The differences between white wines and red wines are mainly these two: color and tannin.
Even though the color has pale, medium and deep intensity, the red wines have deep red color while the white are transparent yellow. The red wines have more or less tannin, but most of white wines haven’t. The red wine are made from the red or black grapes, mainly because of the deep color. And the skin of the red grapes gives the red wine color, while the pulps are almost no color. So the red winemaking process needs the participation of the red grape skins. The red winemaking process has the following stages.
Harvesting
When the color of the grapes turned black from green and the sugar reached the expected level, the grapes are ripe and need to harvest immediately in order to avoid the decrease of the acidity and the late autumn rains.
Some wine regions prefer to harvest the grapes in the early morning in order to maintain the high acidity and freshness of the grapes.
The high volume production wineries tend to use machine harvesting. If the yields are controlled carefully and viticulture are professional, they also can make high quality wines.
Small wineries end to use human harvest. Some specified areas, such as the vineyards on the steep slopes, or the grape used for Icewine or botrytised wine, those all need to use the manual harvest.
After the grapes are picked from the vines, they need to be transported to the winery immediately. The grapes are likely to be oxidized when too much time are wasted on the transporting process.
Sorting
Once the grapes arrive at the winery, people start the sorting process. They will pick out the unripened grapes, the rotten grapes and things other than grapes. Only healthy grapes are used in the fermentation process.
Destemming
Most wineries choose to destem the grapes. It’s considered that the stems will give the wine coarse and bitter tannin.
Some wineries choose to keep the stems, because they think the stems will add more tannin and structures to the wines, especially the wines with light body, such as Pinot Noir grapes. The stems also helps to wine juice drainage in the pressing process after the fermentation and maceration processes.
Anyway, it’s an optional process.
Crushing
In order to let the grape juice flow out, the grapes have to be crushed. The yeast can touch the sugar in the grape juice and the alcoholic fermentation can start.
Fermentation
It is the core process. The sugar in the grapes will be converted into alcohol by the yeast added while the heat and the carbon dioxide are generated. A lot of factors that can influence the fermentation process, such as fermentation temperature and fermentation vessels. The skins and seeds will float onto the surface because of the carbon dioxide have generated. Winemakers can use the pumping over or punching down technique so that more tannin, color and flavor compounds can be extracted from the skins.
Maceration
After the alcoholic fermentation is finished, the wine juice and the skin will macerate for 10-15 days. The maceration of the skins will give more tannin, structure, color and flavors to the wines.
Pressing
Pressing allows the wine juice separates from the skin. Part of wines will directly flow out because of earth gravity. This part is called free run wine. The rest have to be pressed and called pressed wine. Those two parts will blend together. But some wineries bottle the wine using only free run wine for elegance.
Maturation
Maturation process lasts for several months or years. It depends on the wine style that expected. For example, some wineries just put the wine in the stainless steel for three to six months to preserve the fruity of the wine for early consumption. Some wineries would prefer to age the wine in the oak barrel for 12 to 24 months, to extract more tannin and flavor compounds from the oak and to make more complex and powerful wine for high aging potential purpose.
Filtration
Before bottling, the wine has to be filtered to remove any deposits in the wine. This process can be done through clarification or filtration.
Bottling
The final stage is bottling. Several decisions the winemaker has to make, like what kind of bottle should be used, which volume standard and what stoppers for closure purpose. Cork is a traditional closure and is widely used in the old world wine producing areas while the screw cap is a new choice and is widely used in the new world wine producing areas, such as New Zealand and Australia. The cork is thought to have breathability and the wine can be oxidized and to develop more complex flavors. The screw cap is considered to preserve the freshness of the wine and the screw cap is absolutely easier to open than the cork.