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The phenolic content in wine refers to the phenolic compounds—
natural phenol In biochemistry, naturally occurring phenols are natural products containing at least one phenol functional group. Phenolic compounds are produced by plants and microorganisms. Organisms sometimes synthesize phenolic compounds in response to ecol ...
and
polyphenol Polyphenols () are a large family of naturally occurring organic compounds characterized by multiples of phenol units. They are abundant in plants and structurally diverse. Polyphenols include flavonoids, tannic acid, and ellagitannin, some ...
s—in
wine Wine is an alcoholic drink typically made from Fermentation in winemaking, fermented grapes. Yeast in winemaking, Yeast consumes the sugar in the grapes and converts it to ethanol and carbon dioxide, releasing heat in the process. Different ...
, which include a large group of several hundred
chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...
s that affect the
taste The gustatory system or sense of taste is the sensory system that is partially responsible for the perception of taste (flavor). Taste is the perception produced or stimulated when a substance in the mouth reacts chemically with taste receptor ...
,
color Color (American English) or colour (British English) is the visual perceptual property deriving from the spectrum of light interacting with the photoreceptor cells of the eyes. Color categories and physical specifications of color are associ ...
and
mouthfeel Mouthfeel refers to the physical sensations in the mouth caused by food or drink, making it distinct from taste. It is a fundamental sensory attribute which, along with taste and smell, determines the overall flavor of a food item. Mouthfeel ...
of wine. These compounds include
phenolic acid Phenolic acids or phenolcarboxylic acids are types of aromatic acid compounds. Included in that class are substances containing a phenolic ring and an organic carboxylic acid function (C6-C1 skeleton). Two important naturally occurring types of ph ...
s,
stilbenoid Stilbenoids are hydroxylated derivatives of stilbene. They have a C6–C2–C6 structure. In biochemical terms, they belong to the family of phenylpropanoids and share most of their biosynthesis pathway with chalcones. Most stilbenoids are prod ...
s,
flavonol Flavonols are a class of flavonoids that have the 3-hydroxyflavone backbone (IUPAC name : 3-hydroxy-2-phenylchromen-4-one). Their diversity stems from the different positions of the phenolic -OH groups. They are distinct from flavanols (with " ...
s, dihydroflavonols,
anthocyanin Anthocyanins (), also called anthocyans, are water-soluble vacuolar pigments that, depending on their pH, may appear red, purple, blue, or black. In 1835, the German pharmacist Ludwig Clamor Marquart gave the name Anthokyan to a chemical com ...
s,
flavanol Flavan-3-ols (sometimes referred to as flavanols) are a subgroup of flavonoids. They are derivatives of flavans that possess a 2-phenyl-3,4-dihydro-2''H''-chromen-3-ol skeleton. Flavan-3-ols are structurally diverse and include a range of compo ...
monomers (
catechin Catechin is a flavan-3-ol, a type of secondary metabolite providing antioxidant roles in plants. It belongs to the subgroup of polyphenols called flavonoids. The name of the catechin chemical family derives from ''catechu'', which is the tanni ...
s) and
flavanol Flavan-3-ols (sometimes referred to as flavanols) are a subgroup of flavonoids. They are derivatives of flavans that possess a 2-phenyl-3,4-dihydro-2''H''-chromen-3-ol skeleton. Flavan-3-ols are structurally diverse and include a range of compo ...
polymers ( proanthocyanidins). This large group of natural phenols can be broadly separated into two categories,
flavonoid Flavonoids (or bioflavonoids; from the Latin word ''flavus'', meaning yellow, their color in nature) are a class of polyphenolic secondary metabolites found in plants, and thus commonly consumed in the diets of humans. Chemically, flavonoids ...
s and non-flavonoids. Flavonoids include the
anthocyanin Anthocyanins (), also called anthocyans, are water-soluble vacuolar pigments that, depending on their pH, may appear red, purple, blue, or black. In 1835, the German pharmacist Ludwig Clamor Marquart gave the name Anthokyan to a chemical com ...
s and
tannin Tannins (or tannoids) are a class of astringent, polyphenolic biomolecules that bind to and precipitate proteins and various other organic compounds including amino acids and alkaloids. The term ''tannin'' (from Anglo-Norman ''tanner'' ...
s which contribute to the color and mouthfeel of the wine. The non-flavonoids include the
stilbenoid Stilbenoids are hydroxylated derivatives of stilbene. They have a C6–C2–C6 structure. In biochemical terms, they belong to the family of phenylpropanoids and share most of their biosynthesis pathway with chalcones. Most stilbenoids are prod ...
s such as
resveratrol Resveratrol (3,5,4′-trihydroxy-''trans''-stilbene) is a stilbenoid, a type of natural phenol, and a phytoalexin produced by several plants in response to injury or when the plant is under attack by pathogens, such as bacteria or fungi. Sourc ...
and
phenolic acid Phenolic acids or phenolcarboxylic acids are types of aromatic acid compounds. Included in that class are substances containing a phenolic ring and an organic carboxylic acid function (C6-C1 skeleton). Two important naturally occurring types of ph ...
s such as benzoic, caffeic and cinnamic acids.


