Potent aroma compounds of two red wine vinegars

Gas chromatography olfactometry (GCO) was used to determine key aroma compounds of two red wine vinegars. Sensory analysis was performed to choose the best neutralization agent of acetic acid (NaOH or MgO) and to test representativeness of four extracts obtained by different methods (dichloromethane extraction, XAD-2, mixture of XAD-2 and XAD-7, and Extrelut resins extraction). Neutralization with NaOH followed by dichloromethane extraction was selected to extract volatile compounds of vinegars. Key odorant compounds were determined by GCO based on detection frequency with 13 people. In the two red wine vinegars, 13 odors were perceived by at least 70% of the panelists, and 8 compounds among the 13 were identified: acetic acid, 3-methylbutyric acid, 2-phenyl-1-ethanol, 2, 3-butanedione, butyric acid, 2-methylbutyric acid, mixture of 2- and 3-methyl-1-butanol, and two newly identified compounds in vinegar, 3-hydroxy-2-pentanone and 3-(methylthio)-1-propanal. Quantification of all the volatile compounds was performed by GC-FID, and 10 other compounds were identified for the first time in wine vinegar.     

Characterization of the aroma of a wine from maccabeo. Key role played by compounds with low odor activity values

An extract from a dry young wine from Maccabeo was studied by aroma extract dilution analysis (AEDA), quantitative gas chromatography, and different sensory studies. In a first study, 53 different aroma compounds were quantified and used to prepare aroma models. 2-Methyl-3-furanthiol (FD = 16) and 4-methyl-4-mercaptopentan-2-one (FD = 2), could not be quantified and were not included in those models, which were not very similar to the original wine. Omission tests did not show the existence of impact compounds. In another set of experiments, selected aroma chemicals were added to the original wine, but in only in two cases (isoamyl acetate and gamma-nonalactone) was a positive effect noted, on banana and citric notes, respectively. After these discouraging results, 4-methyl-4-mercaptopentan-2-one and 2-methyl-3-furanthiol were quantified and included in the models. The concentration of the former was as low as 5 ng x L(-)(1) (odor threshold = 0.8 ng x L(-)(1)); however, its inclusion in the synthetic mixture had a significant effect, making it very close to the original wine. Its role was confirmed by omission tests. Results are briefly discussed.     

优选非酿酒酵母胞外酶增香酿造干白葡萄酒效果

为了研究非酿酒酵母胞外酶促进葡萄酒发酵产香的效果,该文在爱格丽葡萄汁酒精发酵12 h后,分别添加优选胶红酵母(Rhodotorula mucilaginosa,RM)胞外酶液,优选发酵毕赤酵母(Pichia fermentans,PF)胞外酶液和商业糖苷酶制剂(almondβ-glucosidase,AG)(10 mU/mL),以不添加酶制剂的酿酒酵母纯发酵为对照,发酵过程中每24 h取样,采用HS-SPME-GC/MS(headspace solid-phase microextraction-gas chromatography/mass spectrometry)监测挥发性成分的生成变化。葡萄酒含糖量低于2 g/L时终止发酵,低温满罐密封储存,次年4月,进行葡萄酒香气仪器和感官量化分析。胞外酶液共测得6种风味酶活性,其中RM酶液中的β-D-葡萄糖苷酶、α-L-鼠李糖苷酶、β-D-木糖苷酶活性均显著(P<0.05)高于PF中的,而α-L-阿拉伯糖苷酶和酯酶在PF酶液中活性更高(P<0.05)。发酵过程中,胞外酶处理显著促进了(P<0.05)品种香气和发酵香气物质的生成,其中RM酶液显著提高了萜烯类物质和苯乙基类化合物含量,其作用效果分别比商业酶处理高41.7%和31.8%,PF酶液显著促进了发酵香气化合物的生成,尤其是脂肪酸乙酯含量约为对照的2倍。酒样感官分析结果显示,两株酵母的胞外酶处理表现出各自增香酿造的优势,其中RM酶液促进温带酸果类香气的效果突出,PF酶液显著提升了柑橘类香气。研究结果为酵母风味酶应用于葡萄酒的增香酿造提供了理论和实践指导。     

