IVAS 2022 banner
IVES 9 IVES Conference Series 9 IVAS 9 IVAS 2022 9 Exploring and unravelling the complex toasted oak wood (Q. sp.) volatilome using GCxGC-TOFMS technique

Exploring and unravelling the complex toasted oak wood (Q. sp.) volatilome using GCxGC-TOFMS technique

Abstract

For coopers, toasting process is considered as a crucial step in barrel production where oak wood develops several specific aromatic nuances released to the wine during its maturation. Toasting is applying varying degrees of heat to a barrel over a specific amount of time. Today it is well known that as the temperature increases, thermal degradation of oak wood structure produces a huge range of chemical compounds. Indeed, many works were conducted to identify key aroma volatile compounds (e.g., whisky-lactone, furfural, maltol, eugenol, guaiacol, vanillin) using the traditional gas chromatography coupled with olfactometry and mass spectrometry (GC-O-MS).

Inspired by recent untargeted approaches in food “omics”, this work aims at expanding our knowledge on oak wood volatile composition by bi-dimensional comprehensive gas chromatography-time of flight mass spectrometry (GCxGC-TOFMS, BT4D, Leco).

In a first experiment, five toasting levels were selected and applied to Q. sessilis oak wood samples (control, 160 °C, 180 °C, 200 °C and 220 °C, 30 min, n=3). Organic extracts were prepared (dichloromethane, 50 g/L) and analysed by GCxGC-TOFMS on conventional column combination nonpolar/midpolar (DB-5ms/Rxi-17Sil). The separation was followed by a non-targeted approach for data processing. The resulting mass spectra (TIC) were de convoluted (ChromaTOF software) and compared to spectra from a database for tentative peak identification. It was necessary to restrict the number of processed peaks by applying some “filters” such as signal to noise (S/N > 50), linear retention index (LRI ± 30), mass spectra similarity (> 750) and repeatability level. Supervised multivariate and univariate statistical approaches were used to identify potential markers of toasting intensity. Thanks to R script, reproducible peaks number was reduced from about 15000 to 568. By comparing observed retention indices with those found in the literature, 77 of the identifications have been confirmed and associated with an increase in toasting intensity. Some of them were sensory active and well known in oak wood, such as guaiacol, creosol and isoeugenol. Others were identified for the first time in toasted oak wood such as 2-methylbenzofurane (burnt) and 2-hydroxy-2-cyclopenten-1-one (caramel).Additional results were also discussed on the capability of GCxGC-TOFMS to identify oak wood botanic origins (Q. robur, Q. alba

DOI:

Publication date: June 23, 2022

Issue: IVAS 2022

Type: Article

Authors

Courregelongue Marie1,², Albertin Warren1,³, Prida Andrei2 and Pons Alexandre1,²

¹UMR ŒNOLOGIE (OENO), ISVV, UMR 1366, Université de Bordeaux, INRAE, Bordeaux INP
²Tonnellerie Seguin Moreau, Merpins, France
³ENSCBP, Bordeaux INP, 33600, Pessac, France

Contact the author

Keywords

non-targeted analysis, GCxGC-TOFMS, oak wood, toasting process, volatile compounds

Tags

IVAS 2022 | IVES Conference Series

Citation

Related articles…

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.

Bioclimatic shifts and land use options for Viticulture in Portugal

Land use, plays a relevant role in the climatic system. It endows means for agriculture practices thus contributing to the food supply. Since climate and land are closely intertwined through multiple interface processes, climate change may lead to significant impacts in land use. In this study, 1-km observational gridded datasets are used to assess changes in the Köppen–Geiger and Worldwide Bioclimatic (WBCS)

Downscaling of remote sensing time series: thermal zone classification approach in Gironde region