Origin of the phenolic compounds

The natural phenols are not evenly distributed within the fruit. Phenolic acids are largely present in the pulp,
anthocyanin Anthocyanins (), also called anthocyans, are water-soluble vacuolar pigments that, depending on their pH, may appear red, purple, blue, or black. In 1835, the German pharmacist Ludwig Clamor Marquart gave the name Anthokyan to a chemical com ...
s and
stilbenoid Stilbenoids are hydroxylated derivatives of stilbene. They have a C6–C2–C6 structure. In biochemical terms, they belong to the family of phenylpropanoids and share most of their biosynthesis pathway with chalcones. Most stilbenoids are prod ...
s in the skin, and other phenols (
catechin Catechin is a flavan-3-ol, a type of secondary metabolite providing antioxidant roles in plants. It belongs to the subgroup of polyphenols called flavonoids. The name of the catechin chemical family derives from ''catechu'', which is the tanni ...
s, proanthocyanidins and
flavonol Flavonols are a class of flavonoids that have the 3-hydroxyflavone backbone (IUPAC name : 3-hydroxy-2-phenylchromen-4-one). Their diversity stems from the different positions of the phenolic -OH groups. They are distinct from flavanols (with " ...
s) in the skin and the seeds. During the growth cycle of the grapevine, sunlight will increase the concentration of phenolics in the grape berries, their development being an important component of canopy management. The proportion of the different phenols in any one wine will therefore vary according to the type of vinification.
Red wine Red wine is a type of wine made from dark-colored grape varieties. The color of the wine can range from intense violet, typical of young wines, through to brick red for mature wines and brown for older red wines. The juice from most purple gr ...
will be richer in phenols abundant in the skin and seeds, such as anthocyanin, proanthocyanidins and flavonols, whereas the phenols in
white wine White wine is a wine that is Fermentation in winemaking, fermented without skin contact. The wine color, colour can be straw-yellow, yellow-green, or yellow-gold. It is produced by the alcoholic fermentation of the non-coloured Juice vesicles, ...
will essentially originate from the pulp, and these will be the phenolic acids together with lower amounts of catechins and stilbenes. Red wines will also have the phenols found in white wines. Wine simple phenols are further transformed during
wine aging The aging of wine is potentially able to improve the quality of wine. This distinguishes wine from most other consumable goods. While wine is perishable and capable of deteriorating, complex chemical reactions involving a wine's sugars, acids an ...
into complex molecules formed notably by the condensation of proanthocyanidins and anthocyanins, which explains the modification in the color. Anthocyanins react with catechins, proanthocyanidins and other wine components during wine aging to form new polymeric pigments resulting in a modification of the wine color and a lower astringency. Average total polyphenol content measured by the Folin method is 216 mg/100 ml for red wine and 32 mg/100 ml for white wine. The content of phenols in rosé wine (82 mg/100 ml) is intermediate between that in red and white wines. In
winemaking Winemaking or vinification is the production of wine, starting with the selection of the fruit, its fermentation into alcohol, and the bottling of the finished liquid. The history of wine-making stretches over millennia. The science of wine and ...
, the process of maceration or "skin contact" is used to increase the concentration of phenols in wine. Phenolic acids are found in the pulp or juice of the wine and can be commonly found in white wines which usually do not go through a maceration period. The process of
oak aging Oak is used in winemaking to vary the color, flavor, tannin profile and texture of wine. It can be introduced in the form of a barrel during the fermentation or aging periods, or as free-floating chips or staves added to wine fermented in a vess ...
can also introduce phenolic compounds into wine, most notably
vanillin Vanillin is an organic compound with the molecular formula . It is a phenolic aldehyde. Its functional groups include aldehyde, hydroxyl, and ether. It is the primary component of the extract of the vanilla bean. Synthetic vanillin is now u ...
which adds
vanilla Vanilla is a spice derived from orchids of the genus '' Vanilla'', primarily obtained from pods of the Mexican species, flat-leaved vanilla ('' V. planifolia''). Pollination is required to make the plants produce the fruit from whic ...
aroma An odor (American English) or odour (Commonwealth English; see spelling differences) is caused by one or more volatilized chemical compounds that are generally found in low concentrations that humans and animals can perceive via their sens ...
to wines.J. Robinson (ed), ''"The Oxford Companion to Wine"''. Third Edition, pp 517-518. Oxford University Press 2006 . Most wine phenols are classified as secondary metabolites and were not thought to be active in the primary
metabolism Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run ...
and function of the grapevine. However, there is evidence that in some plants
flavonoid Flavonoids (or bioflavonoids; from the Latin word ''flavus'', meaning yellow, their color in nature) are a class of polyphenolic secondary metabolites found in plants, and thus commonly consumed in the diets of humans. Chemically, flavonoids ...
s play a role as endogenous regulators of
auxin Auxins (plural of auxin ) are a class of plant hormones (or plant-growth regulators) with some morphogen-like characteristics. Auxins play a cardinal role in coordination of many growth and behavioral processes in plant life cycles and are essenti ...
transport. They are
water-soluble In chemistry, solubility is the ability of a substance, the solute, to form a solution with another substance, the solvent. Insolubility is the opposite property, the inability of the solute to form such a solution. The extent of the solub ...
and are usually secreted into the
vacuole A vacuole () is a membrane-bound organelle which is present in plant and fungal cells and some protist, animal, and bacterial cells. Vacuoles are essentially enclosed compartments which are filled with water containing inorganic and organic m ...
of the grapevine as
glycosides In chemistry, a glycoside is a molecule in which a sugar is bound to another functional group via a glycosidic bond. Glycosides play numerous important roles in living organisms. Many plants store chemicals in the form of inactive glycosides. ...
.


Grape polyphenols

''
Vitis vinifera ''Vitis vinifera'', the common grape vine, is a species of flowering plant, native to the Mediterranean region, Central Europe, and southwestern Asia, from Morocco and Portugal north to southern Germany and east to northern Iran. There are cur ...
'' produces many phenolic compounds. There is a varietal effect on the relative composition.


Flavonoids

In red wine, up to 90% of the wine's phenolic content falls under the classification of flavonoids. These phenols, mainly derived from the stems, seeds and skins are often leached out of the grape during the maceration period of winemaking. The amount of phenols leached is known as
extraction Extraction may refer to: Science and technology Biology and medicine * Comedo extraction, a method of acne treatment * Dental extraction, the surgical removal of a tooth from the mouth Computing and information science * Data extraction, the pr ...
. These compounds contribute to the
astringency An astringent (sometimes called adstringent) is a chemical that shrinks or constricts body tissues. The word derives from the Latin ''adstringere'', which means "to bind fast". Calamine lotion, witch hazel, and yerba mansa, a Californian plan ...
, color and mouthfeel of the wine. In white wines the number of flavonoids is reduced due to the lesser contact with the skins that they receive during winemaking. There is on-going study into the health benefits of wine derived from the
antioxidant Antioxidants are compounds that inhibit oxidation, a chemical reaction that can produce free radicals. This can lead to polymerization and other chain reactions. They are frequently added to industrial products, such as fuels and lubrica ...
and chemopreventive properties of flavonoids.J. Robinson (ed), ''"The Oxford Companion to Wine"''. Third Edition, pp. 273-274. Oxford University Press 2006 .


