GC/MS-positive ion chemical ionization and MS/MS study of volatile benzene compounds in five different woods used in barrel making

Extracts from acacia, chestnut, cherry, mulberry, and oak wood, used in making barrels for aging wine and spirits were studied by GC/MS positive ion chemical ionization (PICI). Wood chips were extracted by a 50% water/ethanol solution and a tartrate buffer pH 3.2-12% ethanol (model wine) solution. The principal compounds identified in extracts were guaiacol-containing aldehydes and alcohols, such as benzaldehyde and derivatives, vanillin and syringaldehyde, cinnamaldehyde and coniferaldehyde, eugenol and methoxyeugenol, guaiacol and methoxyguaiacol derivatives. PICI using methane as reagent gas produced a high yield of the protonated molecular ion of volatile phenols, compound identification was confirmed by collision-induced-dissociation (CID) experiments on [M + H](+) species. MS/MS fragmentation patterns were studied with standard compounds: guaiacol-containing molecules were characterized by neutral methyl and methanol losses, benzaldehyde derivatives by CO loss. Acacia wood extracts contained significant syringaldehyde and anisaldehyde, but no eugenol and methoxyeugenol. Significant syringaldehyde, eugenol and methoxyeugenol, and high vanillin were found in chestnut and oak wood extracts; low presence of volatile benzene compounds was found in mulberry wood extracts. Cherry wood extracts were characterized by the presence of several benzaldehyde derivatives and high trimethoxyphenol.     

Effect of the aging on lees and other alternative techniques on the low molecular weight phenols of Tempranillo red wine aged in oak barrels

The effect of different alternative techniques to the traditional aging on lees on the low molecular weight phenolic compounds of red wines was study as well as their evolution during the aging in oak wood barrels for six months. The study was carried out with Tempranillo red grapes from two consecutive vintages. The techniques assayed were the traditional aging on lees with or without the addition of exogenous β-glucanase enzymes, the use of yeast derivative preparations also with or without the addition of exogenous β-glucanase enzymes, the micro-oxygenation applied together with the aging on lees, and the use of non-toasted oak wood chips.     

Analysis for low molecular weight phenolic compounds in a red wine aged in oak chips

The evolution of low molecular weight polyphenols in a red wine aging in different systems (barrels, oak chips and oak staves) made of different oak species was studied. All were placed under the same aging conditions in a wine cellar participating the Cigales Appellation of Origin programme (Spain). The wine aged in contact with oak chips experienced a quicker aging and loss of certain compounds, and a greater number of polymerisations than the wine aged in barrels. The discriminant analysis showed that samples of the same source wine aged in barrels, oak chips and oak staves tended to group together according to the aging system when wood from different botanical species is used (American, French or Hungarian).     

Improved method for extraction of aroma compounds in aged brandies and aqueous alcoholic wood extracts using ultrasound

This work presents a rapid method for dichloromethane extraction of aroma compounds from brandies and aqueous-alcoholic wood extracts, in brandy-like ageing conditions, using ultrasound. The dichloromethane extracts were injected in split mode on a gas chromatographic (GC) system, separated on a DB-WAX capillary column and detected by flame ionisation. The method allowed satisfactory quantification of 37 volatile compounds in brandies (alcohols, esters, acids, furanics, aldehydes and phenols) and 16 volatile compounds in aqueous-alcoholic oak extracts. Linear responses were obtained (0.99-1.00). The repeatability and the detection and quantification limits were also evaluated. The analysis of spiked samples showed that matrix effects do not affect the method performance for the majority of the volatile compounds analysed.     

Changes in wine volatile compounds of varietal wines during ageing in wood barrels

Twelve single-variety wines were aged in new American oak barrels. A control wine of each variety without ageing in wood was also studied. The volatile aroma composition of these wines was analysed after the following combinations of time in wood and time in bottle: 0 months in wood plus 18 months in bottle, 4 months in wood plus 14 months in bottle, 9 months in wood plus 12 months in barrel and 12 months in barrel plus 6 months in bottle.The data obtained were studied by two different multivariate methods: factor analysis by principal components and stepwise linear discriminant analysis. The results obtained showed that the capacity of wine to extract the volatile compounds from the wood depended on the variety of grape used. Furthermore, it was also found that the changes in the volatile composition of the wines induced by the wood ageing were more important during the first 4 months. In addition, the volatile compounds studied allowed to differentiate and correctly classify the wines according to the time they had been in contact with the wood.     

