Approaches to spirit aroma: contribution of some aromatic compounds to the primary aroma in samples of orujo spirits

Terpenes and C(13) norisoprenoids are among the most important aromatic compounds found in a volatile and nonvolatile form in grapes. Aromatic typicity of a spirit could be attributed to these compounds despite the very important presence of volatile compounds produced during alcoholic fermentation. In this study, following a solid phase extraction stage, the determination of the varietal aromatic compounds by gas chromatography was performed on 15 samples of Galician orujo spirits. The results show that significant differences (p < 0.05) exist in the concentrations of varietal aromatic compounds in Galician spirits obtained from different varieties of grapes. alpha-Ionona is the varietal aromatic compound that is most likely to contribute to the aroma of all of the spirits studied. The spirits from Catalan Roxo are the most aromatic, with floral and fruity nuances, while the spirits from Godello were the less aromatic group as far as the varietal compounds studied are concerned. Spirits from Mencia and Treixadura show a similar profile, but the former has a more intensive aroma due to beta-pinene, citronellol, and alpha-ionone. Albari?o spirits stand out because of their profile that is marked by the contributions of eugenol and linalool.     

Sensory and chemical characterization of the aroma of a white wine made with Devín grapes

The aroma profile of a Slovak white wine made with Devín grapes was evaluated by 13 expert judges. The panel evaluated the orthonasal and retronasal aroma profiles, as well as the profile of residual wine aroma found in the empty glass after the consumption. For the majority of attributes, the orthonasal perception was the most intense, followed by retronasal, and finally by the residual odor. Varietal wine Devín possessed primarily a "Muscat" odor by nose, together with intense fruity, sweet, and herbaceous notes. Data were analyzed by generalized procrustes analysis. Two primary clusters separated orthonasal ratings from both retronasal and residual odor ratings. Similar results were obtained by analysis of variance. The relative proportion of "heavy" aroma notes, likely related to polar odorants, increased in retronasal and residual odor profiles. The gas chromatography-olfactometry profile revealed a great complexity and showed that the characteristic aroma of this variety seems to be a mixture of Muscat, Gewürztraminer, and Sauvignon-Blanc, being rich in linalool, cis-rose oxide, and 4-methyl-4-mercaptopentanone.     

Changes in the volatile profile of oats induced by processing

Samples of an Australian oat cultivar, Echidna, were pilot-scale processed. At each stage of the processing (raw oats, groats, kiln dried dehulled oats (KDHO), and rolled (flaked)) samples were removed for later sensory and GC-MS analysis of the flavor components. Mean taste panel scores from a trained taste panel were calculated according to attributes (cereal, burnt, toasted, floury, and yeasty). Attributes were generally similar for both KDHO and flaked oats except in the yeasty attributes. Panelists were able to differentiate between groats, KDHO, and flaked oats (raw oats were not included). The largest effects of heat processing were found for the attributes toasted and yeasty aroma; toasted, cereal, and yeasty flavor; and toasted and yeasty aftertaste. A multi-organoleptic sensor analyzer was able to differentiate all samples when the output was subjected to discriminant function analysis. A reintroduced sample was recognized with a confidence level better than 96%. Solid-phase microextraction (SPME) of headspace followed by GC--MS was used to identify volatiles after either dry or slurry heating. Several SPME fiber types were evaluated as to their ability to sorb oat volatiles. A 100-microm poly(dimethylsiloxane) SPME fiber was found to provide the best adsorption profile as measured by number of compounds sorbed and peak area response. A range of alcohols, aldehydes, alkyl benzenes, dienes, and ketones was identified in the processed samples.     

Quality and aromatic sensory descriptors (mainly fresh and dry fruit character) of Spanish red wines can be predicted from their aroma-active chemical composition

A satisfactory model explaining quality could be built in a set of 25 high quality Spanish red wines, by aroma-active chemical composition. The quality of the wines was positively correlated with the wine content in fruity esters, acids, enolones, and wood derived compounds, and negatively with phenylacetaldehyde, acetic acid, methional, and 4-ethylphenol. Wine fruitiness was demonstrated to be positively related not only to the wine content on fruity esters and enolones, but to wine volatile fatty acids. Fruitiness is strongly suppressed by 4-ethylphenol, acetic acid, phenylacetaldehyde, and methional, this involved in the perception of dry-fruit notes. Sensory effects were more intense in the presence of β-damascenone and β-ionone. A satisfactory model explaining animal notes could be built. Finally, the vegetal character of this set of wines could be related to the combined effect of dimethylsulfide (DMS), 1-hexanol, and methanethiol.     

Monitoring toasting intensity of barrels by chromatographic analysis of volatile compounds from toasted oak wood.

