Winemaking, white aroma

The future will be to manage the extraction of precusors of aromas from the grape during the skin contact steps of white and red winemakings... 

Dry white table wines differ from red table wines in characteristics other than color. They contain lower concentrations of the puckery and astringent tannins. They usually have a higher acid content which makes them somewhat lighter in body and fresher on the palate. Dry white wines also are usually simpler in their aroma in contrast to the complicated aroma and bouquet that can develop in a red table wine. While it is possible to make white table wines from red-skinned varieties, for the home winemaker this task is very difficult because it is almost impossible to remove all traces of the pigment-containing skins from the juice quickly enough to prevent some reddish or amber color from developing. 

By careful processing, the winemaker brings the wine to a finished state. The white and rose wines will have maintained their bouquet and aroma and flavors. The red table wines will have been softened by careful fining with such agents as gelatin and PVPP, will be fruity, and will have distinctive varietal aromas and flavors with minimal astringency. 

The fluidity of the plasmatic membrane is considerably affected by temperature (Rodriguez et al. 2007) and ethanol concentration (Jones and Greenfield 1987). Therefore, during alcoholic fervaeniaiionSaccharomyces cerevisiae must adapt the fluidity of the membrane to the changing environmental conditions. It should be emphasized that the temperature of fermentation and aeration depend on the type of winemaking. Usually, white wines are made at low temperatures (14-18 °C) and without aeration to conserve aromas whereas red wines are fermented at relatively high temperatures (28-30 °C) and are aerated in order to enhance colour extraction. 

Grape and wine proteins have been of interest to winemakers for many years. This interest is primarily due to the ability of these proteins to aggregate together in finished white wines and form unattractive hazes and sediments. Proteins are significant in wine because they are a nuisance Endogenous wine proteins, of course, also have other roles in wine and have been examined for their impact on the aroma and... 

The addition of enzymes during winemaking is a common practice to improve the extraction of colour and aroma compounds, the clarification of the white wines and the filtration processes of musts and wines (Doco et al. 2007). More information about the behaviour of enzymes during winemaking is described in Chapter 4 (Enzymes in winemaking). 

Finally, another defect well known to winemakers is the premature aging of bottled white wines. Although this has been associated with oxidative development, it has not been fully explained by enologists. This defect can affect any type of white wine, dry or sweet, still or sparkling, and whatever the grape variety or origin. It leads to the early disappearance of varietal aromas, the absence of reduction bouquet and, above all, the appearance of a characteristic, heavy smell, reminiscent of rancid beeswax, stale honey and, in extreme cases, naphthalene. Neither the compounds responsible for these odors, nor the mechanisms that produce them, nor the means of preventing this phenomenon, have yet been elucidated. 

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. 

Immediately after extraction, the juice should be protected from oxidation by sulfiting (5-8 g/hl). In theory, clarification seems less important in rose winemaking than in white winemaking, but this practice refines wine aroma and diminishes the iron concentration. Must can be treated with bentonite. Anthocyanin fixation results in a slight color decrease but it is brighter and less sensitive to oxidation. It is not advisable to use bentonite with pectolytic enzymes. 

---