Volatile compounds as markers of ageing in Tempranillo red wines from La Mancha D.O. stored in oak wood barrels

Solid-phase extraction cartridges (SPE)-GC/MS method was used to analyse red wines aromas. The matrix effect was studied with chemicals standard prepared in synthetic wines with water/alcohol solutions (12% ethanol, v/v) following the procedure proposed. The method offers good reproducibility since the relative standard deviations (RSD%) for the volatile compounds levels were less than 9%. This method was used to differentiate the aroma of one hundred mono-varietal young, crianza, reserva and gran reserva La Mancha D.O. wines (cv. Tempranillo) on the basis of oak barrel contact period. Samples were checked at ten time points over 36 months. Sixty important wine odorants, such as volatile phenols, vanillin derivatives, lactones, norisoprenoids, benzene compounds, esters and terpenols, can be quantitatively determined in a single run. Results showed significant quantitative differences in the volatile profiles of wines depending on the length of time in contact with wood, even in wines belonging to the same commercial category. Stepwise multiple linear regression (SMLR) was used to obtain a model that predicted the time of barrel ageing to which wines were submitted in relation with the wine volatile composition. A successful function based on eight compounds with a mean deviation of 0.37 months in the predictions, was obtained.     

Application of Chromatography and Spectrometry to the Authentication of Alcoholic Beverages

The use of gas chromatography (GC), gas chromatography–mass spectrometry (GC–MS), and UV–VIS spectrophotometry for identifying the falsification of strong alcoholic beverages (vodka, gin, cognac, and whiskey) was considered. In the GC analysis of ethyl alcohol and vodkas based on it, the test alcohol was assigned to synthetic alcohol or to biochemically produced alcohol using a set of typical impurities, markers of the alcohol nature, which present in the test alcohol in a certain ratio and can be determined by GC or GC–MS analysis. The multicomponent analysis of cognacs and related liquors can reveal the replacement of cognac spirit with alcohol produced from nongrape raw materials, to determine whether the cognac spirit was in contact with oak wood and how long was the duration of its aging, and to detect the falsification of the age by adding certain ingredients. The limitations of chromatographic and spectrometric analytical techniques in the identification of adulterated alcoholic beverages was demonstrated. The validation criteria for testing the identification of alcoholic beverage components by chromatographic techniques received special attention.     

Nontargeted GC–MS approach for volatile profile of toasting in cherry,chestnut, false acacia,and ash wood

By using a nontargeted GC–MS approach, 153 individual volatile compounds were found in extracts from untoasted, light toasted and medium‐toasted cherry, chestnut, false acacia, as well as European and American ash wood, used in cooperage for aging wines, spirits and other beverages. In all wood types, the toasting provoked a progressive increase in carbohydrate derivatives, lactones and lignin constituents, along with a variety of other components, thus increasing the quantitative differences among species with the toasting intensity. The qualitative differences in the volatile profiles allow for identifying woods from cherry (being p‐anisylalcohol, p‐anisylaldehyde, p‐anisylacetone, methyl benzoate and benzyl salicylate detected only in this wood), chestnut (cis and trans whisky lactone) and false acacia (resorcinol, 3,4‐dimethoxyphenol, 2,4‐dihydroxy benzaldehyde, 2,4‐dihydroxyacetophenone, 2,4‐dihydroxypropiophenone and 2,4‐dihydroxy‐3‐methoxyacetophenone), but not those from ash, because of the fact that all compounds present in this wood are detected in at least one other. However, the quantitative differences can be clearly used to identify toasted ash wood, with tyrosol being most prominent, but 2‐furanmethanol, 3‐ and 4‐ethylcyclotene, α‐methylcrotonolactone, solerone, catechol, 3‐methylcatechol and 3‐hydroxybenzaldehyde as well. Regarding oak wood, its qualitative volatile profile could be enough to distinguish it from cherry and acacia woods, and the quantitative differences from chestnut (vanillyl ethyl ether, isoacetovanillone, butirovanillone, 1‐(5‐methyl‐2‐furyl)‐2‐propanone and 4‐hydroxy‐5,6‐dihydro‐(2H)‐pyran‐2‐one) and ash toasted woods. Copyright © 2014 John Wiley & Sons, Ltd.     

