Here are some of our analysis results of our Cabernet Sauvignon 2012 grapes from the month before harvest to November, showing how the chemistry changes when grapes transform into young wine.
For the decision when to harvest, we follow the development of Brix (sugar content), pH, and TA (acidity). Picking the grapes at the right moment is important for creating a balanced wine
As soon as yeast is added to the grape must for primary fermentation, sugar is converted into alcohol and CO2. The Brix line went down, and the alcohol level went up to 13%. When fermentation is done, we stop measuring Brix/SG.
Malolactic fermentation (MLF)
After completion of the primary fermentation, we added a malolactic bacteria culture that converts tart-tasting malic acid (think green apples), to softer-tasting lactic acid. This process increases the pH and lowers the acidity. We had to make a small pH adjustment, allowing for a lower sulfite level to protect the wine against spoilage and oxidation.
While wine chemistry can be a lot of fun, frequent tasting remains the most important and rewarding aspect of wine making!