If we cut a red grape from it, we will find that only the skin is red and the flesh is white. This indicates that the red pigment of the grape is only present in the skins. Therefore, if you want to produce white wine, you should press the must quickly to prevent the pigments in the skins from dissolving in the must. In order to produce red wine, the red pigment in the grape skins should dissolve in the must, i.e. the must and skins must be mixed together, which is the maceration of the grape skins by the grape juice.
Therefore, the main difference between the red wine and white wine production process is that white wines are fermented with clarified grape juice, while red wines are fermented with pomace (including skins, seeds and stems) and grape juice. Therefore, in the fermentation of red wines, alcohol fermentation and maceration of solids coexist. The former converts sugar into alcohol, while the latter dissolves phenolic substances (such as tannins and pigments in solids) into the wine. Therefore, the color, aroma and taste of red wine are closely related to the phenolic substances.
White wine is an alcoholic beverage obtained through the alcoholic fermentation of white grape juice. During the fermentation process, the must is not impregnated in the solid part of the grapes. In addition, the quality of dry white wine depends mainly on the primary aromas of the grape variety, the secondary aromas of the alcoholic fermentation and the phenolic content. Therefore, under certain grape variety conditions, the rate and quality of must extraction, factors affecting the formation of secondary aromas, and the oxidation of must and wine become important process conditions that affect the quality of dry white wines.
In summary, the main differences between red and white wines are
There are three types of grape varieties according to their color: white varieties (white skin and white flesh), red varieties (red skin and white flesh) and dyed varieties (red skin and red flesh). Only white wines can be made from white varieties, only red wines can be made from dyed varieties, and wines of all colors, from white to deep red, can be made from red varieties.
2. White wines are fermented with white grape juice, while red wines are fermented with grape juice (liquid part) and grape pomace (solid part). The depth of color depends on the strength of the liquid part of the maceration of the solid part: the stronger the maceration, the darker the color.
The solid part brings not only pigments to the wine, but also tannins, which are the same phenolic substances as the pigments. The darker the wine, the higher the content of phenolic substances composed of pigments and tannins.
Therefore, the main difference between red and white wines is the amount and type of phenolics between them.
The color of red wine depends on the ratio of different forms of anthocyanins (i.e., red pigments), i.e., the ratio of free anthocyanins to anthocyanin and tannin complexes. Free anthocyanins give red wine its orange or purple color.
A series of studies have shown that spectrophotometers can measure the color of red wines at a spectrum of 520 μm. Further findings also indicate that various phenolic substances have different effects on the color of red wines.
–Free anthocyanins (AL) have little effect on wine color and gradually decrease with age. Tannins and anthocyanin (T-A) complexes are the main components that determine the color of red wines (about 50%) and their effect does not vary with the age of the wine.
–The effect of polymeric tannins on wine color continues to increase as the effect of free anthocyanins diminishes during the maturation process.
In summary, the color of new wines is determined primarily by the T-a complex and free anthocyanins. The color of mature wines depends on the T-A complex and the polymeric tannins.
Therefore, if you need to obtain a new wine with a darker color, and if the color needs to change slowly during the aging process, you need to ensure that.
(i) sufficient tannins and anthocyanins are extracted during the winemaking process.
② Provide conditions conducive to the combination of these two phenolic substances during storage.
If there is not enough T-A complex in the wine, it will quickly turn a reddish color due to the breakdown of anthocyanins.
The analytical index used to study the effect of phenolics on the sensory properties of wine is the “gelatin index”. This index indicates the ability of tannin molecules to bind to proteins and therefore reflects the intensity of astringency (astringency) of the wine.
Pure solutions of tannins and synthetic tannins extracted from grape seeds were reacted with gelatin. The results showed that the reaction strength of polymeric tannins was greater than that of small molecule tannins. However, if the molecular weight was too large, the reaction strength gradually decreased. This may explain, to some extent, the largely positive correlation between the polymeric tannins and the gelatin index of new wines, but the gelatin index of mature wines is usually very low despite their high polymeric tannin content. This phenomenon in adult wines may be due to the following reasons.
(i) The polymeric tannin molecule is too large.
(2) Combination of tannins with other components.
(3) Changes in the molecular structure of the tannins during the polymerization process.
In addition, the tannin-polyethylene glycol complex is an element that contributes to the “round” and “fatty” quality characteristics of red wines.
