Titratable acidity (TA) is a measure of the tartaric acid content in the grape, measured by neutralising a set amount of juice with an accurately measured alkaline solution. Use the same berries for determining TA that you used for determining sugar content.
Jon Pollard at Gusbourne Estate, UK, recommends picking and testing a minimum of 6 bunches per varietal-clone combination for ripeness, and increasing that number based on the variability within a varietal-clone block.
The Sectormentor Ripeness Indicator allows you to instantly visualise how acidity and sugar is changing, as most of the time ripening isn’t linear. There are often clear trends for different varietals and clones over multiple years, despite varying weather conditions.
The balance between acidity and sugar is key when judging the quality of grapes. From veraison, and as your grapes are ripening, take weekly Brix and TA measurements. You will see the values gradually moving towards an optimum, with the TA level dropping and Brix increasing.
It can be good practice to let the grapes hang after they first reach this optimum. That is part of the art of winemaking, and all depends on how quickly the ripening happened – was there a short heat wave, meaning the grape flavour isn’t fully mature? This ripening process can be easily visualised alongside grape pH using theRipeness Indicator charts on Sectormentor.
