Napa Valley Wine Radio

Question from Dave: I always thought that the level of alcohol in a wine is dictated by the amount of sugar in the grape. Basically if you are producing a dry wine doesn’t the amount of sugar in the grapes dictate the percent of alcohol? I ask this because the wines in France are all in the 12 to 13 percent range. Is it because they harvest earlier not letting the sugar level in the grape get higher? Thanks, Dave

Reply: Hi, Dave! Thanks for writing! You are absolutely right. The alcohol moves with the sugar for dry table wines.

The main force at work here is climate. Here in sunny Napa Valley, when we complain, it’s often because there have been too many warm days. Heat sends the grape-sugar up and the acid down. On hot years the sugar may rise faster than the flavor matures. Since winemakers place a high value on flavor maturity, they may decide to wait for flavor development knowing that the resulting alcohol is likely to be a little higher than they wish (too much alcohol may feel hot on the palate and overwhelm the fruity aromas). That’s why the last three vintages have been such a blessing. The weather has been mild. Some viticulture professors believe that this may be the beginning of a trend, oddly enough, due to global warming.

Wine Refractometer Alcohol Tester

In France, and other famous European growing regions, the more common concern is lack of heat and the threat of rain. Their warm years are usually the best ones (recently 2003, 2005). Some regions permit sugar additions (regulated by the local wine laws) in order to bring the alcohol up (if the alcohol isn’t high enough the wine may lack body and won’t feel satisfying on the palate). Many regions have established minimum alcohol levels in order to qualify for AOC status, or the equivalent for their country. They worry about high acidity, we worry about low acidity. So, climate change is working in their favor, too. They’re even expanding the wine-grape plantings in southern England, believe it or not!

So, that’s a long answer to a short question, but I hope it helps. Cheers! Nancy