Reconstitution of the flavor signature of Dornfelder red wine on the basis of the natural concentrations of its key aroma and taste compounds

By application of aroma extract dilution analysis (AEDA) on the volatile fraction isolated from a Dornfelder red wine, 31 odor-active compounds were identified by means of HRGC-MS and comparison with reference compounds. A total of 27 odorants, judged with high FD factors by means of AEDA, was quantitated by means of stable isotope dilution assays, and acetaldehyde was determined enzymatically. In addition, 36 taste-active compounds were analyzed by means of HPLC-UV, HPLC-MS/MS, and ion chromatography. The quantitative data obtained for the identified aroma and taste compounds enabled for the first time the reconstruction of the overall flavor of the red wine. Sensory evaluation of both the aroma and taste profiles of the authentic red wine and the recombinate revealed that Dornfelder red wine was closely mimicked. Moreover, it was demonstrated that the high molecular weight fraction of red wine is essential for its astringent taste impression. By comparison of the overall odor of the aroma recombinate in ethanol with that of the total flavor recombinate containing all tastants, it was shown for the first time that the nonvolatile tastants had a strong influence on the intensity of certain aroma qualities.     

Characterization of odor-active compounds in guava wine

The volatile compounds of guava wine were isolated by continuous solvent extraction and analyzed by GC-FID and GC-MS. A total of 124 volatile constituents were detected, and 102 of them were positively identified. The composition of guava wine included 52 esters, 24 alcohols, 11 ketones, 7 acids, 6 aldehydes, 6 terpenes, 4 phenols and derivatives, 4 lactones, 4 sulfur-compounds, and 5 miscellaneous compounds. The aroma-active areas in the gas chromatogram were screened by application of the aroma extract dilution analysis and by odor activity values. Twelve odorants were considered as odor-active volatiles: (E)-β-damascenone, ethyl octanoate, ethyl 3-phenylpropanoate, ethyl hexanoate, 3-methylbutyl acetate, 2-methyltetrahydrothiophen-3-one, 2,5-dimethyl-4-methoxy-3(2H)-furanone, ethyl (E)-cinnamate, ethyl butanoate, (E)-cinnamyl acetate, 3-phenylpropyl acetate, and ethyl 2-methylpropanoate.     

An assessment of the role played by some oxidation-related aldehydes in wine aroma

The levels of important oxidation-related aldehydes, such as methional, phenylacetaldehyde, (E)-2-hexenal, (E)-2-heptenal, (E)-2-octenal, (E)-2-nonenal, methylpropanal, 2-methylbutanal, and 3-methylbutanal, were determined in 41 different wines belonging to different types (young whites and reds, natural sparkling wines, oxidized young whites and reds, Sherry, aged red wines, Port wines). Except (E)-2-hexenal and (E)-2-heptenal, all of them could be found at levels above threshold. Different compositional patterns were identified: Sherry wines have large amounts of branched aldehydes but not of (E)-2-alkenals, wines exposed to oxygen can have large amounts of (E)-2-alkenals but not of branched aldehydes, while aged wine and Port have relatively large amounts of both classes of compounds. Different sensory tests confirmed the active sensory role of these compounds and revealed the existence of interactions (additive or synergic) between them and with other wine volatiles. (E)-2-Alkenals are related to flavor deterioration, while branched aldehydes enhance dried fruit notes and mask the negative role of (E)-2-alkenals.     

Concurrent phenomena contributing to the formation of the aroma of wine during aging in oak wood: an analytical study

Red wine was stored in different oak barrels or in stainless steel, and samples were taken for two years to determine 79 aroma compounds. Aging in oak affects 41 compounds. The type of wood affects 11 compounds. At least seven different processes seem to take place concurrently in aroma evolution, and five such processes, affecting 37 compounds, are linked to the oak cask. These are extraction from the wood, oxidation of wine alcohols and amino acids, microbiological formation of ethyl phenols, sorption processes, and condensation of acetaldehyde with polyphenols. The wood can release linear gamma- and delta-lactones, beta-damascenone, and ionones. Some compounds are released very fast from wood, which suggests they lie in the external part of the wood. Some extraction profiles are too complex to be explained by physical processes. Finally, the levels of 2,5-dimethyl-4-hydroxy-3(2H)-furanone and 2-ethyl-5-methyl-4-hydroxy-3(2H)-furanone increase even in the reference wine, which suggests the presence of a precursor.     

