Publications by authors named "Denis Dubourdieu"

57 Publications

Isolation of Taste-Active Triterpenoids from : Sensory Assessment and Identification in Wines and Spirit.

J Nat Prod 2020 05 28;83(5):1611-1622. Epub 2020 Apr 28.

Univ. Bordeaux, ISVV, Unité de Recherche Œnologie, EA 4577, USC 1366 INRA, ISVV, 33882 Villenave d'Ornon Cedex, France.

Six new triterpenoids (-), two known genins ( and ), and five known functionalized triterpenoids (-) were isolated from a heartwood extract. The purification protocol was guided by LC-HRMS by searching for structural analogues of bartogenic acid on the basis of their putative empirical formula. The structures of the new compounds were unequivocally elucidated using HRESIMS and 1D/2D NMR experiments. Sensory analyses were performed in water and in a non-oaked white wine on the pure compounds - at 5 mg/L. All molecules were perceived as bitter in water and wine, but they were mostly reported as modifying the wine taste balance. Using LC-HRMS, compounds - were observed in oaked red wine and cognac and were semiquantified in oak wood extracts. The influence of two cooperage parameters, oak species and toasting process, on compounds - content was studied. All compounds were found in quantities significantly higher in pedunculate than in sessile oak wood. Toasting is a key step in barrel manufacture and modulates the concentration of the discussed compounds. Significantly higher quantities were observed in untoasted wood compared to medium or highly toasted wood. These findings provide new insights into the molecular origin of taste changes due to oak aging.
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http://dx.doi.org/10.1021/acs.jnatprod.0c00106DOI Listing
May 2020

Natural allelic variations of Saccharomyces cerevisiae impact stuck fermentation due to the combined effect of ethanol and temperature; a QTL-mapping study.

BMC Genomics 2019 Aug 28;20(1):680. Epub 2019 Aug 28.

University of Bordeaux, ISVV, Unité de recherche OEnologie EA 4577, USC 1366 INRA, 33140, Bordeaux INP, Villenave d'Ornon, France.

Background: Fermentation completion is a major prerequisite in many industrial processes involving the bakery yeast Saccharomyces cerevisiae. Stuck fermentations can be due to the combination of many environmental stresses. Among them, high temperature and ethanol content are particularly deleterious especially in bioethanol and red wine production. Although the genetic causes of temperature and/or ethanol tolerance were widely investigated in laboratory conditions, few studies investigated natural genetic variations related to stuck fermentations in high gravity matrixes.

Results: In this study, three QTLs linked to stuck fermentation in winemaking conditions were identified by using a selective genotyping strategy carried out on a backcrossed population. The precision of mapping allows the identification of two causative genes VHS1 and OYE2 characterized by stop-codon insertion. The phenotypic effect of these allelic variations was validated by Reciprocal Hemyzygous Assay in high gravity fermentations (> 240 g/L of sugar) carried out at high temperatures (> 28 °C). Phenotypes impacted were mostly related to the late stage of alcoholic fermentation during the stationary growth phase of yeast.

Conclusions: Our findings illustrate the complex genetic determinism of stuck fermentation and open new avenues for better understanding yeast resistance mechanisms involved in high gravity fermentations.
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http://dx.doi.org/10.1186/s12864-019-5959-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6714461PMC
August 2019

Triterpenoids from Quercus petraea: Identification in Wines and Spirits and Sensory Assessment.

J Nat Prod 2019 02 28;82(2):265-275. Epub 2019 Jan 28.

Univ. Bordeaux , Unité de Recherche Oenologie, EA 4577, USC 1366 INRA, ISVV, 33882 Villenave d'Ornon Cedex , France.

Eight new triterpenoids (1-8), the known genin (9), and two known functionalized triterpenoids (10 and 11) were isolated from a Quercus petraea heartwood extract. The structures of the new compounds were unequivocally elucidated using HRESIMS and 1D/2D NMR experiments. Sensory analyses were performed in a non-oaked wine on the pure compounds 1-11. Except compounds 1 and 11, all molecules exhibited a sweet taste at 5 mg/L that was particularly intense for compounds 3 and 9. Using LC-HRMS, compounds 1-11 were observed in an oak wood extract and in oaked red wine and cognac. They were also semiquantified in several samples of sessile ( Q. petraea) and pedunculate ( Q. robur) oak wood extract. All compounds were found in quantities significantly higher in sessile than in pedunculate oak wood. These results support the hypothesis of their contribution to the increase in sweetness during oak aging and show that they can be used as chemical markers to identify the species of oak used for cooperage.
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http://dx.doi.org/10.1021/acs.jnatprod.8b00682DOI Listing
February 2019

Taste-guided isolation of sweet-tasting compounds from grape seeds, structural elucidation and identification in wines.

Food Chem 2019 Jan 18;272:388-395. Epub 2018 Aug 18.

