Evolution of Markers Involved in the Fresh Mushroom Off-Flavor in Wine During Alcoholic Fermentation.

The fresh mushroom off-flavor (FMOff) is due to several C8 compounds such as 1-octen-3-one, 1-octen-3-ol and 1-hydroxyoctan-3-one, among others. Recently, glycosidic precursors of some FMOff compounds have been identified in grape musts, but the evolution of such compounds during alcoholic fermentation (AF) remains poorly studied. Therefore, the aim of this work was to monitor both FMOff glycosidic precursors and volatile compounds during AF by comparing healthy and -contaminated musts.

Evidence of Enzymatic and Chemical Interconversions of Barley Malt 3-Sulfanylhexanol Conjugates during Mashing.

Recent studies have highlighted in malt the occurrence of the glutathionylated precursor of 3-sulfanylhexanol (G-3SHol) at concentrations reaching hundreds of μg/kg. Here, SIDA-LC-MS/MS was used to investigate the potential conversion of G-3SHol to its dipeptide and cysteinyl analogues during mashing. At 45 and 55 °C, malt γGT and carboxypeptidase activities quickly degrade G-3SHol (up to 90% loss), first to the cysteinylglycine conjugate and then to the cysteine conjugate (up to 205% increase).

New Insights on the Scalping Phenomenon of Volatile Sulphur Compounds on Micro-Agglomerated Wine Closures.

Flavour scalping in wine is a well-known phenomenon that is defined as the sorption of flavour compounds on wine closures. While the impact of closure type was the object of several studies, no research has addressed the impact of wine closure permeability on flavour scalping. For that purpose, the adsorption of volatile sulphur compounds (VSCs) on four micro-agglomerated wine cork closures was investigated by soaking them in model and Shiraz wines for 7 days.

Unravelling copper effect on the production of varietal thiols during Colombard and Gros Manseng grape juices fermentation by .

Nowadays the rapidly increasing organic vineyard management with the utilization of copper as sole fungal control pesticide against downy mildew raises once again the question of copper impact on varietal thiols in wine. For this purpose, Colombard and Gros Manseng grape juices were fermented under different copper levels (from 0.2 to 3.

New Fungus-Resistant Grapevine and L. × Derivative Hybrids Display a Drought-Independent Response in Thiol Precursor Levels.

The use of new disease-resistant grapevine varieties is a long-term but promising solution to reduce chemical inputs in viticulture. However, little is known about water deficit effects on these varieties, notably regarding berry composition. The aim of this study was to characterize the primary metabolites and thiol precursors levels of 6 fungi-resistant varieties and Syrah.

New Light on the Varietal Thiols Pathway during Alcoholic Fermentation: Role of 3--(-Acetyl-cysteinyl)-hexan-1-ol (NAC3SH).

For many years, knowledge on thiol precursors has been limited to -conjugates of glutathione (G3SH), cysteine (Cys3SH), and later on the dipeptides γ-GluCys and CysGly. In this work, we took the parallel between precursor degradation and the glutathione-mediated detoxification pathway a step further by considering a new type of derivative, 3--(-acetyl-l-cysteinyl)hexanol (NAC3SH). This compound was synthesized and then added to the existing liquid chromatography with tandem mass spectrometry (LC-MS/MS) method of thiol precursors.

First identification of a new molecule involved in the fresh mushroom off-flavor in wines: 1-hydroxyoctan-3-one.

The fresh mushrooms off-flavor (FMOff) has been appearing in wines since the 2000 s; the C8 compounds, 1-octen-3-one, 1-octen-3-ol and 3-octanol are involved in this specific taint, yet they alone do not fully explain its occurrence. The objective of this work was to identify by GC-MS new FMOff markers in contaminated matrices, to correlate compound levels with wine sensory characterization and to determine the sensory attributes of 1-hydroxyoctan-3-one, a new candidate involved in FMOff. In practice, grape musts were artificially contaminated with Crustomyces subabruptus, and fermented to obtain tainted wines.

Identification of a Glycosylated Fraction Involved in Mushroom Off-Flavors in Grapes: Influence of Gray Rot, Powdery Mildew and .

