Phenolic compounds in wine - AbsoluteAstronomy.com

The phenolic compounds - natural phenol

Natural phenol

Natural phenols, bioavailable phenols, plant phenolics, low molecular weight phenols or phenoloids are a class of natural products. They are small molecules containing one or more phenolic group. These molecules are smaller in size than polyphenols, containing less than 12 phenolic groups...

and polyphenol

Polyphenol

Polyphenols are a structural class of natural, synthetic, and semisynthetic organic chemicals characterized by the presence of large multiples of phenol structural units...

s - in wine

Wine

Wine is an alcoholic beverage, made of fermented fruit juice, usually from grapes. The natural chemical balance of grapes lets them ferment without the addition of sugars, acids, enzymes, or other nutrients. Grape wine is produced by fermenting crushed grapes using various types of yeast. Yeast...

include a large group of several hundred chemical compound

Chemical compound

A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...

s that affect the taste, color and mouthfeel of wine. These compounds include phenolic acids

Phenol

Phenol, also known as carbolic acid, phenic acid, is an organic compound with the chemical formula C6H5OH. It is a white crystalline solid. The molecule consists of a phenyl , bonded to a hydroxyl group. It is produced on a large scale as a precursor to many materials and useful compounds...

, stilbene

Stilbene

-Stilbene, is a diarylethene, i.e., a hydrocarbon consisting of a trans ethene double bond substituted with a phenyl group on both carbon atoms of the double bond. The name stilbene is derived from the Greek word stilbos, which means shining....

s, flavonols, dihydroflavonols, anthocyanin

Anthocyanin

Anthocyanins are water-soluble vacuolar pigments that may appear red, purple, or blue according to pH...

s, flavanol monomers (catechin

Catechin

Catechin is a natural phenol antioxidant plant secondary metabolite. The term catechins is also commonly used to refer to the related family of flavonoids and the subgroup flavan-3-ols ....

s) and flavanol polymers (proanthocyanidin

Proanthocyanidin

Proanthocyanidins, also known as OPCs or condensed tannins, are a subgroup of the flavonoid class of polyphenols...

s). This large group of natural phenols can be broadly separated into two categories - flavonoid

Flavonoid

Flavonoids , are a class of plant secondary metabolites....

s and non-flavonoids. Flavonoids include the anthocyanin

Anthocyanin

Anthocyanins are water-soluble vacuolar pigments that may appear red, purple, or blue according to pH...

s and tannin

Tannin

A tannin is an astringent, bitter plant polyphenolic compound that binds to and precipitates proteins and various other organic compounds including amino acids and alkaloids.The term tannin refers to the use of...

s which contribute to the color and mouthfeel of the wine. The non-flavonoids include the stilbenoids such as resveratrol

Resveratrol

Resveratrol is a stilbenoid, a type of natural phenol, and a phytoalexin produced naturally by several plants when under attack by pathogens such as bacteria or fungi....

and phenolic acids

Phenol

such as benzoic, caffeic

Caffeic acid

Caffeic acid is a hydroxycinnamic acid, a naturally occurring organic compound. This yellow solid consists of both phenolic and acrylic functional groups...

and cinnamic

Cinnamic acid

Cinnamic acid is a white crystalline organic acid, which is slightly soluble in water.It is obtained from oil of cinnamon, or from balsams such as storax. It is also found in shea butter and is the best indication of its environmental history and post-extraction conditions...

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

Anthocyanin

Anthocyanins are water-soluble vacuolar pigments that may appear red, purple, or blue according to pH...

s and stilbene

Stilbene

s in the skin, and other phenols (catechin

Catechin

Catechin is a natural phenol antioxidant plant secondary metabolite. The term catechins is also commonly used to refer to the related family of flavonoids and the subgroup flavan-3-ols ....

s, proanthocyanidin

Proanthocyanidin

Proanthocyanidins, also known as OPCs or condensed tannins, are a subgroup of the flavonoid class of polyphenols...

s and flavonols) 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 will be richer in phenols abundant in the skin and seeds, such as anthocyanin, proanthocyanidins and flavonols, whereas the phenols in white wine 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

Aging of wine

The aging of wine, and its ability to potentially improve wine quality, distinguishes wine from most other consumable goods. While wine is perishable and capable of deteriorating, complex chemical reactions involving a wine's sugars, acids and phenolic compounds can alter the aroma, color,...

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

Folin-Ciocalteu reagent

The Folin–Ciocalteu reagent or Folin's phenol reagent or Folin–Denis reagent, also called the Gallic Acid Equivalence method , is a mixture of phosphomolybdate and phosphotungstate used for the colorimetric assay of phenolic and polyphenolic antioxidants...

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

Winemaking, or vinification, is the production of wine, starting with selection of the grapes or other produce and ending with bottling the finished wine. Although most wine is made from grapes, it may also be made from other fruit or non-toxic plant material...