Univ de Bordeaux, ISVV, EA 4577, Unité de recherche OENOLOGIE, F-33882 Villenave d'Ornon, France; INRA, ISVV, USC 1366 OENOLOGIE, F-33882 Villenave d'Ornon, France. Electronic address:

This work aimed at improving knowledge about sweetness in dry wines. Following on from the empirical observations of winegrowers, we assessed the contribution of grape seeds to wine sensory properties. An inductive fractionation method guided by gustatometry was used to isolate and characterize sweet-tasting compounds from grapes. Fractionation of grape seed macerates was achieved by liquid-liquid extraction, centrifugal partition chromatography (CPC) and preparative HPLC. Then, the structures of the purified compounds were elucidated by use of FTMS and NMR. Five compounds were identified: two new compounds, 2-hydroxy-3-methylpentanoic-2-O-β-glucopyranoside (H3MP-G) and 2-hydroxy-4-methylpentanoic-2-O-β-glucopyranoside acids (H4MP-G), along with gallic-4-O-β-glucopyranoside acid (AG-G), 3-indolyl-(2R)-O-β-d-glycoside lactic acid (ILA-G) and epi-DPA-3'-O-β-glucopyranoside acid (epi-DPA-G). These compounds exhibited various levels of sweetness in a hydro-ethanolic solution and in white and red wines. Additionally, H3MP-G, H4MP-G and epi-DPA-G were identified for the first time in grapes and wines, whereas AG-G has already been reported in white grapes but never in wine.
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http://dx.doi.org/10.1016/j.foodchem.2018.08.070DOI Listing
January 2019

Study of the contribution of massoia lactone to the aroma of Merlot and Cabernet Sauvignon musts and wines.

Food Chem 2017 Oct 30;232:229-236. Epub 2017 Mar 30.

Univ. de Bordeaux, ISVV, EA4577 Œnologie, F-33140 Villenave d'Ornon, France; INRA, ISVV, USC 1366 Œnologie, F-33140 Villenave d'Ornon, France.

Organic extracts of musts and red wines marked by dried fruit and cooked fruit aromas were analyzed by gas chromatography coupled to olfactometry and mass spectrometry. Thanks to this analytical approach we identified a fragrant lactone corresponding to an odorant zone reminiscent of coconut and dried figs as 5,6-dihydro-6-pentyl-2H-pyran-2-one (C10 massoia lactone). Using chiral GC-GC-MS, we show that only the (R)-C10 massoia lactone is found in musts and wines. Its detection thresholds were 10µg/L and 11µg/L in must and wine model solution, respectively. In Merlot and Cabernet Sauvignon musts marked by dried fruit flavors from overripe grapes, its concentration reached 68µg/L. In contrast, in wines marked by these flavors, it never exceeded 20µg/L. We show that (R)-C10 massoia lactone is reduced to (R)-δ-decalactone during alcoholic fermentation. In addition, we underline the contribution of temperature during the growing season on its level in old red wines.
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http://dx.doi.org/10.1016/j.foodchem.2017.03.151DOI Listing
October 2017

Toward a Molecular Understanding of the Typicality of Chardonnay Wines: Identification of Powerful Aromatic Compounds Reminiscent of Hazelnut.

J Agric Food Chem 2017 Feb 26;65(5):1058-1069. Epub 2017 Jan 26.

Université de Bordeaux, ISVV , EA 4577, Unité de recherche ŒNOLOGIE, F-33882 Villenave d'Ornon, France.

Chardonnay wines impart a unique complex aroma characterized by its buttery, yellow stone fruit, melon, bready, and woody notes. Among the terms used in the sensory analysis of these wines, this study investigated hazelnut-like attributes. Multidimensional gas chromatography coupled to olfactometry identified five pyrroles reminiscent of hazelnut: 1-ethylpyrrole-2-carboxaldehyde, 1H-pyrrole, 2-acetyl-1H-pyrrole (first identification in wine), 1-methylpyrrole-2-carboxaldehyde, and 1H-pyrrole-2-carboxaldehyde. Quantitative analyses demonstrated their significantly higher abundance in Chardonnay wines. However, they proved irrelevant in sensory terms, given the low amounts measured in wine compared to their olfactory detection threshold. Nevertheless, the presence of methanethiol derivatives from these pyrroles was investigated in wine. 1-Methylpyrrole-2-methanethiol and 1-ethylpyrrole-2-methanethiol were identified and exhibited hazelnut-like aroma. These compounds, which have not been observed in natural products to date, are potent volatile compounds with detection thresholds of 0.7 and 1.4 ng/L, respectively, in model wine. These findings open up promising perspectives concerning the interpretation of the typical aromatic nuances of some Chardonnay wines.
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http://dx.doi.org/10.1021/acs.jafc.6b04516DOI Listing
February 2017

Taste-Guided Isolation of Bitter Lignans from Quercus petraea and Their Identification in Wine.

J Nat Prod 2016 10 29;79(10):2432-2438. Epub 2016 Sep 29.

Université de Bordeaux, ISVV , EA 4577, Unité de Recherche OENOLOGIE, 210 Chemin de Leysotte, CS 50008, 33882 Villenave d'Ornon, France.

Quercoresinosides A and B (1 and 2), two new lignans, were isolated from a toasted Quercus petraea heartwood extract along with a known compound, 3-methoxy-4-hydroxyphenol 1-O-β-d-(6'-O-galloyl)glucopyranoside (3). The purification protocol was based on a taste-guided approach that sought to reveal new bitter compounds released from oak wood into wines and spirits. HRMS and NMR data were used to establish that compounds 1 and 2 are lignan derivatives bearing a glucosyl unit and a galloyl unit at the same positions. Hydrolysis of these compounds showed that they could be distinguished by the absolute configuration of their respective lyoniresinol genin as determined by chiral LC-HRMS in comparison with (+)- and (-)-lyoniresinol standards. Sensory analyses were performed in a non-oaked wine on the pure compounds 1-3. The three molecules exhibited a bitter taste at 2 mg/L that was particularly intense for compounds 2 and 3. Finally, LC-HRMS demonstrated the occurrence of compounds 1-3 in oaked wine and brandy, which supports the hypothesis of their contributions to the increase in bitterness during oak aging.
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http://dx.doi.org/10.1021/acs.jnatprod.6b00142DOI Listing
October 2016

Identification and analysis of piperitone in red wines.

