How To Adjust The Level Of Acidity In Your Wine

HOW TO TEST & ADJUST THE LEVE LEVEL OF ACIDITY IN YOUR WINE By Dr. Frank Puzio Acid measurements can be measured and adjusted accordingly using titration and pH methods. Literature suggests that the total acidity endpoint of finished red wine should be in a range of 0.55 – 0.60% TA and have a pH of 3.4 – 3.6. Acid adjustment is one of the most important and most difficult decisions to calculate quantitatively. Accuracy of acid adjustment will have a significant influence on the ultimate taste of the finished wine and on pH. The right amount of acid helps provide a pleasing bite or tang to the finished wine. Low levels of acid produce bland tasting wines and high levels produce a harsh taste to the palate. Generally, California grapes are deficient in acid and an adjustment is required with the addition of a natural acid in grape called tartaric acid. There are also less dominant acids in grapes, malic and citric, but tartaric has the most influence on taste. Publications advise avoiding using acid blend products. Acid adjustments are advised prior to yeast inoculation/fermentation. When we measure total acidity it is expressed in terms of grams/ liter or percent. As an example, 6.5 grams/liter = 0.65%TA. When an acid level is derived from titration or from pH it is important to note that they do not measure exactly the same thing or correlate, but in the decision making process both methods are helpful. It is often stated that despite all the chemistry, personal taste is the ultimate variable. Some suggest adjust acid conservatively in the beginning before fermentation since minor adjustments can be made during subsequent stages. Since fermentation decreases acid levels during fermentation it is advised to reach a minimum target acid level of 0.70% and even as high as 0.80% if red wine is to be ultimately aged in wood. At this stage of my winemaking experience I will aim for an acid level of 0.75% prior to fermentation.

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MEASUREMENT OF TOTAL ACID Titration Method to Calculate Total Acidity (TA) grams/liter
Use a TA testing kit for this calculation. NOTE: 1ml = 1cc.
Boil 3 oz., approximately 90ml/cc of distilled H2O and place in a glass beaker or (Erlenmeyer flask). Exacting amounts of water do not influence the conclusion because water is void of acid and base.
Add exactly 15ml/cc of must/juice into the water.
Add 5 drops of phenolphthalein indicator solution and swirl to mix.
Using the syringe draw out 20ml/cc of reagent 0.1N sodium hydroxide (NaOH). If 0.2N is used, the endpoint is twice the amount of cc used. If possible use a burette w/ a stopcock apparatus to obtain more exacting values than with a syringe.
Against a bright background add the sodium hydroxide slowly while swirling continuously. Eventually the wine color turns to a constant grey bluish-green just prior to the endpoint. Continue to titrate slowly until the solution first turns a constant pink color.
Record the exact amount of NaCL used if possible to a .1 increment using a burette and stopcock.
The number of ml/cc used to reach neutralization is divided by 2.
If you used 12.5 ml/cc… 12.5 ÷ 2 = 6.25ppt of Tartaric Acid = TA of 0.625%
Finished red wine may be considered optimum at 6.5 grams/liter or 0.625% TA, however, due to fermentation influences eventual barrel aging we may decide our target TA should be 0.75%.
0.8 minus 0.625 = 0.125.

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Adjustment Standard: 18 grams of tartaric acid will raise the TA of 5 gallons of must by 0.1%






An increase of 0.1 = 18 grams of tartaric per 5 gallons. For our calculation, move the decimal point of 0.175 to the right = 1.75. 1.25 x 18 grams = 22.5 grams of tartaric acid per 5 gallons of must. My fermenters are 30 gallons each or 6 x 5 gallons. 6 x 22.5 = 135 grams of TA to be added per fermenter in this example Calculations can be double checked using the following table:

Using pH to Estimate Total Acidity With the titration method discussed subjective color estimates are sometimes difficult to estimate. pH measurement of acid is considered by some to be more accurate. Optimum pH of finished red wine is 3.3 – 3.6. Accuracy has a profound influence on final wine quality, it allows SO2 to be more effective as an antimicrobial agent, it enhances fruity esters, optimizes color, and has a very positive influence on the ultimate taste. Make note that a higher pH value is lower in acid. If the pH of the must after crushing is higher than 3.5 (less acidic) delay beginning yeast inoculation and fermentation until the acid level has been lowered (made more acidic) by adjustments with tartaric acid to lower the pH reading to 3.5. Provided compliments of

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Measurement of Total Acidity (TA) with pH meter
Measuring acidity in wine using a pH meter is very similar to the titration method but with a difference that does not rely on difficult to observe color changes to determine endpoint.
Add 0.2N NaOH (sodium hydroxide) 1-2 drops at a time until the pH meter reads 8.2. 8.2 is the same pH at which phenolphthalein changes color (to pink).
If 0.1N reagent is used, divide the amount of NaOH used in half.
Place a 15cc sample of wine in a small beaker or Erlenmeyer flask.
Fill syringe with 0.2N NaOH
Record the exact cc amount of 0.2N NaOH used to reach end-point neutralization. As with the titration method, for each cc of reagent used it equals 0.1% g/L TA. For example, if we used 6cc this equals 0.6% TA.
I used 0.1N NaOH, the cc’s used to reach 8.2 pH was 12 divided by 2 = 6 or .6%.
Follow the addition of tartaric calculations as outlined previously.
During fermentation there is sometimes a decrease in TA and an increase in pH. Monitor the pH during fermentation especially with red wines and add tartaric acid as needed to hold pH in line until fermentation is completed. PLEASE NOTE: This Primer Is Provided Free of Charge. Please respect the fact that this valuable document was put together by Dr. Frank Puzio, an avid homemade wine enthusiast, strictly for the benefit of other fellow wine makers to learn. Feel free to share it with your wine making colleagues as you see fit but don’t copy it and call it your own. If you learned something from this document and would like to pass on a comment or a word of thanks please email Scott “The Wine Making Guy” at [email protected] and he’ll be sure to pass it along to Dr. Puzio!

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