Flavonols

Within the flavonoid category is a subcategory known as
flavonol Flavonols are a class of flavonoids that have the 3-hydroxyflavone backbone (IUPAC name : 3-hydroxy-2-phenylchromen-4-one). Their diversity stems from the different positions of the phenolic -OH groups. They are distinct from flavanols (with " ...
s, which includes the yellow
pigment A pigment is a colored material that is completely or nearly insoluble in water. In contrast, dyes are typically soluble, at least at some stage in their use. Generally dyes are often organic compounds whereas pigments are often inorganic compou ...
-
quercetin Quercetin is a plant flavonol from the flavonoid group of polyphenols. It is found in many fruits, vegetables, leaves, seeds, and grains; capers, red onions, and kale are common foods containing appreciable amounts of it. It has a bitter flavor ...
. Like other flavonoids, the concentration of flavonols in the grape berries increases as they are exposed to sunlight. Wine grapes facing too much sun exposure can see an accelerated ripening period, leading to a lessened ability for the synthesis of flavonols. Some viticulturalists will use measurement of flavonols such as quercetin as an indication of a vineyard's sun exposure and the effectiveness of canopy management techniques.


Anthocyanins

Anthocyanins are phenolic compounds found throughout the plant kingdom, being frequently responsible for the blue to red colors found in
flower A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants (plants of the division Angiospermae). The biological function of a flower is to facilitate reproduction, usually by providing a mechanis ...
s,
fruit In botany, a fruit is the seed-bearing structure in flowering plants that is formed from the ovary after flowering. Fruits are the means by which flowering plants (also known as angiosperms) disseminate their seeds. Edible fruits in partic ...
s and
leaves A leaf ( : leaves) is any of the principal appendages of a vascular plant stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, st ...
. In wine grapes, they develop during the stage of '' veraison,'' when the skin of red wine grapes changes color from green to red to black. As the sugars in the grape increase during ripening so does the concentration of anthocyanins. An issue associated with climate change has been the accumulation of sugars within the grape accelerating rapidly and outpacing the accumulation of anthocyanins. This leaves viticulturists with the choice of harvesting grapes with too high sugar content or with too low anthocyanin content. In most grapes anthocyanins are found only in the outer cell layers of the skin, leaving the grape juice inside virtually colorless. Therefore, to get color pigmentation in the wine, the
fermenting Fermentation is a metabolic process that produces chemical changes in organic substrates through the action of enzymes. In biochemistry, it is narrowly defined as the extraction of energy from carbohydrates in the absence of oxygen. In food p ...
must Must (from the Latin ''vinum mustum'', "young wine") is freshly crushed fruit juice (usually grape juice) that contains the skins, seeds, and stems of the fruit. The solid portion of the must is called pomace and typically makes up 7–23% of th ...
needs to be in contact with the grape skins in order for the anthocyanins to be extracted. Hence, white wine can be made from red wine grapes in the same way that many white
sparkling wine Sparkling wine is a wine with significant levels of carbon dioxide in it, making it fizzy. While the phrase commonly refers to champagne, European Union countries legally reserve that term for products exclusively produced in the Champagne regi ...
s are made from the red wine grapes of
Pinot noir Pinot Noir () is a red-wine grape variety of the species ''Vitis vinifera''. The name may also refer to wines created predominantly from pinot noir grapes. The name is derived from the French words for ''pine'' and ''black.'' The word ''pine ...
and Pinot Meunier. The exception to this is the small class of grapes known as
teinturier Teinturier grapes are grapes whose flesh and juice is red in colour due to anthocyanin pigments accumulating within the pulp of the grape berry itself. In most cases, anthocyanin pigments are confined to the outer skin tissue only, and the squee ...
s, such as
Alicante Bouschet Alicante Bouschet or Alicante Henri Bouschet is a wine grape variety that has been widely cultivated since 1866. It is a cross of Petit Bouschet (itself a cross of the very old variety Teinturier du Cher and Aramon) and Grenache.J. Robinson (ed), ''"The Oxford Companion to Wine"''. Third Edition, p. 24. Oxford University Press 2006 . There are several types of anthocyanins (as the
glycoside In chemistry, a glycoside is a molecule in which a sugar is bound to another functional group via a glycosidic bond. Glycosides play numerous important roles in living organisms. Many plants store chemicals in the form of inactive glycosides. ...
) found in wine grapes which are responsible for the vast range of coloring from ruby red through to dark black found in wine grapes.
Ampelographer Ampelography ( ἄμπελος, "vine" + γράφος, "writing") is the field of botany concerned with the identification and classification of grapevines, ''Vitis'' spp. Traditionally this has been done by comparing the shape and colour of the ...
s can use this observation to assist in the identification of different
grape varieties This list of grape varieties includes cultivated grapes, whether used for wine, or eating as a table grape, fresh or dried (raisin, currant, sultana). For a complete list of all grape species including those unimportant to agriculture, see V ...
. The European vine family ''
Vitis vinifera ''Vitis vinifera'', the common grape vine, is a species of flowering plant, native to the Mediterranean region, Central Europe, and southwestern Asia, from Morocco and Portugal north to southern Germany and east to northern Iran. There are cur ...
'' is characterized by anthocyanins that are composed of only one molecule of
glucose Glucose is a simple sugar with the molecular formula . Glucose is overall the most abundant monosaccharide, a subcategory of carbohydrates. Glucose is mainly made by plants and most algae during photosynthesis from water and carbon dioxide, u ...
while non-''vinifera'' vines such as hybrids and the American '' Vitis labrusca'' will have anthocyanins with two molecules. This phenomenon is due to a double mutation in the
anthocyanin 5-O-glucosyltransferase Anthocyanin 5-O-glucosyltransferase is an enzyme that forms anthocyanin 3,5-O-diglucoside from anthocyanin 3-O-glucoside. There are several types of anthocyanins (as the glycoside) found in wine grapes which are responsible for the vast range of ...
gene of ''V. vinifera''. In the mid-20th century, French ampelographers used this knowledge to test the various vine varieties throughout France to identify which vineyards still contained non-''vinifera'' plantings. Red-berried Pinot grape varieties are also known to not synthesize para-coumaroylated or
acetylated anthocyanin : In organic chemistry, acetylation is an organic esterification reaction with acetic acid. It introduces an acetyl group into a chemical compound. Such compounds are termed ''acetate esters'' or simply ''acetates''. Deacetylation is the oppo ...
s as other varieties do. The color variation in the finished red wine is partly derived from the
ionization Ionization, or Ionisation is the process by which an atom or a molecule acquires a negative or positive charge by gaining or losing electrons, often in conjunction with other chemical changes. The resulting electrically charged atom or molecul ...
of anthocyanin pigments caused by the
acidity In computer science, ACID ( atomicity, consistency, isolation, durability) is a set of properties of database transactions intended to guarantee data validity despite errors, power failures, and other mishaps. In the context of databases, a ...
of the wine. In this case, the three types of anthocyanin pigments are red, blue and colorless with the concentration of those various pigments dictating the color of the wine. A wine with low pH (and such greater acidity) will have a higher occurrence of ionized anthocyanins which will increase the amount of bright red pigments. Wines with a higher pH will have a higher concentration of blue and colorless pigments. As the wine ages, anthocyanins will react with other acids and compounds in wines such as tannins,
pyruvic acid Pyruvic acid (CH3COCOOH) is the simplest of the alpha-keto acids, with a carboxylic acid and a ketone functional group. Pyruvate, the conjugate base, CH3COCOO−, is an intermediate in several metabolic pathways throughout the cell. Pyruvic aci ...
and
acetaldehyde Acetaldehyde (IUPAC systematic name ethanal) is an organic chemical compound with the formula CH3 CHO, sometimes abbreviated by chemists as MeCHO (Me = methyl). It is a colorless liquid or gas, boiling near room temperature. It is one of the ...
which will change the color of the wine, causing it to develop more "brick red" hues. These molecules will link up to create
polymer A polymer (; Greek '' poly-'', "many" + '' -mer'', "part") is a substance or material consisting of very large molecules called macromolecules, composed of many repeating subunits. Due to their broad spectrum of properties, both synthetic a ...
s that eventually exceed their
solubility In chemistry, solubility is the ability of a substance, the solute, to form a solution with another substance, the solvent. Insolubility is the opposite property, the inability of the solute to form such a solution. The extent of the solubi ...
and become sediment at the bottom of wine bottles.
Pyranoanthocyanins The pyranoanthocyanins are a type of pyranoflavonoids. They are chemical compounds formed in red wines by yeast during fermentation processes or during controlled oxygenation processes during the aging of wine. The different classes of pyranoantho ...
are chemical compounds formed in red
wine Wine is an alcoholic drink typically made from Fermentation in winemaking, fermented grapes. Yeast in winemaking, Yeast consumes the sugar in the grapes and converts it to ethanol and carbon dioxide, releasing heat in the process. Different ...
s by
yeast Yeasts are eukaryotic, single-celled microorganisms classified as members of the fungus kingdom. The first yeast originated hundreds of millions of years ago, and at least 1,500 species are currently recognized. They are estimated to constit ...
during
fermentation Fermentation is a metabolic process that produces chemical changes in organic substrates through the action of enzymes. In biochemistry, it is narrowly defined as the extraction of energy from carbohydrates in the absence of oxygen. In food p ...
processes or during controlled oxygenation processes during the
aging of wine The aging of wine is potentially able to improve the quality of wine. This distinguishes wine from most other consumable goods. While wine is perishable and capable of deteriorating, complex chemical reactions involving a wine's sugars, acids an ...
.