Possible mechanism for involvement of cysteine in aroma production in wine

Under conditions close to those of wine, that is, low pH, aqueous medium, and low temperatures, this work describes N-(2-sulfanylethyl)-2-oxopropanamide (1), a new intermediate in the formation of 2-acetylthiazole from methylglyoxal and cysteine. 1 was characterized by MS, derivatization MS, and (1)H and (13)C NMR and was synthesized from 2-sulfanylethanamine and ethyl pyruvate. A formation pathway for 2-acetylthiazole from methylglyoxal and cysteine is proposed, in which 1 is a new intermediate in Maillard-type reactions in systems under mild conditions.     

Influence of wine turbidity on the accumulation of volatile compounds from the oak barrel

In this work the influence of the turbidity of a red wine aged in oak barrels on the accumulation of volatile compounds has been studied. From the results obtained, it may be concluded that the wine turbidity had an effect on the concentration of many of the oak volatile compounds, especially furanic and phenolic compounds. In all cases the concentrations of furanic aldehydes and vanillin were significantly higher (p < 0.01) in the filtered wine than in the unfiltered wine. However, in the unfiltered wine the concentrations of gamma-butyrolactone and eugenol were higher. This difference in the concentrations would be due to the different compositions of the wines and the binding of compounds to some components of the lees. Likewise, it has been observed that the composition of the lees is fundamental in the binding of volatile compounds to the lees as the fermentative lees behave differently from the lees from the wine aging in barrels.     

Interactions between yeast lees and wine polyphenols during simulation of wine aging: I. Analysis of remnant polyphenolic compounds in the resulting wines

Wine aging on yeast lees is a traditional enological practice used during the manufacture of wines. This technique has increased in popularity in recent years for the aging of red wines. Although wine polyphenols interact with yeast lees to a limited extent, such interactions have a large effect on the reactivity toward oxygen of wine polyphenolic compounds and yeast lees. Various domains of the yeast cell wall are protected by wine polyphenols from the action of extracellular hydrolytic enzymatic activities. Polysaccharides released during autolysis are thought to exert a significant effect on the sensory qualities of wine. We studied the chemical composition of polyphenolic compounds remaining in solution or adsorbed on yeast lees after various contact times during the simulation of wine aging. The analysis of the remnant polyphenols in the wine indicated that wine polyphenols adsorption on yeast lees follows biphasic kinetics. An initial and rapid fixation is followed by a slow, constant, and saturating fixation that reaches its maximum after about 1 week. Only very few monomeric phenolic compounds remained adsorbed on yeast lees, and no preferential adsorption of low or high polymeric size tannins occurred. The remnant condensed tannins in the wine contained fewer epigallocatechin units than the initial tannins, indicating that polar condensed tannins were preferentially adsorbed on yeast lees. Conversely, the efficiency of anthocyanin adsorption on yeast lees was unrelated to its polarity.     

Effect of oak extract application to Verdejo grapevines on grape and wine aroma

Volatile compounds from a commercial aqueous oak extract application to white Verdejo grapevines at veraison have been studied. Treated grapes under two types of formulation (25% and 100%) have been analyzed at the optimum maturation time, and winemaking was then subsequently carried out. The volatile compounds were analyzed by stir bar sorptive extraction-gas chromatography-mass spectrometry. The results suggest that after the grapevine treatments, grapes store the volatiles in the form of nonvolatile precursors, and some of the volatiles are released during the winemaking process, especially six months after the alcoholic fermentation. The sensory analysis shows that wines maintain the typical aroma properties of Verdejo wines at the end of fermentation; but after six months, the wine color is greener and more astringent, and, in terms of aroma, it has wooden notes as if the wine has been aged in oak barrels.     

