As harvest approaches (way too quickly), we thought it might be interesting to describe the process in a manner that might require you to know some basic vineyard and winemaking terminology. So here are some things that you might hear a vineyard manager say around harvest, followed by a layman’s definition.
Brix
Brix (pronounced like “bricks” here in America) is a measurement that is roughly equal to the percent of sugar within crushed grapes or grape juice. Welch’s Grape Juice is probably about 20-22 Brix, which is very sweet. I might tell our winemaker “Hey Mike, our Pinot Noir hit 20 degrees Brix today.” What I’m telling him is that the grapes are roughly 20 percent sugar, and are getting close to needing to be picked. Champagne and sparkling wine is commonly picked around 20 Brix, most French pick at between 21-23 Brix, and high-end New World growers often get 23-25 Brix. An easy (if not oversimplified) method of determining potential alcohol in grape juice (if one wants to know how much alcohol will be in the final wine) is to divide the Brix in half and add a percentage point and a half. So for instance 24 Brix Pinot Noir grapes will make wine around 13.5% alcohol (24 divided by 2 = 12 + 1.5 = 13.5 alcohol).
pH / Total Acidity
pH is a measure of hydrogen ion activity (acidity) within a solution. Grape juice is quite acidic—and has a fairly low pH. Simplified, the lower the pH, the more acidic the solution. Solution with a pH under 2 can easily injure or even burn. Water has a pH around 7, egg white around 8, grape juice runs from about 2.5 (very unripe) to over 4.0 (very overripe). We like to pick white grapes at about 3.2-3.3 pH and red grapes (Pinot Noir specifically) around 3.35-3.4 pH. One might imagine that it’s easy to decide when to pick—wait for the sugar to hit 24 degrees Brix and the pH to hit 3.2-3.4. Unfortunately, it’s not that easy. Just because the numbers are right doesn’t guarantee that the grapes are truly physically ripe. pH is often tricky. Even though you pick at a certain pH, the final pH of the wine will be different because of chemical changes that occur during primary and secondary fermentations. These numbers (pH and Brix) are rough parameters for harvesting fruit—many vineyard managers use their own palate to judge ripeness of fruit (they taste the grapes) and some actually have expensive equipment that can measure ripeness by describing the qualities of phenolic compounds in the grapes. Measuring Total Acidity (which is tested by finding how many grams of acid are in a liter of grape juice) is considered a more accurate (and more lab-intensive).
Phenolic Compounds
Without getting too technical, phenolics are compounds within the grape skins: pulp and seeds that provide flavor and complexity in the wine. Some phenolics cause red wines to have deep coloration (anthocyanins, commonly referred to as tannins), others may cause a white wine to smell floral (monoterpene), or some might be unwanted. An example: grapes that have had no sun exposure but still contain high levels of pyrazines, which smell vegetal, and have an odor something like green bell pepper (methoxypyrazine). The trick in winemaking is to keep the juice of red wine varieties in contact with the skins just long enough to extract the perfect balance of phenolics without going too far. Wines described as “highly phenolic” can be a bit astringent (from extracting too many seed, skin or stem phenolics) and often lose elegance and balance. Most winemakers use their own smell and taste skills to judge how long to keep red wines in contact with the crushed skins. White wine is most often pressed the same day it is picked, and contains only the phenolic compounds pressed into the juice. Setting the pressure inside of the press can influence quality and concentration of phenolic compounds in white wine.
Of course there are other factors to be taken into consideration when deciding on a picking day. Everything from impending rain, scorching heat, flocks of birds, grape skin color, labor availability and the color of the seeds influences the final decision to pick.
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