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.     

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.     

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).     

Comparison of wine aromas with different tannic content aged in French oak barrels

A method has been developed to determine the most significant volatiles of a wine aged in barrels: trans- and cis-whiskylactone, guaiacol, 4-ethylguaiacol, eugenol, 4-ethylphenol, vanillin, furfural and γ-butyrolactone. This method consists in an extraction with dichloromethane, according to classical methods, but emulsion formation is avoided and the later analysis is carried out by thermal desorption-gas chromatography with mass spectrometric detection. This method is quite rapid and gives calibration graphs with linear regression coefficients between 0.97 and 0.99 for each compound and variation coefficients of variation <10%. This method has been applied to three wines with different tannic content (free-run or base wine and two other from base wine by adding both enological tannin and its own press wine) aged 6 months in French oak barrels (Allier). Sensorial analyses were carried out by expert tasters. All results were used in discriminant analyses, but only the lactones and vanillin were necessary to properly classify all the wines according to tannic content.     

Beyond the characterization of wine aroma compounds: looking for analytical approaches in trying to understand aroma perception during wine consumption

The volatile compounds present in wines are responsible for the quality of the wine aroma. The analysis of these compounds requires different analytical techniques depending on the type of compounds and their concentration. The importance at sensorial level of each compound should be evaluated by using olfactometric techniques and reconstitution and omission studies. In addition, wine aroma is influenced by other factors such as wine matrix, which could affect the compounds’ volatility, decreasing or increasing their concentration in the headspace above the wine. Moreover, when a wine is consumed, several oral physiological variables could affect aroma perception. The focus of this review is to outline the most recent advances in wine aroma analysis and the most innovative techniques in trying to elucidate the main factors that influence wine aroma perception during consumption.     

Evaluation of two commercial solid-phase microextraction fibres for the analysis of target aroma compounds in cooked beef meat

The aroma profile of cooked beef meat has been investigated by solid-phase microextraction (SPME) combined with gas chromatography-mass spectrometry (GC-MS). Out of more than 200 volatile compounds, 36 key odour-active compounds were selected for analysis. Several extraction times, desorption times, temperature conditions and fibre types were tested to achieve a fast and reproducible extraction, and a representative analysis of the aroma profile of cooked beef. Extraction conditions and fibre type significantly affected the majority of the target compounds. Divinylbenzene-carboxen-polydimethylsiloxane (DVB-CAR-PDMS) fibre presented a better reproducibility at all extraction times and extracted more efficiently the less volatile compounds than the carboxen-polydimethylsiloxane (CAR-PDMS) fibre. The high molecular weight compounds seemed to achieve faster the equilibrium between the headspace and DVB-CAR-PDMS fibre. The use of SPME was shown to be a simple, sensitive, selective, representative, fast, and low-cost method for the evaluation of key odour-active compounds in cooked beef meat, even if further research on quantitative analysis of volatiles using SPME on solid samples has to be done.     

Extraction of aroma compounds in a HFMC: Dynamic modelling and simulation

In the present work the dynamic behaviour of hollow-fiber membrane contactors (HFMCs) used for the recovery of aroma compounds from an aqueous feed phase with the help of a conventional solvent has been studied. Many aroma compounds play a significant role in the production of flavorants, which are used in the food industry to flavor, improve and increase the appeal of their products. Various aroma compounds with different physico-chemical characteristics have been chosen for this study. A real dynamic model of membrane-based solvent extraction (MBSE) process was developed. In the studied system, the aqueous feed and solvent phases are re-circulated to their respective storage tanks after contacting in a hollow fibres membrane contactor. The developed dynamic model was verified with experimental data from the literature and good level of agreement was found. It has been used as a tool to simulate and conclude about the influence of various module configurations, membrane characteristics and hydrodynamic conditions on the extraction of various aroma compounds. It was noted that transient models of membrane-based separation need attention to improve the simulation studies and experimental validity to encourage it at larger scales.     