Tannins

Tannins refer to the diverse group of chemical compounds in wine that can affect the color, aging ability and texture of the wine. While tannins cannot be smelled or tasted, they can be perceived during
wine tasting Wine tasting is the sensory examination and evaluation of wine. While the practice of wine tasting is as ancient as its production, a more formalized methodology has slowly become established from the 14th century onward. Modern, professional w ...
by the
tactile Tactile may refer to: * Tactile, related to the sense of touch * Haptics (disambiguation) * Tactile (device), a text-to-braille translation device See also * Tangibility, in law * Somatosensory system In physiology, the somatosensory system ...
drying sensation and sense of bitterness that they can leave in the mouth. This is due to the tendency of tannins to react with
protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, res ...
s, such as the ones found in
saliva Saliva (commonly referred to as spit) is an extracellular fluid produced and secreted by salivary glands in the mouth. In humans, saliva is around 99% water, plus electrolytes, mucus, white blood cells, epithelial cells (from which DNA can ...
. In food and wine pairing, foods that are high in proteins (such as
red meat In gastronomy, red meat is commonly red when raw and a dark color after it is cooked, in contrast to white meat, which is pale in color before and after cooking. In culinary terms, only flesh from mammals or fowl (not fish) is classified a ...
) are often paired with tannic wines to minimize the astringency of tannins. However, many wine drinkers find the perception of tannins to be a positive trait—especially as it relates to mouthfeel. The management of tannins in the winemaking process is a key component in the resulting quality.J. Robinson (ed), ''"The Oxford Companion to Wine"''. Third Edition, p. 680. Oxford University Press 2006 . Tannins are found in the skin, stems, and seeds of wine grapes but can also be introduced to the wine through the use of oak barrels and chips or with the addition of tannin powder. The natural tannins found in grapes are known as proanthocyanidins due to their ability to release red anthocyanin pigments when they are heated in an acidic solution. Grape extracts are mainly rich in monomers and small oligomers (mean degree of polymerization < 8). Grape seed extracts contain three monomers (catechin, epicatechin and epicatechin gallate) and procyanidin oligomers. Grape skin extracts contain four monomers (catechin, epicatechin, gallocatechin and epigallocatechin), as well as procyanidins and prodelphinidins oligomers. The tannins are formed by
enzymes Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products. ...
during metabolic processes of the grapevine. The amount of tannins found naturally in grapes varies depending on the variety with
Cabernet Sauvignon Cabernet Sauvignon () is one of the world's most widely recognized red wine grape varieties. It is grown in nearly every major wine producing country among a diverse spectrum of climates from Australia and British Columbia, Canada to Lebanon ...
,
Nebbiolo Nebbiolo (, ; pms, nebieul ) is an Italian red wine grape variety predominantly associated with its native Piedmont region, where it makes the '' Denominazione di Origine Controllata e Garantita'' (DOCG) wines of Barolo, Barbaresco, Roero ...
,
Syrah Syrah (), also known as Shiraz, is a dark-skinned grape variety grown throughout the world and used primarily to produce red wine. In 1999, Syrah was found to be the offspring of two obscure grapes from southeastern France, Dureza and Mondeuse ...
and Tannat being 4 of the most tannic grape varieties. The reaction of tannins and anthocyanins with the phenolic compound
catechin Catechin is a flavan-3-ol, a type of secondary metabolite providing antioxidant roles in plants. It belongs to the subgroup of polyphenols called flavonoids. The name of the catechin chemical family derives from ''catechu'', which is the tanni ...
s creates another class of tannins known as pigmented tannins which influence the color of red wine.Compositional investigation of pigmented tannin. Kennedy James A. and Hayasaka Yoji, A.C.S. symposium series, 2004, vol. 886, pp. 247-264, Commercial preparations of tannins, known as ''enological tannins'', made from
oak wood An oak is a tree or shrub in the genus ''Quercus'' (; Latin "oak tree") of the beech family, Fagaceae. There are approximately 500 extant species of oaks. The common name "oak" also appears in the names of species in related genera, notably ''L ...
,
grape A grape is a fruit, botanically a berry, of the deciduous woody vines of the flowering plant genus '' Vitis''. Grapes are a non- climacteric type of fruit, generally occurring in clusters. The cultivation of grapes began perhaps 8,000 years a ...
seed and skin, plant
gall Galls (from the Latin , 'oak-apple') or ''cecidia'' (from the Greek , anything gushing out) are a kind of swelling growth on the external tissues of plants, fungi, or animals. Plant galls are abnormal outgrowths of plant tissues, similar to be ...
,
chestnut The chestnuts are the deciduous trees and shrubs in the genus ''Castanea'', in the beech family Fagaceae. They are native to temperate regions of the Northern Hemisphere. The name also refers to the edible nuts they produce. The unrel ...
, quebracho, gambierIdentification of the origin of commercial enological tannins by the analysis of monosaccharides and polyalcohols. Luz Sanz M., Martinez-Castro Isabel and Moreno-Arribas M. Victoria, ''Food chemistry'', 2008, vol. 111, no3, pp. 778-783, and
myrobalan The common name myrobalan can refer to several unrelated fruit-bearing plant species: * Myrobalan plum (''Prunus cerasifera''), also called cherry plum and myrobalan plum * Emblic myrobalan (''Phyllanthus emblica''), also called Amla and Amalaki In ...
