Comparison of extraction methods for volatile compounds of Muscat grape juice

Typical flavour of Muscat d’Alexandrie wines is mainly due to volatile compounds coming from grapes of this variety. Therefore, the choice of grapes is crucial to obtain musts with a great aromatic potential, which will contribute to the final aroma of wines derived from those musts. In this study, three sampling techniques, liquid-liquid extraction (LLE), solid phase extraction (SPE) and simultaneous distillation-extraction (SDE), were compared for the analysis of volatile compounds in Muscat grape juice. Results showed that although the three techniques can be recommended for the quantitative analysis of volatile compounds from musts, LLE and SPE are better sample preparation techniques than SDE, mainly for determination of polar compounds such as acids or alcohols.     

Effect of Sonication Treatment and Maceration Time in the Extraction of Polysaccharide Compounds during Red Wine Vinification

The application of high-power ultrasounds (US) at 28 kHz to the crushed grapes and the use of different pomace contact times caused changes in the content and composition of monosaccharides and polysaccharides in the musts and wines. These differences were maintained from the moment of pressing (end of maceration) until the end of the alcoholic fermentation. The US increased the content of monosaccharides and polysaccharides in the musts by facilitating their extraction from the solid parts during maceration. The application of medium maceration time (3 days) to sonicated grapes led to an extraction of polysaccharides rich in arabinose and galactose, rhamnogalacturonan type II (RG-II) and mannoproteins (MP), similar to that observed in the control wines made with an extended maceration of 7 days (968.21 vs. 1029.45; 895.04 vs. 1700.50; 356.81 vs. 343.95, respectively). This fact was attributed to a higher extraction in the must during the sonication process and to an important release of pectic polysaccharides during the pressing of the sonicated pomace, which is reported here for the first time. Therefore, the US technology could be useful for increasing the polysaccharide content in the wines or for reducing the maceration time needed to achieve certain levels of wine polysaccharides.     

Headspace solid-phase microextraction–gas chromatography–mass spectrometry for profiling free volatile compounds in Cabernet Sauvignon grapes and wines

The complex aroma of wine is derived from many sources, with grape-derived components being responsible for the varietal character. The ability to monitor grape aroma compounds would allow for better understanding of how vineyard practices and winemaking processes influence the final volatile composition of the wine. Here, we describe a procedure using GC–MS combined with headspace solid-phase microextraction (HS-SPME) for profiling the free volatile compounds in Cabernet Sauvignon grapes. Different sample preparation (SPME fiber type, extraction time, extraction temperature and dilution solvent) and GC–MS conditions were evaluated to optimize the method. For the final method, grape skins were homogenized with water and 8 ml of sample were placed in a 20 ml headspace vial with addition of NaCl; a polydimethylsiloxane SPME fiber was used for extraction at 40 °C for 30 min with continuous stirring. Using this method, 27 flavor compounds were monitored and used to profile the free volatile components in Cabernet Sauvignon grapes at different maturity levels. Ten compounds from the grapes, including 2-phenylethanol and β-damascenone, were also identified in the corresponding wines. Using this procedure it is possible to follow selected volatiles through the winemaking process.     

The Impact of Type of Brandy on the Volatile Aroma Compounds and Sensory Properties of Grape Brandy in Montenegro

This paper presents the results of a study that examined the impact of grape variety on the volatile aroma compounds and sensory properties of standard and Muscat grape brandy produced in the Podgorica sub-region (Montenegro) in vintages 2011, 2012, and 2013. The brandies were prepared by the distillation of crushed grapes, from the autochthonous varieties of Vranac and Kratošija, and Muscat grapes, in a traditional copper alembic, under the same conditions. The gas chromatographic-mass spectrometric (GC/MS) method of 82 volatile aroma compounds that belong to the group (alcohols, volatile acids, volatile esters, terpenes, volatile aldehydes, acetals, ethers, ketones, and alkanes) and an evaluation of the sensory properties of brandies were carried out to determine the typical characteristics of the examined brandies. Alcohols, fatty acid esters, and terpene compound contents were significantly more abundant in all Muscat grape brandies compared to the brandies from the Vranac and Kratošija wine varieties (Standard brandy). Research results revealed that variety had a significant impact on the volatile aroma compound and sensory properties of brandy. The varietal effect was also confirmed, by multivariate analysis, based on the aroma volatile composition, which showed a grouping by type of grape brandy (varietal origin). Sensory analyses showed that all the brandies belonged to the category of high-quality brandies.     