, the process of maceration

Maceration (wine)

Maceration is the winemaking process where the phenolic materials of the grape— tannins, coloring agents and flavor compounds— are leached from the grape skins, seeds and stems into the must. Maceration is the process by which the red wine receives its red color, since 99% of all grape juice is...

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 can also introduce phenolic compounds into wine, most notably vanillin

Vanillin

Vanillin is a phenolic aldehyde, an organic compound with the molecular formula C8H8O3. Its functional groups include aldehyde, ether, and phenol. It is the primary component of the extract of the vanilla bean. It is also found in Leptotes bicolor, roasted coffee and the Chinese red pine...

which adds vanilla

Vanilla

Vanilla is a flavoring derived from orchids of the genus Vanilla, primarily from the Mexican species, Flat-leaved Vanilla . The word vanilla derives from the Spanish word "", little pod...

aroma to wines.

Most wine phenols are classified as secondary metabolite

Secondary metabolite

Secondary metabolites are organic compounds that are not directly involved in the normal growth, development, or reproduction of an organism. Unlike primary metabolites, absence of secondary metabolities does not result in immediate death, but rather in long-term impairment of the organism's...

s and were not thought to be active in the primary metabolism

Metabolism

Metabolism is the set of chemical reactions that happen in the cells of living organisms to sustain life. These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments. Metabolism is usually divided into two categories...

and function of the grapevine. However, there is evidence that in some plants flavonoid

Flavonoid

Flavonoids , are a class of plant secondary metabolites....

s play a role as endogenous regulators of auxin

Auxin

Auxins are a class of plant hormones with some morphogen-like characteristics. Auxins have a cardinal role in coordination of many growth and behavioral processes in the plant's life cycle and are essential for plant body development. Auxins and their role in plant growth were first described by...

transport. They are water soluble and are usually secreted into the vacuole

Vacuole

A vacuole is a membrane-bound organelle which is present in all 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 molecules including enzymes in solution, though in certain...

of the grapevine as glycosides.

Grape polyphenols - 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. These compounds contribute to the astringency, 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

Antioxidant

An antioxidant is a molecule capable of inhibiting the oxidation of other molecules. Oxidation is a chemical reaction that transfers electrons or hydrogen from a substance to an oxidizing agent. Oxidation reactions can produce free radicals. In turn, these radicals can start chain reactions. When...

and chemopreventive properties of flavonoids.

Flavonols

Within the flavonoid category is a subcategory known as flavonols, which includes the yellow pigment

Pigment

A pigment is a material that changes the color of reflected or transmitted light as the result of wavelength-selective absorption. This physical process differs from fluorescence, phosphorescence, and other forms of luminescence, in which a material emits light.Many materials selectively absorb...

- quercetin

Quercetin

Quercetin , a flavonol, is a plant-derived flavonoid found in fruits, vegetables, leaves and grains. It also may be used as an ingredient in supplements, beverages or foods.-Occurrence:...

. Like other flavonoids, the concentration of flavonols in the grape berries increases as they are exposed to sunlight. 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

Flower

A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants . The biological function of a flower is to effect reproduction, usually by providing a mechanism for the union of sperm with eggs...

s, fruit

Fruit

In broad terms, a fruit is a structure of a plant that contains its seeds.The term has different meanings dependent on context. In non-technical usage, such as food preparation, fruit normally means the fleshy seed-associated structures of certain plants that are sweet and edible in the raw state,...

s and leaves

Leaf

A leaf is an organ of a vascular plant, as defined in botanical terms, and in particular in plant morphology. Foliage is a mass noun that refers to leaves as a feature of plants....

. In wine grapes, they develop during the stage of veraison
Veraison
Véraison is a viticulture term meaning "the onset of ripening". It is originally French, but has been adopted into English use...

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. 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 must

Fermentation (wine)

The process of fermentation in wine turns grape juice into an alcoholic beverage. During fermentation, yeast interact with sugars in the juice to create ethanol, commonly known as ethyl alcohol, and carbon dioxide...

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

Sparkling wine is a wine with significant levels of carbon dioxide in it making it fizzy. The carbon dioxide may result from natural fermentation, either in a bottle, as with the méthode champenoise, in a large tank designed to withstand the pressures involved , or as a result of carbon dioxide...

s are made from the red wine grapes of Pinot noir

Pinot Noir

Pinot noir is a black wine grape variety of the species Vitis vinifera. The name may also refer to wines created predominantly from Pinot noir grapes...

and Pinot meunier

Pinot meunier

Pinot Meunier, , also known as Meunier or Black Riesling, is a variety of black wine grape most noted for being one of the three main grapes used in the production of champagne...

. The exception to this is the small class of grapes known as teinturier

Teinturier

Teinturier, a French language term meaning to dye or stain, is a wine term applied to 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...

s, such as Alicante Bouschet

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 and Grenache. Alicante is a teinturier, a grape with red flesh. It is one of the few teinturier grapes that belong to the Vitis vinifera species...

