**6. Conclusions**

There is no doubt that wine is an extremely complex medium and that polyphenolic compounds play an essential role on its final sensory properties. There is an inestimable chemical diversity of polyphenols in both grapes and wines. Each family can be present in free or conjugated forms, with different hydroxylation levels and substitutions or even forming adducts between them. Starting with the raw material, phenolic compounds in grapes can vary substantially depending on several factors as ripening, viticulture practices, environmental conditions, and varietal or genetic differences. Such is the case that each cultivar may be considered as "exclusive" and consequently, the resulting wine too. Anthocyanins (mainly present in skins) and flavan-3-ols and condensed tannins (mainly present in skins and seeds) are the most abundant polyphenols in grapes. On the one hand, anthocyanins are responsible of the color of red wines, and their profile can be used as an analytical tool for authenticity certification. On the other hand, flavan-3-ols and condensed tannins are key compounds due to their implication on color

**17**

**Author details**

is opened.

Michaël Jourdes1

Ruth Hornedo-Ortega1

and Pierre-Louis Teissedre1

\*Address all correspondence to: pierre-louis.teissedre@u-bordeaux.fr

2 Tonnellerie Nadalié, Ludon-Médoc, France

provided the original work is properly cited.

*Phenolic Compounds of Grapes and Wines: Key Compounds and Implications in Sensory…*

stabilization and astringent and bitter properties. Finally, other phenolics as flavonols and hydroxycinnamic acids are mainly known for acting as copigments. Oak wood is commonly used during fermentation and/or aging of wines. The phenolic composition of oak wood will vary depending on species, geographical origin, and grain or wood processing. In quantitative terms, ellagitannins are the major phenolic constituents of oak wood, and their level and profile may affect the astringency and bitterness of wine. Winemaking produces important changes in polyphenolic composition. In fact, phenolics participate in several reactions such as copigmentation, cycloaddition, polymerization, and oxidation. Thus, new compounds as vitisins, ethyl-bridged anthocyanin-flavanol derivatives, or pyroanthocyanins are formed. Furthermore, wine aging in contact with oak wood affects the degree of complexity of phenolic compounds. In this sense, ellagitannins are actively engaged in oxidation reactions that favor the polymerization between flavanols and between

Overwhelming evidence has demonstrated that tannins (mostly condensed tannins), thanks to their ability to precipitate salivary proteins, are implicated on wine astringency. Astringency intensity, even if it is a multifaceted sensation complicated by a number of variables, is more influenced by the source of proanthocyanidin (seed or skin) and by well-defined proanthocyanidin fractions (oligomeric or polymeric). Up to now, ellagitannins' direct impact on astringency and bitterness sensation remains still unknown. One of the major limitations of the half-tongue test used to evaluate their sensory impact is the absence of contact between the ellagitannins and the entire oral cavity. Further studies are needed under wine conditions. Additionally, recent studies highlight that other phenolic compounds such as anthocyanins/pyranoanthocyanins or flavanols may also interact with salivary proteins and bitterness receptors. Thus, a new research line in the field of sensory properties linked to wine phenolic compounds sensory properties

, María Reyes González-Centeno1,2, Kleopatra Chira1,2,

\*

1 Axe Qualité et Identité du Vin, Unité de Recherche Œnologie, Institut des Sciences de la Vigne et du Vin (ISVV), Université de Bordeaux, Villenave d'Ornon, France

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

*DOI: http://dx.doi.org/10.5772/intechopen.93127*

flavanols and anthocyanins.

*Phenolic Compounds of Grapes and Wines: Key Compounds and Implications in Sensory… DOI: http://dx.doi.org/10.5772/intechopen.93127*

stabilization and astringent and bitter properties. Finally, other phenolics as flavonols and hydroxycinnamic acids are mainly known for acting as copigments. Oak wood is commonly used during fermentation and/or aging of wines. The phenolic composition of oak wood will vary depending on species, geographical origin, and grain or wood processing. In quantitative terms, ellagitannins are the major phenolic constituents of oak wood, and their level and profile may affect the astringency and bitterness of wine. Winemaking produces important changes in polyphenolic composition. In fact, phenolics participate in several reactions such as copigmentation, cycloaddition, polymerization, and oxidation. Thus, new compounds as vitisins, ethyl-bridged anthocyanin-flavanol derivatives, or pyroanthocyanins are formed. Furthermore, wine aging in contact with oak wood affects the degree of complexity of phenolic compounds. In this sense, ellagitannins are actively engaged in oxidation reactions that favor the polymerization between flavanols and between flavanols and anthocyanins.

Overwhelming evidence has demonstrated that tannins (mostly condensed tannins), thanks to their ability to precipitate salivary proteins, are implicated on wine astringency. Astringency intensity, even if it is a multifaceted sensation complicated by a number of variables, is more influenced by the source of proanthocyanidin (seed or skin) and by well-defined proanthocyanidin fractions (oligomeric or polymeric). Up to now, ellagitannins' direct impact on astringency and bitterness sensation remains still unknown. One of the major limitations of the half-tongue test used to evaluate their sensory impact is the absence of contact between the ellagitannins and the entire oral cavity. Further studies are needed under wine conditions. Additionally, recent studies highlight that other phenolic compounds such as anthocyanins/pyranoanthocyanins or flavanols may also interact with salivary proteins and bitterness receptors. Thus, a new research line in the field of sensory properties linked to wine phenolic compounds sensory properties is opened.
