IVAS 2022 banner
IVES 9 IVES Conference Series 9 IVAS 9 IVAS 2022 9 An Ag+ SPE method combined with Deans’ switch heart-cutting MDGC–MS/Olfactometry approach for identifying unknown volatile thiols in wine

An Ag+ SPE method combined with Deans’ switch heart-cutting MDGC–MS/Olfactometry approach for identifying unknown volatile thiols in wine

Abstract

Wine aroma is a crucial quality criterion. A multitude of volatile compounds have been identified and correlated to the aroma attributes perceived in wine. Volatile thiols are a category of volatile sulfur compounds that are well-recognized as potent aroma-impacting odorants contributing to various aroma attributes of many wines because of their low odor detection thresholds (ng/L). However, volatile thiols are highly reactive and generally present at ultra-trace concentrations (ng/L) in wines, causing major analytical difficulties. For more than two decades, the identifications of new volatile thiols were nearly exclusively achieved by the use of organomercuric compounds for thiol extraction, followed by conventional gas chromatography and mass spectrometry/olfactometry (GC–MS/O) for chromatographic separation, odorous zone profiling, and MS detection. However, such analytical protocols required the use of highly toxic organomercuric chemicals and are often laborious. Meanwhile, olfactometry data of other unknown thiol odorous zones has been reported but their identities were not pursued.
This work focused on the aroma of premium red wines and aimed to identify unknown volatile thiols. First, we developed a silver ion solid-phase extraction (Ag+ SPE) method for thiol isolation. Ag+ SPE cartridge selectivity, cartridge wettability, reservoir material, and elution reagent were evaluated. The developed Ag+ SPE method was safe, simple, scalable, selective, and artefact resistant, suitable for qualitative identification tasks. Low thermal mass (LTM) Deans’ switch (DS) heart-cutting multidimensional GC–MS/O (H/C MDGC–MS/O) was optimized for its performance using three model volatile thiol analytes. Significant impacts of instrument parameters including main host oven temperature, H/C width, and cryogenic trapping on the separation and detection were observed. Main host oven at high temperature was required to maintain flow balance for H/C operation. Narrow H/C width was selected to avoid irregular chromatographic behavior. Cryogenic trapping at the optimal temperature was needed to effectively capture the H/C effluent at the inlet of second column and to significantly enhance peak detection. The development of the Ag+ SPE H/C MDGC–MS/O protocol was applied to screen a selection of several premium Bordeaux red wines presenting a bouquet with intense empyreumatic nuances. In selected wines, a number of odorous zones with such aroma descriptors were characterized. Supported by olfactometric results, retention data, and corresponding mass spectra, the identification of odorous thiols that were not previously reported in wine was described. The identification of unknown thiols expands our understanding of the volatile molecular markers contributing to the aroma quality of premium wines

DOI:

Publication date: June 22, 2022

Issue: IVAS 2022

Type: Article

Authors

Chen Liang¹* and Darriet Philippe¹

¹Univ. Bordeaux, INRAE, Bordeaux INP, UMR1366 Œnologie, ISVV, F-33140 Villenave d’Ornon, France

Contact the author

Keywords

red wine, aroma, volatile thiols, extraction, identification

Tags

IVAS 2022 | IVES Conference Series

Citation

Related articles…

How does aromatic composition of red wines, resulting from varieties adapted to climate change, modulate fruity aroma?

One of the major issues for the wine sector is the impact of climate change linked to the increasing temperatures which affects physicochemical parameters of the grape varieties planted in Bordeaux vineyard and consequently, the quality of wine. In some varietals, the attenuation of their fresh fruity character is accompanied by the accentuation of dried-fruit notes [1]. As a new adaptive strategy on climate change, some winegrowers have initiated changes in the Bordeaux blend of vine varieties [2]. This study intends to explore the fruitiness in wines produced from grape varieties adapted to the future climate of Bordeaux. 10 commercial single–varietal wines from 2018 vintage made from the main grape varieties in the Bordeaux region (Cabernet franc, Cabernet-Sauvignon and Merlot) as well as from indigenous grape varieties from the Mediterranean basin, such as Cyprus (Yiannoudin), France (Syrah), Greece (Agiorgitiko and Xinomavro), Portugal (Touriga Nacional) and Spain (Garnacha and Tempranillo), were selected among 19 samples using sensory descriptive analyses. Both sensory and instrumental analyses were coupled, to investigate their fruity aroma expression. For sensory analysis, samples were prepared from wine, using a semi preparative HPLC method which preserves wine aroma and isolates fruity characteristics in 25 specific fractions [3,4]. Fractions of interest with intense fruity aromas were sensorially selected for each wine by a trained panel and mixed with ethanol and microfiltered water to obtain fruity aromatic reconstitutions (FAR) [5]. A free sorting task was applied to categorize FAR according to their similarities or dissimilarities, and different clusters were highlighted. Instrumental analysis of the different FAR and wines demonstrated variations in their molecular composition. Results obtained from sensory and gas chromatography analysis enrich the knowledge of the fruity expression of red wines from “new” grape varieties opening up new perspectives in wine technology, including blending, thus providing new tools for producers.