An organoleptic defect, termed fresh mushroom off-flavor and mainly caused by the C8 compounds 1-octen-3-one, 3-octanol and 1-octen-3-ol, has been identified in wines and spirits since the 2000s. The aim of this work was to identify the presence of glycosidic precursors of these C8 compounds and to evaluate the influence of different molds on the glycosylated fractions of three grape varieties. Must samples contaminated by molds (gray rot, powdery mildew and ) and three levels of attack severity (from healthy to 10-15%) were studied.

Impact of accentuated cut edges, yeast strain, and malolactic fermentation on chemical and sensory profiles of Sauvignon blanc wine.

This pioneering investigation involved the application of accentuated cut edges (ACE) technique to Sauvignon blanc winemaking. The concentration of varietal thiol precursors in juice was significantly higher for ACE treatment compared to conventional crushing, with two-way or three-way interactions of the experimental factors, which included yeast strain and malolactic fermentation, being determined from the wine data. ACE yielded higher concentrations of 4-methyl-4-sulfanylpentan-2-one (4-MSP) and enantiomers of 3-sulfanylhexanol (3-SH) and 3-sulfanylhexyl acetate (3-SHA) in wines that were more abundant in phenolic compounds.

Impact of accentuated cut edges (ACE) technique on volatile and sensory profiles of Shiraz wines.

Varietal thiols are important wine aroma compounds that are generally less abundant in red wines. Accentuated cut edges (ACE), known for accelerating phenolic extraction, was applied to Shiraz winemaking and compared with conventional crushing (NOACE) to examine the effects on varietal thiol precursor extraction and thiol formation. Water addition to grape must and skin contact time (SCT) during fermentation were also assessed.

Chiral analysis of cis-2-methyl-4-propyl-1,3-oxathiane and identification of cis-2,4,4,6-tetramethyl-1,3-oxathiane in wine.

cis-2-Methyl-4-propyl-1,3-oxathiane (cis-2-MPO), arising from 3-sulfanylhexan-1-ol (3-SH) and acetaldehyde, was recently identified in wine, but the enantiomeric distribution was unknown. Such information could reveal influences on wine aroma, given the impact of chirality on odorant molecules. Herein, a stable isotope dilution assay employing headspace solid-phase microextraction with chiral gas chromatography-mass spectrometry was developed, validated, and applied to a selection of wines.

Spotlight on release mechanisms of volatile thiols in beverages.

Volatile thiols are very strong-smelling molecules that can impact the aroma of numerous beverages. Several thiols and thiol precursors have been reported previously in different plants used as raw material for beverages, some of which are fermented. We focused on thiols in beverages and their release mechanisms from precursors during processing.

Evolution and Correlation of -2-Methyl-4-propyl-1,3-oxathiane, Varietal Thiols, and Acetaldehyde during Fermentation of Sauvignon blanc Juice.

-2-Methyl-4-propyl-1,3-oxathiane (-2-MPO) was recently identified in wine and proposed to arise from the reaction of 3-sulfanylhexan-1-ol (3-SH) and acetaldehyde. However, the evolution profile of -2-MPO during alcoholic fermentation (AF) and storage and its relationship with varietal thiols and acetaldehyde production were unknown. These aspects were investigated by fermenting Sauvignon blanc juice with J7 and/or VIN13 yeast strains and assessing the stability of -2-MPO during wine storage.

Impact of harvest maturity on the aroma characteristics and chemistry of Cascade hops used for dry-hopping.

The impact of ripening on the dry-hop aroma potential and chemical development of Cascade hops is not well understood. Therefore, 5-6 weekly hop samples were collected over the 2014, 2015 and 2016 harvests. Concentrations of humulones did not change as a function of harvest date, while total hop essential oil content displayed significant positive trends.

Revisiting the evaluation strategy of varietal thiol biogenesis.

The varietal thiols 3-mercaptohexan-1-ol (3MH), 3-mercaptohexyl acetate (3MHA), and 4-mercapto-4-methylpentan-2-one (4MMP) are key aroma compounds in wine due to the tropical notes they impart. They are released by yeast during alcoholic fermentation from different precursors. However, a large part of 3MH origin remains unknown.

First identification and quantification of S-3-(hexan-1-ol)-γ-glutamyl-cysteine in grape must as a potential thiol precursor, using UPLC-MS/MS analysis and stable isotope dilution assay.

Varietal thiols are key aroma compounds in wine issued from multiple and complex origins. Several precursor families have been identified in grapes and must and have been widely studied. But a large part of thiol origin still remains unknown.

