Phenolic content in wine

The phenols in wine include a group of several hundred chemical substances from the substance group of polyphenols. The phenols substantially affect the color, the smell, the taste and the texture of the wine. You are responsible for the difference between white and red wine. In addition to the visual and gustatory properties of the reactive group has antibacterial and antioxidant action, have an influence on the vitamin content of wine and seem to have a positive effect on the course of heart and circulatory diseases to have. In this context, they are responsible for the phenomenon of the French Paradox. The vast majority of the phenols is counted to the family of secondary metabolites of the vine, that is, they seem to be dispensable for the survival of the plant. The water-soluble phenols are usually stored in the vacuoles of berry in the form of glycosides.

Part of the phenols ( mostly non- flavonoid substances ) is contained in the juice and pulp of the grape. On its share of the wine of the winery has only a small influence and essentially represents the characteristic of the variety dar. In the grape skins, the seeds and the stems and the stem structure focus the flavonoids. By techniques such as wine making the life of the maceration, the percentage of stems in the mash, etc., the amount of the extracted components can be controlled in the wine. Too high a proportion of flavonoids in white wine or sparkling wine is undesirable. During the wine making and the subsequent aging changes the chemical structure of many of the phenols contained in the wine. About the change mechanisms are still unknown.

By choosing the fermentation and expansion tank various phenols can be introduced into the wine. The new oak barriques of can bsw. depending on the origin and degree of roasting bring a hint of vanilla in the form of vanillin.

Gustatory perception

Currently it is assumed that at least five basic qualities of gustatory perception:

Since the beginning of the 20th century is known that the different taste qualities are perceived by all the sensitive areas of the tongue. The differences between the tab portions relative to the sensitivity to individual grades are small in humans. Nevertheless, in many textbooks is still a division of the tongue be found in " taste zones ".

The taste- phenols are mainly attributable to the group of bitter substances.

The substances

Flavonoids

Flavonoids are a group of water-soluble plant pigments and play an important role in the metabolism of many plants. According to DGE there are over 6500 different flavonoids. Most flavonoids are bound to glucose or rhamnose - hence they are called glycosides. Only the flavanols and the proanthocyanidins are not bound to sugar molecules ( = aglycones ).

Flavones

Flavones are yellow plant pigments. There are about 300 known naturally occurring flavones. Like other flavonoids, they occur as water-soluble glycosides, hyperoside and quercitrin eg, hesperidin, luteolin or chrysin. The yellow color in the white wine ranges from pale yellow to deep green to golden yellow. The former color is mostly white wines from the northern wine regions own. Typical is the pale yellow-green for a Chablis or a Riesling from the Mosel wine region.

Between the Green and golden yellow, the very common straw yellow joins. The Gold Yellow indicates generally a high-quality sweet wine like a German Beerenauslese or Trockenbeerenauslese or the Bordeaux growths of Sauternes and Barsac. White wines win - unlike red wines - with increasing aging in the bottle to color intensity.

Anthocyanins

Anthocyanins (from Greek anthos = flower, flowering, kyáneos = dark blue) are water-soluble plant pigments that are found in almost all higher plants and give the flowers, fruits and some leaves the red, purple, blue or blue- black color. Add the grapes, the anthocyanins develop with the onset of maturity (stage 81 of the BBCH-scale for vines ). At this stage, the color of the grape skin red grape varieties will change from green to red to blue- black. In most cases, the plant pigments found exclusively in the grape skins, while the juice and the pulp of the berry is colorless. This also explains that you can win even white wines from this red grape varieties ( → Blanc de Noirs ). Especially common this practice is in Champagne, where the Pinot Noir (Pinot Noir ) and the Müllerrebe (Pinot Meunier ) in large numbers white sparkling wine produced. To win a red wine, the dye must be triggered from the grape skins. This happens during the maceration period where the fermenting or already fermented juice of the grape skins remain in contact.

The proportion of tannins and anthocyanins may vary by year depending by 100%, the acid content by 50% and the must weight by up to 15-20%. Anthocyanins have among its tasks, protect the plants from strong UV light from the sun by absorbing certain wavelengths in the plants. Thus damage to the proteins in the cell and the DNA in the cell nuclei is prevented. The amount of dye formed depends also on the intensity of the radiation. Thus one finds in northern growing areas almost exclusively white grape. Red berries, which did not reach to the phenolic ripeness, produce wines with herbaceous character.

