In recent years, you might have noticed that some wines that were previously 12 percent alcohol are now weighing in at 14 to 16.5 percent. What's going on? Some winemakers are allowing grapes to ripen on the vine longer to produce wines with more intensity (just like a tomato on the vine, a grape's flavor gets sweeter as it ripens). The grape sugars present at harvest determine the alcohol content that the finished wine might have. In short, the riper the grape, the higher the alcohol level in the wine.