, which have a small amount of anthocyanins in the pulp that produces pigmented juice.

There are several types of anthocyanins (as the glycoside

Glycoside

In chemistry, a glycoside is a molecule in which a sugar is bound to a non-carbohydrate moiety, usually a small organic molecule. Glycosides play numerous important roles in living organisms. Many plants store chemicals in the form of inactive glycosides. These can be activated by enzyme...

) found in wine grapes which are responsible for the vast range of coloring from ruby red through to dark black found in wine grapes. Ampelographers can use this observation to assist in the identification of different grape varieties. The European vine family Vitis vinifera
Vitis vinifera
Vitis vinifera is a species of Vitis, native to the Mediterranean region, central Europe, and southwestern Asia, from Morocco and Portugal north to southern Germany and east to northern Iran....

is characterized by anthocyanins that are composed of only one molecule of glucose

Glucose

Glucose is a simple sugar and an important carbohydrate in biology. Cells use it as the primary source of energy and a metabolic intermediate...

while non-vinifera vines such as hybrids and the American Vitis labrusca
Vitis labrusca
Vitis labrusca is a species of grapevines belonging to the Vitis genus in the flowering plant family Vitaceae. The vines are native to the eastern United States and are the source of many grape cultivars, including Catawba and Concord grapes, and many hybrid grape varieties such as Agawam,...

will have anthocyanins with two molecules. 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.

The color variation in the finished red wine is partly derived from the ionization

Ionization

Ionization is the process of converting an atom or molecule into an ion by adding or removing charged particles such as electrons or other ions. This is often confused with dissociation. A substance may dissociate without necessarily producing ions. As an example, the molecules of table sugar...

of anthocyanin pigments caused by the acidity 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

In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...

(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

Aging of wine

, anthocyanins will react with other acids and compounds in wines such as tannins, pyruvic acid

Pyruvic acid

Pyruvic acid is an organic acid, a ketone, as well as the simplest of the alpha-keto acids. The carboxylate ion of pyruvic acid, CH3COCOO−, is known as pyruvate, and is a key intersection in several metabolic pathways....

and acetaldehyde

Acetaldehyde

Acetaldehyde is an organic chemical compound with the formula CH3CHO or MeCHO. It is one of the most important aldehydes, occurring widely in nature and being produced on a large scale industrially. Acetaldehyde occurs naturally in coffee, bread, and ripe fruit, and is produced by plants as part...

which will change the color of the wine, causing it to develop more "brick red" hues. These molecules will link up to create polymer

Polymer

A polymer is a large molecule composed of repeating structural units. These subunits are typically connected by covalent chemical bonds...

s that eventually exceed their solubility

Solubility

Solubility is the property of a solid, liquid, or gaseous chemical substance called solute to dissolve in a solid, liquid, or gaseous solvent to form a homogeneous solution of the solute in the solvent. The solubility of a substance fundamentally depends on the used solvent as well as on...

and become sediment at the bottom of wine bottles. Pyranoanthocyanins are chemical compounds formed in red wine

Wine

s by yeast during fermentation

Fermentation (wine)

processes or during controlled oxygenation

Microoxygenation

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 winemaking following the 1996 authorization by the...

processes during the aging of wine

Aging of wine

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 can not be smelled or tasted, they can be perceived during wine tasting

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 onwards...

by the tactile 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

Protein

Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...

s, such as the ones found in saliva

Saliva

Saliva , referred to in various contexts as spit, spittle, drivel, drool, or slobber, is the watery substance produced in the mouths of humans and most other animals. Saliva is a component of oral fluid. In mammals, saliva is produced in and secreted from the three pairs of major salivary glands,...

. In food and wine pairing, foods that are high in proteins (such as red meat

Red meat

Red meat in traditional culinary terminology is meat which is red when raw and not white when cooked. In the nutritional sciences, red meat includes all mammal meat. Red meat includes the meat of most adult mammals and some fowl ....

) 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.

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 proanthocyanidin

Proanthocyanidin

Proanthocyanidins, also known as OPCs or condensed tannins, are a subgroup of the flavonoid class of polyphenols...

s 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 during metabolic processes of the grapevine. The amount of tannins found naturally in grapes varies depending on the variety with Cabernet Sauvignon

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 Canada's Okanagan Valley to Lebanon's Beqaa Valley...

