Macrowine 2021
IVES 9 IVES Conference Series 9 Long-term sensorial and compositional effects of copper fining on the wine containing ‘reductive’ and ‘tropical’ volatile sulfur compounds

Long-term sensorial and compositional effects of copper fining on the wine containing ‘reductive’ and ‘tropical’ volatile sulfur compounds

Abstract

The aim of this study was to investigate long-term sensorial and compositional effects of copper addition to the white wine naturally high in varietal thiol levels, with added volatile sulfur compounds [hydrogen sulfide (H2S) and methanethiol (MeSH)]. The novelty of this study lies in the inclusion of sensory analysis at each time point by using Check-All-That-Apply and Descriptive Analysis methods to evaluate the sensory interaction between ‘reductive’ thiols and tropical thiols after copper fining. The Chenin Blanc wine was used as control (base) wine to which combinations of 40 µg/L H2S and 20 µg/L of MeSH were added, followed by an addition of 0,3 mg/L of copper to selected samples. The wine samples were stored for 24 hours, 6 weeks and 1 year. At each time point chemical analysis of varietal thiols, volatile sulfur compounds and copper levels were performed. The chemical results after 1 year of wine storage, showed a significant increase in the levels of varietal thiol 3-sulfanylhexanol (3-SH) and a decrease of 3-sulfanylhexyl acetate (3-SHA) concentration levels. However, a significant loss of 3-SH occurred in all the copper treated wines after 1 year of storage. On the other hand, the decrease of 3-SHA levels over time was less influenced by copper treatment, but rather due to acid hydrolyses and a subsequent increase in 3-SH (Makhotkina & Kilmartin, 2012). The presence of copper seem to further increase levels of bound- H2S in wine samples, which after 1 year of storage amounted to more than 25 µg/L. Chemical analysis of MeSH showed the significant increase in free and bound MeSH after 1 year of storage in wine samples spiked with MeSH. However, the addition of copper to the MeSH-spiked samples resulted in significant decrease of free and bound MeSH. The most significant sensory impact of the addition of H2S and MeSH to control wine was the suppression effect on “fruitiness” of wine after 24 hours which after 6-weeks and 1-year wine storage period decreased, potentially due to wine matrix absorption of H2S and MeSH (Nikolantonaki & Waterhouse, 2012). Sensory results after 1 year of wine storage showed that “guava”, a “tropical” attribute, was not suppressed with the addition of H2S and MeSH and low doses of “reductive” aromas deriving from H2S and MeSH in wine might even contributed to its sensory perception. Copper additions mainly decreased the perception of “guava” after 1 year. In contrast, the “passionfruit”, also a “tropical” attribute, was slightly suppressed when H2S and MeSH were present. The perception of the ester-derived attributes namely “peach” and “banana” increased in the samples containing copper after 1 year of storage, suggesting that a decrease of the 3-SH varietal thiol due to copper addition may enhance the perception of ester-derived aromas in wine.

DOI:

Publication date: September 14, 2021

Issue: Macrowine 2021

Type: Article

Authors

Matija Lesković

*South African Grape and Wine Research Institute/Department Viticulture and Oenology, University of Stellenbosch, Private Bag X1, Matieland (Stellenbosch) 7602, South Africa,Marlize BEKKER † Jeanne BRAND * Allie KULCSAR † Wessel DU TOIT * *South African Grape and Wine Research Institute/Department Viticulture and Oenology, University of Stellenbosch, Private Bag X1, Matieland (Stellenbosch) 7602, South Africa † The Australian Wine Research Institute, P.O. Box 197, Glen Osmond, South Australia, 5064.

Contact the author

Keywords

varietal thiols, volatile sulfur compounds, wine copper fining, ‘reductive’ and ‘tropical’ volatile sulfur compounds, copper fining and wine storage, wine sensory analysis

Citation

Related articles…

Climate ethnography and wine environmental futures

Globalisation and climate change have radically transformed world wine production upsetting the established order of wine ecologies. Ecological risks and the future of traditional agricultural systems are widely debated in anthropology, but very little is understood of the particular challenges posed by climate change to viticulture which is seen by many as the canary in the coalmine of global agriculture. Moreover, wine as a globalised embedded commodity provides a particularly telling example for the study of climate change having already attracted early scientific attention. Studies of climate change in viticulture have focused primarily on the production of systematic models of adaptation and vulnerability, while the human and cultural factors, which are key to adaptation and sustainable futures, are largely missing. Climate experts have been unanimous in recognising the urgent need for a better understanding of the complex dynamics that shape how climate change is experienced and responded to by human systems. Yet this call has not yet been addressed. Climate ethnography, coined by the anthropologist Susan Crate (2011), aims to bridge this growing disjuncture between climate science and everyday life through the exploration of the social meaning of climate change. It seeks to investigate the confrontation of its social salience in different locations and under different environmental guises (Goodman 2018: 340). By understanding how wine producers make sense of the world (and the environment) and act in it, it proposes to focus on the co-production of interdisciplinary knowledge by identifying and foreshadowing problems (Goodman 2018: 342; Goodman & Marshall 2018). It seeks to offer an original, transformative and contrasted perspective to climate change scenarios by investigating human agency -individual or collective- in all its social, political and cultural diversity. An anthropological approach founded on detailed ethnographies of wine production is ideally placed to address economic, social and cultural disruptions caused by the emergence of these new environmental challenges. Indeed, the community of experts in environmental change have recently called for research that will encompass the human dimension and for more broad-based, integrated through interdisciplinarity, useful knowledge (Castree & al 2014). My paper seeks to engage with climate ethnography and discuss what it brings to the study of wine environmental futures while exploring the limitations of the anthropological environmental approach.

