Wine aroma phenolic compounds

Pectinases and (3-glucanases are the only enzymes allowed in wine-making by European legislation. They are used as clarification and filtration agents and also to release aroma compounds that are mostly present in grape as nonvolatile glycosidic precursors. Pectolytic enzymes are also reported to increase extraction of phenolic compounds and wine color... 

Since yeast lees may adsorb some aroma compounds responsible of off-flavours in wines (volatile phenols), these components have been also proposed such as a cost-effective and efficient approach to remove or to decrease organoleptic defects in wine (Chassagne et al. 2005). 

Benzene compounds. Benzene compounds are an important group in varietal aroma, abimdant in wines, including aromatic alcohols, aldehydes, volatile phenols and shikimic acid derivates. The volatile phenols in wines can come from grapes, both as free and bound aroma, or be generated during the alcoholic fermentation by chemical reactions such as phenolic add degradation, or in the case of vinylphenols due to brettanomyces contamination (Suarez et al., 2007). Volatile phenols are considered characteristic components of wine aroma, although their influence on the final product may be positive or... 

While oxidation of phenolic compounds induces colour changes in the must and wine, and the formation of acrid and bitter substances, other constituents of juice and wine, such as compounds related to aroma, are also oxidised (Peynaud, 1984). 

PVP forms insoluble complexes with phenolic compounds and, therefore, is applied as a clarifying agent in the beverage industry (beer, wine, fruit juice). Furthermore, it serves as a binding and thickening agent, and as a stabilizer, e. g., of vitamin preparations. Its tendency to form films is utilized in protective food films (particle solubility enhancement and aroma fixation in instant tea and coffee production). 

The maximum tank temperature is related to all of these factors by complex laws and is difficult to predict. Depending on the circumstances, the maximum temperature can be compatible with red winemaking. In this case, a maximum temperature between 25 and 30°C ensures sufficient extraction of phenolic compounds from the solid parts during maceration. In other cases, refrigeration is necessary to avoid exceeding the maximum temperature limit. Refrigeration is always necessary for white wines their fermentation must be carried out at around 20°C to retain their aromas. 

The main substrates for wine bacteria known to date are simple molecules sugars and organic acids. Although their transformation is not currently verified, other more complex wine components, such as phenolic compounds, aromatic compounds or aroma precursors, present in small quantities, are without doubt partially metabolized. The repercussion of these minor transformations on organoleptic characters can be (depending on the molecules concerned) at least as important as the principal reactions. 

This reaction is slow. It protects wines from chemical oxidations, but it has no effect on enzymatic oxidations, which are very quick. SO2 protects wine from an excessively intense oxidation of its phenolic compounds and certain elements of its aroma. It prevents madeirization. It also contributes to the establishment of a sufficiently low oxidation-reduction potential, favoring wine aroma and taste development during storage and aging. 

In general, grape maturation results from several biochemical transformations that are not necessarily related to each other. To simplify matters, the increase in sugar concentration and the decrease in acidity are monitored. The accumulation and refinement of white grape aromas and phenolic compounds in red grapes should also be taken into account. The essential property of a quality wine-producing area is to permit a favorable maturation. This corresponds with a harmonious evolution of the various transformations to reach the optimum point simultaneously at the time of the harvest. 

Red wines are macerated wines. Maceration is responsible for all of the specific characteristics of sight, smell and taste that differentiate red wines from white wines. Phenolic compounds (antho-cyanins and tannins) are primarily extracted, participating in the color and overall structure of wine. Yet aromas and aroma precmsors, nitrogen compounds, polysaccharides (in particular, pectins) and minerals are also liberated in the must or wine dm-ing maceration. 

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