, Nebbiolo, Syrah and Tannat

Tannat

Tannat is a red wine grape, historically grown in South West France in the Madiran AOC and is now one of the most prominent grapes in Uruguay, where it is considered the "national grape". It is also grown in Argentina, Australia, Brazil, Peru, and in Italy's Puglia region where it is used as a...

being 4 of the most tannic grape varieties. The reaction of tannins and anthocyanins with the phenolic compound catechin

Catechin

Catechin is a natural phenol antioxidant plant secondary metabolite. The term catechins is also commonly used to refer to the related family of flavonoids and the subgroup flavan-3-ols ....

s creates another class of tannins known as pigmented tannins which influence the color of red wine. Commercial preparations of tannins, known as enological tannins, made from oak wood, grape

Grape

A grape is a non-climacteric fruit, specifically a berry, that grows on the perennial and deciduous woody vines of the genus Vitis. Grapes can be eaten raw or they can be used for making jam, juice, jelly, vinegar, wine, grape seed extracts, raisins, molasses and grape seed oil. Grapes are also...

seed and skin, plant gall

Gall

Galls or cecidia are outgrowths on the surface of lifeforms caused by invasion by other lifeforms, such as parasites or bacterial infection. Plant galls are abnormal outgrowths of plant tissues and can be caused by various parasites, from fungi and bacteria, to insects and mites...

, chestnut

Chestnut

Chestnut , some species called chinkapin or chinquapin, is a genus of eight or nine species of deciduous trees and shrubs in the beech family Fagaceae, native to temperate regions of the Northern Hemisphere. The name also refers to the edible nuts they produce.-Species:The chestnut belongs to the...

, quebracho, gambier

Uncaria gambir

Uncaria gambir, the gambier or gambir, is a species in the genus Uncaria found in Indonesia.Gambier is used in Indonesia for chewing with areca and betel, for tanning, and for dyeing. It contains many flavan-3-ols which are known to have many medicinal properties and are components of Chinese...

and myrobalan 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

Gallic acid is a trihydroxybenzoic acid, a type of phenolic acid, a type of organic acid, also known as 3,4,5-trihydroxybenzoic acid, found in gallnuts, sumac, witch hazel, tea leaves, oak bark, and other plants. The chemical formula is C6H23COOH. Gallic acid is found both free and as part of...

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 the harvest

Harvest (wine)

The harvesting of wine grapes is one of the most crucial steps in the process of winemaking. The time of harvest is determined primarily by the ripeness of the grape as measured by sugar, acid and tannin levels with winemakers basing their decision to pick based on the style of wine they wish to...

. 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

Albumin refers generally to any protein that is water soluble, which is moderately soluble in concentrated salt solutions, and experiences heat denaturation. They are commonly found in blood plasma, and are unique to other blood proteins in that they are not glycosylated...

, casein

Casein

Casein is the name for a family of related phosphoprotein proteins . These proteins are commonly found in mammalian milk, making up 80% of the proteins in cow milk and between 60% and 65% of the proteins in human milk....

and gelatin

Gelatin

Gelatin is a translucent, colorless, brittle , flavorless solid substance, derived from the collagen inside animals' skin and bones. It is commonly used as a gelling agent in food, pharmaceuticals, photography, and cosmetic manufacturing. Substances containing gelatin or functioning in a similar...

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. Oxygen

Oxygen

Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

can bind with tannin molecules to make them larger and thus seem softer on the palate. The winemaking technique of micro-oxygenation and decanting wine 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 proanthocyanidin

Proanthocyanidin

Proanthocyanidins, also known as OPCs or condensed tannins, are a subgroup of the flavonoid class of polyphenols...

s, 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 anthocyanidin

Anthocyanidin

Anthocyanidins are common plant pigments. They are the sugar-free counterparts of anthocyanins based on the flavylium ion or 2-phenylchromenylium, which is a type of oxonium ion . They form a large group of polymethine dye. In particular anthocyanidins are salt derivatives of the...

s 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, grape

Grape

seed and skin, plant gall

Gall

, chestnut

Chestnut

, quebracho, gambier

Uncaria gambir

and myrobalan 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

and often accentuated by heavy oak

Oak

An oak is a tree or shrub in the genus Quercus , of which about 600 species exist. "Oak" may also appear in the names of species in related genera, notably Lithocarpus...

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

Polymerization

In polymer chemistry, polymerization is a process of reacting monomer molecules together in a chemical reaction to form three-dimensional networks or polymer chains...

) into delicious and complex elements of "bottle bouquet" when the wine is cellared under appropriate temperature conditions, preferably in the range of a constant 55 to 60 °F (12.8 to 15.6 C). 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

Bordeaux is a port city on the Garonne River in the Gironde department in southwestern France.The Bordeaux-Arcachon-Libourne metropolitan area, has a population of 1,010,000 and constitutes the sixth-largest urban area in France. It is the capital of the Aquitaine region, as well as the prefecture...

), tannic grapes such as Cabernet Sauvignon

Cabernet Sauvignon

are blended with lower-tannin grapes such as Merlot

Merlot

Merlot is a darkly blue-coloured wine grape, that is used as both a blending grape and for varietal wines. The name Merlot is thought to derive from the Old French word for young blackbird, merlot, a diminutive of merle, the blackbird , probably from the color of the grape. Merlot-based wines...

or Cabernet Franc

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...

