Terroir 2020 banner
IVES 9 IVES Conference Series 9 Intraregional profiles of varietal thiols and precursors in Sauvignon Blanc juices and wines from the Adelaide Hills

Intraregional profiles of varietal thiols and precursors in Sauvignon Blanc juices and wines from the Adelaide Hills

Abstract

Aims: To investigate the intraregional variation of varietal thiol precursors and free thiols in Sauvignon blanc grape juices and experimental wines arising from the Adelaide Hills Geographical Indication (GI) in South Australia.

Methods and ResultsVitis vinifera L. cv Sauvignon blanc grape parcels (n = 21, approx. 8 kg each, encompassing 5 clones) were hand harvested from different blocks within seven commercial vineyards in the Adelaide Hills GI during the 2018 vintage. Parcels were divided into subsets for winemaking and freezing experiments. Amino acid (AA) and thiol precursor concentrations in juice were determined using high performance liquid chromatography (HPLC) with fluorescence detection and stable isotope dilution assay (SIDA) using HPLC with tandem mass spectrometry (MS/MS), respectively, and free thiols in wine were quantified by SIDA with HPLC-MS/MS, after derivatisation with 4,4’-dithiodipyridine. Intraregional variations in grape ripeness were evident according to total soluble solids content, pH, and titratable acidity, even within single locations or for the same clones. Significant differences in the glutathionylated precursor to 3-sulfanylhexan-1-ol (3-SH) were found among several locations whereas for the cysteinylated variant of 3-SH, one location was distinct from the rest. Variation in precursor concentrations was also noted from different blocks within a single vineyard location but was not dependent on grape ripeness. Fermentations progressed without any obvious relationship to location, and wines that were high in 3-SH were also usually high in 3-sulfanylhexyl acetate (3-SHA). One location had significantly higher levels of thiols in wine despite the juice not being the highest for grape-derived precursors, and also gave a substantial concentration of 4-methyl-4-sulfanylpentan-2-one in comparison to other locations within the GI. The AA profile of juices was found to vary according to location, and certain AAs were strongly correlated to thiol precursor concentrations, but relationships of AAs with free thiols in wine were generally weak. Additionally, enhancements in the concentrations of precursors in juice (up to 19-fold) and free thiols in wine (up to 10-fold) were revealed from freezing whole grape bunches in contrast to using fresh juice.

Conclusions: 

Intraregional variation was noted for thiols in wine, and precursors and amino acids in juice, for 21 Sauvignon blanc samples collected from within the Adelaide Hills region. The effects of terroir were implicated in explaining the differences in grape composition, and the potential interactions among grape amino acids and thiol precursors in berries and thiols in wine were revealed.

Significance and Impact of the Study: Sauvignon blanc is a significant variety produced in the Adelaide Hills GI but no information was available on the effects of location within the GI on grape and wine composition with respect to varietal thiols. This was the first study of intraregional variations of thiol precursors, amino acids, and free thiols in Sauvignon blanc juices and wines that were produced in a consistent manner. A remarkable enhancing effect of freezing was noted for thiol precursors in juice, and importantly, free thiols in wine.

DOI:

Publication date: March 17, 2021

Issue: Terroir 2020

Type: Video

Authors

Liang Chen1,a, Dimitra L. Capone1,2, Emily L. Nicholson3, David W. Jeffery1,2*

1 School of Agriculture, Food and Wine, The University of Adelaide, Waite Campus, PMB 1 Glen Osmond, SA 5064, Australia
2 Australian Research Council Training Centre for Innovative Wine Production, The University of Adelaide, PMB 1 Glen Osmond, SA 5064, Australia
3 CSIRO Agriculture and Food, Locked Bag 2, Glen Osmond, SA 5064, Australia

aPresent address: Institut des Sciences de la Vigne et du Vin, Université de Bordeaux, 210 chemin de Leysotte CS 50008, 33882 Villenave d’Ornon Cedex, France

Contact the author

Keywords

List of different keywords (keyword1, keyword2, keyword3)

Tags

IVES Conference Series | Terroir 2020

Citation

Related articles…

Is wine terroir a valid concept under a changing climate?

The OIV[i] defines terroir as a concept referring to an area in which collective knowledge of the interactions between the physical and biological environment (soil, topography, climate, landscape characteristics and biodiversity features) and vitivinicultural practices develops, providing distinctive wine characteristics. Those are perceptible in the taste of wine, which drives consumer preference and, therefore, wine’s value in the marketplace. Geographical indications (GI) are recognized regulatory constructs formalizing and protecting the nexus between wine taste and the terroir generating it. Despite considering updates, GIs do not consider the nexus as a dynamic one and do not anticipate change, namely of climate. Being climate a fundamental feature of terroir, it strongly impacts wine characteristics, such as taste. According to IPCC[ii], many widespread, rapid and unprecedented changes of climate occurred, some being irreversible over hundreds to thousands of years. Climatic shifts and atmospheric-driven extreme events have been widely reported worldwide. Recent climatic trends are projected to strengthen in upcoming decades, whereas extremes are expected to increase in frequency and intensity, forcing wines away from GI definitions. Geographical shifts of viticultural suitability are projected, often moving into regions and countries different from current ones. Some authors propose adaptation in viticulture, winemaking and product innovation. We show evidence of climate changing wine characteristics in the Douro valley, home of 270-year-old Port GI. We discuss herein resist or adapt stances for when climate changes the nexus between terroir and wine characteristics. Using the MED-GOLD[iii] dashboard, a tool allowing for easy visual navigation of past and future climates, we demonstrate how policymakers can identify future moments, throughout the 21st century under different emission scenarios, when GI specifications will likely need updates (e.g., boundaries, varieties) to reduce climate-change impacts.

