If you’re around winemakers at harvest, you’ll inevitably hear someone say the word Brix. Pronounced “bricks,” it’s an estimation of the sugar content of grape juice or fermenting wine.
It originated in the 18th century when German scientist Adolf Ferdinand Wenceslaus Brix created a set of standards to accurately measure the sugar (or sucrose) content of liquids. These guidelines are still used in the food and beverage industry today.
The measurement is referred to as “degree Brix,” abbreviated °Bx, where each degree equals 1 gram of sugar per 100 grams of liquid. So, you might hear a winemaker say, “I harvested at 23 degrees Brix” or simply, “23 Brix.”
Vineyard workers and winemakers measure Brix for an array of reasons.
As harvest approaches, winemakers use Brix as a rough evaluation of grape maturity.
“Testing for Brix is fast, and it has the strongest correlation to ripeness of any of the factors that we look at,” says Josh Maloney, who consults for a number of Washington wineries.
Winemakers target a specific range based on variety, region, vintage and house style. Sparkling wines might be picked as low as 17 or 18 Brix, white wines generally 20 to 24 and red wines 22 to 26, though higher numbers are possible. As Brix approach their target range, winemakers know it’s time to taste grapes and think about when to pick.
“I usually don’t start getting serious about picking until I hit about 24 or 25 [Brix],” Maloney says of his red wines. “I get nervous when it gets above 26. So, it’s a fairly narrow window.”
Determining Potential Alcohol
Once grapes are harvested, Brix measurements serve a different purpose.
“It gives us a pretty good reflection of how much sugar is present and, therefore, the potential alcohol of the finished wine,” says Sabrina Lueck, interim director of winemaking at the Institute for Enology and Viticulture at Walla Walla Community College.
As grape juice ferments, yeasts convert sugar into alcohol. A simple rule of thumb is Brix multiplied by 0.6 equals potential alcohol, though the actual conversion rate can vary between 0.55 to 0.65. So grapes at 24 Brix, for example, would be expected to have a potential alcohol around 14.4%. Knowing this aids winemaking decisions.
“It tells me if there might be some adjustments that need to be made,” says David Merfeld, winemaker at Northstar Winery in Walla Walla, Washington.
Potential adjustments include chaptalization, or adding sugar during fermentation to increase potential alcohol in a process. This tends to be done in some cooler regions or vintages.
Alternately, in warmer regions or vintages, winemakers might add water to lower potential alcohol, which is referred to as “watering back.” The overall goal is to ensure the wine is balanced.
After crushing grapes, winemakers check Brix daily to monitor fermentation. As yeasts convert sugar to alcohol, Brix drops, slowly at first and then more quickly.
If one is fermenting to dryness, as opposed to leaving residual sugar, Brix readings ultimately go below zero. If Brix stalls before a wine is dry, that means yeasts have stopped converting sugar to alcohol. This is referred to as a “stuck fermentation.”
“If I go two or three days and the Brix hasn’t changed, there’s a problem,” says Merfeld.
How to Measure Brix
There are three tools winemakers use to measure Brix. The first is a refractometer, a device that leverages light refracting differently in a liquid based on its density. Most of the density in grape juice comes from sugar.
“It can only be used before fermentation, but it’s fantastically convenient and is a good tool in the vineyard,” says Lueck.
The second is a hydrometer, used once juice is fermenting. This is a glass tube with a lead weight on the bottom. How high the tube floats reflects density and, therefore, sugar content.
The last device is a densitometer, which measures density by causing a juice sample to oscillate. This is by far the most expensive of the three. Basic refractometers and hydrometers cost about $20; densitometers can run upward of $3,000.