Terroir 2004 banner
IVES 9 IVES Conference Series 9 Sugar loading and phenolic accumulation as affected by ripeness level of Syrah/R99 grapes

Sugar loading and phenolic accumulation as affected by ripeness level of Syrah/R99 grapes

Abstract

[English version below]

Le chargement et l’accumulation des sucres ainsi que la biosynthèse des phénols ont été étudiés sur la Syrah, dans le cadre d’un programme de recherche de paramètres qui permettraient de déterminer une ou plusieurs qualités de raisin en relation avec des styles de vins pour un terroir donné. La relation entre la dynamique d’accumulation des sucres et, en parallèle, la biosynthèse des phénols a été étudiée sur Syrah/99R plantée dans un vignoble situé sur la station expérimentale de ARC Infruitec-Nietvoorbij, Stellenbosch (Afrique du Sud). La cinétique des analyses a été réalisée depuis le stade post floraison (nouaison) jusqu’au stade sur-maturation. Les vignes sont conduites en Espalier (2,75m x 1,5m), les rangs sont orientés nord – sud, le vignoble est en pente orientée est. Une irrigation par micro aspersion est appliquée de la nouaison à la véraison. La hauteur de végétation est de 1,4 m, avec 3 hauteurs de fils de palissage. Les vignes sont ébourgeonnées, palissées et écimées. La dynamique d’accumulation des sucres par baie a été étudiée à l’aide d’un protocole développé par Deloire et al., 2004 (sous presse). La biosynthèse des phénols (tanins totaux et leur degré de polymérisation, proanthocyanidols et anthocyanes) a été étudiée par spectrophotométrie et HPLC pour les anthocyanes. Le sucre est utilisé comme indicateur des relations vigne – baie (relations source – puits).
Les tanins totaux (TT) de la baie sont synthétisés depuis l’anthèse jusqu’à la véraison. Leur concentration augmente durant la croissance herbacée des baies. Elle diminue en concentration de véraison à maturation, alors que durant cette période, la quantité de TT par baie est stable. Quand les sucres sont utilisés comme indicateur physiologique, il ressort clairement que la biosynthèse des anthocyanes évolue, par baie, jusqu’à ce que ces dernières atteignent un contenu en sucre de 20 – 21 °Brix. Après ce point, l’évolution des anthocyanes par baie est indépendante de l’évolution du contenu en sucre par baie, qui se fait alors essentiellement par concentration (perte d’eau de la baie). Le chargement actif des baies en sucre est dépendant de la photosynthèse des feuilles et la régulation du déchargement phloémien du sucre dans les baies semble en partie dépendante du microclimat des grappes et des baies elles mêmes. Le chargement actif en sucre de la baie n’est pas directement corrélé à son volume.

Sugar loading and phenolic accumulation in Syrah grapes were investigated as part of an elaborate study to determine parameters that would indicate high grape quality and different grape and wine styles on a particular terroir. The relationship between the dynamics of sugar loading and phenolic accumulation in the berries of a Syrah/R99 vineyard, situated at the ARC Infruitec-Nietvoorbij , in the Stellenbosch region (South Africa), was investigated from pea size stage (green berry) to late maturity. Vines were vertically trained and spaced 2.75 x 1.5 m in north-south orientated rows on a terroir with Glenrosa soil and a west-facing slope. Microsprinkler-irrigation was applied at pea berry size and at véraison stages. The 1.4 m high canopies were suckered, shoot-positioned and topped and accommodated by means of three sets of double wires. The dynamics of berry sugar loading were studied by a method from Deloire et al, 2004 (under publication), the berry phenolic composition (total tannins and polymerisation, proanthocyanidins, anthocyanins) was analysed by spectrophotometry and anthocyanins by HPLC. Sugar was used as physiological indicator of the plant-berry (source-sink) relationship and as bunch microclimatic indicator.
The total tannin (TT) component in the berry was synthesised from anthesis to véraison. The TT concentration increased during the green berry growth stages and decreased during ripening as the berry increased in volume. The TT per berry also increased during the green berry growth stages, but kept stable during ripening. When sugar content per berry is used as physiological indicator, it is clear that anthocyanin biosynthesis occurred until a specific berry sugar content, i.e. 20 – 21 0Brix, is reached. After this point, anthocyanin evolution per berry seemed independent of berry sugar evolution, which is at that time mainly due to concentration (berry water loss) than to loading. Thus, although berry sugar loading is dependent on photosynthetic activity of the leaves, the regulation of sugar phloem unloading in the berry sink seemed to be, in part, affected by the microclimate that the berry experienced. Berry sugar loading was not directly correlated with berry volume.

