Phenolic content in wine

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Tannins (wine)
)
The phenolic compounds in Syrah grapes contribute to the taste, color and mouthfeel of the wine.

The phenolic content in wine refers to the phenolic compounds—

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,

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

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

aroma to wines.[5]

Most wine phenols are classified as

glycosides
.

Grape polyphenols

Vitis vinifera produces many phenolic compounds. There is a varietal effect on the relative composition.

Flavonoids

Main article:
Flavonoids
The process of maceration or extended skin contact allows the extraction of phenolic compounds (including those that form a wine's color) from the skins of the grape into the wine.

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

chemopreventive properties of flavonoids.[7]

Flavonols

Main article: Flavonols

Within the flavonoid category is a subcategory known as

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

Main article: Anthocyanin

Anthocyanins are phenolic compounds found throughout the

teinturiers, such as Alicante Bouschet, which have a small amount of anthocyanins in the pulp that produces pigmented juice.[9]

There are several types of anthocyanins (as the

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 gene of V. vinifera.[10] 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.[9]

Red-berried

para-coumaroylated or acetylated anthocyanins as other varieties do.[11]

Tempranillo has a high pH level which means that there is a higher concentration of blue and colorless anthocyanin pigments in the wine. The resulting wine's coloring will have more blue hues than bright ruby red hues.

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

fermentation processes[12] or during controlled oxygenation processes[13] during the aging of wine.[14]

Tannins

Main article: Tannin

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

food and wine pairing, foods that are high in proteins (such as red meat) 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.[16]

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

ellagic and gallic acid found in the wood.[16]

Fermenting with the stem, seeds and skin will increase the tannin content of the wine.

In the vineyards, there is also a growing distinction being made between "ripe" and "unripe" tannins present in the grape. This "

decanting wine use oxygen to partially mimic the effect of aging on tannins.[16]

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.[21]

Reactions of tannins with the phenolic compound anthocyanidins creates another class of tannins known as pigmented tannins which influences the color of red wine.[18]

Addition of enological tannins

Commercial preparations of tannins, known as enological tannins, made from

quebracho, gambier[19] and myrobalan fruits,[20]
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

nouveau wines
) typically have lower tannin levels.

Other flavonoids

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 and especially Syrah have very low levels.[17]
As an antioxidant, there are some studies into the health benefits of moderate consumption of wines high in catechins.[24]

In red grapes, the main flavonol is on average quercetin, followed by myricetin, kaempferol, laricitrin, isorhamnetin, and syringetin.[25] 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.[25]

Myricetin, laricitrin[26] and syringetin,[27] flavonols which are present in red grape varieties only, can be found in red wine.[28]

Non-flavonoids

See also:
Wine and health

Hydroxycinnamic acids

Hydroxycinnamic acids are the most important group of nonflavonoid phenols in wine. The four most abundant ones are the

p-coumaric, and trans-ferulic acids).[29]

Stilbenoids

V. vinifera also produces stilbenoids.

Muscadines and the Pinot family having high levels while the 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.[32]

Piceatannol is also present in grape [33] from where it can be extracted and found in red wine.[28]

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.[34]

Phenols from oak ageing

Phenolic compounds like tannins and vanillin can be extracted from aging in oak wine barrels.

Oak barrel will add compounds such as

hydrolyzable tannins present in oak are derived from lignin structures in the wood. They help protect the wine from oxidation and reduction.[35]

4-ethylguaiacol are produced during ageing of red wine in oak barrels that are infected by brettanomyces .[36]

Natural phenols and polyphenols from cork stoppers

Extracted cork closure inscribed with "Bottled at origin" in Spanish

Low molecular weight polyphenols, as well as ellagitannins, are susceptible to be extracted from

vescalagin and castalagin.[38]

Guaiacol is one of the molecules responsible for the cork taint wine fault.[39]

Phenolic content in relation with wine making techniques

Extraction levels in relation with grape pressing techniques

Flash release is a technique used in wine pressing.[40] The technique allows for a better extraction of phenolic compounds.[41]

Microoxygeneation

The exposure of wine to oxygen in limited quantities affects phenolic content.[42]

Phenolic compounds found in wine

LC chromatograms at 280 nm of a pinot red wine (top), a Beaujolais rosé (middle) and a white wine (bottom). The picture shows peaks corresponding to the different phenolic compounds. The hump between 9 and 15 minutes corresponds to the presence of tannins, mostly present in the red 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.

Effects

Polyphenol compounds may interact with

HDL cholesterol, but high-quality clinical trials have not confirmed such effects, as of 2017.[50]

See also

References

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External links
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