Food Chem 2016 Sep 19;206:191-6. Epub 2016 Mar 19.

Univ. Bordeaux, ISVV, EA 4577, Unité de recherche OENOLOGIE, F-33882 Villenave d'Ornon, France; INRA, ISVV, USC 1366 Œnologie, F-33140 Villenave d'Ornon, France.

The present study concerns the search for new aroma compounds associated with the flavor of aged and prematurely aged red wines. Sensory descriptive analysis associated with gas chromatography-olfactometry was first performed to find specific odoriferous zones. One of the zones, reminiscent of mint, was found in red wines with a prune flavor. Thanks to several analytical approaches including preparative gas chromatography, p-menth-1-en-3-one (piperitone), has been identified in red wines. The olfactory detection threshold of this terpene reminiscent of mint was 0.9μg/L in model hydroalcoholic solution and 70μg/L in red wines. Chiral multidimensional GC-MS was used to show that piperitone was present mainly in the (R) form in red wines. The concentration of piperitone in aged red wines ranged from a few ng/L to 435ng/L, but the level was not linked to the age of the wine nor to its premature evolution.
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http://dx.doi.org/10.1016/j.foodchem.2016.03.064DOI Listing
September 2016

Development of a quantitation method to assay both lyoniresinol enantiomers in wines, spirits, and oak wood by liquid chromatography-high resolution mass spectrometry.

Anal Bioanal Chem 2016 05 21;408(14):3789-99. Epub 2016 Mar 21.

Univ. de Bordeaux, ISVV, EA 4577, Unité de recherche Oenologie, 33882, Villenave d'Ornon, France.

Wine taste balance evolves during oak aging by the release of volatile and non-volatile compounds from wood. Among them, an enantiomer of lyoniresinol, (+)-lyoniresinol, has been shown to exhibit bitterness. To evaluate the impact of (+)-lyoniresinol on wine taste, a two-step quantitation method was developed and validated. First, (±)-lyoniresinol was assayed in wines, spirits, and oak wood macerates by C-18 liquid chromatography-high resolution mass spectrometry (LC-HRMS). Then, the lyoniresinol enantiomeric ratio was determined by chiral LC-HRMS in order to calculate the (+)-lyoniresinol content. In red and white wines, the average concentrations of (+)-lyoniresinol were 1.9 and 0.8 mg/L, respectively. The enantiomer proportions were not affected by bottle aging, and lyoniresinol appeared to remain stable over time. The sensory study of (+)-lyoniresinol established its perception threshold at 0.46 mg/L in wine. All the commercial wines quantitated were above this perception threshold, demonstrating its impact on wine taste by an increase in bitterness. In spirits, (+)-lyoniresinol ranged from 2.0 to 10.0 mg/L and was found to be released continuously during oak aging. Finally, neither botanical origin nor toasting was found to significantly affect the (+)-lyoniresinol content of oak wood. Graphical abstract From oak wood to wine: evaluation of the influence of (+)-lyoniresinol on the bitterness of wines and spirits.
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http://dx.doi.org/10.1007/s00216-016-9466-3DOI Listing
May 2016

Identification of S-3-(hexanal)-glutathione and its bisulfite adduct in grape juice from Vitis vinifera L. cv. Sauvignon blanc as new potential precursors of 3SH.

Food Chem 2016 May 17;199:711-9. Epub 2015 Dec 17.

Univ. de Bordeaux, ISVV, EA4577 Œnologie, FR-33140 Villenave d'Ornon, France.

Two main precursors (S-3-(hexan-1-ol)-l-cysteine and S-3-(hexan-1-ol)-l-glutathione) of 3-sulfanylhexanol (3SH, formerly named 3-mercaptohexanol) have been identified so far in grape juice but a correlation between precursor concentrations in grape juices and 3SH concentrations in wines is not always observed. This suggests that there may be other compounds associated with the aromatic potential. In this work, S-3-(hexanal)-glutathione (Glut-3SH-Al) and its bisulfite (Glut-3SH-SO3) adduct were identified in Sauvignon blanc grape juice by liquid chromatography coupled to Fourier transform mass spectrometry experiments. A partial purification of the compounds was carried out by Medium Pressure Liquid Chromatography (MPLC) on the reverse phase using 5L of grape juice. The addition of synthetized Glut-3SH-Al and Glut-3SH-SO3 in the synthetic medium induced a significant release of 3SH after fermentation. Moreover, we demonstrate that Glut-3SH-Al and its bisulfite adduct are present in grape juice and could be considered as new direct 3SH precursors with molar conversion yields close to 0.4%.
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http://dx.doi.org/10.1016/j.foodchem.2015.12.069DOI Listing
May 2016

New Approach for Differentiating Sessile and Pedunculate Oak: Development of a LC-HRMS Method To Quantitate Triterpenoids in Wood.

J Agric Food Chem 2016 Jan 12;64(3):618-26. Epub 2016 Jan 12.

Université de Bordeaux , ISVV, EA 4577, Unité de recherche Oenologie, F-33882 Villenave d'Ornon, France.