Current climate change in the Oplenac wine-growing district (Serbia)

Serbian autochthonous vine varieties Smederevka (for white wines) and Prokupac (for rosé and red wines) are the primary representatives of typical characteristics of wines and terroir of numerous wine-growing areas in Serbia. In the past, these varieties were the leading vine varieties, however, as the result of globalization of winemaking and the trend of consumption of wines from widely prevalent vine varieties, they were replaced by introduced international varieties. Smederevka and Prokupac vine varieties are characterized by later time of grape ripening, and relative sensitivity to low temperatures. Climate conditions can be a restrictive factor for production of high-quality grapes and wine and for the spatial spreading of these varieties in hilly continental wine-growing areas.
This paper focuses on the spatial analysis of changes of main climate parameters, in particular, analysis of viticultural bioclimatic indices that were determined for the purposes of viticulture zoning of wine-growing areas in the period 1961-2010, and those same parameters determined for the current, that is, referential climate period (1988-2017). Results of the research, that is, analysis of climate changes indicate that the majority of examined climate parameters in the Oplenac wine-growing district improved from the perspective of Smederevka and Prokupac vine varieties. These studies of climate conditions indicate that changes of analyzed climate parameters, that is, bioclimatic indices will be favorable for cultivation of varieties with later grape ripening times and those more sensitive to low temperatures, such as the autochthonous vine varieties Smederevka and Prokupac, therefore, it is recommended to producers to more actively plant vineyards with these varieties in the territory of the Oplenac wine-growing district.

Climate change impacts: a multi-stress issue

With the aim of producing premium wines, it is admitted that moderate environmental stresses may contribute to the accumulation of compounds of interest in grapes. However the ongoing climate change, with the appearance of more limiting conditions of production is a major concern for the wine industry economic. Will it be possible to maintain the vineyards in place, to preserve the current grape varieties and how should we anticipate the adaptation measures to ensure the sustainability of vineyards? In this context, the question of the responses and adaptation of grapevine to abiotic stresses becomes a major scientific issue to tackle. An abiotic stress can be defined as the effect of a specific factor of the physico-chemical environment of the plants (temperature, availability of water and minerals, light, etc.) which reduces growth, and for a crop such as the vine, the yield, the composition of the fruits and the sustainability of the plants. Water stress is in many minds, but a systemic vision is essential for at least two reasons. The first reason is that in natural environments, a single factor is rarely limiting, and plants have to deal with a combination of constraints, as for example heat and drought, both in time and at a given time. The second reason is that plants, including grapevine, have central mechanisms of stress responses, as redox regulatory pathways, that play an important role in adaptation and survival. Here we will review the most recent studies dealing with this issue to provide a better understanding of the grapevine responses to a combination of environmental constraints and of the underlying regulatory pathways, which may be very helpful to design more adapted solutions to cope with climate change.

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.

Grape must quality and mesoclimatic variability in Fruška Gora wine-growing region, Serbia

The Fruška Gora mountain is a traditional wine-growing region in Serbia situated in the Pannonian Basin. Due to such a position, the vicinity of the Danube River and the presence of concave configuration, it is suitable for grape production. This paper provides analyses of spatial variations in meteorological parameters and grape juice quality within Fruška Gora wine region over three consecutive vintages (2018-2020). The examined period can be defined as warm with cool nights during September (AVG 18,9°C; GDD 1918°C; CI 12°CF) and with the presence of mesoclimatic variability. The East part of the study area was somewhat drier and hotter compared to other parts of the region. The analyses of grape must samples (190 in total) of five cultivars (Cabernet-Sauvignon, Merlot, Chardonnay, Sauvignon blanc and Grašac (Welschriesling)) commonly grown across the region (19 sites), were performed using Fourier Transform Infrared Technology (FTIR). Among all cultivars, Sauvignon blanc was harvested first in the East area (DOY=246±5, GDD at harvest=1552±74, 22.2±0.7 °Brix), while the latest harvest was recorded for Cabernet-Sauvignon in the West (DOY=283±5, GDD at harvest=1936±187, 23.4±1.0 °Brix ). Both the red and white cultivars had higher acidity and YAN in the grape must if the vines were grown in the North and East compared to South and West areas. According to PCA analysis, Grašac showed the lowest variation in grape must chemical composition. Thus, the results confirm that Grašac is the most stable cultivar in Fruška Gora. All monitored cultivars reached technological fruit ripeness by the end of the growing season. However, it was difficult to reach full ripeness of red cultivars, mostly beacuse of uncoupling of technolocical and phenolic ripeness. Thus, Cabernet-Sauvignon had higher variations in GDD sums at harvest compared to other cultivars, which probably increased variations in grape must quality.