, 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-ol
Flavan-3-ols are a class of flavonoids that use the 2-phenyl-3,4-dihydro-2H-chromen-3-ol skeleton. These compounds include the catechins and the catechin gallates....

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 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

Downy mildew

Downy mildew refers to any of several types of oomycete microbes that are obligate parasites of plants. Downy mildews exclusively belong to Peronosporaceae. In commercial agriculture, they are a particular problem for growers of crucifers, grapes and vegetables that grow on vines...

. 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

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.

In red grapes, the main flavonol is on average quercetin

Quercetin

Quercetin , a flavonol, is a plant-derived flavonoid found in fruits, vegetables, leaves and grains. It also may be used as an ingredient in supplements, beverages or foods.-Occurrence:...

, followed by myricetin

Myricetin

Myricetin is a naturally occurring flavonol, a flavonoid found in many grapes, berries, fruits, vegetables, herbs, as well as other plants. Walnuts are a rich dietary source. Trace amounts can be found as glycosides. It is one of the phenolic compounds present in red wine.Myricetin has antioxidant...

, kaempferol

Kaempferol

Kaempferol is a natural flavonol, a type of flavonoid, that has been isolated from tea, broccoli, Delphinium, Witch-hazel, grapefruit,cabbage, kale, beans, endive, leek, tomato, strawberries, grapes, brussels sprouts, apples and other plant sources. Kaempferol is a yellow crystalline solid with a...

, laricitrin

Laricitrin

Laricitrin is a O-methylated flavonol, a type of flavonoid. It is found in red grape and in Vaccinium uliginosum . It is one of the phenolic compounds present in wine.-Metabolism:...

, isorhamnetin

Isorhamnetin

Isorhamnetin is an O-methylated flavonol, a type of chemical compound. It can be found in Tagetes lucida, a psychedelic plant from Mexico and Central America.-Metabolism:...

, and syringetin

Syringetin

Syringetin is a O-methylated flavonol, a type of flavonoid. It is found in red grape , in Lysimachia congestiflora and in Vaccinium uliginosum...

. 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

Myricetin

, laricitrin

Laricitrin

Laricitrin is a O-methylated flavonol, a type of flavonoid. It is found in red grape and in Vaccinium uliginosum . It is one of the phenolic compounds present in wine.-Metabolism:...

and syringetin

Syringetin

Syringetin is a O-methylated flavonol, a type of flavonoid. It is found in red grape , in Lysimachia congestiflora and in Vaccinium uliginosum...

, flavonols which are present in red grape varieties only, can be found in red wine.

Grape phenols - Non-flavonoids

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

Resveratrol

Resveratrol

Resveratrol is a stilbenoid, a type of natural phenol, and a phytoalexin produced naturally by several plants when under attack by pathogens such as bacteria or fungi....

is a phenolic compound 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 have resveratrol but more frequent use of skin contact and maceration in red winemaking means that red wines will normally have 10 times more resveratrol than white wines. It generally produced by grape vines as a means of microbial defense, though production can be artificially stimulated by ultraviolet radiation. Grapevines in cool, damp regions with higher risk of grape diseases, such as Bordeaux and Burgundy, tend to produce grapes with higher levels of resveratrol than warmer, drier wine regions like California and Australia. Additionally, different grape varieties are prone to differing levels with Muscadine

Muscadine

Muscadines are a grapevine species native to the present-day southeastern United States that has been extensively cultivated since the 16th Century. It differs from Vitis spp. in its number of chromosomes and its morphology...

s and the Pinot family having high levels while the Cabernet family being noted for 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

French paradox

The French Paradox is the observation that French people suffer a relatively low incidence of coronary heart disease, despite having a diet relatively rich in saturated fats...

involving the health of wine drinkers in France.

Piceatannol

Piceatannol

Piceatannol is a stilbenoid, a type of phenolic compound. It is a metabolite of resveratrol found in red wine.Astringin is a piceatannol glucoside.-Health effects:...

is also present in grape from where it can be extracted and found in red wine.

Vanillin

Vanillin

is a phenolic aldehyde

Aldehyde

An aldehyde is an organic compound containing a formyl group. This functional group, with the structure R-CHO, consists of a carbonyl center bonded to hydrogen and an R group....

most commonly associated with the vanilla notes in wines that have been aged in oak. Some trace amounts of vanillin are found naturally in the grapes themselves but they are most prominent in the lignin

Lignin

Lignin or lignen is a complex chemical compound most commonly derived from wood, and an integral part of the secondary cell walls of plants and some algae. The term was introduced in 1819 by de Candolle and is derived from the Latin word lignum, meaning wood...

structure of oak barrels. Newer barrels will impart more vanillin, with the concentration present decreasing with each subsequent usage.