Climate, Viticulture, and Wine … my how things have changed!

The planet is warmer than at any time in our recorded past and increasing greenhouse emissions and persistence in the climate system means that continued warming is highly likely. Climate change has already altered the basic framework of growing grapes for wine production worldwide and will likely continue to do so for years to come. The wine sector can continue to play an important role in leading the agricultural sector in addressing climate change. From developing on…

Mapping and tracking canopy size with VitiCanopy

Understanding vineyard variability to target management strategies, apply inputs efficiently and deliver consistent grape quality to the winery is essential. However, despite inherent vineyard variability, the majority are managed as if they are uniform. VitiCanopy is a simple, grower-friendly tool for precision/digital viticulture that allows users to collect and interpret objective spatial information about vineyard performance. After four years of field and market research, an upgraded VitiCanopy has been created to achieve a more streamlined, technology-assisted vine monitoring tool that provides users with a set of superior new features, which could significantly improve the way users monitor their grapevines. These new features include:
• New user interface
• User authentication
• Batch analysis of multiple images
• Ease the learning curve through enhanced help features
• Reporting via the creation of colour maps that will allow users to assess the spatial differences in canopies within a vineyard.
Use-case examples are presented to demonstrate the quantification and mapping of vineyard variability through objective canopy measurements, ground-truthing of remotely sensed measurements, monitoring of crop conditions, implementation of disease and water management decisions as well as creating a history of each site to forecast quality. This intelligent tool allows users to manage grapevines and make informed management choices to achieve the desired production targets and remain profitable.

Modelling vine water stress during a critical period and potential yield reduction rate in European wine regions: a retrospective analysis

Most European vineyards are managed under rainfed conditions, where seasonal water deficit has become increasingly important. The flowering-veraison phenophase represents an important period for vine response to water stress, which is seldomly thoroughly evaluated. Therefore, we aim to quantify the flowering-veraison water stress levels using Crop Water Stress Indicator (CWSI) over 1986–2015 for important European wine regions, and to assess the respective potential Yield Lose Rate (YLR). Additionally, we also investigate whether an advanced flowering-veraison phase may help alleviating the water stress with improved yield. A process-based grapevine model STICS is employed, which has been extensively calibrated for flowering and veraison stages using observed data at 38 locations with 10 different grapevine varieties. Subsequently, the model is being implemented at the regional level, considering site-specific calibration results and gridded climate and soil datasets. The findings suggest wine regions with stronger flowering-veraison CWSI tend to have higher potential YLR. However, contrasting patterns are found between wine regions in France-Germany-Luxembourg and Italy-Portugal-Spain. The former tends to have slight-to-moderate drought conditions (CWSI<0.5) and a negligible-to-moderate YLR (<30%), whereas the latter possesses severe-to-extreme CWSI (>0.5) and substantial YLR (>40%). Wine regions prone to a high drought risk (CWSI>0.75) are also identified, which are concentrated in southern Mediterranean Europe. An advanced flowering-veraison phase may have benefited from cooler temperatures and a higher fraction of spring precipitation in wine regions of Italy-Portugal-Spain, resulting in alleviated CWSI and moderate reductions of YLR. For those of France-Germany-Luxembourg, this can have reduced flowering-veraison precipitation, but prevalent alleviations of YLR are also found, possibly because of shifted phase towards a cooler growing season with reduced evaporative demands. Overall, such a retrospective analysis might provide new insights towards better management of seasonal water deficit for conventionally vulnerable Mediterranean wine regions, but also for relatively cooler and wetter Central European regions.

Elevational range shifts of mountain vineyards: Recent dynamics in response to a warming climate

Increasing temperatures worldwide are expected to cause a change in spatial distribution of plant species along elevational gradients and there are already observable shifts to higher elevations as a consequence of climate change for many species. Not only naturally growing plants, but also agricultural cultivations are subject to the effects of climate change, as the type of cultivation and the economic viability depends largely on the prevailing climatic conditions. A shift to higher elevations therefore represents a viable adaptation strategy to climate change, as higher elevations are characterized by lower temperatures. This is especially important in the case of viticulture because a certain wine-style can only be achieved under very specific climatic conditions. Although there are several studies investigating climatic suitability within winegrowing regions or longitudinal shifts of winegrowing areas, little is known about how fast vineyards move to higher elevations, which may represent a viable strategy for winegrowers to maintain growing conditions and thus wine-style, despite the effects of climate change. We therefore investigated the change in the spatial distribution of vineyards along an elevational gradient over the past 20 years in the mountainous wine-growing region of Alto Adige (Italy). A dataset containing information about location and planting year of more than 26000 vineyard parcels and 30 varieties was used to perform this analysis. Preliminary results suggest that there has been a shift to higher elevations for vineyards in general (from formerly 700m to currently 850 m a.s.l., with extreme sites reaching 1200 m a.s.l.), but also that this development has not been uniform across different varieties and products (i.e. vitis vinifera vs hybrid varieties and still vssparkling wines). This is important for climate change adaptation as well as for rural development. Mountain areas, especially at mid to high elevations, are often characterized by severe land abandonment which can be avoided to some degree if economically viable and sustainable land management strategies are available.