha processing for acrylamide mitigation, formation of potent odorants, and suppression of degradation of tea catechins.     

Characterization of the most odor-active compounds in an American Bourbon whisky by application of the aroma extract dilution analysis

Application of the aroma extract dilution analysis (AEDA) on the volatile fraction carefully isolated from an American Bourbon whisky revealed 45 odor-active areas in the flavor dilution (FD) factor range of 32-4096 among which (E)-beta-damascenone and delta-nonalactone showed the highest FD factors of 4096 and 2048, respectively. With FD factors of 1024, (3S,4S)-cis-whiskylactone, gamma-decalactone, 4-allyl-2-methoxyphenol (eugenol), and 4-hydroxy-3-methoxy-benzaldehyde (vanillin) additionally contributed to the overall vanilla-like, fruity, and smoky aroma note of the spirit. Application of GC-Olfactometry on the headspace above the whisky revealed 23 aroma-active odorants among which 3-methylbutanal, ethanol, and 2-methylbutanal were identified as additional important aroma compounds. Compared to published data on volatile constituents in whisky, besides ranking the whisky odorants on the basis of their odor potency, 13 aroma compounds were newly identified in this study: ethyl (S)-2-methylbutanoate, (E)-2-heptenal, (E,E)-2,4-nonadienal, (E)-2-decenal, (E,E)-2,4-decadienal, 2-isopropyl-3-methoxypyrazine, ethyl phenylacetate, 4-methyl acetophenone, alpha-damascone, 2-phenylethyl propanoate, 3-hydroxy-4,5-dimethyl-2(5H)-furanone, trans-ethyl cinnamate, and (Z)-6-dodeceno-gamma-lactone.     

Volatile flavor components in red fermented soybean (Glycine max) curds

Red fermented soybean (Glycine max) curds (FSC) were extracted with a simultaneous steam distillation and extraction (SDE) apparatus and analyzed by gas chromatography-mass spectrometry (GC-MS) and further evaluated by gas chromatography-mass spectrometry-flame ionization detector-olfactometry (GC-MS-FID-O). A combined total of 89 compounds were identified from three samples (A-C). The numbers of components identified (samples A-C) were 87, 85, and 81, respectively, which were divided into 10 compound classes. The quantity of 48 compounds was statistically significant (p < 0.05). Sample B generally had the lowest level, whereas sample C had the higher level of each common component among the samples. GC-MS-FID-O analyses showed that the majority of the fruity, diacetyl, cantaloupe-like odors were eluted early during the run (RI < 1100), followed by the meaty flavor, rosy, and prune-like aromas (RI > 1100). Ethyl 2-methylpropanoate, 2,3-butanedione, ethyl butanoate, ethyl 2-methylbutanoate, 3-(methylthio)propanal, benzeneacetaldehyde, and ethyl 3-phenylpropionate were found to be important common components contributing to the characteristic aroma of red FSCs.     

Comparison of the key aroma compounds in organically grown, raw West-African peanuts (Arachis hypogaea) and in ground, pan-roasted meal produced thereof

Application of an aroma extract dilution analysis on an aroma distillate prepared from organically grown, raw West-African peanuts (Cameroon) revealed 36 odor-active areas in the flavor dilution (FD) factor range of 1 to 2048. The identification experiments, which were all performed by using the respective reference chemicals, revealed 2-isopropyl-3-methoxypyrazine (earthy, pea-like), 2-isobutyl-3-methoxypyrazine (bell pepper-like, earthy), and trans-4,5-epoxy-(E)-2-decenal (metallic) with the highest FD factors among the 36 aroma compounds identified. The two last mentioned odorants and another set of 22 further odorants were identified for the first time in raw peanuts. A comparative aroma extract dilution analysis applied on distillates prepared from either the raw peanuts or ground peanut meal roasted in a pan showed 52 odor-active areas in the FD factor range of 8 to 2048 in the roasted nut material. The identification experiments in combination with the FD factors revealed that among them, 2-acetyl-1-pyrroline and 4-hydroxy-2,5-dimethyl-3-(2H)-furanone showed the most significant contribution to the overall aroma, followed by 1-octen-3-one, 2-isopropyl-3-methoxypyrazine, (E, E)-2,4-decadienal, and trans-4,5-epoxy-(E)-2-decenal. As a further result, 20 aroma compounds were newly identified in roasted peanuts, such as 2-propionyl-1-pyrroline and 2-acetyltetrahydropyridine (both popcorn-like). In particular, 2-acetyl-1-pyrroline and 4-hydroxy-2,5-dimethyl-3(2 H)-furanone showed the most pronounced increase after roasting.     

