Winemaking, white aging

Q. alba (American oak) is used less frequently with white wines than red wines, and it is widely acknowledged that American oak has a distinctively different effect on wines chemical and sensory properties than does European oak. The strong and distinctive oakiness of Q. alba can overwhelm the varietal character of a white wine, if not used with care. Some winemakers combine use of both European and American oak in their oak-aging practices. 

In California, winemakers do not want white wine to undergo the bacterial malo-lactic fermentation that changes malic acid to lactic acid. The loss of acidity, increased pH, and freshness is considered to be detrimental. On the other hand, malo-lactic fermentation of red wines before secondary fermentation is common. This is because red wines undergo malo-lactic fermentation more easily than do whites and they generally are aged longer before use. The producers do not want a malo-lactic fermentation in the bottle. 

The systematic improvement in the protein stability of white wines during barrel aging on the lees is easily verified by winemakers (Ledoux et al.,... 

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 production of sulfur derivatives by yeast during fermentation is described below. The various molecules and their formation mechanisms are discussed, as well as methods for eliminating them. Although red wines may be affected, this issue is particularly important for white wines. The effect of winemaking techniques and barrel aging on the presence of sulfur derivatives is described elsewhere (Volume 1, Section 13.9.1). 

A number of winemaking factors, such as maintaining them on their lees throughout barrel aging, preserve the fruity character of young dry white wines and minimize or delay their premature aging. 

Late barreling (after alcoholic fermentation) and prematurely eliminating lees will produce white wines with excessive wood character. These methods have unfortunately been practiced in the past in certain regions, where winemakers have applied red wine aging techniques to white wine. 

---