Polydimethylsiloxane solid-phase microextraction-gas chromatography method for the analysis of volatile compounds in wines. Its application to the characterization of varietal wines

A study was made of the validity of the solid-phase microextraction method, using a polydimethylsiloxane coated fused-silica fiber, for the extraction-desorption of the minor volatile compounds from wine before their gas chromatographic analysis. The aspects considered were the influence of ethanol on extraction, repeatability, limits of detection, linearity and recovery of compounds. This method, together with the direct injection of the major volatile compounds, was applied to 16 varietal wines. The findings indicate that the method is a highly suitable technique for the analysis of wines and that the volatile composition of wines depends, at least partly, on the grapes with which they have been made.     

Rapid determination of volatile compounds in grapes by HS-SPME coupled with GC-MS

Volatile compounds of grapes are responsible of varietal aroma. At the moment, methods used for analysis of these compounds are solvent-based, time-consuming and generally require large amounts of sample. In order to obtain an appropriate technique to study grape volatile compounds, HS-SPME method has been developed. The optimal sampling conditions were: 70 °C for 20 min with a 65-μm PDMS/DVB fibre. Sixteen volatile compounds have been quantified in pulp and skins of Muscat grapes. Terpenes, mainly linalool, geraniol and nerol, have been the volatiles present in the highest concentration, since these compounds contribute, to a larger extent, to the aroma of Muscat grapes and wines. So the proposed technique can be used for the characterisation of grape varieties or cultivars and for the determination of the aromatic maturity of grapes.     

Phenolic potential of Tannat, Cabernet-Sauvignon and Merlot grapes and their correspondence with wine composition

The phenolic potential of Tannat, Cabernet-Sauvignon and Merlot grapes was evaluated in 2001 and 2002 and its correspondence with the colour and composition of the respective wines was established. Three vineyards of each variety, situated in the south of Uruguay were considered. Two samples of each vineyard were taken at the moment of the harvest. Phenolic richness, extractable anthocyanins contents and total potential in anthocyanins of the grapes were estimated. Two fermentations on skins were carried out for each vineyard using 50 kg of grape in each one. The anthocyanic and total polyphenols contents of the musts were analysed every 24 h, and skins extractions were carried out in parallel in the laboratory. The duration of the maceration for each variety was decided in function of the analytical results in the grapes, musts and skins extractions. Wines were analysed 2 months after the alcoholic fermentation, determining its phenolic composition and colour. Tannat grapes presented anthocyanic and total polyphenols contents significantly higher in both years. Therefore, wines from this variety presented colour intensity and phenolic contents statistically higher than Cabernet-Sauvignon and Merlot. The correlations between the phenolic contents of the grapes, skins, musts and wines were very significant. Colour intensity and phenolic contents of the wines were highly correlated with the total polyphenols of the grapes and with anthocyanins of the grapes, skins, musts and wines. The estimate of the phenolic potential of the grapes and the extractability of the pigments allows to manage more adequately the fermentation on skins and is an interesting tool to predict the colour and the composition of the wines.     