Comparison of the most odor-active compounds in fresh and dried hop cones (Humulus lupulus L. variety spalter select) based on GC-olfactometry and odor dilution techniques

Application of aroma extract dilution analysis on the volatiles obtained from dried cones of Spalter Select hops grown in the German hop-growing area of Hallertau revealed 23 odorants in the flavor dilution (FD) factor range of 16-4096, 20 of which could be identified. On the basis of high FD factors, trans-4, 5-epoxy-(E)-2-decenal, linalool, and myrcene were identified as the most potent odorants, followed by ethyl 2-methylpropanoate, methyl 2-methylbutanoate, (Z)-1,5-octadien-3-one, nonanal, (E,Z)-1,3, 5-undecatriene, 1,3(E),5(Z),9-undecatetraene, propyl 2-methylbutanoate, 4-ethenyl-2-methoxyphenol, and 1-octen-3-one. Ten of the high-impact hop aroma compounds had previously not been identified as hop constituents and, in particular, 1,3(E),5(Z), 9-undecatetraene has not yet been reported as a food odorant. In an extract obtained from fresh hops, in addition to the odorants found in dry hops, (Z)-3-hexenal was characterized as a further key odorant rendering an additional green aroma note to the fresh material.     

Evaluation of aroma differences between hand-squeezed juices from Valencia late and Navel oranges by quantitation of key odorants and flavor reconstitution experiments

Twenty-five odor-active compounds were quantified in hand-squeezed juices of Valencia late and Navel oranges using stable isotope dilution assays. Odor activity values (OAVs, ratio of the concentration to odor thresholds) based on odor thresholds in water were calculated for the entire set of aroma compounds in both varieties. It was shown that due to their high OAVs, the fruity-smelling esters ethyl 2-methylpropanoate, ethyl butanoate, (S)-ethyl 2-methylbutanoate, and 3a,4,5,7a-tetrahydro-3,6-dimethyl-2(3H)-benzofuranone (wine lactone), the grassy smelling (Z)-hex-3-enal, and the citrus-like decanal were the most potent odorants in both juices. The weaker fruity note in the Navel oranges was clearly correlated with significantly lower OAVs of all fruity-smelling esters but a higher OAV of (Z)-3-hexenal compared to Valencia late. Model solutions simulating the odor of both orange varieties confirmed the findings of the quantitation studies.     

Impact of growing environment on chickasaw blackberry (Rubus L.) aroma evaluated by gas chromatography olfactometry dilution analysis

The aroma extract of Chickasaw blackberry (Rubus L.) was separated with silica gel normal phase chromatography into six fractions. Gas chromatography-olfactometry (GCO) was performed on each fraction to identify aroma active compounds. Aroma extraction dilution analysis (AEDA) was employed to characterize the aroma profile of Chickasaw blackberries from two growing regions of the United States: Oregon and Arkansas. Comparative AEDA analysis showed that the berries grown in the two regions had similar aroma compositions; however, those odorants had various aroma impacts in each region. The compounds with high flavor dilution factors in Oregon's Chickasaw were ethyl butanoate, linalool, methional, trans,cis-2,6-nonadienal, cis-1,5-octadien-3-one, and 2,5-dimethyl-4-hydroxy-3(2H)-furanone, whereas in the Chickasaw grown in Arkansas, they were ethyl butanoate, linalool, methional, ethyl 2-methylbutanoate, beta-damascenone, and geraniol.     

Glycosidically bound aroma compounds and impact odorants of four strawberry varieties

This paper reports the determination of glycosidically bound aroma compounds and the olfactometric analysis in four strawberry varieties (Fuentepina, Camarosa, Candonga and Sabrina). Different hydrolytic strategies were also studied. The results showed significant differences between acid and enzymatic hydrolysis. In general terms, the greater the duration of acid hydrolysis, the higher was the content of norisoprenoids, volatile phenols, benzenes, lactones, Furaneol, and mesifurane. A total of 51 aglycones were identified, 38 of them unreported in strawberry. Olfactometric analyses revealed that the odorants with higher modified frequencies were Furaneol, γ-decalactone, ethyl butanoate, ethyl hexanoate, ethyl 3-methylbutanoate, diacetyl, hexanoic acid, and (Z)-1,5-octadien-3-one. This last compound, described as geranium/green/pepper/lettuce (linear retention index = 1378), was identified for the first time. Differences with regard to fruity, sweet, floral, and green aroma characters were observed among varieties. In Candonga and Fuentepina, the green character overpowered the sweet. In the other two strawberry varieties sweet attributes were stronger than the rest.     

Studies on the key odorants formed by roasting of wild mango seeds (Irvingia gabonensis)

Application of the aroma extract dilution analysis on a concentrate of volatiles obtained by solvent extraction and high vacuum distillation from roasted seeds (180 degrees C; 15 min) of wild mango (Irvingia gabonensis) revealed 32 odor-active compounds with flavor dilution (FD) factors ranging from 8 (low odor activity) to 2048 (high odor activity). The identification experiments based on the use of reference odorants revealed methional (cooked potato-like) followed by 2-acetyl-1-pyrroline (roasty, popcorn-like), butan-2,3-dione, pentan-2,3-dione, 2-ethyl-3,5-dimethylpyrazine, and 2,3-diethyl-5-methylpyrazine as the key aroma compounds among the 27 odorants identified. All odorants are reported for the first time as components of roasted wild mango seeds.     