fruits, can be added at different stages of the wine production to improve color durability. The tannins derived from oak influence are known as "hydrolysable tannins" being created from the ellagic and
gallic acid Gallic acid (also known as 3,4,5-trihydroxybenzoic acid) is a trihydroxybenzoic acid with the formula C6 H2( OH)3CO2H. It is classified as a phenolic acid. It is found in gallnuts, sumac, witch hazel, tea leaves, oak bark, and other plants ...
found in the wood. In the vineyards, there is also a growing distinction being made between "ripe" and "unripe" tannins present in the grape. This " physiological ripeness", which is roughly determined by tasting the grapes off the vines, is being used along with sugar levels as a determination of when to
harvest Harvesting is the process of gathering a ripe crop from the fields. Reaping is the cutting of grain or pulse for harvest, typically using a scythe, sickle, or reaper. On smaller farms with minimal mechanization, harvesting is the most l ...
. The idea is that "riper" tannins will taste softer but still impart some of the texture components found favorable in wine. In winemaking, the amount of the time that the must spends in contact with the grape skins, stems and seeds will influence the amount of tannins that are present in the wine with wines subjected to longer maceration period having more tannin extract. Following harvest, stems are normally picked out and discarded prior to fermentation but some winemakers may intentionally leave in a few stems for varieties low in tannins (like Pinot noir) in order to increase the tannic extract in the wine. If there is an excess in the amount of tannins in the wine, winemakers can use various fining agents like
albumin Albumin is a family of globular proteins, the most common of which are the serum albumins. All the proteins of the albumin family are water- soluble, moderately soluble in concentrated salt solutions, and experience heat denaturation. Album ...
,
casein Casein ( , from Latin ''caseus'' "cheese") is a family of related phosphoproteins ( αS1, aS2, β, κ) that are commonly found in mammalian milk, comprising about 80% of the proteins in cow's milk and between 20% and 60% of the proteins in hum ...
and
gelatin Gelatin or gelatine (from la, gelatus meaning "stiff" or "frozen") is a translucent, colorless, flavorless food ingredient, commonly derived from collagen taken from animal body parts. It is brittle when dry and rubbery when moist. It may also ...
that can bind to tannins molecule and precipitate them out as sediments. As a wine ages, tannins will form long polymerized chains which come across to a taster as "softer" and less tannic. This process can be accelerated by exposing the wine to
oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements ...
, which oxidize tannins to quinone-like compounds that are polymerization-prone. The winemaking technique of
micro-oxygenation Micro-oxygenation is a process used in winemaking to introduce oxygen into wine in a controlled manner. Developed in 1991 by Patrick DuCournau, working with the exceptionally tannic grape Tannat in Madiran, the process gained usage in modern win ...
and
decanting wine A decanter is a vessel that is used to hold the decantation of a liquid (such as wine) which may contain sediment. Decanters, which have a varied shape and design, have been traditionally made from glass or crystal. Their volume is usually ...
use oxygen to partially mimic the effect of aging on tannins. A study in wine production and consumption has shown that tannins, in the form of proanthocyanidins, have a beneficial effect on vascular health. The study showed that tannins suppressed production of the peptide responsible for hardening arteries. To support their findings, the study also points out that wines from the regions of southwest France and Sardinia are particularly rich in proanthocyanidins, and that these regions also produce populations with longer life spans. Reactions of tannins with the phenolic compound anthocyanidins creates another class of tannins known as ''pigmented tannins'' which influences the color of red wine.


= Addition of enological tannins

= Commercial preparations of tannins, known as ''enological tannins'', made from
oak wood An oak is a tree or shrub in the genus ''Quercus'' (; Latin "oak tree") of the beech family, Fagaceae. There are approximately 500 extant species of oaks. The common name "oak" also appears in the names of species in related genera, notably ''L ...
,
grape A grape is a fruit, botanically a berry, of the deciduous woody vines of the flowering plant genus '' Vitis''. Grapes are a non- climacteric type of fruit, generally occurring in clusters. The cultivation of grapes began perhaps 8,000 years a ...
seed and skin, plant
gall Galls (from the Latin , 'oak-apple') or ''cecidia'' (from the Greek , anything gushing out) are a kind of swelling growth on the external tissues of plants, fungi, or animals. Plant galls are abnormal outgrowths of plant tissues, similar to be ...
,
chestnut The chestnuts are the deciduous trees and shrubs in the genus ''Castanea'', in the beech family Fagaceae. They are native to temperate regions of the Northern Hemisphere. The name also refers to the edible nuts they produce. The unrel ...
, quebracho, gambier and
myrobalan The common name myrobalan can refer to several unrelated fruit-bearing plant species: * Myrobalan plum (''Prunus cerasifera''), also called cherry plum and myrobalan plum * Emblic myrobalan (''Phyllanthus emblica''), also called Amla and Amalaki In ...
fruits, can be added at different stages of the wine production to improve color durability.