DOI:

Publication date: January 10, 2022

Issue: Terroir 2004

Type: Article

Authors

A. Deloire (1), E. Kraeva (1), M. Martin (2) et J.J. Hunter (3)

(1) Agro Montpellier, UMR 1083 « sciences pour l’œnologie et la viticulture », 2 place Viala, 34060 Montpellier cedex 1, France
(2) INRA, Unité expérimentale de Pech Rouge, 11430 Gruissan, France
(3) ARC Infruitec-Nietvoorbij, Private Bag X5026, 7599 Stellenbosch, South Africa

Contact the author

Keywords

Vitis vinifera, bunch, sugar, microclimate, indicator, vine functioning

Tags

IVES Conference Series | Terroir 2004

Citation

Related articles…

Leaf vine content in nutrients and trace elements in La Mancha (Spain) soils: influence of the rootstock

The use of rootstock of American origin has been the classic method of fighting against Phylloxera for more than 100 years. For this reason, it is interesting to establish if different rootstock modifies nutrient composition as well as trace elements content that could be important for determining the traceability of the vine products. A survey of four classic rootstocks (110-Richter, SO4, FERCAL and 1103-Paulsen) and four new ones (M1, M2, M3 and M4) provided by Agromillora Iberia. S.L.U., all of them grafted with the Tempranillo variety, has been carried out during 2019. The eight rootstocks were planted in pots of 500 cc, on three soils with very different characteristics from Castilla-La Mancha (Spain). In the month of July, the leaves were collected and dried in a forced air oven for seven days at 40ºC. Then, the samples were prepared for the analysis determination, carried out by X-Ray fluorescence spectrometry. The results obtained showed that in the case of content in mineral elements in leaf, separated by soil type, we can report the importance of few elements such as Si, Fe, Pb and, especially, Sr. The rootstock does not influence the composition of the vine leaf for the studied elements that are the most important in determining the geochemical footprint of the soil. The influence of the soil can be discriminated according to some elements such as Fe, Pb, Si and, especially, Sr.

How does aromatic composition of red wines, resulting from varieties adapted to climate change, modulate fruity aroma?

One of the major issues for the wine sector is the impact of climate change linked to the increasing temperatures which affects physicochemical parameters of the grape varieties planted in Bordeaux vineyard and consequently, the quality of wine. In some varietals, the attenuation of their fresh fruity character is accompanied by the accentuation of dried-fruit notes [1]. As a new adaptive strategy on climate change, some winegrowers have initiated changes in the Bordeaux blend of vine varieties [2]. This study intends to explore the fruitiness in wines produced from grape varieties adapted to the future climate of Bordeaux. 10 commercial single–varietal wines from 2018 vintage made from the main grape varieties in the Bordeaux region (Cabernet franc, Cabernet-Sauvignon and Merlot) as well as from indigenous grape varieties from the Mediterranean basin, such as Cyprus (Yiannoudin), France (Syrah), Greece (Agiorgitiko and Xinomavro), Portugal (Touriga Nacional) and Spain (Garnacha and Tempranillo), were selected among 19 samples using sensory descriptive analyses. Both sensory and instrumental analyses were coupled, to investigate their fruity aroma expression. For sensory analysis, samples were prepared from wine, using a semi preparative HPLC method which preserves wine aroma and isolates fruity characteristics in 25 specific fractions [3,4]. Fractions of interest with intense fruity aromas were sensorially selected for each wine by a trained panel and mixed with ethanol and microfiltered water to obtain fruity aromatic reconstitutions (FAR) [5]. A free sorting task was applied to categorize FAR according to their similarities or dissimilarities, and different clusters were highlighted. Instrumental analysis of the different FAR and wines demonstrated variations in their molecular composition. Results obtained from sensory and gas chromatography analysis enrich the knowledge of the fruity expression of red wines from “new” grape varieties opening up new perspectives in wine technology, including blending, thus providing new tools for producers.