Oak aging is a crucial step in winemaking during which the organoleptic properties of wine are modified. Various parameters affect the chemical composition of oak wood including botanical origin, which has been previously shown to be a determinant factor. This study focused on the development of a LC-HRMS method to assay four recently discovered taste-active triterpenes (three sweet and one bitter). The method was applied to evaluate the effect of oak species (Quercus petraea and Quercus robur) on the concentration of these molecules in wood. The results showed that sessile oak was richer in sweet triterpenes and poorer in the bitter one than pedunculate oak, with high interindividual variations within species. Furthermore, a triterpenoid index was calculated to reveal the triterpenoid composition of oak wood. This index appears to be a promising tool for the unambiguous discrimination of oak species and could offer new insights into oak wood selection by coopers and the monitoring of oak aging by winemakers.
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http://dx.doi.org/10.1021/acs.jafc.5b05056DOI Listing
January 2016

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

Anal Chim Acta 2015 Aug 10;888:191-8. Epub 2015 Aug 10.

Université de Bordeaux, ISVV, EA 4577, Unité de recherche OENOLOGIE, F-33882 Villenave d'Ornon, France; INRA, ISVV, USC 1366 OENOLOGIE, 33882 Villenave d'Ornon, France. Electronic address:

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.
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http://dx.doi.org/10.1016/j.aca.2015.06.061DOI Listing
August 2015

Fermentative conditions modulating sweetness in dry wines: genetics and environmental factors influencing the expression level of the Saccharomyces cerevisiae HSP12 gene.

J Agric Food Chem 2015 Jan;63(1):304-11

Yeast lees influence the organoleptic properties of wines by increasing their sweet taste. This effect is in part due to the protein Hsp12p, which is regulated by different stress response pathways in Saccharomyces cerevisiae. This work investigated the genetics and environmental factors influencing the expression level of the HSP12 gene in an enological context. RT-qPCR confirmed that the HSP12 expression level is regulated by temperature change and ethanol content during the alcoholic fermentation but not by the sugar content. Moreover, this gene shows an important variation according to the yeast strain used. For the first time yeast strain is demonstrated to play an important role in the perception of sweetness in red wine due to post-fermentation lees autolysis. Interestingly, a correlation between the expression level of HSP12 and the sweetness perception was found using yeast strains of different origins. All of the findings provide new insights on the contribution of yeast to wine taste.
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http://dx.doi.org/10.1021/jf504408tDOI Listing
January 2015

Development of an analytical methodology using Fourier transform mass spectrometry to discover new structural analogs of wine natural sweeteners.

Anal Chim Acta 2015 Jan 1;853:425-434. Epub 2014 Nov 1.

Univ. de Bordeaux, ISVV, EA 4577, Unité de recherche OENOLOGIE, F-33882 Villenave d'Ornon, France; INRA, ISVV, USC 1366 OENOLOGIE, 33882 Villenave d'Ornon, France.

Volatile and non-volatile molecules are directly responsible for the thrill and excitement provided by wine-tasting. Their elucidation requires powerful analytical techniques and innovative methodologies. In a recent work, two novel sweet compounds called quercotriterpenosides (QTT) were identified in oak wood used for wine-ageing. The aim of the present study is to discover structural analogs of such natural sweeteners in oak wood. For this purpose, an analytical approach was developed as an alternative to chemical synthesis. Orbitrap mass spectrometry proved to be a crucial technique both to demonstrate the presence of QTT analogs in oak wood by targeted screening and to guide the purification pathway of these molecules using complementary chromatographic tools. Four compounds were isolated and identified for the first time: two isomers, one glucosyl derivative and one galloyl derivative of QTT. Their tasting showed that only the two new isomers were sweet, thus demonstrating both the pertinence of the strategy and the influence of functional groups on gustatory properties. Finally, this paper presents some developments involving multistage Fourier transform mass spectrometry (FTMS) to provide solid structural information on these functional groups prior to any purification of compounds. Such analytical developments could be particularly useful for research on taste-active or bio-active products.
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http://dx.doi.org/10.1016/j.aca.2014.10.039DOI Listing
January 2015

Role of 3-methyl-2,4-nonanedione in the flavor of aged red wines.

J Agric Food Chem 2013 Jul 17;61(30):7373-80. Epub 2013 Jul 17.

SEGUIN MOREAU France, ZI Merpins, Cognac, France.

GC-MS in chemical ionization mode (CI) was used as a simple, sensitive method for assaying 3-methyl-2,4-nonanedione (MND) in 67 red wines. MND content was shown to be lower in nonoxidized red wines and higher in oxidized red wines, that is, systematically exceeding the perception threshold (62 ng/L). Concentrations up to 340 ng/L in the most oxidized red wines were also evidenced. According to these quantitative data, the presence of MND alone was shown to modify significantly the flavor of the red wine as evaluated from fresh fruit flavor in red wine without MND to aromatic expression of rancio in wines with elevated concentrations (308.9 ng/L). Incidence of oxygen on its formation was also investigated. For the first time, elevated concentrations of this compound in various wines were demonstrated, that is, white, rosé, botrytized wines, and fortified wines made with over-ripened grapes. The lowest levels (2.9 ng/L) were found in nonoxidized white wines, whereas the highest levels were found in oxidized botrytized wines (293.8 ng/L). These results tend to demonstrate that MND is in general a good marker of oxidation in wines made with a maceration step between the skin and the pulp. These preliminary results provide a new analytical explanation of what is known in enology as the "vin de garde" concept.
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http://dx.doi.org/10.1021/jf400348hDOI Listing
July 2013

Identification of new natural sweet compounds in wine using centrifugal partition chromatography-gustatometry and Fourier transform mass spectrometry.

