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…

Traditional agroforestry vineyards, sources of inspiration for the agroecological transition of viticulture

A unique “terroir” can be found in southern Bolivia, which combines the specific features of climate, topography and altitude of high valleys, with the management of grapevines staked on trees. It is one of the rare remnants of agroforestry viticulture. A survey was carried out among 29 grapegrowers in three valleys, to characterize the structure and management of these vineyards, and identify the services they expect from trees. Farms were small (2.2 ha on average) and 85% of vineyards were less than 1 ha. Viticulture was associated with vegetable, fruit and fodder production, sometimes in the same fields. Molle trees were found in all plots, together with one or two other native tree species. Traditional grapevine varieties such as Negra Criolla, Moscatel de Alejandría and Vicchoqueña were grown with a large range of densities from 1550 to 9500 vines ha-1. From 18 to 30% of them were staked on trees, with 1.2 to 4.9 vines per tree. The management of these vineyards (irrigation, fertilization and grapevine protection) was described, the most particular technical operation being the coordinated pruning of trees and grapevines. Three types of management could be identified in the three valleys. Grapegrowers had a clear idea of the ecosystem services they expected from trees in their vineyards. The main one was protection against climate hazards (hail, frost, flood). Then they expected benefits in terms of pest and disease control, improvement of soil fertility and resulting yield. At last, some producers claimed that tree-staking was quicker and cheaper than conventional trellising. It can be hypothesized then that agroforestry is a promising technique for the agroecological transition of viticulture. Its contribution to the “terroir” of the high valleys of southern Bolivia and its link with the specificities of the wines and spirits produced there remain to be explored.

Towards a regional mapping of vine water status based on crowdsourcing observations

Monitoring vine water status is a major challenge for vineyard management because it influences both yield and harvest quality. It is also a challenge at the territorial scale for identifying periods of high water restriction or zones regularly impacted by water stress. This information is of major importance for defining collective strategies, anticipating harvest logistic or applying for irrigation authorisation. At this spatial scale, existing tools and methods for monitoring vine water status are few and often require strong assumptions (e.g. water balance model). This paper proposes to consider a collaborative collection of observations by winegrowers and wine industry stakeholders (crowdsourcing) as an interesting alternative. Indeed, it allows the collection of a large number of field observations while pooling the collection effort. However, the feasibility of such a project and its interest in monitoring vine water status at regional scale has never been tested.

The objective of this article is to explore the possibility of making a regional map of vine water status based on crowdsourcing observations. It is based on the study of the free mobile application ApeX-Vigne, which allows the collection of observations about vine shoot growth. This information is easy to collect and can be considered, under certain conditions, as a proxy for vine water status. This article presents the first results obtained from the nearly 18,000 observations collected by winegrowers and wine industry stakeholders during 2019, 2020 and 2021 seasons. It presents the vine shoot growth maps obtained at regional scale and their evolution over the three vintages studied. It also proposes an analysis of the factors that favoured the number of observations collected and those that favoured their quality. These results open up new perspectives for monitoring vine water status at a regional scale but above they provide references for other crowdsourcing projects in viticulture.

Influence of weather and climatic conditions on the viticultural production in Croatia

The research includes an analysis of the impact of weather conditions on phenological development of the vine and grape quality, through monitoring of four experimental cultivars (Chardonnay, Graševina, Merlot and Plavac mali) over two production years. In each experimental vineyard, which were evenly distributed throughout the regions of Slavonia and The Croatian Danube, Croatian Uplands,

austrianvineyards.com: online viewer of all designations of Austrian wine

To digitally record and present all the origins of Austrian wines in the same perfect and clear way was the motivation for the Austrian Wine Marketing Board (Austrian Wine) to start with the project in 2018. In June 2021 the results were presented to the public in an online viewer showing all the designations of Austrian wine, available at https://austrianvineyards.com in a largely barrier-free manner. The online viewer provides tailored individual maps fitted to the respective zoom level. The smallest unit of wine-origins in Austria is called Ried and is displayed in a plot-specific manner highlighting areas under vine. Information on the Ried include administrative district, winegrowing municipality, cadastral municipality, large collective vineyard site, specific winegrowing region, generic winegrowing region, winegrowing area and, in many cases, an illustrative picture. Complementary data on the size, elevation (minimum-maximum), orientation (in 8 sectors plus flat) and gradient (minimum, maximum, average) are based on the area under vine according to the EU’s Integrated Administration and Control System. Additional information covers climate data. The diagrams are taken from the monthly breakdown of data in the annals of the Central Institute for Meteorology and Geodynamics, Austria provide a display of values for air temperature, precipitation, and sunshine hours for the reference year and the long-term average. Seasonal aggregated data on temperature, precipitation, and sunshine hours complete the display. Short descriptions with emphasis on geology and soil, field name in historical maps, etymology of the denomination, and main planted variety complements the available information for the main designations in the online viewer. These descriptions are compiled by winegrowers, geologists, historians, and journalists. All the information and data can be extracted to a pdf-file. Printed vineyard maps are also available. Missing content regarding wine origins in Styria will be completed in winter 2021/22.

The impact of leaf canopy management on eco-physiology, wood chemical properties and microbial communities in root, trunk and cordon of Riesling grapevines (Vitis vinifera L.)

In the last decades, climate change required already adaptation of vineyard management. Increase in temperature and unexpected weather events cause changes in all phenological stages requiring new management tools. For example, defoliation can be a useful tool to reduce the sugar content in the berries creating differences in the wine profiles. In a ten-year field experiment using Riesling (Vitis vinifera L, planted 1986, Geisenheim, Germany), various mechanical defoliation strategies and different intensities were trialed until 2016 before the vineyard was uprooted. Wood was sampled from the plant compartments root, trunk, cordon and shoot for analyses of physicochemical properties (e.g. lignin and element content, pH, diameter), nonstructural carbohydrates and the microbial communities. The aim of the study was to investigate the influence of reduced canopy leaf area on the sink-source allocation into different compartments and potential changes of the fungal and prokaryotic wood-inhabiting community using a metabarcoding approach. Severe summer pruning (SSP) of the canopy and mechanical defoliation (MDC) above the bunch zone decreased the leaf area by 50% compared to control (C). SSP reduced the photosynthetic capacity, which resulted in an altered source-sink allocation and carbohydrate storage. With lower leaf area, less carbohydrates are allocated. This for example resulted in a decreased trunk diameter. Further, it affected the composition of the grapevine wood microbiota. SSP and MDC management changed significantly the prokaryotic community composition in wood of the root samples, but had no effect in other compartments. In general, this study found strong compartment and less management effects of the microbial community composition and associated physicochemical properties. The highest microbial diversities were identified in the wood of the trunk, and several species were recorded the first time in grapevine.