Potential Mitigation of Smoke Taint in Wines by Post-Harvest Ozone Treatment of Grapes

When bushfires occur near grape growing regions, vineyards can be exposed to smoke, and depending on the timing and duration of grapevine smoke exposure, fruit can become tainted. Smoke-derived volatile compounds, including volatile phenols, can impart unpleasant smoky, ashy characters to wines made from smoke-affected grapes, leading to substantial revenue losses where wines are perceivably tainted. This study investigated the potential for post-harvest ozone treatment of smoke-affected grapes to mitigate the intensity of smoke taint in wine. Merlot grapevines were exposed to smoke at ~7 days post-veraison and at harvest grapes were treated with 1 or 3 ppm of gaseous ozone (for 24 or 12 h, respectively), prior to winemaking. The concentrations of smoke taint marker compounds (i.e., free and glycosylated volatile phenols) were measured in grapes and wines to determine to what extent ozonation could mitigate the effects of grapevine exposure to smoke. The 24 h 1 ppm ozone treatment not only gave significantly lower volatile phenol and volatile phenol glycoside concentrations but also diminished the sensory perception of smoke taint in wine. Post-harvest smoke and ozone treatment of grapes suggests that ozone works more effectively when smoke-derived volatile phenols are in their free (aglycone) form, rather than glycosylated forms. Nevertheless, the collective results demonstrate the efficacy of post-harvest ozone treatment as a strategy for mitigation of smoke taint in wine.     

Wine flavor: chemistry in a glass

Although hundreds of chemical compounds have been identified in grapes and wines, only a few compounds actually contribute to sensory perception of wine flavor. This critical review focuses on volatile compounds that contribute to wine aroma and provides an overview of recent developments in analytical techniques for volatiles analysis, including methods used to identify the compounds that make the greatest contributions to the overall aroma. Knowledge of volatile composition alone is not enough to completely understand the overall wine aroma, however, due to complex interactions of odorants with each other and with other nonvolatile matrix components. These interactions and their impact on aroma volatility are the focus of much current research and are also reviewed here. Finally, the sequencing of the grapevine and yeast genomes in the past approximately 10 years provides the opportunity for exciting multidisciplinary studies aimed at understanding the influences of multiple genetic and environmental factors on grape and wine flavor biochemistry and metabolism (147 references).     

Commercial Mannoproteins Improve the Mouthfeel and Colour of Wines Obtained by Excessive Tannin Extraction

In the production of red wines, the pressing of marcs and extended maceration techniques can increase the extraction of phenolic compounds, often imparting high bitterness and astringency to finished wines. Among various oenological products, mannoproteins have been shown to improve the mouthfeel of red wines. In this work, extended maceration (E), marc-pressed (P), and free-run (F) Sangiovese wines were aged for six months in contact with three different commercial mannoprotein-rich yeast extracts (MP, MS, and MF) at a concentration of 20 g/hL. Phenolic compounds were measured in treated and control wines, and sensory characteristics related to the astringency, aroma, and colour of the wines were studied. A multivariate analysis revealed that mannoproteins had a different effect depending on the anthocyanin/tannin (A/T) ratio of the wine. When tannins are strongly present (extended maceration wines with A/T = 0.2), the MP conferred mouthcoating and soft and velvety sensations, as well as colour stability to the wine. At A/T = 0.3, as in marc-pressed wines, both MF and MP improved the mouthfeel and colour of Sangiovese. However, in free-run wine, where the A/T ratio is 0.5, the formation of polymeric pigments was allowed by all treatments and correlated with silk, velvet, and mouthcoat subqualities. A decrease in bitterness was also obtained. Commercial mannoproteins may represent a way to improve the mouthfeel and colour of very tannic wines.     

Study of volatile aroma components in young Tokaji Aszu wines by GC-MS

Summary “Tokaji Aszu”. is the most famous Hungarian wine type with a very delicious, unique aroma. Tokaji Aszu wines are produced from noble rotten grapes by a special vinification technology. In the last few years certain wineries have made an effort to introduce some changes into this traditional process. The present work examines the effect of different vinification technologies on some aroma components in one year old Aszu wines. The volatile aroma components were determined by gas chromatography-mass spectrometry using a Supelcowax 10 60m×0.32 mm capillary column. Wine samples were extracted with Freon 11 prior to the analysis. The chromatograms contained 150–190 peaks. About 40 aroma components were used for comparison of the wines. The results show some limited changes in the aroma composition of the wines due to vinification technological changes. Higher levels of several hydroxy-, oxo-, dicarboxylic acid esters and lactones were found in Aszu wines produced in the traditional way. Attempts have been made to compare instrumental data to sensory properties of the wines. Presented at Balaton Symposium on High Performance Separation Methods, Siófok, Hungary, September 1–3, 1999     