= Effects of tannins on the drinkability and aging potential of wine

= Tannins are a natural preservative in wine. Un-aged wines with high tannin content can be less palatable than wines with a lower level of tannins. Tannins can be described as leaving a dry and puckered feeling with a "furriness" in the mouth that can be compared to a stewed tea, which is also very tannic. This effect is particularly profound when drinking tannic wines without the benefit of food. Many wine lovers see natural tannins (found particularly in varietals such as
Cabernet Sauvignon Cabernet Sauvignon () is one of the world's most widely recognized red wine grape varieties. It is grown in nearly every major wine producing country among a diverse spectrum of climates from Australia and British Columbia, Canada to Lebanon ...
and often accentuated by heavy oak barrel aging) as a sign of potential longevity and ageability. Tannins impart a mouth-puckering astringency when the wine is young but "resolve" (through a chemical process called
polymerization In polymer chemistry, polymerization (American English), or polymerisation (British English), is a process of reacting monomer molecules together in a chemical reaction to form polymer chains or three-dimensional networks. There are many f ...
) into delicious and complex elements of "bottle bouquet" when the wine is cellared under appropriate temperature conditions, preferably in the range of a constant . Such wines mellow and improve with age with the tannic "backbone" helping the wine survive for as long as 40 years or more. In many regions (such as in
Bordeaux Bordeaux ( , ; Gascon oc, Bordèu ; eu, Bordele; it, Bordò; es, Burdeos) is a port city on the river Garonne in the Gironde department, Southwestern France. It is the capital of the Nouvelle-Aquitaine region, as well as the prefectu ...
), tannic grapes such as
Cabernet Sauvignon Cabernet Sauvignon () is one of the world's most widely recognized red wine grape varieties. It is grown in nearly every major wine producing country among a diverse spectrum of climates from Australia and British Columbia, Canada to Lebanon ...
are blended with lower-tannin grapes such as
Merlot Merlot is a dark blue–colored wine grape variety, that is used as both a blending grape and for varietal wines. The name ''Merlot'' is thought to be a diminutive of ''merle'', the French name for the blackbird, probably a reference to the ...
or
Cabernet Franc Cabernet Franc is one of the major black grape varieties worldwide. It is principally grown for blending with Cabernet Sauvignon and Merlot in the Bordeaux style, but can also be vinified alone, as in the Loire's Chinon. In addition to being u ...
, diluting the tannic characteristics. White wines and wines that are vinified to be drunk young (for examples, see nouveau wines) typically have lower tannin levels.


Other flavonoids

Flavan-3-ol Flavan-3-ols (sometimes referred to as flavanols) are a subgroup of flavonoids. They are derivatives of flavans that possess a 2-phenyl-3,4-dihydro-2''H''-chromen-3-ol skeleton. Flavan-3-ols are structurally diverse and include a range of comp ...
s (catechins) are flavonoids that contribute to the construction of various tannins and contribute to the perception of bitterness in wine. They are found in highest concentrations in grape seeds but are also in the skin and stems. Catechins play a role in the
microbial A microorganism, or microbe,, ''mikros'', "small") and ''organism'' from the el, ὀργανισμός, ''organismós'', "organism"). It is usually written as a single word but is sometimes hyphenated (''micro-organism''), especially in olde ...
defense of the grape berry, being produced in higher concentrations by the grape vines when it is being attacked by grape diseases such as downy mildew. Because of that grape vines in cool, damp climates produce catechins at high levels than vines in dry, hot climates. Together with anthocyanins and tannins they increase the stability of a wines color-meaning that a wine will be able to maintain its coloring for a longer period of time. The amount of catechins present varies among grape varieties with varietals like Pinot noir having high concentrations while
Merlot Merlot is a dark blue–colored wine grape variety, that is used as both a blending grape and for varietal wines. The name ''Merlot'' is thought to be a diminutive of ''merle'', the French name for the blackbird, probably a reference to the ...
and especially Syrah have very low levels. As an antioxidant, there are some studies into the health benefits of moderate consumption of wines high in catechins.J. Robinson (ed), ''"The Oxford Companion to Wine"''. Third Edition, p. 144. Oxford University Press 2006 . In red grapes, the main flavonol is on average
quercetin Quercetin is a plant flavonol from the flavonoid group of polyphenols. It is found in many fruits, vegetables, leaves, seeds, and grains; capers, red onions, and kale are common foods containing appreciable amounts of it. It has a bitter flavor ...
, followed by myricetin, kaempferol, laricitrin, isorhamnetin, and syringetin. In white grapes, the main flavonol is quercetin, followed by kaempferol and isorhamnetin. The delphinidin-like flavonols myricetin, laricitrin, and syringetin are missing in all white varieties, indicating that the enzyme flavonoid 3',5'-hydroxylase is not expressed in white grape varieties. Myricetin, laricitrin and syringetin, flavonols which are present in red grape varieties only, can be found in red wine.


Non-flavonoids


Hydroxycinnamic acids

Hydroxycinnamic acids are the most important group of nonflavonoid phenols in wine. The four most abundant ones are the tartaric acid esters caftaric acid, ''trans''-caftaric, ''cis''- and ''trans''-coutaric acid, coutaric, and ''trans''-fertaric acids. In wine they are present also in the free form (''trans''- caffeic, ''trans''-p-coumaric acid, p-coumaric, and ''trans''-ferulic acids).