Phenols from oak ageing

4-Ethylphenol

4-Ethylphenol, often abbreviated to 4-EP, is a phenolic compound with the molecular formula C8H10O. In wine and beer it is produced by the spoilage yeast Brettanomyces. When it reaches concentrations greater than the sensory threshold it can give the wine aromas described as barnyard, medicinal,...

and 4-ethylguaiacol are produced during ageing of red wine in oak barrels.

Natural phenols and polyphenols from cork stoppers

Low molecular weight polyphenols, as well as elagitannins, are susceptible to be extracted from cork stopper

Cork (material)

Cork is an impermeable, buoyant material, a prime-subset of bark tissue that is harvested for commercial use primarily from Quercus suber , which is endemic to southwest Europe and northwest Africa...

s into the wine. The identified polyphenols are gallic, protocatechuic

Protocatechuic acid

Protocatechuic acid is a dihydroxybenzoic acid, a type of phenolic acid. It has mixed effects on normal and cancer cells in in vitro and in vivo studies.-Biological effects:...

, vanillic

Vanillic acid

Vanillic acid is a dihydroxybenzoic acid derivative used as a flavoring agent. It is an oxidized form of vanillin...

, caffeic, ferulic

Ferulic acid

Ferulic acid is a hydroxycinnamic acid, a type of organic compound. It is an abundant phenolic phytochemical found in plant cell wall components such as arabinoxylans as covalent side chains. It is related to trans-cinnamic acid. As a component of lignin, ferulic acid is a precursor in the...

, and ellagic acids; protocatechuic

Protocatechuic aldehyde

Protocatechuic aldehyde is a phenolic aldehyde, a compound released from cork stoppers into wine.This molecule can be used as a precursor in the vanillin synthesis by biotransformation by Capsicum frutescens cell cultures....

, vanillic

Vanillin

, coniferyl

Coniferyl aldehyde

Coniferyl aldehyde is a low molecular weight phenolic compound susceptible to be extracted from cork stoppers into wine.-Metabolism:Coniferyl-alcohol dehydrogenase uses coniferyl alcohol and NADP+ to produce coniferyl aldehyde, NADPH, and H+....

, and sinapic aldehydes; the coumarins aesculetin and scopoletin

Scopoletin

Scopoletin is a coumarin found in the root of plants in the genus Scopolia like Scopolia carniolica or Scopolia japonica, in chicory, in Artemisia scoparia, in the passion flower, in Brunfelsia, in Viburnum prunifolium or Kleinhovia hospita...

; the ellagitannins are roburins A

Roburin A

Roburin A is a tannin found in oak wood or oak cork .It is a dimeric compound, composed of two vescalagin subunits probably linked through an ether bond between the diphenoyl group of one subunit and the triphenoyl moiety of the other one....

and E, grandinin

Grandinin

Grandinin is an ellagitannin. It can be found in Melaleuca quinquenervia leaves and in oaks. It shows antioxydant activity. It is a castalagin glycoside by binding of the pentose lyxose....

, vescalagin and castalagin

Castalagin

Castalagin is a ellagitannin, a type of hydrolyzable tannin, found in oak and chestnut wood and in the stem barks of Anogeissus leiocarpus and Terminalia avicennoides....

.

Guaiacol

Guaiacol

Guaiacol is a naturally occurring organic compound with the formula C6H4. Although it is biosynthesized by a variety of organisms, this colorless aromatic oil is usually derived from guaiacum or wood creosote. Samples darken upon exposure to air and light. Guaiacol is present in wood smoke,...

is one of the molecules responsible for the cork taint

Cork taint

Cork taint is a broad term referring to a wine fault characterized by a set of undesirable smells or tastes found in a bottle of wine, especially spoilage that can only be detected after bottling, aging and opening...

wine fault.

Extraction levels in relation with grape pressing techniques

Flash release

Flash release (oenology)

Flash release is a technique used in wine pressing. The technique allows for a better extraction of phenolic compounds and wine polysaccharides....

is a technique used in wine press

Wine press

A wine press is a device used to extract juice from crushed grapes during wine making. There are a number of different styles of presses that are used by wine makers but their overall functionality is the same. Each style of press exerts controlled pressure in order to free the juice from the fruit...

ing. The technique allows for a better extraction of phenolic compounds.