Influence of sorption and diffusion of aroma compounds in silicone rubber on their extraction by pervaporation

Pervaporation was used to extract aroma compounds from dilute aqueous solutions. The use of a stirred cell allowed the reduction of the boundary layer effect which can be estimated using a mass transfer correlation. A resistance-in-series model was used to describe the flux of organic compounds through a silicone membrane. Calculation of the membrane resistance required the determination of the solubility and diffusion coefficients of the aroma substances in the polymer. These two characteristics were obtained by measuring the quantities of the aroma sorbed on the silicone at equilibrium and by studying the kinetics of sorption. At low concentration ranges, both characteristics were constant. They can be related to the hydrophobicity, the molar volume and the flux of the substances through the silicone membrane during pervaporation.     

Comparison of the volatile aroma components in noble rotted grape berries from two different locations of the Tokaj wine district in Hungary

The most famous wine type of Hungary is Tokaji Aszú. Noble rotted botrytised (Aszú) grape berries and a specific vinification technology give its unique delicious aroma and taste. The present work compares volatile aroma components of noble rotted Aszú grape berries from two different locations in the Tokaj wine district. Aszú grape berries have been soaked in 10% ethanol-containing water solutions and thereafter extracted with Freon 11. Volatile components were determined by gas chromatography-mass spectrometry (GC-MS). The total ion chromatograms contained 220-260 components. More than 80 components are identified, among them alcohols, aldehydes, acids, acetals, esters, epoxides, nitrils, furan derivatives and lactones. The compositional differences between the two Aszú grape samples are analysed according to the different component classes. The differences are quantitative rather than qualitative. Some δ-lactones are identified for the first time in noble rotted berries from Tokaj. These substances have very characteristic odor notes such as coconut, chocolate, peach, fruity. Together with the identified γ-lactones they seem to be characteristic aroma components of Tokaji Aszú wines.     

Application of zNosetrade mark for the analysis of selected grape aroma compounds

A novel and portable gas chromatograph (GC, zNose™) has been evaluated for the measurement in grape berries of selected six-carbon compounds; namely, hexanal, cis-2-hexen-1-ol, cis-3-hexen-1-ol and trans-2-hexenal. The zNose™ is a handheld GC which uses purge and trap for concentration, and has a surface acoustic wave (SAW) sensor as a detector. Operation of the zNose™ using direct aspiration of the sample failed to detect the compounds at the reported odour threshold values. Pre-concentration by Tenax^® trapping and solid-phase microextraction (SPME) were investigated to improve the zNose™ sensitivity. Use of a Tenax^® pre-trap with the zNose™ allowed detection of the compounds at concentration levels in the order of their threshold values. Excessive bleed from the SPME fibre prevented the use of SPME with zNose™.     

Extraction of aroma compounds in blackcurrant buds by alternative solvents: Theoretical and experimental solubility study

This study was designed to evaluate the performance of nine alternative solvents (α-pinene, MeTHF, ethyl acetate, methyl acetate, ethyl lactate, butanol, isopropanol, ethanol and CO₂ supercritical fluid) for extracting aromas from blackcurrant buds (Ribes nigrum L) compared to that of n-hexane, commonly used. This study has been performed via experimentation and simulation using Hansen solubility methodology for the comprehension of the dissolving mechanism. Experimentally, the extracts were analysed to compare the solvents performance in terms of aroma compositions. The results indicated that an alternative solvent, i.e. MeTHF, could be the most promising one for n-hexane substitution with good yield and selectivity of aromas.     

Modeling and analysis of vacuum membrane distillation for the recovery of volatile aroma compounds from black currant juice

A vacuum membrane distillation (VMD) model has been developed and validated with experimental data. The model consists of an extended transport model for the VMD process and is able to predict the effects of concentration and temperature polarization on the overall process performance. To validate the model, first it was tested with few experimental case studies from literature [S. Bandini, G.G. Sarti, Heat and mass transport resistances in vacuum membrane distillation per drop, AIChE J. 45 (7) (1999) 1422–1433; K.W. Lawson, D.R. Lloyd, Membrane distillation. I. Module design and performance evaluation using vacuum membrane distillation, J. Membr. Sci. 120 (1996) 111–121; A.M. Urtiaga, G. Ruiz, I. Ortiz, Kinetic analysis of the vacuum membrane distillation of chloroform from aqueous solutions, J. Membr. Sci. 165 (2000) 99–110]. Then the VMD model has been validated with experimental data collected from the recovery of aroma compounds from black currant [R.B. Jørgensen, A.S. Meyer, C. Varming, G. Jonsson, Recovery of volatile aroma compounds from black currant juice by vacuum membrane distillation, J. Food Eng. 64 (2004) 23–31]. In this work, recovery of 12 characteristic volatile aroma compounds from black currant juice has been studied. The simulated results from the VMD model, in terms of aroma concentration in the permeate have been compared with those obtained from laboratory experiments. The validated model has been used to study the effects of various process and membrane parameters on the concentration factor. The physical properties of various aroma compounds have been predicted using group contribution method as a function of temperature.     