Measurement of dissolved oxygen during red wines tank aging with chips and micro-oxygenation

Nowadays, micro-oxygenation is a very important technique used in aging wines in order to improve their characteristics. The techniques of wine tank aging imply the use of small doses of oxygen and the addition of wood pieces of oak to the wine. Considering the low dissolved oxygen (DO) levels used by micro-oxygenation technique it is necessary to choose the appropriate measurement principle to apply the precise oxygen dosage in wine at any time, in order to assure its correct assimilation. This knowledge will allow the oenologist to control and run the wine aging correctly.This work is a thorough revision of DO measurement main technologies applied to oenology. It describes the strengths and weaknesses of each of them, and draws a comparison of their workings in wine measurement. Both, the traditional systems by electrochemical probes, and the newest photoluminescence-based probes have been used. These probes adapted to red wines ageing study are then compared.This paper also details the first results of the dissolved oxygen content evolution in red wines during a traditional and alternative tank aging. Samples have been treated by three different ageing systems: oak barrels, stainless-steel tanks with small oak wood pieces (chips) and with bigger oak pieces (staves) with low micro-oxygenation levels. French and American oak barrels manufactured by the same cooperage have been used.     

Aging markers from bottled red wine aged with chips, staves and barrels

This paper shows the results of the experiments carried on Spanish red wines aged through alternative as well as traditional oak barrel systems, i.e., chips stainless steel tanks and staves stainless steel tanks, at the same time and under the same conditions.Wine aging through wood pieces is not accepted as an enological practice by the European Union and, in fact, it is considered a fraud. It is, then, of a great interest to identify those parameters able to establish the aging technique that had been used in a wine ready to be consumed. With this idea in mind, the development of the same wine has been studied while aging for 3 years in three different systems.During the first six aging months wines stored with staves obtained characteristics that were halfway between wines treated with chips and those aged in barrels. However, as wood contact period length increased so did the differences between wines stored in traditional and alternative systems (either with staves or chips). These differences grew during the bottling period, so that after a 2-year bottling period wines from the three systems became different enough to tell them apart. Discriminant analysis of the variables studied made it possible to establish these differences. The most meaningful variables were yellow colour component, anthocyanins (cyanidin-3-glucoside, vitisin A and sum of pcoumaryl derivates), vanillin acid, protocachuic aldehyde and epicatechin.     

蛇油的挥发性成分分析和脱腥

采用水蒸汽蒸馏、黏土吸附、乙醇-乙酸乙酯共沸的方法除去蛇油的腥味,运用顶空固相微萃取(SPME)-气相色谱(GC)-质谱(MS)联用技术分析脱腥前后蛇油中挥发性成分的变化,并运用GC-MS联用技术分析脱腥后的蛇油中的脂肪酸.结果表明水蒸汽蒸馏是效果最佳的脱腥方法,它可使蛇油挥发性成分的量降至脱腥前的38%,使腥味的主要成分减少60%～100%,同时较大程度地保留了多不饱和脂肪酸.     

Effect of γ-irradiation on volatile compounds of dried Welsh onion (Allium fistulosum L.)

The volatile compounds of γ-irradiated dried Welsh onion were isolated by simultaneous distillation–extraction (SDE) technique and then analyzed by gas chromatography–mass spectrometry (GC–MS) along with their non-irradiated counterparts. A total of 35 volatile compounds were identified in non-irradiated and 1 kGy irradiated samples and 36 volatile compounds were identified in 3, 5, 10 and 20 kGy irradiated samples so far belong to chemical classes of acid, alcohol, aldehyde, ester, furan, ketone and S-containing compound. S-containing compounds were detected as major volatile compounds of all experimental samples. Though the content of several compounds was increased after irradiation, content of major S-containing compounds was found to decreased in the process. Application of high-dose irradiation if required for microbial decontamination of dried Welsh onion is feasible as it enhanced the total concentration of volatile compounds by 31.60% and 24.85% at 10 and 20 kGy, respectively.     