Toasting changes both the quantity and the quality of the extractable substances in the oak wood of barrels used for the aging of fine wines and spirits. Mastery and repeatability of toasting are vital in the production of quality barrels to be used for the aging of wines and spirits. In this study, we show that it is possible for a given cooperage to differentiate barrel toasting levels by analyzing a certain number of volatile and semivolatile compounds resulting from the thermal degradation of oak. Toasted wood components, which can be extracted by the wines or spirits during the aging process, are normally analyzed after the wood has soaked in standard alcoholic solutions and can be used to control the intensity of the wood toasting. The results of the comparative analysis presented in this work show that headspace analysis with a microextractive method using a stationary polydimethylsiloxane type phase is a promising technique for analyzing toasted oak wood from barrels. It is easier to use than the traditional maceration and extraction method and provides similar information.     

Correlating volatile compounds, sensory attributes, and quality parameters in stored fresh-cut cantaloupe

Changes in post-cutting volatiles, quality, and sensory attributes during fresh-cut storage (4 degrees C) of cantaloupe (Cucumis melo L. var. Reticulatus, Naudin, cv. 'Sol Real') harvested at four distinct maturities (1/4-, 1/2-, 3/4-, and full-slip) were investigated after 0, 2, 5, 7, 9, 12, and 14 days in a 2-year study. Increased fruity and sweet taste attributes were negatively correlated with percent acetates, aromatic acetates, and total aromatic compounds, and positively correlated with percentage non-acetate esters. Ethyl hexanoate was strongly positively correlated with fruity and sweet taste. Cucurbit, water-like, hardness, cohesiveness, and denseness were positively correlated with percentage acetates, aromatic acetates, and total aromatic compounds, and negatively correlated with percentage non-acetate esters. Several non-acetate esters such as ethyl 2-methyl propanoate, ethyl butanoate, ethyl 2-methyl butanoate, and ethyl hexanoate were negatively (often strongly) correlated with cucurbit. Hardness was positively and strongly correlated with aromatic acetates and all aromatic (benzyl) compounds. In summary, firmer and denser cubes contained more acetates and fewer non-acetate esters. The apparently negative or undesirable attributes cucurbit and water-like were associated with higher acetates and aromatic compounds. Overall, relatively strong (year x maturity x day) correlations among numerous physiological, volatile, and sensory measures were found in this study. Highly significant (stronger) correlations were found in a year x day analysis used to pair maturity means; however, year and interaction effects require prudence when interpreting that data. Nonetheless, both analyses delivered almost identical trends, and strong correlations occurred even though samples were randomized from numerous fruits, per maturity, per juice catcher container, over 2 years. Further interpretation and biochemical explanation are needed to rationalize why mainly only non-acetate esters were highly correlated with desirable sensory and quality parameters.     

Influence of packaging on the aroma stability of strawberry syrup during shelf life

Different types of packaging (glass bottle, PVC, and PET) were compared for the preservation of aroma quality of a strawberry syrup during shelf life. Esters, alcohols, and aldehydes were analyzed by solid-phase micro-extraction (SPME) and solvent extraction. During storage, hydrolysis of esters in acids and alcohols led to a modification of the aroma profile which can be explained by the replacement of "fruity" and "fresh" notes by "dairy note" in the syrup. Aroma compounds that are responsible for fruity notes, such as methyl cinnamate, methyl anthranilate, and methyl dihydrojasmonate, were strongly reduced after 90 days. This could be explained by a selective interaction of these compounds with the polymer matrix (PET or PVC). After 330 days, a later and important decrease of the "fruity notes" occurred in both PETs; so PVC2 and the glass bottle were found to be able to maintain a balanced aroma for long-term storage.     

Quantification of selected volatile constituents and anions in Mexican Agave spirits (Tequila, Mezcal, Sotol, Bacanora)

A large collection (n = 95) of Mexican Agave spirits with protected appellations of origin (Tequila, Mezcal, Sotol, and Bacanora) was analyzed using ion and gas chromatography. Because of their production from oxalate-containing plant material, all Agave spirits contained significant concentrations of oxalate (0.1-9.7 mg/L). The two Tequila categories ("100% Agave" and "mixed") showed differences in the methanol, 2-/3-methyl-1-butanol, and 2-phenylethanol concentrations with lower concentrations in the mixed category. Mezcal showed no significant differences in any of the evaluated parameters that would allow a classification. Sotol showed higher nitrate concentrations and lower 2-/3-methyl-1-butanol concentrations. Bacanora was characterized by exceptionally high acetaldehyde concentrations and a relatively low ethyl lactate content. The methanol content was the most problematic compound regarding the Mexican standards: two Tequilas (4%), five Sotols (31%), and six Bacanoras (46%) had levels above the maximum methanol content of 300 g/hL of alcohol. In conclusion, the composition of Mexican Agave spirits was found to vary over a relatively large range.     