Anal Chem 2011 Dec 14;83(24):9629-37. Epub 2011 Nov 14.

Université de Bordeaux, ISVV, EA 4577, Unité de Recherche OENOLOGIE, Villenave d'Ornon, France.

Sweetness contributes notably to the taste-balance of dry wines and increases during oak-barrel aging owing to the release of natural sweeteners from wood. The search for such taste-active molecules, which are sometimes present at very low concentrations in wine or other complex matrixes, requires both reliable purification tools and powerful identification techniques. Here, we report the development of an original inductive method using centrifugal partition chromatography (CPC) and sensorial analysis. This method, called CPC-gustatometry, was implemented to isolate a sweet fraction with only four compounds from a complex oak wood extract. The recently developed Fourier transform mass spectrometry (FT-MS, Orbitrap analyzer) was used jointly with two-dimensional nuclear magnetic resonance (2D (1)H and (13)C NMR) to obtain the structural elucidation of the purified compounds. The tandem mass spectrometry (MS/MS) spectra obtained with resonant and nonresonant fragmentation modes were compared, thus providing complementary information about the molecular structure. Two oleanane-type triterpenoids substituted with galloyl and glucosyl moieties were identified, one of which exhibits sweet properties. We term these compounds which have never been reported, Quercotriterpenoside I and II.
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http://dx.doi.org/10.1021/ac202499aDOI Listing
December 2011

The grape must non-Saccharomyces microbial community: impact on volatile thiol release.

Int J Food Microbiol 2011 Dec 8;151(2):210-5. Epub 2011 Sep 8.

Université de Bordeaux-Segalen, ISVV, Bordeaux Aquitaine, USC INRA/IPB/UBS, 210 Chemin de Leysotte, CS 50008, 33882 Villenave d'Ornon Cedex, France.

Several studies have reported the beneficial influence of non-Saccharomyces yeasts and their potential applications in the wine industry, mainly in mixed-culture fermentation with S. cerevisiae. The potential impact of 15 non-Saccharomyces strains from 7 species on 4-methyl-4-sulfanylpentan-2-one (4MSP) and 3-sulfanylhexan-1-ol (3SH) release in model medium and Sauvignon Blanc must was evaluated after partial fermentation. Whereas the impact of non-Saccharomyces on 4MSP release in both media was low, some M. pulcherrima, T. delbrueckii and K. thermotolerans strains had a high capacity to release 3SH, despite their minimal fermentation activity. As previously demonstrated for Saccharomyces yeast, this contribution is strain dependant. Taking into account their dynamic and quantitative presence during the whole process, the real impact of non-Saccharomyces yeast on 4MSP and 3SH release was evaluated using a recreated community simulating the yeast ecosystem. Our results revealed a positive impact on 3SH release in Sauvignon Blanc wines by promoting non-Saccharomyces yeast activity and delaying the growth of S. cerevisiae. Some non-Saccharomyces yeast strains are capable of making a positive contribution to volatile thiol release in wines, essentially during the pre-fermentation stage in winemaking, when this microbiological sub-population is dominant.
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http://dx.doi.org/10.1016/j.ijfoodmicro.2011.08.026DOI Listing
December 2011

Determination of 3-methyl-2,4-nonanedione in red wines using methanol chemical ionization ion trap mass spectrometry.

J Chromatogr A 2011 Sep 16;1218(39):7023-30. Epub 2011 Aug 16.

SEGUIN MOREAU France, Z.I. Merpins, BP 94, 16103 Cognac, France.

A compound associated with oxidized flavor in red wines was recently-identified as 3-methyl-2,4-nonanedione (MND). In order to quantify it, positive chemical ionization (PCI) in an ion trap was studied using conventional liquid reagents such as methanol, acetonitrile, and acetone, as well as non-conventional liquid reagents such as ethyl acetate, diethyl ether, pentane, isohexane, and heptane. Under laboratory conditions, very different response factors were obtained with MND depending on the gas. We also compared the detection limit of conventional CI with hybrid chemical ionization (HCI). Finally, this compound was quantified in red wines by liquid/liquid extraction without any derivatization steps, followed by GC/MS-CI analysis, using methanol as the reagent gas. Coelutions of compounds with the same m/z were checked using methanol-d(4). The method we developed was linear in the 10-300 ng/L range of MND concentrations, with satisfactory repeatability. The detection limit was 4.3 ng/L, over 3 times lower than the olfactory perception threshold of this compound (16 ng/L). The suitability of this method for assaying this diketone in red wine was demonstrated by the analyzing many wines from different vintages.
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http://dx.doi.org/10.1016/j.chroma.2011.08.017DOI Listing
September 2011

Influence of yeast macromolecules on sweetness in dry wines: role of the saccharomyces cerevisiae protein Hsp12.

J Agric Food Chem 2011 Mar 19;59(5):2004-10. Epub 2011 Jan 19.

UMR 1219 Oenologie, Institut des Sciences de la Vigne et du Vin, Université Victor Segalen Bordeaux 2 , 210 chemin de Leysotte CS 50008, 33882 Villenave d'Ornon Cedex, France.