Stilbenoids

''V. vinifera'' also produces
stilbenoid Stilbenoids are hydroxylated derivatives of stilbene. They have a C6–C2–C6 structure. In biochemical terms, they belong to the family of phenylpropanoids and share most of their biosynthesis pathway with chalcones. Most stilbenoids are prod ...
s. Resveratrol is found in highest concentration in the skins of wine grapes. The accumulation in ripe berries of different concentrations of both bound and free resveratrols depends on the maturity level and is highly variable according to the genotype. Both red and white wine grape varieties contain resveratrol, but more frequent skin contact and maceration leads to red wines normally having ten times more resveratrol than white wines. Resveratrol produced by grape vines provides defense against microbes, and production can be further artificially stimulated by ultraviolet radiation. Grapevines in cool, damp regions with higher risk of grape diseases, such as Bordeaux (wine), Bordeaux and Burgundy (wine), Burgundy, tend to produce grapes with higher levels of resveratrol than warmer, drier wine regions such as California (wine), California and Australia (wine), Australia. Different grape varieties tend to have differing levels, with Muscadines and the Pinot family having high levels while the Cabernet Sauvignon, Cabernet family has lower levels of resveratrol. In the late 20th century interest in the possible health benefits of resveratrol in wine was spurred by discussion of the French paradox involving the health of wine drinkers in France.J. Robinson (ed), ''"The Oxford Companion to Wine"''. Third Edition, p. 569. Oxford University Press 2006 . Piceatannol is also present in grape from where it can be extracted and found in red wine.


Phenolic acids

Vanillin is a phenolic aldehyde most commonly associated with the vanilla notes in wines that have been aged in oak. Trace amounts of vanillin are found naturally in grapes, but they are most prominent in the lignin structure of oak barrels. Newer barrels will impart more vanillin, with the concentration present decreasing with each subsequent usage.J. Robinson (ed), ''"The Oxford Companion to Wine"''. Third Edition, p. 727. Oxford University Press 2006 .


Phenols from oak ageing

Oak barrel will add compounds such as
vanillin Vanillin is an organic compound with the molecular formula . It is a phenolic aldehyde. Its functional groups include aldehyde, hydroxyl, and ether. It is the primary component of the extract of the vanilla bean. Synthetic vanillin is now u ...
and hydrolysable tannins (ellagitannins). The hydrolyzable tannins present in oak are derived from lignin structures in the wood. They help protect the wine from oxidation and redox, reduction.J. Robinson (ed), ''"The Oxford Companion to Wine"''. Third Edition, p. 492, Oxford University Press 2006, . 4-Ethylphenol and 4-ethylguaiacol are produced during ageing of red wine in oak barrels that are infected by brettanomyces .


Natural phenols and polyphenols from cork stoppers

Low molecular weight polyphenols, as well as ellagitannins, are susceptible to be extracted from Cork (material), cork stoppers into the wine. The identified polyphenols are gallic, protocatechuic acid, protocatechuic, vanillic acid, vanillic, caffeic, ferulic acid, ferulic, and ellagic acids; protocatechuic aldehyde, protocatechuic, vanillic acid, vanillic, coniferyl aldehyde, coniferyl, and sinapic aldehyde, sinapic aldehydes; the coumarins aesculetin and scopoletin; the ellagitannins are roburins roburin A, A and roburin E, E, grandinin, vescalagin and castalagin. Guaiacol is one of the molecules responsible for the cork taint wine fault.


Phenolic content in relation with wine making techniques


Extraction levels in relation with grape pressing techniques

Flash release (oenology), Flash release is a technique used in wine pressing (wine), pressing. The technique allows for a better extraction of phenolic compounds.


Microoxygeneation

The exposure of wine to microoxygenation, oxygen in limited quantities affects phenolic content.


