 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

VviSOC1a and VviAG1 act antagonistically in the regulation of flower formation

The SUPPRESSOR OF OVEREXPRESSION OF CONSTANS1 (SOC1) is a key floral activator that coordinates external and internal stimuli to ensure timely flowering. During early stages of flower formation, SOC1 represses floral organ identity genes such as AGAMOUS (AG) to prevent premature organ differentiation. In addition to floral organ specification, AG has been shown to regulate fleshy fruit expansion and ripening and, as such, is an important contributor to fruit quality traits. Currently, little is known about the function and gene regulatory network of the grapevine homologs VviSOC1a and VviAG1. As such, the aim of this study was to functionally characterise both genes by overexpressing them in tomato and performing phenotypic and gene expression studies.

On the stability of spectral features of four vine varieties in Brazil, Chile and France

Satellite images of vineyards in France, Chile, and Brazil are used to study spectral differences between the vine varieties Cabernet Sauvignon, Merlot, Pinot Noir, and Chardonnay, to verify if features of a given variety are conserved at vineyards in completely different terroirs.

Analysis of voltammetric fingerprints of different white grape musts reveals genotype-related oxidation patterns

Must oxidation is a complex process involving multiple enzymatic transformations, including the oxidation of phenolics containing an ortho-diphenol function. The latter process has a primary influence on wine aroma characteristics and stability, due to the central role of ortho-diphenols in the non-enzymatic oxidative reactions taking place during winemaking and in finished wine. Although oxidation of must is traditionally avoided, in recent years its contribution to wine quality has been revisited, and in some cases improvements to wine aroma have been observed with the application of controlled must oxidation. Nowadays there is a great interest in the wine industry towards the identification of specific markers or patterns to characterize and classify the response of grape must to oxidation.

Dimethyl sulfide transfer through wine closures during bottle aging: implications for wine aroma management

Dimethyl sulfide (DMS) is a volatile sulfur compound with a complex role in wine aroma, contributing both desirable and undesirable sensory characteristics depending on its concentration (1).

PINKING PHENOMENA ON WHITE WINES: RELATION BETWEEN PINKING SUSCEPTIBILITY INDEX (PSI) AND WINE ANTHOCYANINS CONTENT

Pinking is the emergence of pink tones in white wines exclusively produced from white grape varieties, known as pinking phenomena for many years. Pinking is essentially appeared when white wines are produced under reducing conditions [1,2,3]. Pinking usually occurs after bottling and storage of white wines, but its appearance has also been described after alcoholic fermentation or even as soon as the grape must is extracted [4]. Therefore, the purpose of this work was to investigate the existence of an-thocyanins in white wines made from different white grape varieties and grown locations and critically evaluate the most common method used for predicting pinking appearance in white wines: the Pinking Susceptibility Index (PSI).