IVAS 2022 banner
IVES 9 IVES Conference Series 9 IVAS 9 IVAS 2022 9 The inhibition of hydrogen sulfide and methanethiol accumulation in wine by Cu(II): The influence of temperature on the duration of protection

The inhibition of hydrogen sulfide and methanethiol accumulation in wine by Cu(II): The influence of temperature on the duration of protection

Abstract

Hydrogen sulfide and methanethiol are recognised as two of the most significant contributors to reductive off-flavours in wine. Cu(II) in wine is known to interact with both sulfhydryl compounds, lowering the concentration of their aroma-active forms while transitioning Cu(II) to a sulfhydryl-bound form. Both hydrogen sulfide and methanethiol can form during the aging of wine in low oxygen conditions, such as during bottle aging, and
their production is known to be accelerated by wine storage temperature. Consequently, the protection offered by Cu(II) to inhibit accumulation of the reductive aroma compounds during bottle aging will be limited by the Cu(II) concentration at the bottling and of rate sulfhydryl compound formation. Although insights have been made on the typical rates of binding of Cu(II) in wines in cellar conditions (i.e., 14 °C), the impact of elevated storage
conditions is not certain, but likely to influence the duration of time that Cu(II) can inhibit reductive wine characters. This study determines the rates of Cu binding during the storage of wine at variable temperatures.

Four red and three white wines were bottled with low (< 0.2 mg/L) and high (0.6 mg/L) Cu(II) concentrations. The wines were stored at 14 °C and 40 °C and measured at 0, 1, 3, 7 and 12
months, and 0, 3, 5 and 12 days, respectively. The different forms of Cu were quantified by colorimetry for white wine, and stripping potentiometry for red wine, and enabled calculation of Cu(II) binding rates during wine aging and estimation of activation energies for binding. The formation of free and salt-releasable hydrogen sulfide and methanethiol were determined by gas chromatography with chemiluminescence detection.

The results showed that the rate of Cu(II) binding was dramatically higher at 40 °C than 14°C, with complete binding of Cu(II) in the order of 3 – 8 months and 1 – 5 days, respectively, for the wines bottled with high Cu(II). The relative order of Cu(II) binding rates amongst wines was temperature dependent, whereby Cu(II) binding rates became more uniform across wines when stored at the higher temperatures. This implied limitations in utilising high storage temperatures to predict Cu(II) binding at lower storage temperatures. The accumulation of the aroma active forms of sulfhydryl compounds, that is, the free hydrogen
sulfide and free methanethiol, only occurred after Cu(II) was converted to its bound form and then also required a further lag time. These results provide critical insights into the time-line of protection afforded to wines by Cu(II) against the emergence of reductive characters during bottle aging.

DOI:

Publication date: June 23, 2022

Issue: IVAS 2022

Type: Article

Authors

Zhang Xinyi1, Langford Kylie2 and Clark Andrew C1

1Gulbali Institute, Charles Sturt University, School of Agricultural, Environmental and Veterinary Sciences, Charles Sturt University, Wagga Wagga, NSW 2678, Australia
2Treasury Wine Estates, 97 Sturt Highway, Nuriootpa, SA 5355, Australia

Contact the author

Keywords

Copper, reduction, hydrogen sulfide, methanethiol, bottle-aging

Tags

IVAS 2022 | IVES Conference Series

Citation

Related articles…

Adaptability of grapevines to climate change: characterization of phenology and sugar accumulation of 50 varieties, under hot climate conditions

Climate is the major factor influencing the dynamics of the vegetative cycle and can determine the timing of phenological periods. Knowledge of the phenology of varieties, their chronological duration, and thermal requirements, allows not only for the better management of interventions in the vineyard, but also to predict the varieties’ behaviour in a scenario of climate change, giving the wine producer the possibility of selecting the grape varieties that are best adapted to the climatic conditions of a certain terroir. In 2014, Symington Family Estates, Vinhos, established two grape variety libraries in two different places with distinctive climate conditions (Douro Superior, and Cima Corgo), with the commitment of contributing to a deeper agronomic and oenological understanding of some grape varieties, in hot climate conditions. In these research vineyards are represented local varieties that are important in the regional and national viticulture, but also others that have over time been forgotten — as well as five international reference cultivars. From 2017 to 2021, phenological observations have been made three times a week, following a defined protocol, to determine the average dates of budbreak, flowering and veraison. With the climate data of each location, the thermal requirements of each variety and the chronological duration of each phase have been calculated. During maturation, berry samples have been gathered weekly to study the dynamics of sugar accumulation, between other parameters. The data was analysed applying phenological and sugar accumulation models available in literature. The results obtained show significant differences between the varieties over several parameters, from the chronological duration and thermal requirements to complete the various stages of development, to the differences between the two locations, confirming the influence of the climate on phenology and the stages of maturation, in these specific conditions.

