 IVES 9 IVES Conference Series 9 Shades of shading: chemical and sensory evaluation of riesling grown under various shading techniques

Shades of shading: chemical and sensory evaluation of riesling grown under various shading techniques

Abstract

AIM: Sun exposure is needed for balanced grape ripening and sugar accumulation but is also one of the main drivers for a premature Riesling ageing. The aim of this study was to evaluate the modulation of both intensity and quality of light in the vineyard on key Riesling grape and wine parameters as an adaptation strategy to changing climate. Of particular interest was the kerosene aroma caused by the C13‑norisoprenoid TDN and other compounds associated with light-induced grape compositional changes.

METHODS: Over two vintages shade cloth of three different colours was applied to Riesling vines at bunch zone in South Australia. Light measurements and incident light wavelength assessments were performed during grape ripening, and subsequent grapes and wine were analysed for key bound and free aroma compounds. After 1-year of storage, wines were analysed by Quantitative Descriptive Analysis to quantify the holistic changes of light modulation to the sensory profile.

RESULTS: Depending on colour, shade cloth was successful in modulating either the quantity and/or wavelength of light, as well as showed different response of sugar accumulation. Shading reduced TDN concentrations and kerosene aroma in wines, with very little effect on other sensory descriptors. Interestingly, while presumed C13-norisoprenoid precursor profiles were altered between shading treatments, no significant differences were observed in resulting TDN levels.

CONCLUSIONS

This study highlights the importance of light intensity over examined light wavelength in the vineyard to manipulate TDN. Additionally, light conditions differently affected maturity with possible implications for harvest timing and climate-induced vintage compression.

DOI:

Publication date: September 13, 2021

Issue: Macrowine 2021

Type: Article

Authors

Yevgeniya Grebneva

The Australian Wine Research Institute & the Department of Microbiology and Biochemistry, Hochschule Geisenheim University,Markus, HERDERICH, The Australian Wine Research Institute, Adelaide 5064, Australia Doris, RAUHUT, Department of Microbiology and Biochemistry, Hochschule Geisenheim University Eleanor, BILOGREVIC, The Australian Wine Research Institute, Adelaide 5064, Australia Josh, HIXSON, The Australian Wine Research Institute, Adelaide 5064, Australia

Contact the author

Keywords

riesling, norisoprenoid, tdn, shade cloth

Citation

THE ROLE OF CELL WALL POLYSACCHARIDES IN THE EXTRACTION OF ANTHOCYANINS AND TANNINS: RESULTS, PERSPECTIVES OF A MORE POSITIVE CONTRIBUTION

The composition of grape berry cell walls was studied on two grape varieties, two years and two maturation levels at the same time as the extraction of anthocyanins and tannins. The chemical composition of skins, seeds, and pulps, focused on polyphenols and polysaccharides, was compared to the chemical composition in polyphenols after extraction from the skins in model solutions or after wine making of the berries. Polyphenols were mainly characterized by UPLC-MS and HPLC-SEC. Polysaccharides were characterized by analysis of the neutral sugar compositions, and also by the CoMPP (comprehensive micropolymer profiling) analysis, a new method which targets the functional groups of cell wall polysaccharides.

Simulated climate change in a Mediterranean organic vineyard altered the plant physiology and decreased the vine production

This study focuses on investigating the effects of climate change on the plant physiology and berries of Vitis vinifera cv “Monastrell” in a commercial vineyard managed organically in Southeastern Spain (Jumilla, Murcia). For this purpose, open top chambers and rainout shelters were employed to simulate warming (~2-7 ºC, W) and rainfall reduction (~30%, RR) respectively. Additionally, a combination of both treatments (W+RR) was employed. Vines without either top chambers or rainout shelters were considered as control (C). The experiment was established in February of 2023. Predawn leaf water potential (measured using a pressure chamber), stomatal conductance (assessed with a porometer at mid-morning) and leaf chlorophyll and flavonoid content (measured using the Dualex® leaf clip sensor) were analyzed at veraison (5 months after the installation of structures).

Impact of soil-applied and foliar-applied nitrogen on grape and wine composition

Foliar application of urea may be an efficient way to alter grape and wine composition without increasing vine vigor. However, we know little about the impact of this practice on phenolic compounds and yeast assimilable nitrogen (YAN). Adequate YAN is required for an efficient and complete fermentation, while phenolics are particularly important for the sensory profile of red wines. The goal of this study is to test the impact of foliar urea application at veraison, compared to the traditional soil-applied nitrogen fertilization early in the season, on Syrah berry and wine composition in field conditions.

Cartography of « Terroir Units » is a Tool to Improve the Ré Island Vineyard Management (France)

A study of « terroirs » was achieved from 2003 to 2005 in the whole vineyard of the Ré island (17, France). Over more than 1,990 ha, a cartography at the 1/10.000 scale, including characterization of climatic, pedological, geological and hydrogeological components of « Basic Terroir Units » (B.T.U.) was made. Also, a survey among wine growers was conducted. All data were treated together in a G.I.S. connected to a data base. 22 kinds of map were built (B.T.U. and components, soil water reserve, vine functioning potentials, varieties, rootstocks, viticultural practices and soil management).

Untangling belowground response of grapevines to cover crop competition

Cover crops are planted in vineyards for multiple benefits including soil conservation, weed management, regulation of grapevine vegetative growth