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.

Pruned vine biomass exclusion from a clay loam vineyard soil – examining the impact on physical/chemical properties

The wine industry worldwide faces increasing challenges to achieve sustainable levels of carbon emission mitigation. This project seeks to establish the feasibility of harvesting winter pruned vineyard biomass (PVB) for potential use in carbon footprint reduction, through its use as a renewable biofuel for energy production. In order to make this recommendation, technical issues such as the potential environmental impact, chemical composition and fuel suitability, and logistical challenges of harvesting biomass needs to be understood to compare with the results from similar studies. Of particular interest is the role PVB plays as a carbon source in vineyard soils and what effect annual removal might have on soil carbon sequestration. A preliminary trial was established in the Waite Campus vineyard (University of Adelaide) to test current management strategies. Vines are grown in a Eutrophic, Red Dermosol clay loam soil with well managed midrow swards. A comparison was undertaken of mid-row treatments in two 0.25 Ha blocks (Shiraz and Semillon), including annual cultivation for seed bed preparation, the deliberate exclusion of PVB (25 years) and incorporation of PVB (13 years) at an average of 3.4 and 5.5 Mg/Ha-1 for Shiraz and Semillon respectively. In both 0-10cm and 10-30cm soil core sample depths, combined soil carbon % measures in the desired range of 1.80 to 3.50, were not significantly different between treatments or cultivars and yielded an estimated 42 Mg/ha-1 of sequestered soil carbon. Other key physical and chemical measures were likewise not significantly different between treatments. Preliminary results suggest that in a temperate zone vineyard, managed such as the one used in this study, there is no long term negative impact on soil carbon sequestration through removing PVB. This implies that growers could confidently harvest PVB for use in several end fates including as a bio fuel.

Use of a new, miniaturized, low-cost spectral sensor to estimate and map the vineyard water status from a mobile 

Optimizing the use of water and improving irrigation strategies has become increasingly important in most winegrowing countries due to the consequences of climate change, which are leading to more frequent droughts, heat waves, or alteration of precipitation patterns. Optimized irrigation scheduling can only be based on a reliable knowledge of the vineyard water status.

In this context, this work aims at the development of a novel methodology, using a contactless, miniaturized, low-cost NIR spectral tool to monitor (on-the-go) the vineyard water status variability. On-the-go spectral measurements were acquired in the vineyard using a NIR micro spectrometer, operating in the 900–1900 nm spectral range, from a ground vehicle moving at 3 km/h. Spectral measurements were collected on the northeast side of the canopy across four different dates (July 8th, 14th, 21st and August 12th) during 2021 season in a commercial vineyard (3 ha). Grapevines of Vitis vinifera L. Graciano planted on a VSP trellis were monitored at solar noon using stem water potential (Ψs) as reference indicators of plant water status. In total, 108 measurements of Ψs were taken (27 vines per date).

Calibration and prediction models were performed using Partial Least Squares (PLS) regression. The best prediction models for grapevine water status yielded a determination coefficient of cross-validation (r2cv) of 0.67 and a root mean square error of cross-validation (RMSEcv) of 0.131 MPa. This predictive model was employed to map the spatial variability of the vineyard water status and provided useful, practical information towards the implementation of appropriate irrigation strategies. The outcomes presented in this work show the great potential of this low-cost methodology to assess the vineyard stem water potential and its spatial variability in a commercial vineyard.