Macrowine 2021
IVES 9 IVES Conference Series 9 Relevance of the polyphenolic profile during oxidative aging in the accumulation and disappearance of oxidative and varietal aromas

Relevance of the polyphenolic profile during oxidative aging in the accumulation and disappearance of oxidative and varietal aromas

Abstract

The main objective of this work is to study and model the impact of the polyphenolic profile on the stability and quality of wine aroma during oxidative aging. Aromas considered in the study are grape-derived varietal aromas, such as linalool, geraniol and 1,1,6-trimethyl-1,2-dihydronaphthalene (TDN), yeast-released varietal mercaptans, such as 4-mercapto-4-methyl-2-pentanone (4MMP), 3-mercaptohexyl acetate (MHA) and 3-mercaptohexan-1-ol (3MH)) and also oxidation-related aroma compounds, such as acetaldehyde and Strecker aldehydes: isobutyraldehyde, 2-methylbutyraldehyde, isovaleraldehyde, methional and phenylacetaldehyde. Fifteen aromatic phenolic fractions (FFAs) were extracted from garnacha, moristel and tempranillo grapes; FFAs were chemically characterized and were further reconstituted with water, alcohol, metal cations, amino acids and polyfunctional mercaptans so that differences were limited to the polyphenolic profile and to levels of precursors to varietal aroma compounds. Reconstituted samples were supplied with oxygen (50 mg/L) and aged during 35 days at 35ºC. Results show that the accumulation of acetaldehyde is uniform and very low in all the FFAs, confirming previous results about the low accumulation of this compound during oxidation. Nevertheless, acetaldehyde accumulation seems to be correlated with the sum of phenolic acids. Accumulation of Strecker aldehydes between samples differs by a 2.5 factor, with much higher levels in reconstitutions with FFAs from Garnacha and Moristel varieties. Levels of Strecker aldehydes were positively correlated to the sum of flavanols, phenolic acids and with the percentage of unpigmented tannins. Also, they appear to be negatively correlated with color, pigmented and total tannin concentrations and delphinidins. Polyfunctional mercaptans reacted spontaneously even in anoxia, so that final levels were significant only in unoxidized controls. In these samples, levels between different FFAs differed by factors of up to 2.6 and were negatively correlated to the contents of unpigmented tannins. The other varietal aromas (linalool, geraniol and TDN), were not affected by oxidation. All of this demonstrates that the phenolic composition plays a crucial role in the development of Strecker aldehydes during oxidative aging, likely due the differential reactivity of the quinones formed. The strong reactivity of wine polyphenols to polyfunctional mercaptans was not expected and should be further studied.

DOI:

Publication date: September 14, 2021

Issue: Macrowine 2021

Type: Article

Authors

Elena Bueno-Aventín

Laboratory for Aroma Analysis and Enology (LAAE), Department of Analytical Chemistry, Faculty of Chemistry. E-50009, Zaragoza, Spain,Vicente Ferreira-González, Ana Escudero-Carra   Laboratory for Aroma Analysis and Enology (LAAE), Department of Analytical Chemistry, Faculty of Chemistry. E-50009, Zaragoza, Spain

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Keywords

polyphenol; acetaldehyde; aldehydes; polyfunctional mercaptans; oxidation

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Macrowine 2021
IVES 9 IVES Conference Series 9 Relevance of the polyphenolic profile during oxidative aging in the accumulation and disappearance of oxidative and varietal aromas

Relevance of the polyphenolic profile during oxidative aging in the accumulation and disappearance of oxidative and varietal aromas

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Adapting the vineyard to climate change in warm climate regions with cultural practices

Since the 1980s global regime shift, grape growers have been steadily adapting to a changing climate. These adaptations have preserved the region-climate-cultivar rapports that have established the global trade of wine with lucrative economic benefits since the middle of 17th century. The advent of using fractions of crop and actual evapotranspiration replacement in vineyards with the use of supplemental irrigation has furthered the adaptation of wine grape cultivation. The shift in trellis systems, as well as pruning methods from positioned shoot systems to sprawling canopies, as well as adapting the bearing surface from head-trained, cane-pruned to cordon-trained, spur-pruned systems have also aided in the adaptation of grapevine to warmer temperatures. In warm climates, the use of shade cloth or over-head shade films not only have aided in arresting the damage of heat waves, but also identified opportunities to reduce the evapotranspiration from vineyards, reducing environmental footprint of vineyard. Our increase in knowledge on how best to understand the response of grapevine to climate change was aided with the identification of solar radiation exposure biomarker that is now used for phenotyping cultivars in their adaptability to harsh environments. Using fruit-based metrics such as sugar-flavonoid relationships were shown to be better indicators of losses in berry integrity associated with a warming climate, rather than solely focusing on region-climate-cultivar rapports. The resilience of wine grape was further enhanced by exploitation of rootstock × scion combinations that can resist untoward droughts and warm temperatures by making more resilient grapevine combinations. Our understanding of soil-plant-atmosphere continuum in the vineyard has increased within the last 50 years in such a manner that growers are able to use no-till systems with the aid of arbuscular mycorrhiza fungi inoculation with permanent cover cropping making the vineyard more resilient to droughts and heat waves. In premium wine grape regions viticulture has successfully adapted to a rapidly changing climate thus far, but berry based metrics are raising a concern that we may be approaching a tipping point.