Add the berries are ampelographers find a wealth of anthocyanins, which are responsible for the full range of colors. The most important are cyanidin, peonidin, petunidin, delphinidin and malvidin the. The compilation of the dyes depends on the grape variety. This fact make the ampelographers to identify individual varieties advantage. In the middle of the 20th century, they also took advantage of a peculiarity of the noble vine Vitis vinifera to check whether the ban on so-called hybrid vines or vines Americans was respected. While the anthocyanins of Vitis vinifera are almost exclusively bound to a sugar molecule, they are bound at Vitis riparia and the descendant of Vitis rupestris varieties at two sugar molecules.

Red wines are found in very different hues that of a strong pink-red of all shades of red ( purple ruby, garnet ) after aging to reddish brown or amber tones change.

Whether an anthocyanin rather assumes a red or blue tone depends on the pH of the wine. A wine with low pH (ie, a strong acid) favors the red appearance; at high pH values ​​outweigh blue. When the bottle storage located in the wine anthocyanins react with acids and tannins. Collapse of the products and can form a bottle depot. The color of the wine tends then to a reddish brown, this is a sign of a longer aging in the bottle in the ideal case. Red wines lose color intensity with increasing age.

Tannins

The group of tannins affect the color of the wine, the required storage period up to the Maturity as well as the texture of the wine. The content of tannins and structure are a key determinant of the quality of a wine. Part is mistakenly assumed that red wines are more or less long depending on the tannin durable. Although tannins prevents the oxidation of the wine, but this can be achieved by the addition of potassium ( potassium pyrosulfite ) nowadays. It gives the wine a characteristic rough touch of dryness, the so-called astringency. Bitterness is caused by a reaction between the tannins and some proteins in saliva. The ability to react with proteins determined essential, what food goes with which wine. The Enology knows about 30 different tannins today. Some are for the quality of the wine of meaning, others are classified as unfavorable. Basically play tannins in red wines a greater role than in white wines, as with the dyes always tannins are extracted from the grape skins. These natural tannins are not susceptible to hydrolysis and are formed by enzymes in the metabolism of berry. The grape varieties Cabernet Sauvignon, Nebbiolo, Syrah and Tannat have a very high proportion of natural tannins.

Tannin is also transferred from oak barrels for wine (barriques ), if they were not made wine in green. However, the supply of oxygen promotes the polymerization with anthocyanins, so that the tannin content of the wine after the Barrique is usually less than before. The tannins from the Faßausbau susceptible to hydrolysis (eg gallotannins as a product of gallic acid, ellagic acid as a product of ellagitannins ).

The tannin content of a wine decides less about the shelf life, but rather about its bearing means test: In the course of aging in the bottle the tannins polymerize with anthocyanins to not astringent, long-chain molecules. The astringency of the wine going back, ever, making the wine leaves a pleasant drink. This requires the presence of a sufficient concentration of anthocyanins ( dyes). With the technique of micro-oxygenation trying to reduce the storage need.

Late Vintage and high physiological maturity provide more mature and experienced as soft tannins. Unripe green tannins, however, taste, aggressive and furry.

Catechins

The grapes of the noble vine (Vitis vinifera ) is rich in ( )- catechin, (-)- epicatechins, ( )- Gallocatechine, (-)- epigallocatechols, and the esterified form, the epicatechins -3-O - gallate. These flavanols of flavan -3-ols group have a bitter and astringent taste and are located exclusively in the nuclei of berries. The content of catechins varies in function de grape variety, the terroir, the vintage and the phenolic ripeness of the berries. The Merlot and Cabernet Sauvignon have extremely high amounts of flavanols.

In wine making, the winemaker can influence the extraction content of phenols from grape skins and seeds on various parameters of the mash fermentation. In red wine, the amounts of catechins vary as follows.

In the Middle therefore are 238 mg / L flavonols in red wine. This corresponds to an amount of 28.5 mg in a wine glass, 12 cl

Phenolic acids

Phenolic acids ( phenolic carboxylic acids), aromatic chemical compounds belonging to the group of hydroxybenzoic acids or hydroxycinnamic acids. The berries and the wine contains benzoic and cinnamic acid. In red wine, the concentration is from 100-200 mg / L, in the white wine with only 10-20 mg / l Of the seven known benzoic acids only the salicylic acid and gentisic acid are present in traces. In the must, the cinnamic acids are present in esterified form with tartaric acid. In the perception of both acid families are colorless and odorless, but represent the precursor of volatile phenols dar.