Phenolic compounds found in wine

Depending on the methods of production, wine type, grape varieties, ageing processes, the following phenolics can be found in wine. The list, sorted in alphabetical order of common names, is not exhaustive. * Acutissimin A * aesculetin * Anthocyanidin-caftaric acid adducts * Astilbin * Astringin * B type proanthocyanidin dimers * B type proanthocyanidin trimers * Caffeic acid * Caftaric acid * Castalagin * Castavinol C1 * Castavinol C2 * Castavinol C3 * Castavinol C4 * Catechin * Catechin-(4,8)-malvidin-3-O-glucoside * Compound NJ2 * Coniferyl aldehyde * Coumaric acid * Coutaric acid * Cyanidin * Cyanin (anthocyanin), Cyanin (Cyanidin-3,5-O-diglucoside) * Cyanidin 3O-glucoside * Cyanidin acetyl 3O glucoside * Cyanidin coumaroyl 3O glucoside * Cyanidin-3-O-glucoside-pyruvic acid * Cyanidin-3-O-acetylglucoside-pyruvic acid * Cyanidin-coumaroylglucoside-pyruvic acid * Delphinidin * Delphinidin 3O glucoside * Delphinidin acetyl-3O glucoside * Delphinidin coumaroyl 3O glucoside * Delphinidin-3-O-glucoside-pyruvic acid * Delphinidin-3-O-acetylglucoside-pyruvic acid * Delphinidin-3-O-coumaroylglucoside-pyruvic acid * Delphinidin-3-O-glucoside-4-vinylcatechol * Delphinidin-3-O-acetylglucoside-4-vinylcatechol * Delphinidin-3-O-coumaroylglucoside-4-vinylcatechol * Delphinidin-3-O-glucoside-4-vinylphenol * Delphinidin-3-O-acetylglucoside-4-vinylphenol * Delphinidin-3-O-coumaroylglucoside-4-vinylphenol * Delphinidin-3-O-glucoside-4-vinylguaiacol * Delphinidin-3-O-glucoside-4-vinyl(epi)catechin * Delphinidin-3-O-acetylglucoside-4-vinyl(epi)catechin * Delta-viniferin * Dihydro-resveratrol * Ellagic acid * Engeletin * Epicatechin gallate * Epigallocatechin * Epsilon-viniferin * Ethyl caffeate * Ethyl gallate * Ethyl protocatechuate * 4-Ethylguaiacol * 4-Ethylphenol * Fertaric acid * Ferulic acid * Gallic acid * Gentisic acid * Grandinin * Grape reaction product (GRP) * Guaiacol * Hopeaphenol * p-Hydroxybenzoic acid * Isorhamnetol 3-glucoside * Kaempferol * Kaempferol glucoside (astragalin) * Kaempferol glucuronide * Malvidin * Malvidin 3O-glucoside (oenin) * Malvidin acetyl-3O-glucoside * Malvidin cafeoyl-3O-glucoside * Malvidin coumaroyl-3Oglucoside * Malvidin glucoside-ethyl-catechin * Malvidin-3-O-glucoside-pyruvic acid * Malvidin-3-O-acetylglucoside-pyruvic acid * Malvidin-3-O-coumaroylglucoside-pyruvic acid * Malvidin-3-O-glucoside-acetaldehyde * Malvidin-3-O-acetylglucoside-acetaldehyde * Malvidin-3-O-coumaroylglucoside-acetaldehyde * Malvidin-3-O-glucoside-4-vinylcatechol * Malvidin-3-O-acetylglucoside-4-vinylcatechol * Malvidin-3-O-coumaroylglucoside-4-vinylcatechol * Malvidin-3-O-glucoside-4-vinylphenol * Malvidin-3-O-acetylglucoside-4-vinylphenol * Malvidin-3-O-coumaroylglucoside-4-vinylphenol * Malvidin-3-O-caffeoylglucoside-4-vinylphenol * Malvidin-3-O-glucoside-4-vinylguaiacol * Malvidin-3-O-acetylglucoside-4-vinylguaiacol * Malvidin-3-O-coumaroylglucoside-vinylguaiacol * Malvidin-3-O-glucoside-4-vinyl(epi)catechin * Malvidin-3-O-acetylglucoside-4-vinyl(epi)catechin * Malvidin-3-O-coumaroylglucoside-4-vinyl(epi)catechin * Methyl gallate * Myricetol * Myricetol 3-glucoside * Myricetol 3-glucuronide * Oxovitisin A * Pallidol * Pelargonin (Pelargonidin 3,5-O-diglucoside) * Peonidin 3O-glucoside * Peonidin acetyl-3O-glucoside * Peonidin-3-(6-p-caffeoyl)-glucoside * Peonidin coumaroyl 3O-glucoside * Peonidin-3-O-glucoside-pyruvic acid * Peonidin-3-O-acetylglucoside-pyruvic acid * Peonidin-3-O-coumaroylglucoside-pyruvic acid * Peonidin-3-O-glucoside-4-vinylcatechol * Peonidin-3-O-acetylglucoside-4-vinylcatechol * Peonidin-3-O-coumaroylglucoside-4-vinylcatechol * Peonidin-3-O-glucoside-4-vinylphenol * Peonidin-3-O-acetylglucoside-4-vinylphenol * Peonidin-3-O-coumaroylglucoside-4-vinylphenol * Peonidin-3-O-glucoside-4-vinylguaiacol * Peonidin-3-O-glucoside-4-vinyl(epi)catechin * Peonidin-3-O-acetylglucoside-4-vinyl(epi)catechin * Petunidin * Petunidin 3O glucoside * Petunidin acetyl-3O-glucoside * Petunidin coumaroyl-3O glucoside * Petunidin-3-O-glucoside-pyruvic acid * Petunidin-3-O-acetylglucoside-pyruvic acid * Petunidin-3-O-coumaroylglucoside-pyruvic acid * Petunidin-3-O-glucoside-4-vinylcatechol * Petunidin-3-O-acetylglucoside-4-vinylcatechol * Petunidin-3-O-coumaroylglucoside-4-vinylcatechol * Petunidin-3-O-glucoside-4-vinylphenol * Petunidin-3-O-acetylglucoside-4-vinylphenol * Petunidin-3-O-coumaroylglucoside-4-vinylphenol * Petunidin-3-O-glucoside-4-vinylguaiacol * Petunidin-3-O-glucoside-4-vinyl(epi)catechin * Petunidin-3-O-acetylglucoside-4-vinyl(epi)catechin * Phloroglucinol carboxylic acid * Piceatannol * Piceids * Pinotin A * Oligomeric procyanidins : ** Procyanidin B1 ** Procyanidin B2 ** Procyanidin B3 ** Procyanidin B4 ** B1-3-O-gallate ** B2-3-O-gallate ** B2-3'-O-gallate ** procyanidin C1 (epicatechin-(4β→8)-epicatechin-(4β→8)-epicatechin) ** Procyanidin C2 (catechin-(4α→8)-catechin-(4α→8)-catechin) ** procyanidin T2 (trimer) * Protocatechuic acid * protocatechuic aldehyde * Quercetin * Quercetol glucoside * Quercetin 3-O-glucuronide, Quercetol glucuronide * Resveratrol * Roburin A * Roburin E * Scopoletin * Sinapic aldehyde * Sinapinic acid * Syringic acid * Tyrosol * Vanillic acid *
vanillin Vanillin is an organic compound with the molecular formula . It is a phenolic aldehyde. Its functional groups include aldehyde, hydroxyl, and ether. It is the primary component of the extract of the vanilla bean. Synthetic vanillin is now u ...
* Vescalagin * 4-Vinylphenol * Vitisin A (pyranoanthocyanin), Vitisin A * Vitisin B (pyranoanthocyanin), Vitisin B * Vinylpyranomalvidin-3O-glucoside-procyanidin dimer * VinylpyranoMv-3-coumaroylglucoside-procyanidin dimer * Vinylpyranomalvidin-3O-glucoside-catechin * Vinylpyranomalvidin-3O-coumaroylglucoside-catechin * Vinylpyranomalvidin-3O-phenol * Vinylpyranopetunidin-3O-glucoside-catechin * Vinylpyranopeonidin-3O-glucoside-catechin * Vinylpyranomalvidin-3O-acetylglucoside-catechin


Effects

Polyphenol compounds may interact with Volatile organic compounds, volatiles and contribute to the aromas in wine. Although wine polyphenols are speculated to provide
antioxidant Antioxidants are compounds that inhibit oxidation, a chemical reaction that can produce free radicals. This can lead to polymerization and other chain reactions. They are frequently added to industrial products, such as fuels and lubrica ...
or other benefits, there is little evidence that wine polyphenols actually have any effect in humans. Limited preliminary research indicates that wine polyphenols may decrease platelet aggregation, enhance fibrinolysis, and increase HDL cholesterol, but high-quality clinical trials have not confirmed such effects, as of 2017.


See also

* Aging of wine * Clarification and stabilization of wine * Grape seed extract *Phenolic content in tea * Wine chemistry


References


External links


Wine polyphenols vary with age and variety (Polyphenols on www.guideduvin.com)
{{in lang, fr
Polyphenol concentrations in red, white and rosé wines at www.phenol-explorer.eu
Natural phenols Polyphenols Wine chemistry