Evolution of chemical and sensory properties during aging of top-fermented beer

The aging and consequent changes in flavor molecules of a top-fermented beer were studied. Different aging conditions were imposed on freshly bottled beer. After 6 months of aging, the concentration changes were recorded for acetate esters, ethyl esters, carbonyls, Maillard compounds, dioxolanes, and furanic ethers. For some flavor compounds, the changes with time of storage were monitored at different temperatures, either with CO(2) or with air in the headspace of the bottles. For some molecules a relationship was determined between concentration changes and sensory evaluation results. A decrease in volatile esters was responsible for a reduced fruity flavor during aging. On the contrary, various carbonyl compounds, some ethyl esters, Maillard compounds, dioxolanes, and furanic ethers showed a marked increase, due to oxidative and nonoxidative reactions. A very high increase was found for furfural, 2-furanmethanol, and especially the furanic ether, 2-furfuryl ethyl ether (FEE). For FEE a flavor threshold in beer of 6 mug/L was determined. In the aged top-fermented beer, FEE concentrations multiple times the flavor threshold were observed. This was associated with the appearance of a typical solvent-like flavor. As the FEE concentration increased with time at an almost constant rate, with or without air in the headspace, FEE (and probably other furanic ethers) is proposed as a good candidate to evaluate the thermal stress imposed on beer.     

烹饪方式对安岳坛子肉风味的影响

为了解四川安岳坛子肉的特征风味及烹饪方式对其特征风味的影响,采用电子鼻、电子舌及气质联用仪研究不同烹饪方式(蒸制和烤制)对坛子肉风味物质组成及其含量的影响。结果表明,烤制坛子肉与生制坛子肉、蒸制坛子肉与生制坛子肉、烤制坛子肉与蒸制坛子肉的判别因子分析聚类差异极显著(P <0.01)。2种烹饪方式得到的熟制坛子肉的风味化合物主要包括醇类、醛类、酯类、酮类、醚类、含硫化合物和杂环化合物七大类。烤制形成的风味物质种类高达101种,常温蒸制61种,此外,异戊醇、乙醛、丁酸丁酯、乙酸乙酯、正己酸乙酯、吡啶、呋喃和丙酮构成蒸制坛子肉的特征风味,己醛、丁酸丁酯、正己酸乙酯和4-羟基-4-甲基-2-戊酮构成烤制坛子肉的特征风味。本研究结果为坛子肉即食食品的精深加工提供了理论依据。     

Main odorants in Jura flor-sherry wines. Relative contributions of sotolon, abhexon, and theaspirane-derived compounds

The aromatic profile of Jura flor-sherry wines (also called "yellow wines") has been little studied. Only acetaldehyde, diethoxy-1,1-ethane, and sotolon have been described as key odorants. In the present work, three wines (vintages 2002 and 2003) were investigated by gas chromatography-mass spectrometry and gas chromatography-olfactometry (GC-O) aroma extract dilution analysis. The goal was to assess the relative impact of varietal, fermentation, and oak-barrel compounds by using two complementary extraction procedures. No grape terpenoids were found after the long barrel aging (6 years and 3 months). On the other hand, two candy/fruity esters issued from yeast exhibited high flavor dilution factor (FD) values: ethyl isobutyrate (64-1024) and ethyl isovalerate (128-1024). As expected, many oak-related odorants were found in the XAD 2 flavor extracts, mainly homofuraneol [2-ethyl-4-hydroxy-5-methyl-3(2H)-furanone] (cotton candy, FD = 16-256) and cis-β-methyloctalactone (butter, woody, FD = 256). Most probably issued from oxidation of the grape constituent theaspirane, an exceptional grenadine odor was perceived by GC-O up to dilution 64-1024. Chemical oxidation experiments and GC-high-resolution mass spectrometry (HRMS) allowed us to identify it as 4-hydroxy-7,8-dihydro-β-ionone (RI(CPsil5CB) = 1373), a hydrolysis-derived product of dihydrodehydro-β-ionone. With an extraction dedicated to hydrophilic compounds, the key role of sotolon was confirmed (112-387 μg/kg; FD = 256-1024). This procedure enabled us to also evidence its ethyl analogue, abhexon (31-74 μg/kg; FD = 64-256).     

Comparison of the odor-active compounds in unhopped beer and beers hopped with different hop varieties

Odorants comprising the hop aromas of beers were examined. Strongly hopped beers with Saazer, Hersbrucker, and Cascade hops were compared with unhopped beer by gas chromatography-olfactometry (CharmAnalysis) and sensory evaluation. Twenty-seven odorants were revealed as hop-derived, which derived either directly from hops or via metabolization, and 19 components were identified. Of the components, linalool, geraniol, ethyl 2-methylbutanoate, ethyl 3-methylbutanoate, and ethyl 2-methylpropanoate were determined as odor-active components from their Charm values and aroma values. The muscat-like aroma of Cascade beer and the spicy aroma of Hersbrucker beer were predominant in sensory evaluation, and the contributors to these characteristics were investigated.