Legacy of land-cover changes on soil erosion and microbiology in Burgundian vineyards

Soils in vineyards are recognized as complex agrosystems whose characteristics reflect complex interactions between natural factors (lithology, climate, slope, biodiversity) and human activities. To date, most of the unknown lies in an incomplete understanding of soil ecosystems, and specifically in the microbial biodiversity even though soil microbiota is involved in many key functions, such as nutrient cycling and carbon sequestration. Soil biological properties are indicative of soil quality. Therefore, understanding how soil communities are related to soil ecosystem functioning is becoming an essential issue for soil strategy conservation. Here, we propose to assess the importance of land-cover history on the present-day microbiological and physico-chemical properties. The studied area was selected in the Burgundian vineyards (Pernand-Vergelesses, Burgundy, France) where land occupation has been reconstructed over the last 40 years. Soil samples were collected in five areas reflecting various land cover history (forest, vineyards, shifting from forest to vineyards). For each area, physico-chemical parameters (pH, C, N, P, grain size) were measured and DNA was extracted to characterize the abundance and diversity of microbial communities. The obtained results show significant differences in the five areas suggesting that present-day microbial molecular biomass and bacterial taxonomic is partly inherited from past land occupation. Over longer period of time, such study of land-uses legacies may help to better assess ecosystem recovery and the impact of management practices for a better soil quality and vineyards sustainability.

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…

A spatial explicit inventory of EU wine protected designation of origin to support decision making in a changing climate

Winemaking areas recognized as protected designations of origin (PDOs) shape important economic, environmental and cultural values that are tied to closely defined geographic locations. To preserve wine products and wine-growing practices adopted in different PDOs these areas are strictly regulated by legal specifications. However, quality viticulture is increasingly under pressure from climate change, which is altering the local conditions of many winegrowing areas. Therefore, maintaining traditional wine products will require the adoption of tailored adaptation strategies, including possible changes in the legal regulation of protected wines. To this end, it is necessary to have a comprehensive knowledge on PDOs including their extension, products and allowed practices. While there have been efforts to build databases that summarize the characteristics for individual wine PDO areas and to quantify the related effects of climate change, much information is still included only in the official documentation of the EU geographical indication register and has never been collected in a comprehensive manner. With this study we aim at filling this gap by building a spatial inventory of European wine PDOs that supports decision making in viticulture in the context of climate change. To map and characterize European wine PDOs, we analysed their legal documents and extracted relevant information useful for climate change adaptation. The output consists of a comprehensive geographical dataset that identifies the boundaries of all 1200 European wine PDOs at unprecedented spatial resolution and includes a set of legally binding regulations, such as authorized vine varieties, maximum yields and planting density. The inventory will allow researchers to analyse the impacts of climate change on European wine PDOs and support decision makers in developing tailored adaptation strategies. This includes, among others, the evaluation of new vineyard site selection, the expansion of cultivated varieties or the authorization of irrigation in vineyards.

Impact on leaf morphology of Vitis vinifera L. cvs Riesling and Cabernet Sauvignon under Free Air Carbon dioxide Enrichment (FACE)

Atmospheric carbon dioxide (CO2) concentration has continuously increased since pre-industrial times from 280 ppm in 1750, and is predicted to exceed 700 ppm by the end of 21st century. For most of C3 plant species elevated CO2 (eCO2) improve photosynthetic apparatus results in an increased plant biomass production. To investigate the effects of eCO2 on morphological leaf characteristics the two Vitis vinifera L. cultivars, Riesling and Cabernet Sauvignon, grown in the Geisenheim VineyardFACE (Free Air Carbon dioxide Enrichment) system were used. The FACE site is located at Geisenheim University (49° 59′ N, 7° 57′ E, 94 m above sea level), Germany and was implemented in 2014 comparing future atmospheric CO2-concentrations (eCO2, predicted for the mid-21st century) with current ambient CO2-conditions (aCO2). Experiments were conducted under rain-fed conditions for two consecutive years (2015 and 2016). Six leaves per repetition of the CO2 treatment were sampled in the field and immediately fixed in a FAA solution (ethanol, H2O, formaldehyde and glacial acetic acid). After 24 h leaf samples were transferred and stored in an ethanol solution. Subsequently, leaf tissue was dehydrated using ethanol series and embedded in paraffin. By using a rotary microtomesections of 5 µm were prepared and fixed on microscopic slides. Subsequent the samples were stained using consecutive staining and washing solutions. Afterwards pictures of the leaf cross-sections were taken using a light microscope and consecutive measurements were conducted with an open source image software. Differences found in leaf cross-sections of the two CO2 treatments were detected for the palisade parenchyma. Leaf thickness, upper and lower epidermis and spongy parenchyma remained less affected under eCO2 conditions. The observed results within grapevine leaf tissues can provide first insights to seasonal adaptation strategies of grapevines under future elevated CO2 concentrations.