IVAS 2022 banner
IVES 9 IVES Conference Series 9 IVAS 9 IVAS 2022 9 The wine: a never-ending source of H2S and methanethiol

The wine: a never-ending source of H2S and methanethiol

Abstract

Volatile sulfur compounds (VSCs), mainly hydrogen sulfide and methanethiol (H2S and MeSH), are the responsible for reductive off-odor in wine. These compounds can remain in the wine under different chemical forms: free forms, bound to metal cations or as oxidized precursors (polysulfides and polysulfanes). Some remediation treatments, such as aeration, micro-oxygenation, copper fining and addition of oenological products are frequently used by the winemakers to eliminate the reductive problems however, they are not completely effective and sometimes this problem can reappear after a certain period of time. Recently, another options (e.g. filtration, purge…) have been also tested but their efficacy at long term is not much better. These strategies act on the free and bonded forms, therefore it has been hypothesized that exist a huge reservoir of VSCs (in oxidized forms) which is not removed by the remediation treatments and that could explain their inefficacy. Nowadays, it does not exist any reliable method to know the amount of oxidized forms in wine which could be the source of H2S and MeSH. This knowledge could help to understand better the problem of reduction of wines and improve the remediation strategies. For that reason, the objective of this work was developing a new system to monitor the release of VSCs during the storage of different wines under anoxia. This system is based on the use of reversible trapping solutions to retain the VSCs at the same time that they are produced in the wine. Different metal cations, in terms of ability and speed have been studied as potential trapping agents. The reversibility of the process to quantify H2S and MeSH was also evaluated. After the system was optimized, it was applied to several wines stored at different temperatures under anoxic conditions. Cu (I) was chosen as the best option to use in the trapping solution and a dilution with brine and addition of tris(2-carboxyethyl)phosphine (TCEP) was selected to revert the trapping process and quantify the analytes. The linearity and the reproducibility of the system was evaluated and satisfactory results were obtained. The stability of the trapping solutions was also studied to know when they should be replaced in the system to avoid problems in the determination of the analytes. The rate of formation of the VSCs on the real wines depended on the storage temperature, ranging the maximum for each wine from 3 µg/hour to 10 µg/hour of H2S at 75ºC and from 0.1 µg/hour to 0.4 µg/hour at 50ºC. In the case of MeSH, the rate was one order of magnitude lower than for H2S. The total amount of VSCs produced was different for each wine and for each temperature, reaching more than 2 mg/L of H2S at 75ºC and more than 200 µg/L at 50ºC after one month of storage. This system could be useful to predict the tendency of a wine to develop the problem of reduction and evaluate the efficacy of different remediation strategies.

DOI:

Publication date: June 23, 2022

Issue: IVAS 2022

Type: Article

Authors

Ontañón Ignacio1, Sánchez-Gimeno Diego1 and Ferreira Vicente1

1University of Zaragoza, Laboratorio de Análisis del Aroma y Enología. Química Analítica. Facultad de Ciencias. Universidad de Zaragoza. C/ Pedro Cerbuna, 12, 50009, Zaragoza, Spain

Contact the author

Keywords

Reduction, sulfur off odors, hydrogen sulfide, sulfide precursors, anoxic storage

Tags

IVAS 2022 | IVES Conference Series

Citation

Related articles…

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,

Inhibition of Oenococcus oeni during alcoholic fermentation by a selected Lactiplantibacillus plantarum strain

The use of selected cultures of the species Lactiplantibacillus plantarum in Oenology has grown in prominence in recent years. While initial applications of this species centred very much around malolactic fermentation (MLF), there is strong evidence to show that certain strains can be harnessed for their bio-protective effects. Unwanted spontaneous MLF during alcoholic fermentation (AF), driven by rogue Oenococcus oeni, is a winemaking deviation that is very difficult to manage when it occurs. This work set out to determine the efficacy of one particular strain of Lactiplantibacillus plantarum(Viniflora® NoVA™ Protect), against this problem in Cabernet Sauvignon must. The work was carried out at commercial scale and in a winery environment and compared the bio-protective culture with the more traditional approach of reducing must pH by the addition of tartaric acid. The combination of both was also investigated. The concentration of both Oenococcus oeni and Lactiplantibacillus plantarum was determined using qPCR. The adventitious Oenococcus oeni showed the most growth during AF in the control wine, whereas in the wines treated with Lactiplantibacillus plantarum a bacteriostatic effect against this species was observed. This effect was comparable to the wines treated with tartaric acid. This has particular commercial relevance for controlling the flora in musts with high pH, or when the addition of tartaric acid is either not permitted or is prohibitive for other reasons.

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.

Effect of one-year cover crop and arbuscular mycorrhiza inocululation in the microbial soil community of a vineyard

The microbial composition of the soil is an important factor to consider in viticulture, since its influence on the “terroir” and on the organoleptic properties of the wine have been demonstrated. Different agronomic techniques have the potential to modify the composition and functionality of the soil microbial community. Maintaining green covers is known to increase soil microbial diversity. The direct application of inoculum of beneficial microorganisms to the soil has also been used to increase their abundance. However, the environmental conditions of each site seem to have a determining weight in the result of these practices. In this study, we compared the effect on the microbial community of a cover crop with legumes in autumn and the inoculation of grapevines with commercial inoculum bases on Rhizophagus irregularis and Funeliformis mosseae in the previous spring. The study has been carried out in a vineyard in Binissalem, Mallorca, Spain. After applying the treatments, we will analyze the soil microbial communities using the data obtained from Illumina amplification of soil DNA from the 16S and ITS regions to analyze bacteria and fungi community, respectively. In addition, we will record the physicochemical characteristics of the soil at each sampling point. The result showed that agronomic management, in the short term, has less influence than soil characteristics on the composition of the soil microbiome. With these results, we can conclude that in a vineyard, agricultural techniques should focus on improving the characteristics of the soil to improve the biodiversity of the soil microbiota.

Modeling island and coastal vineyards potential in the context of climate change

Climate change impacts regional and local climates, which in turn affects the world’s wine regions. In the short term, these modifications rises issues about maintaining quality and style of wine, and in a longer term about the suitability of grape varieties and the sustainability of traditional wine regions. Thus, adaptation to climate change represents a major challenge for viticulture. In this context, island and coastal vineyards could become coveted areas due to their specific climatic conditions. In regions subject to warming, the proximity of the sea can moderate extremes temperatures, which could be an advantage for wine. However, coastal and island areas are particular prized spaces and subject to multiple pressures that make the establishment or extension of viticulture complex.
In this perspective, it seems relevant to assess the potentialities of coastal and island areas for viticulture. This contribution will present a spatial optimization model that tends to characterize most suitable agroclimatic patterns in historical or emerging vineyards according to different scenarios. Thanks to an in-depth bibliography a global inventory of coastal and insular vineyards on a worldwide scale has been realized. Relevant criteria have been identified to describe the specificities of these vineyards. They are used as input data in the optimization process, which will optimize some objectives and spatial aspects. According to a predefined scenario, the objectives are set in three main categories associated with climatic characteristics, vineyards characteristics and management strategies. At the end of this optimization process, a series of maps presents the different spatial configurations that maximize the scenario objectives.