The analysis of volatile trace compounds in landfill gases,compost heaps and forest air

Landfill gas, cryotrapped on a loop fashioned from a length of a capillary gas chromatography (GC) column, was examined for volatile organometallic compounds (VOMCs) and for volatile organic compounds (VOCs) by using GC–mass spectrometry (MS). A large number of organic components were present and many were identified, but the only VOMCs present in high enough concentrations to be detected were trimethylstibine and tetramethyltin. The use of inductively coupled plasma (ICP)‐MS as an element‐specific detector allowed the identification of a number of other organometallic species in the landfill gas, including trimethylarsine and trimethylbismuth, and, for the first time, butyltrimethyltin and dibutyldimethyltin. The presence of molybdenum hexacarbonyl was confirmed. Gas from a large‐scale compost heap and from compost incubated in the laboratory contained iodomethane but no common VOMCs (GC–ICP‐MS). Only VOCs were present in forest air (GC–MS). Copyright © 2003 John Wiley & Sons, Ltd.     

气相色谱-质谱法分析橡苔浸膏中的挥发性化学成分

 用挥发油提取器提取橡苔浸膏中的挥发油,利用气相色谱-质谱法(GC-MS)分析了其中的化学成分,采用GC峰面积归一化法定量,鉴定出24种化合物,共占挥发油总量的83%以上     

Extraction of wood compounds by use of subcritical fluids

Summary A study of the extraction of oak wood compounds with subcritical water-ethanol mixtures as extractants, with an ethanol content between 0 and 60%, is reported. Identification and characterization of the extracted compounds were achieved by spectrophotometry and by gas chromatography with either flame ionization or mass spectrometric detection. Extraction was performed statically by use of a single cycle or repeated cycles. All variables affecting the extraction process were studied and optimized. Extraction time and temperature were 60 min and 200°C, respectively. Comparison of the extract thus obtained with commercial extracts showed the former to be rich in compounds characteristic of the commercial extracts. The method also enables manipulation of extract composition by changing the temperature and the water/ethanol ratio used. It is faster than traditional procedures for obtaining wood extracts.     

The perspectives of ethanol usage as an internal standard for the quantification of volatile compounds in alcoholic products by GC‐MS

The potential use of ethanol as an internal standard (IS) for GC‐MS analysis was studied. The paper describes the analysis of spirit drinks and other alcoholic products which consist of a mixture of water, ethanol, and volatile compounds. In the suggested method, ethanol was employed as an IS for the common procedure of volatile compounds quantification. A number of standard solutions of nine compounds with different concentrations was prepared in a water‐ethanol matrix and measured with GC‐MS in the SIM mode. Two possible approaches were suggested to avoid detector saturation during ethanol detection. The first one consisted in using less abundant m/z 47 as quantifiers. These ions mainly correspond to unfragmented heavy ethanol molecules containing one ¹³C isotope. The second method consisted in reduction of the voltage of MS electron multiplier. The experiment also included the preparation and subsequent dilution of the standard solution and ethanol with water, which determined the linearity of the modified MS response relative to the ethanol content. Analysis of the obtained results revealed that volatile compounds can be successfully accurately determined with GC‐MS by employing ethanol as an IS. Application of the suggested method is not limited to the reported volatile compounds and alcoholic products.     

Online monitoring of higher alcohols and esters throughout beer fermentation by commercial Saccharomyces cerevisiae and Saccharomyces pastorianus yeast

Higher alcohols and esters are among the predominant classes of volatile organic compounds (VOCs) that influence the quality of beer. The concentrations of these compounds are determined through a specific yeast strain selection and fermentation conditions. The effect of yeast strains on the formation of higher alcohols and esters throughout fermentations (at 20°C) was investigated. Flavour-relevant esters (ethyl acetate, isoamyl acetate, ethyl hexanoate and ethyl octanoate) and higher alcohols (isoamyl alcohol, isobutyl alcohol and phenylethyl alcohol) were monitored throughout the fermentation using proton transfer reaction–time of flight–mass spectrometry (PTR-ToF-MS) coupled with an automated sampling system for continuous measurements. Compound identification was confirmed by analysis of samples using gas chromatography–mass spectrometry (GC–MS). Results demonstrated the specific time points where variation in higher alcohol and ester generation between yeast strains occurred. In particular, the concentrations of isoamyl acetate, ethyl octanoate and isoamyl alcohol between yeast strains were significantly different over the first 2 days of fermentation; whereas, after Day 3, no significant differences were observed. The two Saccharomyces pastorianus strains produced comparable concentrations of the key higher alcohols and esters. However, the key higher alcohol and ester concentrations varied greatly between the two S. cerevisiae strains. The use of PTR–ToF–MS to rapidly measure multiple yeast strains provides new insights on fermentation for brewers to modify the sensory profile and optimise quality.     