Impact of toasting oak barrels on the presence of polycyclic aromatic hydrocarbons in wine

Toasting Quercus sp. oak wood is one of the key stages in manufacturing barrels intended for aging wines and spirits. During this operation, the increase in temperature causes variable modifications in the physical structure and, more importantly, the chemical composition of the wood. Polycyclic aromatic hydrocarbons (PAH) are high-risk molecules likely to be formed during toasting of the wood and later extracted by wine or spirits in direct contact with the barrel. In the context of an analysis of all potential sources of risk associated with the manufacture of barrels for winery use [prevention policy defined using a Hazard Analysis Critical Control Point (HACCP) approach], we carried out a preliminary study to provide a more accurate assessment of potential risks related to the presence of PAH in cooperage and winemaking. Wood toasted to different levels under different conditions, as well as wines aged in barrels made using different methods, was analyzed by gas chromatography and mass spectrometry (GC-MS) for the identification of the main PAH present, quantification of each of the molecules extracted, and estimation of any possible toxicological risks, via a comparison of values with those measured in other types of food. The results clearly showed that the heating processes associated with barrel production actually resulted in the formation of various molecules in the PAH family. However, only a minority of the target PAH presented high toxicity, particularly carcinogenic potential. Because of the specific toasting process used, benzo[a]pyrene, the best-known, and one of the most dangerous, contaminants, was not significantly present in toasted barrel wood. In view of the PAH concentrations in wood and the low solubility of these compounds, their extraction in wine is apparently relatively slow and limited. Finally, comparing the overall PAH concentrations, and particularly those of the most toxic compounds, with estimated absorption from food or the environment, we found it was obvious that the contribution of toasted barrels to the total amount was extremely low and should not, therefore, be considered a major health concern.     

Fermentation of white wines in the presence of wood chips of American and French oak

Must obtained from Airén grapes was fermented in the presence of wood chips (4 and 7 g/L) of either French oak (from Vosges, central France, and Allier zones) or American oak. Fermentation yields were higher than in the control fermentations carried out in the absence of wood, and production of volatile substances during fermentation (alcohols, esters, and acetates) was also higher. The volatile substances that leached out of the wood were analyzed by GC-MS-SIR. The results showed that their concentrations depended on the type and amount of the oak; some of these substances were consumed in part by the yeasts during fermentation. A taste panel favorably assessed the wines produced by fermentation in the presence of oak chips, which retained part of the must original fruity aroma.     

Which impact for beta-damascenone on red wines aroma?

beta-Damascenone, a C-13 norisoprenoid compound, is usually presented as an impact odorant in red wines. Its direct contribution to their aroma was investigated. Both free beta-damascenone and beta-damascenone precursors were isolated from various French red wines and then analyzed by gas chromatography-mass spectrometry, revealing concentrations in the vicinity of 1 and 2 microg/L for free compounds and both forms, respectively. Gas chromatography-olfactometry analyses were also performed on dilutions of both red wine extracts and pure beta-damascenone. The very low detection threshold in olfactometry for this compound explains why it is found at the highest dilution factor in aroma extract dilution analysis methods. Moreover, determination of beta-damascenone's odor thresholds confirmed the huge importance of the matrix: beta-Damascenone is characterized by a very low perception threshold in hydroalcoholic solution as compared to red wine, where it is over 1000-fold higher. In hydroalcoholic solution, beta-damascenone enhanced fruity notes of ethyl cinnamate and caproate and masked the herbaceous aroma of IBMP. Globally, these results suggested that beta-damascenone has more an indirect than a direct impact on red wine aroma.     

Volatile components of Loureira, Dona Branca, and Treixadura wines.

White wines experimentally produced from the white grape varieties Loureira, Dona Branca, and Treixadura have been analyzed over four consecutive harvests. The contents of monoterpenes, volatile phenols, alcohols, sulfur components, acetates, fatty acids, and ethyl esters were determined by gas chromatography (FID) and gas chromatography-mass spectrometry. The mean values from four vintages confirmed that these wines have characteristic profiles. Loureira wines are characterized by a high content of free terpenes, 1-hexanol, ethyl acetate, and fatty acids. Dona Branca wines present the highest concentrations of methanol and sulfur constituents, and the lowest concentrations of higher alcohols, acetates, diethyl succinate, and ethyl esters. The levels of monoterpenes in Treixadura wines are very low, but they have the highest concentrations of volatile phenols, principally due to the vanillin, diethyl succinate, ethyl lactate, and ethyl esters. These results were confirmed by principal component and linear discriminant analysis, which show a clear differentiation among these wines as a function of the varietal origin.     