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.     

Studies on the aroma of cupuassu liquor by headspace solid-phase microextraction and gas chromatography

Headspace solid-phase microextraction (HS-SPME) coupled to gas chromatography with ion trap mass spectrometric detection and with atomic emission detection (GC-AED) was employed to identify possible odor-impact volatile organic compounds in cupuassu (Theobroma grandiflorum Spreng) liquor, as well as to quantify alkylpyrazines present in these samples. SPME fibers coated with 100 microm polydimethylsiloxane (PDMS), 65 microm PDMS-divinylbenzene (DVB) and 75 microm Carboxen (CAR)-PDMS were tested, the later being chosen for the optimized extraction procedure. The principal compounds found in the sample headspace were 3-methylbutanal, dimethylsulfide, dimethyldisulfide, beta-linalool and several alkylpyrazines (notably tetramethylpyrazine). The procedure for quantitation of the alkylpyrazines, using GC-AED for their separation and detection, allowed the detection of microg g(-1) levels of the analytes in the samples, with acceptable precision (R.S.D. less than 10%).     

Prediction of phenolic compounds in red wine fermentations by visible and near infrared spectroscopy

Near infrared (NIR) spectroscopy was used to simultaneously predict the concentrations of malvidin-3-glucoside (M3G), pigmented polymers (PP) and tannins (T) in red wine. A total of 495 samples from 32 commercial scale red wine fermentations over two vintages using two grape varieties (Cabernet Sauvignon and Shiraz), and also including as additional variables two types of fermenters, two different yeasts, and three fermentation temperatures were used. Samples were scanned in transmission mode (400-2500 nm) using a monochromator instrument (NIRSystems6500). Calibration equations were developed from high performance liquid chromatography (HPLC) and NIR data using partial least squares (PLS) regression with internal cross validation. Using PLS regression, very good calibration statistics (R_cal²>0.80) were obtained for the prediction of M3G, PP and T with standard deviation (S.D.)/standard error in cross validation (SECV) ratio (residual predictive deviation, RPD)) ranging from 1.8 to 5.8. It was concluded that near infrared spectroscopy could be used as rapid alternative method for the prediction of the concentration of phenolic compounds in red wine fermentations.     

Study on the extraction kinetics of phenolic compounds from petroleum refinery waste lye

A large amount of waste lye is produced in petroleum refineries during alkali cleaning process, which consists of high concentration of phenols, sulfides, oils and other pollutants. In this study, tributyl phosphate (TBP) was used as extraction agent and the extraction kinetics of phenolic compounds was investigated by the constant interfacial cell method. The effects of stirring speed, temperature and specific area on extraction rate were studied. The experimental results show that the extraction of phenols by TBP is a first-order reaction, and the extraction process may be controlled by diffusion. The effects of stirring speed and specific area on extraction rate are significant.     

Review of the role and methodology of high resolution approaches in aroma analysis

Analysis of the odour complexity in food and beverage products demands high resolution approaches for distinguishing individual aroma-impact compound(s), and for assessing their contribution to the global aroma of a sample. This paper aims to review current applications incorporating different advanced separation methodologies, and their roles in achieving high resolution aroma analysis. This includes prior low resolution gas chromatography–olfactometry (GC–O) with fractionation procedures using chemical manipulation, adsorption chromatography and ion exchange separation. Innovative multidimensional gas chromatography (MDGC) arrangements that are appropriately designed with olfactometry are of specific focus here. The revelation of resolved components using these integrated approaches provides significantly improved knowledge of aroma composition in samples.