Napa Valley Wine Radio

Question from Mark: Hi Nancy, What creates a higher alcohol level in wines. Apparently they’re higher in alcohol now then a few years ago.

Answer: Hi, Mark! Thanks for writing!

The alcohol comes from the sugar in the grapes. Fermentation is a natural chemical reaction in which yeast, either added or native, consumes the sugar and converts it to heat, carbon-dioxide gas and alcohol. You can figure the conversion rate to alcohol is between 50 and 60%, depending on the yeast.

The alcohols have been climbing over the past few decades for a few reasons. The biggest one is that winemakers are inclined toward a longer “hangtime” now than in the past, which just means they’re letting the grapes hang on the vine longer and get sweeter than they did in years past. They are waiting for ripe flavors and good seed maturity. The fear is that if they don’t wait long enough the wine will display “green” characteristics.

Plus, winemakers are currently rewarded for producing big, ripe, fruity wines. Even wines from cold-climates, where it’s harder to get the sugar, are often higher in alcohol these days. Big alcohols can give the wine more body and a sense of richness and lately many European brands have been mimicking California-style wines to score big with powerful wine writers.

Aside from harvest decisions we have younger, healthier vines now because we did so much replanting during the phylloxera era in the ’80s and 90s. The vigorous vines are more efficient at converting sunlight to sugar. Another factor is that the yeast strains we use have been “cleaned up” over the last few decades and have a higher conversion rate.

There’s a great deal of study and discussion taking place in the industry about extended hangtime and the associated higher alcohols, so it will be interesting to see where it all takes us.

I hope that helps! Cheers! Nancy