Non exhaustive list of phenolic compounds found in wine

Anthocyanidin-caftaric acid adducts
Astilbin
Astilbin
Astilbin is a flavanonol, a type of flavonoid. Astilbin is the -isomer; neoisoastilbin is the -isomer and isoastilbin is the -isomer....
Astringin
Astringin
Astringin is a stilbenoid. It is the piceatannol glucoside. It can be found in wine....
B type proanthocyanidin dimers
B type proanthocyanidin trimers
Catechin
Catechin
Catechin is a natural phenol antioxidant plant secondary metabolite. The term catechins is also commonly used to refer to the related family of flavonoids and the subgroup flavan-3-ols ....
Caffeic acid
Caffeic acid
Caffeic acid is a hydroxycinnamic acid, a naturally occurring organic compound. This yellow solid consists of both phenolic and acrylic functional groups...
Caftaric acid
Caftaric acid
Caftaric acid is a non-flavanoid that impacts the color of white wine. Many believe this molecule is responsible for the yellowish-gold color seen in some whites wines. Aside from wine, it is abundantly present in raisins....
Castavinol C1
Castavinol C2
Castavinol C3
Castavinol C3
Castavinol C3 is a castavinol, a natural phenolic compound found in red wines.-External links:*...
Castavinol C4
Coumaric acid
Coumaric acid
Coumaric acid is a hydroxycinnamic acid, an organic compound that is a hydroxy derivative of cinnamic acid. There are three isomers, o-coumaric acid, m-coumaric acid, and p-coumaric acid, that differ by the position of the hydroxy substitution of the phenyl group...
Coutaric acid
Coutaric acid
Coutaric acid is an hydroxycinnamic acid found in wine and grape. It is an ester formed from coumaric acid and tartaric acid....
Cyanidin
Cyanidin
Cyanidin is a natural organic compound. It is a particular type of anthocyanidin . It is a pigment found in many red berries including but not limited to grapes, bilberry, blackberry, blueberry, cherry, cranberry, elderberry, hawthorn, loganberry, acai berry and raspberry...
Cyanidin 3O-glucoside
Cyanidin acetyl 3O glucoside
Cyanidin coumaroyl 3Oglucoside
Delphinidin
Delphinidin
Delphinidin is an anthocyanidin, a primary plant pigment, and also an antioxidant. Delphinidin gives blue hues to flowers like violas and delphiniums...
Delphinidin 3Oglucoside
Delphinidin acetyl-3Oglucoside
Delphinidin coumaroyl 3O glucoside
Ellagic acid
Ellagic acid
Ellagic acid is a natural phenol antioxidant found in numerous fruits and vegetables including blackberries, raspberries, strawberries, cranberries, walnuts, pecans, pomegranates, wolfberry and other plant foods...
Engeletin
Engeletin
Engeletin is a phenolic compound found in wine and isolated from the bark of Hymenaea martiana....
Epicatechin gallate
Epicatechin gallate
Epicatechin gallate is a flavan-3-ol, a type of flavonoid, present in green tea. It is also reported in buckwheat and in grape....
Epigallocatechin
4-Ethylguaiacol
4-Ethylphenol
4-Ethylphenol
4-Ethylphenol, often abbreviated to 4-EP, is a phenolic compound with the molecular formula C8H10O. In wine and beer it is produced by the spoilage yeast Brettanomyces. When it reaches concentrations greater than the sensory threshold it can give the wine aromas described as barnyard, medicinal,...
Fertaric acid
Fertaric acid
Fertaric acid is a hydroxycinnamic acid found in wine and grape. It is an ester formed from ferulic acid bound to tartaric acid....
Ferulic acid
Ferulic acid
Ferulic acid is a hydroxycinnamic acid, a type of organic compound. It is an abundant phenolic phytochemical found in plant cell wall components such as arabinoxylans as covalent side chains. It is related to trans-cinnamic acid. As a component of lignin, ferulic acid is a precursor in the...
Gallic acid
Gallic acid
Gallic acid is a trihydroxybenzoic acid, a type of phenolic acid, a type of organic acid, also known as 3,4,5-trihydroxybenzoic acid, found in gallnuts, sumac, witch hazel, tea leaves, oak bark, and other plants. The chemical formula is C6H23COOH. Gallic acid is found both free and as part of...
Grape reaction product
Grape reaction product
The grape reaction product is a phenolic compound found in aged red wines. Its enzymatic production by polyphenol oxidase is important in limiting the browning of musts. The product can be recreated in model solutions...