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.     

Investigation of volatiles evolution during the alcoholic fermentation of grape must using free and immobilized cells with the help of solid phase microextraction (SPME) headspace sampling

A biocatalyst was prepared by immobilization of Saccharomyces cerevisiae strain AXAZ-1 on delignified cellulosic material (DCM). Repeated batch fermentations were conducted using these biocatalysts and free cells, separately, at temperatures of 20, 15, and 10 degrees C. Solid phase microextraction (SPME) was used in monitoring the formation of volatile alcohols, acetate esters, and ethyl esters of fatty acids. The kinetics of volatile production were similar for free and immobilized cells. In all cases immobilized cells showed a better rate of volatile production, which was directly connected to sugar consumption. The main difference observed was in propanol production, which increased with temperature decrease for the immobilized cells, whereas it remained constant for the free ones. In the case of immobilized cells significant amounts of esters were also produced. It is well-known that esters contribute to the fruity aroma of wine. It was also established that SPME is a very sensitive, accurate, and reliable technique and can be used without any reservation in the characterization of volatile constituents of wine.     

Phenolic constituents, furans, and total antioxidant status of distilled spirits.

The concentrations of 11 phenols and 5 furans were measured in 12 categories of distilled spirits by HPLC methodology, together with the total antioxidant status (TAS) of the same beverages. Ellagic acid was the phenol present in highest concentration in all beverages. Moderate amounts of syringaldehyde, syringic acid, and gallic acid, as well as lesser amounts of vanillin and vanillic acid, were measurable in most samples of whiskey, brandy, and rum but were largely undetectable in gin, vodka, liqueurs, and miscellaneous spirits. 5-(Hydroxymethyl)furfural was the predominant furan in the former three beverages, notably cognac, with 2-furaldehyde the next highest, but these were undetectable in most of the latter beverages. Highest TAS values were given by armagnac, cognac, and bourbon whiskey, all three of which tended toward the highest concentrations of phenols. Negative TAS values were exhibited by rum, vodka, gin, and miscellaneous spirits in line with the low or undetectable phenol concentrations in these beverages. Wood aging is the most likely source of phenols and furans in distilled spirits. Those beverages exposed to this treatment contain significant antioxidant activity, which is between the ranges for white and red wines, with the potential to augment the antiatherosclerotic functions attributable to the ethanol that they contain.     

Volatile components in fermented soybean (Glycine max) curds.

Volatile components of three commercial fermented soybean (Glycine max) curds (FSC) (A-C) were extracted using a simultaneous steam distillation and extraction apparatus, and extracts were analyzed by gas chromatography/mass spectrometry. A total of 111 compounds was found. Sixty-three compounds were common to all three brands. Brands A, B, and C contained 90, 90, and 82 components, respectively. Major classes of compounds included alcohols (32) and esters (25). Similarities and differences existed in the composition of the FSC samples. Twelve common compounds including six esters, four alcohols, one ketone, and one miscellaneous compound had a dry weight of >1000 microg/kg of sample. Quantitative differences existed among the commercial brands (p<0.05). The quantity of ethanol detected might produce large numbers of ethyl esters that contribute to the desirable fruity and floral notes for the final products.     

Headspace solid-phase microextraction gas chromatography-mass spectrometry analysis of volatiles in orujo spirits from a defined geographical origin

A headspace solid-phase microextraction (HS-SPME) and gas chromatography-selective ion monitoring/mass spectrometry (GC-SIM/MS) method was optimized for analysis of 22 volatile compounds in orujo spirit samples from the Geographic Denomination "Orujo de Galicia/Augardente de Galicia". HS-SPME experimental conditions, such as fiber coating, extraction temperature, extraction and pre-equilibrium time, sample volume, and the presence of salt, were studied to improve the extraction process. The best results were obtained using a 65 microm Carbowax-divinylbenzene fiber during a headspace extraction at 40 degrees C with constant magnetic stirring for 15 min and after a 5 min period of pre-equilibrium time. The sample volume was 6 mL of orujo containing 25% of NaCl, placed in 12 mL glass vials equipped with a screw cap and PTFE/silicone septum. Desorption was performed directly in the gas chromatograph injector port for 5 min at 250 degrees C using the splitless mode. The proposed method is sensible (with detection limits between 0.0045 and 0.2399 mg/L), precise (with coefficients of variation in the range 0.99-8.18%), and linear over more than 1 order of magnitude. The developed method presented recoveries comprised between 76.0 and 112.4%. The applicability of the new method was demonstrated by determining the considered 22 volatile compounds in nine orujo commercial samples with quality and origin brands.