First step in the preparation of a soil map of the Protected Designation of Origin Valdepeñas (Central, Spain)

This work is a first step to make a map of vineyard soils. The characterization of the soils of the Protected Designation of Origin (D.P.O.) Valdepeñas will allow to group the studied profiles according to their physico-chemical characteristics and the concentrations of most relevant chemical elements. 90 soil profiles were analysed throughout the territory and the soils were sampled and described according to FAO (2006) and classified according to and Soil Taxonomy (2014). All samples were air dried, sieved and some physico-chemical parameters were determined following standard protocols. Also, major and trace elements were analysed by X-ray fluorescence. The statistically study was made using the SPSS program. Trend maps were made using the ArcGIS program. The studied soils have the following average properties: pH, 8.3; electrical conductivity, 0,20 dS/m (low); clay, 18.8% (medium) and CaCO3, 17.1% (high). In the study for the major elements. The major elements of these soils are Si, followed by Ca and Al, with an average content of 203.7 g/kg, 105.5 g/kg and 74.0 g/kg respectively. On the other hand, 27 trace elements have been studied. Of all of them, it can be highlighted the average values of Ba (361.8 mg/kg), Sr (129.3 mg/kg), Rb (83.4 mg/kg), V (74.2 mg/kg) and Ce (70.6 mg/kg). Ba, V and Ce values are higher and the values of Sr and Rb are lower to those found in the literature. The discriminant analysis shows a percentage of grouping of 91%. The content of chemical elements together with the physico-chemical characteristics allows grouping the soils in 4 group according to their order in the classification to Soil Taxonomy; due to the importance of the Calcisols in Castilla-La Mancha, it has been decided to establish them as their own group even if they do not appear in Soil Taxonomy classification.

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.

Climate modeling at local scale in the Waipara winegrowing region in the climate change context

In viticulture, a warming climate can have a very significant impact on grapevine development and therefore on the quality and characteristics of wines across different spatial scales, ranging from global to local. In order to adapt wine-growing to climate change, global climate models can be used to define future scenarios, but only at the scale of major wine regions. Despite the huge progress made over the last ten years in terms of the spatial resolution of climate models (now downscaled to a few square kilometres), they are not yet sufficiently precise to account for the local climate variability associated with such parameters as local topography, in spite of these parameters being decisive for vine and wine characteristics. This study describes a method to downscale future climate scenarios to vineyard scale. Networks of data loggers have been used to collect air temperature at canopy level in the Waipara winegrowing region (New Zealand) over five growing seasons. These measurements allow the creation of fine-scale geostatistical models and maps of temperature (at 100 m resolution) for the growing season. In order to model climate change at pilot site scale, these geostatistical models have been combined with regional climate change predictions for the periods 2031-2050 and 2081-2100 based on the RCP8.5 climate change scenario. The integration of local climate variability with regionalized climate change simulations allows assessment of the impacts of climate change at the vineyard scale. The improved knowledge gained using this methodology results from the increased horizontal resolution that better addresses the concerns of winegrowers. The results provide the local winegrowers with information necessary to understand current processes, as well as historical and future viticulture trends at the scale of their site, thereby facilitating decisions about future response strategies.

Organic recycled mulches in sustainable viticulture: assessment of spontaneous plants communities and weed coverage

In recent years, developing more efficient and sustainable viticulture management has been essential due to the impact of climate change in semiarid regions. For this reason, the use of recycled organic mulching (ROM) in the vineyard has become an interesting strategy to cope with water stress, isolated soil from extreme temperatures and improving soil humidity, control the presence of weeds and therefore reduce the inputs of herbicides and improve soil fertility. This work aimed to analyse the effect of three different organic mulches [straw (S), grape pruning debris (GPD) and spent mushroom compost (SMC)] and two traditional soil management techniques [herbicide (H) and interrow (IN)] on weed coverage and the spontaneous plant communities’ presence. Data sampling was collected throughout the vine vegetative cycle of 2021 in La Rioja, Spain. The different soil management techniques had a clear effect on weed coverage and his development during the vine vegetative cycle. SMC and H were the treatments with the highest and the lowest coverage percentage, respectively. IN had a delayed weed emergence at the beginning of the vine vegetative cycle, but finally it reached maximum values nearby SMC. GPD and S had similar effects on weed emergence, reaching 25-30% of the maximum coverage values. A total of 29 herbaceous species were identified during the vegetative cycle, some of them very isolated and occasional. Principal component analysis (PCAs) showed a good association between spontaneous species and treatments, furthermore, specific species-treatment associations were found. Moreover, three clear groups of herbaceous communities were identified by cluster analysis. This study provides interesting information about the effect of different alternative soil management on herbaceous plant coverage and weed species communities which could contribute to making more sustainable viticulture.