Yeast autolysis during lees contact influences the organoleptic properties of wines especially by increasing their sweet taste. Although observed by winemakers, this phenomenon is poorly explained in enology. Moreover, the compounds responsible for sweetness in wine remain unidentified. This work provides new insights in this way by combining sensorial, biochemical and genetic approaches. First, we verified by sensory analysis that yeast autolysis in red wine has a significant effect on sweetness. Moderate additions of ethanol or glycerol did not have the same effect. Second, a sapid fraction was isolated from lees extracts by successive ultrafiltrations and HPLC purifications. Using nano-LC-MS/MS, peptides released by the yeast heat shock protein Hsp12p were distinctly identified in this sample. Third, we confirmed the sweet contribution of this protein by sensorial comparison of red wines incubated with two kinds of yeast strains: a wild-type strain containing the native Hsp12p and a deletion mutant strain that lacks the Hsp12p protein (Δ°HSP12 strain). Red wines incubated with wild-type strain showed a significantly higher sweetness than control wines incubated with Δ°HSP12 strains. These results demonstrated the contribution of protein Hsp12p in the sweet perception consecutive to yeast autolysis in wine.
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http://dx.doi.org/10.1021/jf103710xDOI Listing
March 2011

3-Sulfanylhexanol precursor biogenesis in grapevine cells: the stimulating effect of Botrytis cinerea.

J Agric Food Chem 2011 Feb 14;59(4):1344-51. Epub 2011 Jan 14.

Université de Bordeaux , UMR 1219 Œnologie, INRA, ISVV, 210 chemin de Leysotte, CS 50008, Villenave d'Ornon, F-33882, France.

Volatile thiols, compounds that contribute strongly to the varietal aroma, are present in much higher concentrations in sweet wines than in dry wines. This positive effect, due to the presence of Botrytis cinerea on the berries, in fact results from a strong enrichment of cysteine S-conjugate precursors in botrytized berries. In the present study, a convenient model was investigated to reproduce and therefore study this phenomenon. A Vitis vinifera cell culture was used as a simple model, and we focused on S-3-(hexan-1-ol)-l-cysteine (P-3SH), the cysteinylated precursor of 3-sulfanylhexanol. We demonstrated that grapevine cells were able to produce P-3SH and that the presence of B. cinerea considerably increased the precursor level (up to 1000-fold). This positive result was determined to be due to metabolites secreted by the fungus. These molecules were temperature sensitive, unstable over time, and their production was activated in the presence of grapevine cells. Moreover, part of the pathway leading to P-3SH was deciphered: it was directly derived from the cleavage of S-3-(hexan-1-ol)-l-glutathione, which itself was generated after a conjugation of glutathione on (E)-2-hexenal.
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http://dx.doi.org/10.1021/jf103915yDOI Listing
February 2011

Identification of a sotolon pathway in dry white wines.

J Agric Food Chem 2010 Jun;58(12):7273-9

SEGUIN MOREAU France, Z. I. Merpins, Cognac, France.

Sotolon (3-hydroxy-4,5-dimethyl-2(5H)-furanone) is a chiral furanone, an aroma compound known to be responsible for premature-aging flavor in dry white wines. Sotolon generally results from mild oxygenation during bottle aging, and until now, its formation pathways had not been elucidated. The ability of the main precursors described in the literature under very different experimental conditions to produce sotolon was tested. In model wine solution maintained at 40 degrees C for 6 months, sotolon was produced by the oxidative degradation of ascorbic acid. By use of GC-MS, 2-ketobutyric acid, produced by the oxidative degradation of the ascorbic acid in the model wine solution, was identified as a potent precursor of sotolon in this pathway. Ascorbic acid is an exogenous compound, added before bottling, but 2-ketobutyric acid was found even in white wines that had not been supplemented. Consequently, this sotolon formation pathway is also valid in white wines with no added ascorbic acid. In addition, we showed that Saccharomyces cerevisiae strains were capable of producing variable concentrations of this ketone during alcoholic fermentation. In model wine solution, certain yeast strains released large quantities of 2-ketobutyric acid, similar to those found in oxidized dry white wines. In view of these results, the role of yeast strains in this premature-aging phenomenon of dry white wines is discussed. Finally, these investigations revealed that one chemical mechanism responsible for the low concentrations of sotolon found in prematurely aged white wines made from various grape varieties was an aldol condensation between 2-ketobutyric acid and acetaldehyde.
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http://dx.doi.org/10.1021/jf100150qDOI Listing
June 2010

Reassessment of phenotypic traits for Saccharomyces bayanus var. uvarum wine yeast strains.

Int J Food Microbiol 2010 Apr 10;139(1-2):79-86. Epub 2010 Feb 10.

ENITA de Bordeaux, 1 Cours du Général de Gaulle, CS 40201, 33175 Gradignan cedex, France.

Among Saccharomyces yeast, S. cerevisiae and S. bayanus var. uvarum are related species, sharing the same ecosystem in sympatry. The physiological and technological properties of a large collection of genetically-identified S. bayanus var. uvarum wine strains were investigated in a biometric study and their fermentation behavior was compared at 24 degrees C and 13 degrees C. The variability of the phenotypic traits was considered at both intraspecific and interspecific levels. Low ethanol tolerance at 24 degrees C and production of high levels of 2-phenylethanol and its acetate were clearly revealed as discriminative technological traits, distinguishing the S. bayanus var. uvarum strains from S. cerevisiae. Although some S. bayanus var. uvarum strains produced very small amounts of acetic acid, this was not a species-specific trait, as the distribution of values was similar in both species. Fermentation kinetics at 24 degrees C showed that S. bayanus var. uvarum maintained a high fermentation rate after Vmax, with low nitrogen requirements, but stuck fermentations were observed at later stages. In contrast, a shorter lag phase compared with S.cerevisiae, higher cell viability, and the ability to complete alcoholic fermentation at 13 degrees C confirmed the low-temperature adaptation trait of S.bayanus var. uvarum. This study produced a phenotypic characterization data set for a collection of S. bayanus var. uvarum strains, thus paving the way for industrial developments using this species as a new genetic resource.
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http://dx.doi.org/10.1016/j.ijfoodmicro.2010.01.038DOI Listing
April 2010

Aromatic potential of botrytized white wine grapes: identification and quantification of new cysteine-S-conjugate flavor precursors.