Development and validation of a high-throughput analysis of glutathione in grapes, musts and wines by Stable Isotope Dilution Assay and LC-MS/MS.

For the first time, we proposed a high-throughput method to quantify glutathione in grapes, musts and wines for all grape varieties using Stable Isotope Dilution Assay (SIDA). Indeed, the use of SIDA as a quantification method is essential to overcome the chemical instability of glutathione. In practice, glutathione was derivatized in-situ with N-ethylmaleimide to block the cysteine residue and to enhance its lipophilic properties.

Development of a routine analysis of 4-mercapto-4-methylpentan-2-one in wine by stable isotope dilution assay and mass tandem spectrometry.

The 4-mercapto-4-methylpentan-2-one (4MMP) is a key aroma compound in wines, especially in Sauvignon Blanc ones. Its accurate quantification is quite difficult due to its traces levels and its reactivity in wine conferred by the thiol function. In this paper, we proposed a new method for its quantification in wine without any sample preparation, based on automated derivatization procedure by methoximation and SIDA-SPME-GC-MS/MS analysis.

Analysis of ochratoxin A in grapes, musts and wines by LC-MS/MS: first comparison of stable isotope dilution assay and diastereomeric dilution assay methods.

Ochratoxin A (OTA) exhibits potent nephrotoxic, carcinogenic and teratogenic effects and its maximum level in wines has been set to 2 μg L(-1) by regulation. Consequently, the analytical procedures for OTA determination in wines have to be both very sensitive and reliable. In this paper, we compared two quantification methods: the stable isotope dilution assay (SIDA) and the diastereomeric dilution assay (DIDA).

First synthesis of a stable isotope of Ochratoxin A metabolite for a reliable detoxification monitoring.

Due to its toxicity and presence in numerous food products, Ochratoxin A (OTA) has drawn attention for decades. This article summarizes the first synthesis of a labeled analogue of Ochratoxin α (OTα), one of the main products generated by the metabolization of OTA by microorganisms. This synthesis also led to a new labeled analogue of OTA with the deuteration located on the dihydroisocoumarin moiety allowing thus both the accurate quantification of OTA and OTα and the establishing of a reliable detoxification rate.

Straightforward synthesis of deuterated precursors to demonstrate the biogenesis of aromatic thiols in wine.

Straightforward synthesis of labeled S-3-(hexan-1-ol)-glutathione and S-4-(4-methylpentan-2-one)-glutathione has been developed through a conjugate addition optimization study. Sauvignon blanc fermentation experiments with the [(2)H(10)] S-4-(4-methylpentan-2-one)-glutathione used as a tracer released the corresponding deuterated thiol, thus proving the direct relationship with the 4-mercapto-4-methylpentan-2-one under enological conditions. The conversion yield of such transformation was estimated to be close to 0.

Evolution of S-cysteinylated and S-glutathionylated thiol precursors during oxidation of Melon B. and Sauvignon blanc musts.

Thiol precursor content in Melon B. and Sauvignon blanc grape juices obtained under vacuum was determined by quantifying cysteinylated and glutathionylated conjugates of 3-mercaptohexan-1-ol (3MH) and 4-methyl-4-mercaptopentan-2-one (4MMP). This characterization allowed the study of thiol precursor evolution during ripening of Sauvignon blanc grapes in several viticultural situations together with grape reaction product (GRP) and the main substrate of polyphenoloxidase, that is, caftaric acid.

Validation of a nanoliquid chromatography-tandem mass spectrometry method for the identification and the accurate quantification by isotopic dilution of glutathionylated and cysteinylated precursors of 3-mercaptohexan-1-ol and 4-mercapto-4-methylpentan-2-one in white grape juices.

A rapid nanoLC-MS/MS method was developed and validated for the simultaneous determination of glutathionylated and cysteinylated precursors of 3-mercapto-hexan-1-ol (3MH) and 4-methyl-4-mercaptopentan-2-one in grape juice using stable isotope dilution assay (SIDA). The analytes were extracted from must using a cation exchange resin and purified on C18 cartridges. They were chromatographically separated on a reverse phase column and finally analyzed by tandem mass spectrometry in selected reaction monitoring mode (SRM) using deuterated analogues as standards except for glutathionylated conjugate of 4MMP which was analyzed by external calibration.