(GRP)
Guaiacol
Guaiacol
Guaiacol is a naturally occurring organic compound with the formula C6H4. Although it is biosynthesized by a variety of organisms, this colorless aromatic oil is usually derived from guaiacum or wood creosote. Samples darken upon exposure to air and light. Guaiacol is present in wood smoke,...
Hopeaphenol
Hopeaphenol
Hopeaphenol is a stilbenoid. It is a resveratrol tetramer isolated from wines.It shows an opposite effect to vitisin A on apoptosis of myocytes isolated from adult rat heart....
Isorhamnetol 3-glucoside
Kaempferol
Kaempferol
Kaempferol is a natural flavonol, a type of flavonoid, that has been isolated from tea, broccoli, Delphinium, Witch-hazel, grapefruit,cabbage, kale, beans, endive, leek, tomato, strawberries, grapes, brussels sprouts, apples and other plant sources. Kaempferol is a yellow crystalline solid with a...
Kaempferol glucoside
Kaempferol glucuronide
Malvidin
Malvidin
Malvidin is an O-methylated anthocyanidin. As a primary plant pigment, its glycosides are highly abundant in nature. It is responsible primarily for the color of red wine, Vitis vinifera being one of its sources...
Malvidin 3O-glucoside (oenin)
Malvidin acetyl-3O-glucoside
Malvidin cafeoyl-3O-glucoside
Malvidin coumaroyl-3Oglucoside
Malvidin glucoside-ethyl-catechin
Myricetol
Myricetol 3-glucoside
Myricetol 3-glucuronide
Pallidol
Pallidol
Pallidol is a resveratrol dimer. It can be found in red wine, in Cissus pallida or in Parthenocissus laetevirens.-External links:*...
Peonidin 3O-glucoside
Peonidin acetyl-3O-glucoside
Peonidin coumaroyl 3O-glucoside
Petunidin
Petunidin
Petunidin is an O-methylated anthocyanidin. It is a natural organic compound and a particular type of anthocyanidin. It is a dark-red or purple water-soluble pigment found in many redberries including chokeberries , Saskatoon berries or different species of grape , and...
Petunidin 3Oglucoside
Petunidin acetyl-3O-glucoside
Petunidin coumaroyl-3Oglucoside
Phloroglucinol carboxylic acid
Phloroglucinol carboxylic acid
Phloroglucinol carboxylic acid is a trihydroxybenzoic acid, a type of phenolic acid. It is a catechin degradation product excreted by the bacterium Acinetobacter calcoaceticus ,a species of bacteria part of the Human body normal flora, grown on catechin as sole source of carbon. It is also found in...
Piceatannol
Piceatannol
Piceatannol is a stilbenoid, a type of phenolic compound. It is a metabolite of resveratrol found in red wine.Astringin is a piceatannol glucoside.-Health effects:...
Piceid
Piceid
Piceid is a stilbenoid glucoside and is a major resveratrol derivative in grape juices. It can also be isolated from Polygonum cuspidatum....

s
Pinotin A
Pinotin A
Pinotin A is a pinotin, a type of pyranoanthocyanins and a class of phenolic compounds found in red wine.-External links:*...
Protocatechuic acid
Protocatechuic acid
Protocatechuic acid is a dihydroxybenzoic acid, a type of phenolic acid. It has mixed effects on normal and cancer cells in in vitro and in vivo studies.-Biological effects:...
Quercetin
Quercetin
Quercetin , a flavonol, is a plant-derived flavonoid found in fruits, vegetables, leaves and grains. It also may be used as an ingredient in supplements, beverages or foods.-Occurrence:...
Quercetol glucoside
Quercetol glucuronide
Resveratrol
Resveratrol
Resveratrol is a stilbenoid, a type of natural phenol, and a phytoalexin produced naturally by several plants when under attack by pathogens such as bacteria or fungi....
Syringic acid
Syringic acid
Syringic acid is a naturally occurring O-methylated trihydroxybenzoic acid, a type of chemical compound. It can be found in the açaí palm and its oil , in Ardisia elliptica...
Tyrosol
Tyrosol
Tyrosol is a natural phenolic antioxidant present in a variety of natural sources. The principal source in the human diet is olive oil. Tyrosol is a derivative of phenethyl alcoholAs an antioxidant, tyrosol can protect cells against injury due to oxidation...
Vanillic acid
Vanillic acid
Vanillic acid is a dihydroxybenzoic acid derivative used as a flavoring agent. It is an oxidized form of vanillin...
4-Vinylphenol
4-Vinylphenol
4-Vinylphenol is a phenolic compound found in wine and beer. It is produced by the spoilage yeast Brettanomyces. When it reaches concentrations greater than the sensory threshold, it can give the wine aromas described as barnyard, medicinal, band-aids, and mousy...
Vitisin A
Vitisin A (pyranoanthocyanin)
Vitisin A is a natural phenol found in red wines. It is a pyranoanthocyanin.-External links:*...
Vitisin B
Vitisin B (pyranoanthocyanin)
Vitisin B is a natural phenol found in red wines. It is a pyranoanthocyanin....

External links

Wine polyphenols vary with age and variety (Polyphenols on www.guideduvin.com)

The source of this article is wikipedia, the free encyclopedia. The text of this article is licensed under the GFDL.

Origin of the phenolic compounds

Grape polyphenols - Flavonoids

Flavonols

Anthocyanins

Tannins

Addition of enological tannins

Effects of tannins on the drinkability and aging potential of wine

Other flavonoids

Grape phenols - Non-flavonoids

Phenols from oak ageing

Natural phenols and polyphenols from cork stoppers

Extraction levels in relation with grape pressing techniques

Non exhaustive list of phenolic compounds found in wine

See also

External links