Anal Chim Acta 2010 Feb 17;660(1-2):190-6. Epub 2009 Oct 17.

Université de Bordeaux, UMR Oenologie, INRA, ISVV, Bordeaux, F-33000, France.

Sweet wines made from botrytized grapes contain much higher concentrations of volatile thiols, especially 3-sulfanylhexan-1-ol (3SH), than dry white wines. Three new specific volatile thiols (3-sulfanylpentan-1-ol (3SP), 3-sulfanylheptan-1-ol (3SHp), and 2-methyl-3-sulfanylbutan-1-ol (2M3SB) were recently identified in Sauternes wines. Like most volatile thiols, these compounds were almost totally absent from must, mainly being formed during alcoholic fermentation. In this work, we describe the identification and quantification of three new cysteine-S-conjugate precursors in must made from Botrytis-infected grapes. S-3-(pentan-1-ol)-L-cysteine (P-3SP), S-3-(heptan-1-ol)-L-cysteine (P-3SHp), and S-3-(2-methylbutan-1-ol)-L-cysteine (P-2M3SB) were identified by direct GC-MS analysis of their derivative forms obtained by silylation of an enriched fraction, isolated from must by affinity chromatography. Concentrations were considerably higher when Botrytis cinerea had developed on the grapes. In botrytized must, the mean levels of P-3SP, P-3SHp, and P-2M3SB were in the vicinity of 700, 50, and 500 nM, respectively, whereas concentrations in healthy must ranged from 0 to 50 nM. This indicated that these three new sulfanyl alcohols, responsible for the characteristic aroma of botrytized wines, were formed by the yeast metabolism during alcoholic fermentation from the corresponding non-volatile cysteine-S-conjugate precursors. Moreover, these results highlighted the predominant role of botrytization in developing grape aroma potential.
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http://dx.doi.org/10.1016/j.aca.2009.10.018DOI Listing
February 2010

Impact of oxygen dissolved at bottling and transmitted through closures on the composition and sensory properties of a Sauvignon Blanc wine during bottle storage.

J Agric Food Chem 2009 Nov;57(21):10261-70

UMR1219 Oenologie, Faculte d'Oenologie-ISVV, 210 chemin de Leysotte, CS 50008, 33882 Villenave d'Ornon, France.

This work outlines the results from an investigation to determine the effect of the oxygen dissolved at bottling and the specific oxygen barrier properties of commercially available closures on the composition, color and sensory properties of a Bordeaux Sauvignon Blanc wine during two years of storage. The importance of oxygen for wine development after bottling was also assessed using an airtight bottle ampule. Wines were assessed for the antioxidants (SO(2) and ascorbic acid), varietal thiols (4-mercapto-4-methylpentan-2-one, 3-mercaptohexan-1-ol), hydrogen sulfide and sotolon content, and color throughout 24 months of storage. In addition, the aroma and palate properties of wines were also assessed. The combination of oxygen dissolved at bottling and the oxygen transferred through closures has a significant effect on Sauvignon Blanc development after bottling. Wines highly exposed to oxygen at bottling and those sealed with a synthetic, Nomacorc classic closure, highly permeable to oxygen, were relatively oxidized in aroma, brown in color, and low in antioxidants and volatile compounds compared to wines sealed with other closures. Conversely, wines sealed under more airtight conditions, bottle ampule and screw cap Saran-tin, have the slowest rate of browning, and displayed the greatest contents of antioxidants and varietal thiols, but also high levels of H(2)S, which were responsible for the reduced dominating character found in these wines, while wines sealed with cork stoppers and screw cap Saranex presented negligible reduced and oxidized characters.
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http://dx.doi.org/10.1021/jf9023257DOI Listing
November 2009

Genetic improvement of thermo-tolerance in wine Saccharomyces cerevisiae strains by a backcross approach.

FEMS Yeast Res 2009 Dec 21;9(8):1148-60. Epub 2009 Jul 21.

Université de Bordeaux, UMR OEnologie, INRA, ISVV, Villenave d'Ornon, France.

During red wine fermentation, high temperatures may cause stuck fermentation by affecting the physiology of fermenting yeast. This deleterious effect is the result of the complex interaction of temperature with other physicochemical parameters of grape juice, such as sugar and lipid content. The genetic background of fermenting yeast also interacts with this complex matrix and some strains are more resistant to high temperatures than others. Here, the temperature tolerance of nine commercial starters was evaluated, demonstrating that, at high sugar concentrations, half of them are sensitive to temperature. Using a classical backcross approach, one thermo-sensitive commercial starter was genetically improved by introducing quantitative trait loci conferring resistance to temperature. With this breeding program it is possible to obtain a thermo-resistant strain sharing most of its genome with the initial commercial starter. The parental and improved strains were compared for population growth and fermentation ability in various conditions. Despite their common genetic background, these two strains showed slight physiological differences in response to environmental changes that enable identification of the key physiological parameters influencing stuck fermentation.
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http://dx.doi.org/10.1111/j.1567-1364.2009.00550.xDOI Listing
December 2009

Examples of perceptive interactions involved in specific "red-" and "black-berry" aromas in red wines.