Influence of Must Clarification Technique on the Volatile Composition of Albariño and Treixadura Wines

Clarification of the musts is carried out to remove particles that cause turbidity, oxidizable polyphenols, and eliminate excess of proteins. However, an excessive clarification of the musts can lead to the reduction of volatile compound concentrations and, as a consequence, modify the sensorial properties of the wines. Therefore, in this study, the influence of two pre-fermentation clarification techniques (static settling and flotation) on the concentrations of volatile compounds has been assessed in Albariño and Treixadura wines. Fermentations were performed at an industrial scale. Volatile compounds have been identified and quantified by gas chromatography (FID and mass spectrometry detection) and expert panelists assessed the sensory properties of the final wines. The results showed effects of the clarification techniques on the volatile composition of wines from both varieties. Flotation significantly increased the concentrations of benzyl alcohol in Treixadura wines, whereas this technique increased the concentration of 1-hexanol, octanoic acid, and furfural in Albariño wines, but without exceeding the corresponding perception thresholds. Panelists tended to score higher the wines coming from flotation, which, together with the shorter application time, makes this technique suitable for clarifying the musts of these two white varieties.     

Characterisation of the flavour profile from Graciano Vitis vinifera wine variety by a novel dual stir bar sorptive extraction methodology coupled to thermal desorption and gas chromatography–mass spectrometry

The aim of this work was to develop a new analytical technique for the study of the organoleptic compounds (flavour profile) of the Graciano Vitis vinifera wine variety. The cv. Graciano is a singular variety of red grapes with its origins in La Rioja and Navarra (northern Spain). This variety transfers an intense red colour, aroma and high acidity to musts and provides greater longevity and, consequently, a better capacity for ageing wine. A new dual-stir bar sorptive extraction approach coupled with thermal desorption (TD) and GC–MS has been used to extract the volatile and semivolatile compounds. In this extraction step, the optimal values for the experimental variables were obtained through the Response Surface Methodology (RSM). Full scan chromatogram data were evaluated with two deconvolution software tools, and the results were compared. The volatile and semivolatile components were identified with an MS match ≥80%. As a result, the flavour metabolome of the Graciano Vitis vinifera wine variety was obtained, and 205 metabolites were identified using different databases. These metabolites were grouped into esters, acids, alcohols, nitrogen compounds, furans, lactones, ketones, aldehydes, phenols, terpenes, norisoprenoids, sulphur compounds, acetals and pyrans. The majority of the metabolites observed had already been reported in the literature; however, this work also identified new, previously unreported metabolites in red wines, which may be characteristic of the Graciano variety.     

Optimization of an extraction method of aroma compounds in white wine using ultrasound

A simple and rapid method is described for the extraction of wine volatile compounds. The procedure was based on the ultrasonic-assisted extraction using a mixing of n-pentane-diethylether (1:2) as solvent. Factorial designs have been used to optimize the sonication process. Factors such as sample volume, extraction time and solvent volume were considered. A statistical approach was used to find suitable conditions for the ultrasound extraction of aroma compounds of wine. A factorial design at two-level revealed that lower sample volume (100 ml instead of 125 ml) and solvent volume of 50 ml instead of 60 ml contributed to improve extraction efficiency. Performance of the method was evaluated, and the procedure applied to the analysis of aroma compound in white wines from 'Condado de Huelva' (Spain).     

