Controlling the fermentation process in winemaking increases or reduces the alcohol level and the corresponding number of complex esters that affect taste and bouquet. Ideally, the vintner strives to use grapes with enough sweetness to produce an ideal alcohol content and flavor profile without adding other sugar and other ingredients. The greatest vintages come from unadulterated grapes and the vintner’s skill in controlling the fermentation process.
Ideal Alcohol Content for Various Wines
Yeast produces various types of alcohol, but most of it is ethyl alcohol with trace amounts of methyl alcohol and other toxic alcohols. Poisonous in large quantities, trace amounts of certain alcohol compounds add signature flavors, aromas and complex esters that interact with the vintage’s acids while wine matures to produce unique, complex flavor profiles.
Ideal alcohol content varies by type of wine and individual taste. Taste tests have found that the ideal alcohol content averages around 13.6 percent. However, certain wines taste best with concentrations that are higher than 14.0 percent. Alcohol ranges for vintages can vary within bottles, but common ranges for types of wine include:
- Zinfandel has a high alcohol content between 14.0 and 15.5 percent.
- Chardonnay tastes best when the alcohol content is between 13.3 and 14.0 percent.
- Rieslings can vary as much as a 7.0-percent low to a 14.0-percent high.
- Rose wines blend the characteristics of red and white and taste best at concentrations between 11.5 and 13.5 percent.
- Good syrah vintages are found with alcohol content between 12.5 and 15.5 percent.
- Look for ripe merlot wines with higher alcohol concentrations between 13.0 and 14.5 percent.
- Cabernet sauvignon grapes generate high alcohol contents between 12.5 and 15.0 percent.
Official Tolerance Variation for Still and Sparkling Wines
Official tolerance for variations in wine content is limited to 1.0 percent on wines that have more than 14-percent alcohol. The rules allow variances of 1.5 percent on wines with lower alcohol content. Consumers will find that many wines are labeled at 12.5 percent to take advantage of the broadest acceptable range of alcohol contents for wines.
How Vintners Control Fermentation
Vintners control fermentation by the amount of sugar in the must and fermenting temperature. Depending on the type of wine, vintners determine when grapes have ripened to the proper degree of ripeness for the desired sugar content before harvesting the grapes. Sugar may be needed for wild grapes, but European grapes seldom need added sugar. Wines continue to ferment until the sugar is converted into alcohol. Diluting the wine with water might be necessary for young, acidic grapes.
Winemakers never follow a strict formula but continue making adjustments throughout the fermentation process. Alcohol content affects aroma and taste in critical ways, and the sugar content of the grapes determines alcohol content. Vintners test wine regularly and add water, sugar or fruit juice to control alcohol level, taste and other characteristics.
Controlling temperature also controls fermentation rates. Yeasts produce different chemical compounds at certain temperatures. Some experimentation occurs in every vintage, which is why wine varietals’ quality varies so greatly based on alcohol content, type of grape, sugar content of the grape, fermentation temperatures, added ingredients and the fermentation tanks that are used.
- Winemaking generates heat, so temperatures change throughout fermentation and must be adjusted.
- The best temperatures for fermenting white wines range between 45-degrees and 60-degrees Fahrenheit.
- Red wines develop best when fermented between 70-degrees and 85-degrees.
- Lower temperatures reduce acidity and preserve volatile aromatics.
- Higher temperatures extract more color and tannins while limiting fruitiness.
The vintner blends science, skill and artistry to produce the best wine possible from each fermentation, so variations in quality and specific alcohol content will always occur even within a vintage.