What Affects Alcohol Percentage of Wine?

By The Wine Guys, Tom Marquardt and Patrick Darr


We were recently enjoying a bottle of Chalk Hill Estate Red, a delightfully rich blend of Bordeaux grapes, when the effect of alcohol began to hit us. Did we drink it too fast? Was it the lack of food? A quick look at the label gave us the obvious cause: 15.5 percent alcohol.


When we first wrote about wine in the 1980s, alcohol levels were generally 13 to 14 percent. Many wines, such as those from Germany, were far less alcoholic. In fact, French winemakers couldn’t get their grapes ripe enough and had to add sugar to unfermented grape must – a process called chaptalization – just to reach 12 percent. Global warming makes the wine a different place today.


It’s not that higher alcohol is bad. Alcohol gives wine body, but your body isn’t going to tolerate a few glasses of these heady wines without some impact. There will be a big difference in a breathalyzer if you and your spouse split a bottle of wine with 16-17 percent alcohol. All of which makes it odd that at a time when consumers are encouraged to cut back on alcohol and when low alcohol wines are gaining traction that top producers are doubling down on high-alcohol wines.


So, why do California wines have higher, brain-numbing alcohol today? There are lots of reasons.


Alcohol starts with sugar. Once yeast is introduced, the sugar is converted to alcohol. The more sugar, the more alcohol. Sweet wines, such as moscato and German riesling, have lower alcohol because some of the sugar is not converted.


Grapes harvested early will contain less sugar, but today Napa growers are picking grapes later to achieve phenolic ripeness. Along with that comes more sugar. This is particularly the case with cabernet sauvignon, which is one of the last grapes typically harvested. This movement is readily seen in the Department of Agriculture’s annual grape crush reports.

Since 1997, average sugar content in cabernet sauvignon never fell below 24 degrees Brix (a measure of sugar that equates to about 14.3 percent alcohol). In 2013, it hit a record 26.3 Brix, or about 15.6 percent alcohol. In 2018, it was a modest, average 25 percent.


Although winemakers are required to report the wine’s alcohol level on the label, they are allowed a one percent error margin. It is widely believed that alcohol is understated. Veteran winemaker Joel Aiken, whose Scattered Peak wines are around 14 percent alcohol, told us he privately tested the alcohol levels of many California cult wines and discovered that they were much higher than stated – as high as 16 percent.


A couple of things happened to launch this popular trend.


Global warming has some impact because warmer temperatures add more sugar to grapes, but more impactful is the location of vineyards. For instance, Central Valley has some of the highest temperatures in California and its heady zinfandels regularly hit 16-17 percent alcohol. Mendocino in northern California struggles for adequate sun. Other regions, such as the Sonoma Coast, are blessed with cooler nights and ocean breezes to give grapes a rest at night.


Also, in the mid-1980s, growers adopted Bordeaux standards and began to plant vines closer to together and on a trellising system that maximized ripeness. However, the tannins were too aggressive, so California growers delayed harvesting to soften the wine. Adjustments have since been made, but the ripeness and the resulting alcohol remains.


More influential to this trend is a shift in style that was provoked – and still rewarded – by renown wine critics. Robert Parker Jr. in particular awarded high scores to showy wines with more alcohol, ripe fruit and subdued tannins. Consumers loved the more approachable style, so winemakers delivered. It wasn’t long before cult producers – Screaming Eagle, Colgin, Abreu, Harlan Estate and more – were getting 100-point scores from Parker and selling their low-production wines for $500 or more. This shift in alcohol levels and style applies mostly to red wines, pinot noir and cabernet sauvignon in particular.


Although their style means the wines don’t require years of aging to be enjoyed, there is debate over whether they are suitable for dinner. Tannins – which make the mouth pucker – aren’t easy to swallow in a cabernet sauvignon aperitif but they marry well with a juicy steak. An extracted California pinot noir makes for a better dessert by itself than a match to delicate sauces at a gourmet dinner. The poor food pairing comes from a lack of acidity, which is needed to offset fat and sweetness.


Europeans don’t care much for this style of wine, although many of them did succumb to Parker’s influence to achieve better scores. We’ve noticed a widening gap between red and white wines from Burgundy versus those from California.


Said Daniel Daou of Daou Vineyards in Paso Robles, ““Asians and Europeans don’t like California wines – that’s a fact --because California wines don’t cut through the acidity of food. Jammy wines don’t do that.”


All of this should help guide you in choosing a wine. Know the alcohol levels in wine and assume it is understated before you embark on dinner out. Understand the impact of this style of wine on the food you intend to serve. If your food has body – beef or a hearty stew, for instance -- your wine should have body. If, however, the food or sauce is delicate – think Dover sole or duck – look for a delicate wine. Wines with high alcohol and bold fruit are not delicate.


Wine picks

  • Jean Dauvissat Vendage Chablis 2018 ($28). Dauvissat makes some of the best, most exclusive chablis in France. This moderately priced version draws chardonnay from several parcels and shows a good balance between the classic minerality and a richness that defies the often-austere character of chablis. Apple and lemon notes.

  • Gary Farrell Olivet Lane Vineyard 2019 ($45). From the Russian River Valley, this delicious and rich chardonnay unveils citrus and grapefruit aromas and stone-fruit flavors with a good dollop of toasty oak notes.

  • Cliff Lede Napa Valley Stags Leap District 2019 ($82). From the estate’s Poetry Vineyard, this wine – blended with a little merlot, cabernet franc and petit verdot – is rich and long in the finish with a velvet mouthfeel, ripe blackberry flavors, a touch of mineral and fine tannins.



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