Rapid analysis of grape aroma glycoconjugates using Fourier-transform infrared spectrometry and chemometric techniques

The varietal aroma of most wines from non-aromatic grapes is partly dependent on the qualitative and quantitative composition of glycosidic precursors in grapes. The only rapid method to assess these glycoconjugates (Red-Free Glycosyl-Glucose (G-G) method) allows only their total quantitation. We developed a new method using Fourier-transform infrared spectrometry (FT-IR) and chemometric techniques allowing these glycosidic precursors to be determined more finely. Vitis vinifera cv. Melon B. grapes grown in different areas of Muscadet vineyard (Northwest France) and harvested at different maturity stages were used to demonstrate the potentiality of this analysis method. Predictive partial least squares (PLS) regressions were established using 39 samples, representative of the glycoside variability. These models allowed the total levels of C13-norisoprenoidic and monoterpenic glycoconjugates, the most relevant aroma glycoconjugates for Muscadet wines, to be determined with a predictive error of 14 and 15%, respectively, and the total levels of the other classes of glycoconjugates with predictive errors ranging from 22% for volatile phenols to 36% for aliphatic and aromatic alcohols.     

Use of solid-phase microextraction-capillary-gas chromatography (SPME-CGC) for the varietal characterization of wines by means of chemometrical methods

The extraction of wine aroma compounds was studied by direct-SPME (DI/SPME), headspace-SPME (HS/SPME) and multiple-headspace-extraction-SPME (MHE/SPME). The aromagrams obtained by HS/SPME-CGC were evaluated with chemometrical methods for the varietal classification of wines. Received: 25 July 1997 / Revised: 24 September 1997 / Accepted: 7 October 1997     

Optimization and evaluation of a procedure for the gas chromatographic-mass spectrometric analysis of the aromas generated by fast acid hydrolysis of flavor precursors extracted from grapes

A procedure has been developed for the GC-MS analysis of the aromas released in fast acid hydrolysis of precursor fractions from grape musts and skins. Different sorbents for the extraction of the precursors were compared. The best results were obtained with LiChrolut EN polymeric resins which displayed two and six-fold more extraction capacity than Amberlite XAD-2 resins and C18 sorbents, respectively. C18 sorbents are more suitable for selective extraction of less polar precursors. The initial version of the method was imprecise and so the imprecision of the different steps was assessed. The maceration of the solid parts and the liquid-liquid extraction of the aromas released in the acid hydrolysis proved to be the critical steps. Greater crushing of the solid parts and solid-phase extraction (SPE) instead of liquid-liquid extraction (LLE) improved reproducibility. In the method finally proposed about 100 aromatic components belonging to four large groups (lipid derivatives, shikimic acid derivatives, norisoprenoids and terpenes) were determined with good reproducibility. Important aroma compounds, such as cis-rose oxide or wine lactone were detected in non-Muscat grapes.     

Two Sides to One Story—Aroma Chemical and Sensory Signature of Lugana and Verdicchio Wines

Lugana and Verdicchio are two Italian white wines with a Protected Designation of Origin (PDO) label. These two wine types are produced in different regions using the same grape variety. The aim of this work is to investigate the existence of volatile chemical markers that could help to elucidate differences between Lugana and Verdicchio wines both at chemical and sensory levels. Thirteen commercial wine samples were analyzed by Gas Chromatography-Mass Spectrometry (GC-MS), and 76 volatile compounds were identified and quantified. Verdicchio and Lugana had been differentiated on the basis of 19 free and glycosidically bound compounds belonging to the chemical classes of terpenes, benzenoids, higher alcohols, C₆ alcohols and norisoprenoids. Samples were assessed by means of a sorting task sensory analysis, resulting in two clusters formed. These results suggested the existence of 2 product types with specific sensory spaces that can be related, to a good extend, to Verdicchio and Lugana wines. Cluster 1 was composed of six wines, 4 of which were Lugana, while Cluster 2 was formed of 7 wines, 5 of which were Verdicchio. The first cluster was described as “fruity”, and “fresh/minty”, while the second as “fermentative” and “spicy”. An attempt was made to relate analytical and sensory data, the results showed that damascenone and the sum of 3 of esters the ethyl hexanoate, ethyl octanoate and isoamyl acetate, was characterizing Cluster 1. These results highlighted the primary importance of geographical origin to the volatile composition and perceived aroma of Lugana and Verdicchio wines.