Hydrolysis of wine aroma precursors during malolactic fermentation with four commercial starter cultures of Oenococcus oeni

The ability of four commercial preparations of Oenococcus oeni lactic acid bacteria (EQ 54, Lalvin OSU, Uvaferm Alpha, and Lalvin 31) to hydrolyze wine aroma precursors was evaluated by measuring the concentration of free and bound aroma compounds at the end of malolactic fermentation carried out in model wines containing a mixture of glycosides extracted from Muscat wine. At pH 3.4 there was a decrease in glycosylated compounds matched by a concomitant increase in free forms in all starter cultures tested. When malolactic fermentation was carried out at pH 3.2, a significant decrease in the ability to hydrolyze aroma precursors was observed for two of the cultures tested (Uvaferm Alpha and Lalvin 31). Large differences in the extent of hydrolysis and in the specificity of this activity toward specific aroma precursors were observed and appeared to be related to the chemical structure of the aglycon as well as to individual characteristics of each starter culture. The amounts of glycosylated aroma compounds released during malolactic fermentation suggest that O. oeni can alter the sensory characteristics of wine through the hydrolysis of aroma precursors.     

Interactions between yeast lees and wine polyphenols during simulation of wine aging. II. Analysis of desorbed polyphenol compounds from yeast lees

In the first part of this work, the analysis of the polyphenolic compounds remaining in the wine after different contact times with yeast lees during simulation of red wine aging was undertaken. To achieve a more precise view of the wine polyphenols adsorbed on lees during red wine aging and to establish a clear balance between adsorbed and remnant polyphenol compounds, the specific analysis of the chemical composition of the adsorbed polyphenolic compounds (condensed tannins and anthocyanins) after their partial desorbtion from yeast lees by denaturation treatments was realized in the second part of the study. The total recovery of polyphenol compounds from yeast lees was not complete, since a rather important part of the initial wine colored polyphenols, especially those with a dominant blue color component, remained strongly adsorbed on yeast lees, as monitored by color tristimulus and reflectance spectra measurements. All anthocyanins were recovered at a rather high percentage (about 62%), and it was demonstrated that they were not adsorbed in relation with their sole polarity. Very few monomeric phenolic compounds were extracted from yeast lees. With the use of drastic denaturing treatments, the total recovery of condensed tannins reached 83%. Such tannins extracted from yeast lees exhibited very high polymeric size and a rather high percentage of galloylated residues by comparison with initial wine tannins, indicating that nonpolar tannins were preferentially desorbed from yeast lees by the extraction treatments.     

Odor potency of aroma compounds in Riesling and Vidal blanc table wines and icewines by gas chromatography-olfactometry-mass spectrometry

This study aimed to elucidate the odor potency of aroma compounds in Riesling and Vidal blanc (syn. Vidal) table wines and icewines from the Niagara Peninsula using stir bar sorptive extraction-gas chromatography-olfactometry-mass spectrometry. Dilution analysis determined the most odor-potent compounds in Vidal and Riesling icewines (n = 2) and table wines (n = 2) from a commercial producer. The top 15 odor-potent compounds in each wine were identified and quantified, resulting in 23 and 24 compounds for Riesling and Vidal, respectively. The most odor-potent compounds were β-damascenone, decanal, 1-hexanol, 1-octen-3-ol, 4-vinylguaiacol, ethyl hexanoate, and ethyl 3-methylbutyrate. In general, icewines had higher concentrations of most aroma compounds compared to table wines. Through computation of odor activity values, the compounds with the highest odor activity for the icewines were β-damascenone, 1-octen-3-ol, ethyl octanoate, cis-rose oxide, and ethyl hexanoate. In table wines the highest odor activity values were found for ethyl octanoate, β-damascenone, ethyl hexanoate, cis-rose oxide, ethyl 3-methylbutyrate, and 4-vinylguaiacol. These findings provide a foundation to determine impact odorants in icewines and the effects of viticultural and enological practices on wine aroma volatile composition.     

Effect of macerating enzymes on red wine aroma at laboratory scale: exogenous addition or expression by transgenic wine yeasts.

