White wines need to be treated more delicately than reds as oxidisation is a common problem. After the grapes are pressed the juice is usually separated from the skins and stalks immediately, although more contact is sometimes allowed to impart more flavour.
To enhance the flavour and preserve the all important freshness of white wine, fermentation takes place at a lower temperature and for a longer period than with reds. The ability of technology to reduce temperatures of wines is one of the most important developments of modern wines.
Malolactic fermentation, the process by which tart tasting malic acid turns into milder lactic acid, is generally prevented from occurring when making white wine.
Sometimes white wine is allowed to make contact with lees, the dead yeasts, to increase the body, and placing the wine in oak barrels adds more complexity and give the wine a “buttery” characteristic.
As white wine is usually more acidic than red, it is usually sweeter than red, although you may not detect this sugar. It is made from grapes that are sweet enough to leave some sugar in the wine after fermentation stops, although sugar may be added to the wine in colder regions like Germany.