Terroir 1996 banner
IVES 9 IVES Conference Series 9 Rapid measurement of phenolic quality as a useful tool for viticultural zoning

Rapid measurement of phenolic quality as a useful tool for viticultural zoning

Abstract

Un des principaux objectifs du zonage viticole est l’individuation des zones plus indiquées à la production de vins de haute qualité en relation aux cépages. Ceperrlant depuis beaucqup d’années, entre les paramètres de qualité du raisin, on n’a pas considéré les substances phénoliques par effet de l!l difficulté d’analyse en temps rapides.
En considérant l’importance des polyphénols sur la qualité du raisin, en particulier le raisin rouge, un nouveau système d’évaluation en temps réel d’un indice de qualité phénolique du raisin rouge a été réalisé.
En utilisant un système d’analyse de la couleur particulier dans le spectrum de réflexion, il est possible d’analyser le raisin pendant la maturation ou de classer le raisin au moment de la livraison à la cave. Il s’agit d’un système d’analyse a posteriori, donc il est possible de réaliser un panorama indicatif de la potentialité phénolique des raisins déjà cultivés en différentes zones viticoles et pour chaque cépage.
Les données du présent travail expérimental sont relatives à des évaluations réalisées en Italie, Espagne et Australie au cours des dernières vendanges dans des domaines intéressées par l’évaluation des polyphénols comme paramètre supplémentaire pour la classification des raisins rouges à la livraison.
Les expériences réalisées ont permis de vérifier qu’il n’y a pas des corrélations significatives entre les polyphénols et les sucres à la récolte, en outre l’indice de qualité phénolique qu’on obtient en temps réel sur un échantillon représentatif est un résultat intéressant pour suivre l’évolution de la maturation en vigne.
La conséquence est que de grands projets de caractérisation des zones viticoles seraient peu significatifs si on néglige le patrimoine phénolique comme indice de qualité.
On peut donc affirmer que le système d’analyse rapide utilisé pourrait devenir un instrument efficace à introduire dans les programmes de zonage pour renouveler les données afin de définir la meilleure combinaison terroir x cépage pour la production de raisin avec un potentiel œnologique élevé.

One of the main aims of viticultural zoning is to identify the areas most suited to the production of high-quality wine in relation to each cultivar. In recent years, however, phenolic content as a parameter for assessing grape quality has often been neglected as it is not easy to measure quickly.
In view of the enormous importance of polyphenols in defining grape quality, in particularly black grapes, a new real-time evaluation system has been devised providing a phenolic quality index for black grapes.
Thanks to a special colorimetric system for assessing the reflectance spectrum, the grapes can be analysed during ripening or classified when delivered to the winery. Since this is a grape quality analysis system, it is possible to obtain an indication of the phenolic potential of the grapes already present in the various vine-growing areas and for each cultivar.
The data provided by this study refer to experiments performed in Italy, Spain and Australia in very recent grape harvests at wineries interested in analysis of polyphenols as an additional parameter for classification of black grapes at delivery, prior to start the winemaking process.
Tests showed that there is no significant correlation between the polyphenols and the sugar level at grape harvest, furthermore, the phenolic quality index obtainable in real time on a representative sample is useful for monitoring ripening in the vineyard. This means that wide­-ranging projects for the characterisation of vine-growing areas would have very little significance if the phenolic content were neglected as an index of grape quality.
In the light of these results, the rapid analysis system used could become a valid tool in zoning programs for updating the existing data in order to identify the area x cultivar combination best suited to the production of grapes with a high enological potential.

 

 

 

DOI:

Publication date: February 15, 2022

Issue: Terroir 2002

Type: Article

Authors

E. CELOTTI, G. CARCERERI DE PRATI, F. BATTISTUTTA and R. ZIRONI

Dipartimento di Scienze degli Alimenti, Università degli Studi di Udine, Via Marangoni 97 -33100 Udine/Italie

Contact the author

Keywords

Zonage, Raisin, Qualité Phénolique, Couleur, Polyphénoles
Zoning, Grape, Phenolic Quality, Colour, Polyphenols

Tags

IVES Conference Series | Terroir 2002

Citation

Related articles…

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)

Underpinning terroir with data: rethinking the zoning paradigm

Agriculture, natural resource management and the production and sale of products such as wine are increasingly data-driven activities. Thus, the use of remote and proximal crop and soil sensors to aid management decisions is becoming commonplace and ‘Agtech’ is proliferating commercially; mapping, underpinned by geographical information systems and complex methods of spatial analysis, is widely used. Likewise, the chemical and sensory analysis of wines draws on multivariate statistics; the efficient winery intake of grapes, subsequent production of wines and their delivery to markets relies on logistics; whilst the sales and marketing of wines is increasingly driven by artificial intelligence linked to the recorded purchasing behaviour of consumers. In brief, there is data everywhere!