How stereochemistry influences the taste of wine: Isolation,characterization and sensory evaluation of lyoniresinol stereoisomers

Wine expresses its beauty by sending a sensory message to the taster through molecules coming from grapes, yeast metabolism or oak wood. Among the compounds released during barrel aging, lyoniresinol has been recently reported as a relevant contributor to wine bitterness. As this lignan contains three stereogenic carbons, this work aimed at investigating the influence of stereochemistry on wine taste by combining analytical and sensorial techniques. First, an oak wood extract was screened by Liquid Chromatography–High Resolution Mass Spectrometry to target isomers separable in a symmetric environment and a diastereoisomer called epi-lyoniresinol was isolated for the first time. Then, an original racemic resolution based on natural xylose-derivatives was carried out to obtain lyoniresinol enantiomers. Chiroptical spectroscopic measurements associated with theoretical calculations allowed the unambiguous determination of their absolute configuration. The taste properties of all these stereoisomers revealed that only one lyoniresinol enantiomer is strongly bitter whereas the other one is tasteless and the diastereoisomer is slightly sweet. The presence of these three compounds was established in an oaked Bordeaux wine by chiral and non-chiral chromatography, suggesting the significant influence of stereochemistry on wine taste.     

LC‐DAD/ESI‐MS/MS study of phenolic compounds in ash (Fraxinus excelsior L. and F. americana L.) heartwood. Effect of toasting intensity at cooperage

The phenolic composition of heartwood extracts from Fraxinus excelsior L. and F. americana L., both before and after toasting in cooperage, was studied using LC‐DAD/ESI‐MS/MS. Low‐molecular weight (LMW) phenolic compounds, secoiridoids, phenylethanoid glycosides, dilignols and oligolignols compounds were detected, and 48 were identified, or tentatively characterized, on the basis of their retention time, UV/Vis and MS spectra, and MS fragmentation patterns. Some LMW phenolic compounds like protocatechuic acid and aldehyde, hydroxytyrosol and tyrosol, were unlike to those for oak wood, while ellagic and gallic acid were not found. The toasting of wood resulted in a progressive increase in lignin degradation products with regard to toasting intensity. The levels of some of these compounds in medium‐toasted ash woods were much higher than those normally detected in toasted oak, highlighting vanillin levels, thus a more pronounced vanilla character can be expected when using toasted ash wood in the aging wines. Moreover, in seasoned wood, we found a great variety of phenolic compounds which had not been found in oak wood, especially oleuropein, ligstroside and olivil, along with verbascoside and isoverbascoside in F. excelsior, and oleoside in F. americana. Toasting mainly provoked their degradation, thus in medium‐toasted wood, only four of them were detected. This resulted in a minor differentiation between toasted ash and oak woods. The absence of tannins in ash wood, which are very important in oak wood, is another peculiar characteristic that should be taken into account when considering its use in cooperage. Copyright © 2012 John Wiley & Sons, Ltd.     

Identification, amounts, and kinetics of extraction of C-glucosidic ellagitannins during wine aging in oak barrels or in stainless steel tanks with oak chips

The C-glucosidic ellagitannins are found in wine as a result of its aging in oak barrels or in stainless steel tanks with oak chips. Once dissolved in this slightly acidic solution, the C-glucosidic ellagitannins vescalagin can react with nucleophilic entities present in red wine, such as ethanol, catechin, and epicatechin, to generate condensed hybrid products such as the β-1-O-ethylvescalagin and the flavano-ellagitannins (acutissimin A/B and epiacutissimin A/B), respectively. During this study, we first monitored the extraction kinetic and the evolution of the eight major oak-derived C-glucosidic ellagitannins in red wines aged in oak barrels or in stainless steel tank with oak chips. Their extraction rates appeared to be faster during red wine aging in stainless steel tanks with oak chips. However, their overall concentrations in wines were found higher in the wine aged in barrels. The formation rates of the vescalagin-coupled derivatives were also estimated for the first time under both red wine aging conditions (i.e., oak barrels or stainless steel tanks with oak chips). As observed for the oak-native C-glucosidic ellagitannins, the concentrations of these vescalagin derivatives were higher in the red wine aged in oak barrels than in stainless steel tanks with oak chips. Despite these differences, their relative composition was similar under both red wine aging conditions. Finally, the impact of the oak chips size and toasting level on the C-glucosidic ellagitannins concentration in wine was also investigated.