In viticulture, the challenges of local climate modelling are multiple: taking into account the local environment, fine temporal and spatial scales, reliable time series of climate data, ease of implementation and reproducibility of the method. At the local scale, recent studies have demonstrated the contribution of spatialization methods for ground-based climate observation data considering topographic factors such as altitude, slope, aspect, and geographic coordinates (Le Roux et al, 2017; De Rességuier et al, 2020). However, these studies have shown questions in terms of the reproducibility and sustainability of this type of climate study. In this context, we evaluated the potential of MODIS thermal satellite images validated with ground-based climate data (Morin et al, 2020). Previous studies have been encouraging, but questions remain to be explored at the regional scale, particularly in the dynamics of the massive use of bioclimatic indices to classify the climate of wine regions. The results at the local scale were encouraging, but this approach was tested in the current study at the regional scale. Several objectives were set: 1) to evaluate the downscaling method for land surface temperature time series, 2) to identify regional thermal structure variations. We used weekly minimum and maximum surface temperature time series acquired by MODIS satellites at a spatial resolution of 1000 m and downscaled at 500 m using topographical variables. Two types of analyses were performed:

Evolution of the amino acids content through grape ripening: Effect of foliar application of methyl jasmonate with or without urea

The parameters that determine the grape quality, and therefore the optimal harvest time, suffer variations during berry ripening, related to climate change, with the widely known problem of the gap between technological and phenolic maturities. However, there are few studies about its incidence on grape nitrogen composition. For this reason, the use of an elicitor, methyl jasmonate (MeJ), alone or with urea, is proposed as a tool to reduce climatic decoupling, allowing to establish the harvest time in order to achieve the optimum grape quality. The aim was to study the effect of MeJ and MeJ+Urea foliar applications on the evolution of Tempranillo amino acids content throughout the grape maturation. Three treatments were foliarly applied, at veraison and 7 days later: control (water), MeJ (10 mM) and MeJ+Urea (10 mM+6 kg N/ha). Grape samples were taken at five stages of maturation: day before the first and second applications, 15 days after the second application (pre-harvest), harvest day, and 15 days after harvest (post-harvest). The amino acids analysis of the samples was carried out by HPLC. Results showed that the evolution of amino acids was similar regardless of the treatment; however, foliar applications influenced the nitrogen compounds content, i.e., there was no qualitative effect but quantitative one. Most of the amino acids reached their maximum concentration in pre-harvest, being higher in grapes from the treatments than in the control. In general, no differences in grape amino acids content were observed between MeJ and MeJ+Urea treatments. Foliar applications with MeJ and MeJ+Urea enhanced the grape amino acids content, without affecting their profile, helping to optimize their quality and allowing to establish a more complete grape ripening standard. Therefore, MeJ and MeJ+Urea foliar applications can be a simple agronomic practice, which has shown promising results in order to enhance the grape quality.

Co-design and evaluation of spatially explicit strategies of adaptation to climate change in a Mediterranean watershed

Climate change challenges differently wine growing systems, depending on their biophysical, sociological and economic features. Therefore, there is a need to locally design and evaluate adaptation strategies combining several technical options, and considering the local opportunities and constraints (e.g. water access, wine typicity). The case study took place in a typical and heterogeneous Mediterranean vineyard of 1,500 ha in the South of France. We developed a participatory modeling approach to (1) conceptualize local climate change issues and design spatially explicit adaptation strategies with stakeholders, (2) numerically evaluate their effects on phenology, yield and irrigation needs under the high-emissions climate change scenario RCP 8.5, and (3) collectively discuss simulation results. We organized five sets of workshops, with in-between modeling phases. A process-based model was developed that allowed to evaluate the effects of six technical options (late varieties, irrigation, water saving by reducing canopy size, adjusting cover cropping, reducing density, and shading) with various distributions in the watershed, as well as vineyard relocation. Overall, we co-designed three adaptation strategies. Delay harvest strategy with late varieties showed little effects on decreasing air temperature during ripening. Water constraint limitation strategy would compensate for production losses if disruptive adaptations (e.g. reduced density) were adopted, and more land got access to irrigation. Relocation strategy would foster high premium wine production in the constrained mountainous areas where grapevine is less impacted by climate change. This research shows that a spatial distribution of technical changes gives room for adaptation to climate change, and that the collaboration with local stakeholders is a key to the identification of relevant adaptation. Further research should explore the potential of adaptation strategies based on soil quality improvement and on water stress tolerant varieties.