The effects of a Trichoderma longibrachiatum endoglucanase and an Aspergillus nidulans endoxylanase on the concentration of free and bound volatiles, color, and phenolics during maceration in red wine vinification has been studied. Two different approaches have been considered for the utilization of these enzymes: (i) direct addition of the enzymes to must and (ii) inoculation of must with recombinant wine yeasts overexpressing these activities. An experimental design based on a Taguchi orthogonal array was carried out in order to evaluate the effects of the enzymatic treatments. The data show that these fungal activities are able to increase the concentrations of free and glycosidically bound flavor compounds, color, and phenolics to similar or greater extents as compared to a commercial pectolytic enzyme preparation. The effects of the two different ways of addition of the enzymes were not always equivalent. These enzymes could be considered to be of potential application in the red wine maceration process.     

Solid-phase microextraction and gas chromatography olfactometry analysis of successively diluted samples. A new approach of the aroma extract dilution analysis applied to the characterization of wine aroma

The relationship between the composition and the aroma of the wine can be established by using gas chromatography with olfactometric detection (sniffing or GCO), which combines the chromatographic response with the human nose response. To evaluate the contribution of the odor compounds in wine aroma, we designed a new approach of the aroma extract dilution analysis (AEDA) that lies in the GCO analysis of serially diluted wine samples using headspace solid-phase microextraction (HS-SPME) as the extraction technique. The fiber coating used was Flex divinyl-carboxen-polydimethylsiloxane. The method developed was applied to determine the aromatic composition of a red Grenache wine from Priorat (Spain). The method allows 38 important odorants to be determined in the AEDA study, 30 of them precisely identified. These results are similar to those reported by other studies related to this variety of wine. HS-SPME is a suitable technique to obtain representative extracts of wine aroma with several advantages such as simplicity, speediness, and little sample manipulation.     

Orosensory-directed identification of astringent mouthfeel and bitter-tasting compounds in red wine

Application of sequential solvent extraction, followed by HPLC combined with the taste dilution analysis, enabled the localization of the most intense velvety astringent, drying, and puckering astringent, as well as bitter-tasting, compounds in red wine, respectively. Isolation of the taste components involving gel adsorption chromatography, ultrafiltration, and synthesis revealed the identification of 26 sensory-active nonvolatiles, among which several hydroxybenzoic acids, hydroxycinnamic acids, flavon-3-ol glycosides, and dihydroflavon-3-ol rhamnosides as well as a structurally undefined polymeric fraction (>5 kDa) were identified as the key astringent components. In contradiction to literature suggestions, flavan-3-ols were found to be not of major importance for astringency and bitter taste, respectively. Surprisingly, a series of hydroxybenzoic acid ethyl esters and hydroxycinnamic acid ethyl esters were identified as bitter compounds in wine. Taste qualities and taste threshold concentrations of the individual wine components were determined by means of a three-alternative forced-choice test and the half-mouth test, respectively.     

戴尔有孢圆酵母调控晚采小芒森葡萄酒乙酸和香气

为降低甜型葡萄酒中的挥发酸,进一步增加其香气复杂度,该研究利用本土戴尔有孢圆酵母R12与酿酒酵母NX11424同时接种和顺序接种发酵,研究其对贺兰山东麓产区晚采小芒森葡萄酒乙酸及香气成分的调控。与酿酒酵母单菌发酵相比,本土戴尔有孢圆酵母与酿酒酵母按照5:1、20:1、50:1的不同菌体数量比例同时接种和间隔5 d顺序接种发酵,均可以显著降低晚采小芒森葡萄酒的乙酸含量,其乙酸产率分别降低19.1%、21.2%、38.2%和48.9%。此外,按20:1比例同时接种发酵,可显著提高晚采小芒森葡萄酒中萜烯类和降异戊二烯类等品种香气物质含量,和乙酸异戊酯、丁酸乙酯及苯乙醇等发酵香气物质的含量。该研究表明合理的酿酒酵母接种发酵能有效降低高糖原料酿造葡萄酒挥发酸含量,为贺兰山东麓产区葡萄酒新产品的开发提供了的技术参考。