J Agric Food Chem 2009 May;57(9):3702-8

Universitéde Bordeaux, Institut des Sciences de la Vigne et du Vin, 210, chemin de Leysotte, CS 50008, F-33882 Villenave d'Ornon cedex, France.

A preparative HPLC method, which preserves wine aromas and isolates fruity characteristics in specific fractions, was applied to red wine aroma extracts. Various odor-active zones were detected in typical fractions by GC-O analysis of their extracts. Through further GC-MS analyses, the aromatic compounds responsible for 15 of these odoriferous zones were identified as various ethyl esters and alkyl acetates. In view of their olfactory thresholds, the concentrations of these compounds had no direct impact on the fruity aroma of red wines. Nevertheless, an overall sensory effect of "red-" or "black-berry" nuances was clearly established. Higher than average levels of ethyl propanoate, ethyl 2-methylpropanoate, and ethyl 2-methylbutanoate were involved in black-berry aromas, whereas ethyl butanoate, ethyl hexanoate, ethyl octanoate, and ethyl 3-hydroxybutanoate conferred red-berry aromas.
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http://dx.doi.org/10.1021/jf803325vDOI Listing
May 2009

Identification and characteristics of new volatile thiols derived from the hop (Humulus luplus L.) cultivar Nelson Sauvin (dagger).

J Agric Food Chem 2009 Mar;57(6):2493-502

Frontier Laboratories of Value Creation, Sapporo Breweries Ltd, Yaizu, Shizuoka, Japan.

Nelson Sauvin (NS) is a unique hop cultivar that was bred and grown in New Zealand. This hop gives a specific flavor (exotic fruit-like, white wine-like) to finished beers. However, the key compounds of this flavor have not yet been identified. We have attempted to identify the specific flavor compounds derived from NS. We focused on certain volatile thiols that are well-known to contribute to wine flavors, especially Sauvignon Blanc. The product made from NS (NS product) lost its specific flavor by contact with copper. Copper is well-known as an absorber of thiols in the field of wine flavor investigations. Therefore, it might point to the existence of thiols. We analyzed the NS product by GC-FPD, GC-olfactometry and GC-MS, and identified two new volatile thiols, 3-sulfanyl-4-methylpentan-1-ol (3S4MP), and 3-sulfanyl-4-methylpentyl acetate (3S4MPA). These compounds have a grapefruit-like and/or rhubarb-like odor, similar to that of Sauvignon Blanc. We quantified these compounds in the NS products and determined their thresholds. As a result, 3S4MP contained about 2-fold of its threshold in beers, and 3S4MPA was included below its threshold. However, it was confirmed that 3S4MP enhanced the flavors of 3S4MPA by synergy. Therefore, we concluded that both of the new volatile thiols would contribute to the specific odor of beers produced with NS.
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http://dx.doi.org/10.1021/jf8034622DOI Listing
March 2009

Quantification and odor contribution of 2-furanmethanethiol in different types of fermented soybean paste miso.

J Agric Food Chem 2009 Mar;57(6):2481-5

Faculty of Education, Iwate University, Morioka, Iwate, Japan.

2-Furanmethanethiol, a compound contained in many kinds of food, was identified for the first time in five types of miso fermented soybean paste (red salty rice miso, thin-colored salty rice miso, weak salty rice miso, barley miso, and soy miso) by specific extraction of volatile thiols using p-hydroxymercuribenzoate. In the triangle test with red salty rice miso, which included a higher concentration of 2-furanmethanethiol, and thin-colored salty rice miso, which included a lower concentration of 2-furanmethanethiol, it was shown that the aroma of thin-colored salty rice miso was similar to that of red salty rice miso by adding 2-furanmethanethiol into thin-colored salty rice miso. In addition, a quantitative descriptive analysis (QDA) clearly shows that 2-furanmethanethiol contributed to the intensity of three odor qualities "thick, complex", "sweet", and "pleasant aroma like coffee beans" in six odor qualities and was a very important component of miso aroma.
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http://dx.doi.org/10.1021/jf803258cDOI Listing
March 2009

New method for reducing the binding power of sweet white wines.

J Agric Food Chem 2008 Sep 29;56(18):8470-4. Epub 2008 Aug 29.

Institut des Sciences Moléculaires, UMR 5255 CNRS - Université Bordeaux 1, 351 Cours de la Libération, F-33405 Talence, France.

Sulfur dioxide is now considered to be a toxic chemical by most world health authorities. However, it remains an irreplaceable additive in enology for wine conservation, combining antioxidant and antibacterial properties. Sweet white wines from botrytized grapes retain particularly high SO 2 levels due to their high sulfur dioxide binding power. This paper presents a new method for reducing this binding power by removing some of the carbonyl compounds responsible, which are naturally present in these wines. The main carbonyl compounds responsible for the SO 2 binding power of sweet wines were removed, that is, acetaldehyde, pyruvic acid, 2-oxoglutaric acid, and 5-oxofructose. The method retained was selective liquid-solid removal, using phenylsulfonylhydrazine as a scavenging agent. The scavenging function was grafted on different classes of porous polymer supports, and its efficiency was evaluated on sweet white wines under conditions intended to conserve their organoleptic qualities. The results obtained showed that the method was efficient for removing carbonyl compounds and significantly reduced the binding power of the wines. Sensory analysis revealed that this process did not deteriorate their organoleptic qualities.
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http://dx.doi.org/10.1021/jf800665eDOI Listing
September 2008