Opinions will vary on whether these developments are a good thing. Those concerned with the ‘mystique’ of wine, or the historical aspects of terroir and its preservation, may find them confronting. In contrast, they offer an opportunity to those interested in the biophysical elements of terroir, and efforts aimed at better understanding how these impact on vineyard performance and the sensory attributes of resultant wines. At the previous Terroir Congress, we demonstrated the potential of analytical methods used at the within-vineyard scale in the development of Precision Viticulture, in contributing to a quantitative understanding of regional terroir. For this conference, we take this approach forward with examples from contrasting locations in both the northern and southern hemispheres. We show how, by focussing on the vineyards within winegrowing regions, as opposed to all of the land within those regions, we might move towards a more robust terroir zoning than one derived from a mixture of history, thematic mapping, heuristics and the whims of marketers. Aside from providing improved understanding by underpinning terroir with data, such methods should also promote improved management of the entire wine value chain.

Climate change projections to support the transition to climate-smart viticulture

The Earth’s system is undergoing major changes through a wide range of spatial and temporal scales as a response to growing anthropogenic radiative forcing, which is pushing the whole system far beyond its natural variability. Sources of greenhouse gases largely exceed their sinks, thus leading to a strengthened greenhouse effect. More energy is thereby being supplied to the system, with inevitable shifts in climatic patterns and weather regimes. Over the last decades, these modifications have been manifested in the full statistical distributions of the atmospheric variables, with dramatic changes in the frequency and intensity of extremes. Natural hazards, such as severe droughts, floods, forest fires, or heatwaves, are being triggered by extreme atmospheric events worldwide, thus threatening human activities. Viticultculture is not only exposed to changing climates but is also highly vulnerable, as grapevine phenology and physiological development are strongly controlled by atmospheric conditions. Therefore, the assessment of climate change projections for a given region is critical for climate change adaptation and risk reduction in viticulture. By adopting timely and suitable measures, the future sustainability and resiliency of the sector can be fostered. Climate-grapevine chain modelling is an essential tool for better planning and management. However, the accuracy of the resulting projections is limited by many uncertainties that must be duly taken into account when transferring knowledge to stakeholders and decision-makers. Climate-smart viticulture will comprise ensembles of locally tuned strategies, envisioning both adaptation and mitigation, assisted by emerging technologies and decision-support systems.

Influence of a spontaneous cover crop on the vineyard and soil erosion under Mediterranean climate

Sixty five % of the agricultural area of the Basque Country located in the DO Ca Rioja corresponds to vineyards. More than 40% of it has an average slope greater than 10%, which makes it sensitive to erosive processes. Furthermore, it is foreseeable that extreme weather events (storms, hail, extreme heat and cold, etc.) will be favored due to climate change. Cover cropping can mitigate this risk, and therefore the objective of this work is to evaluate the impact that a vegetable cover has on the agronomic behavior of the vineyard, the quality of the grape and soil erosion. For this, a trial has been carried out with a Graciano variety vineyard with a slope between 10% -20% during the years 2020 and 2021. Conventional tillage management in the area has been compared (4-6 passes per year of tillage machinery) versus spontaneous vegetation cover management in the vineyard. This implies not tilling and allowing the grass of the land to colonize the range between the lines of vines, controlling their height through 1-3 mowing passes per year, always trying to affect the surface of the land as little as possible. The vegetative growth, yield and quality of the grape and wine was measured. Furthermore, erosion has been measured using Gerlasch boxes. The yield was lower in the second year of the trial in the cover crop treatment, but erosion was significantly reduced.

Assessing the relationship between cordon strangulation, dieback, and fungal trunk disease symptom expression

Grapevine trunk diseases including Eutypa dieback are a major factor in the decline of vineyards and may lead to loss of productivity, reduced income, and premature reworking or replanting. Several studies have yielded results indicating that vines may be more likely to express symptoms of vascular disease if their health is already compromised by stress. In Australia and many other wine-growing regions it is a common practice for canes to be wrapped tightly around the cordon wire during the establishment of permanent cordon arms. It is likely that this practice may have a negative effect on health and longevity, as older cordons that have been trained in this manner often display signs of decay and dieback, with the wire often visibly embedded within the wood of the cordon. It is possible that adopting a training method which avoids constriction of the vasculature of the cordon may help to limit the onset of vascular disease symptom expression. A survey was conducted during the spring of two consecutive growing seasons on vineyards in South Australia displaying symptoms of Eutypa lata infection when symptomless shoots were 50–100 cm long. Vines were assessed as follows: (i) the proportion of cordon exhibiting dieback was rated using a 0–100% scale; (ii) the proportion of canopy exhibiting foliar symptoms of Eutypa dieback was rated using a 0–100% scale; (iii) the severity of strangulation was rated using a 0–4 point scale. Images were also taken of each vine for the purpose of measuring plant area index (PAI) using the VitiCanopy App. The goal of the survey was to determine if and to what extent any correlation exists between severity of strangulation and cordon dieback, in addition to Eutypa dieback foliar symptom expression.