Determining Titratable Acidity with Sodium Hydroxide

Using Phenolphthalein Indicator Solution

Follow these steps to determine the Titratable Acidity (often just referred to as TA) in your must or wine.

  1. Add a known amount of grape juice to a beaker (usually 10 or 15 milliliters).
  2. Add additional water if the juice is rather dark. The amount of water you add is not critical, adding water does not change total amount of acid in your sample. Do not, however, add more water than 5 times the amount of juice.
  3. Add about 5 drops of phenolphthalein. Phenolphthalein is an indicator that is clear when it is in a solution that is acidic, but will change to a purplish color when that solution becomes neutral to basic.
  4. Add 0.1N NaOH (1/10 Normal Sodium Hydroxide) until the solution starts to turn pinkish and stay pinkish then note the amount of NaOH used for the titration. Make NaOH addition using a pipette graduated in milliliters. A 10 ml pipette works well.
  5. Use the following formula to determine the TA of your wine or must. TA = (Number or milliliters of NaOH / Number of milliliters of juice) X 0.75 The units for the TA in this calculation are: Number of grams of tartaric acid per 100 milliliters of juice.

Using a pH Meter

A pH meter substitutes for the color endpoint. When sodium hydroxide is added to wine, it increases the pH. Standard solution, usually at 0.1 N, is added until the pH meter reads 8.2. Follow these steps to determine the Titratable Acidity (often just referred to as TA) in your must or wine.

  1. Calibrate the pH meter using a two point calibration. The most common buffer solutions used for calibration are pH 7 and pH 4 but pH 10 is also available. Our pH meter has two set screws with one marked pH 7 and the other pH 4 or 10. Fresh pH buffer solutions are important to assure accuracy in the calibration of the meter.
  2. First, calibrate with pH 7 buffer because this is a weaker solution. If the meter does not read pH 7 with the pH 7 buffer, we turn set screw marked pH 7.0 to attain 7.0.
  3. Then calibrate with the pH 4 buffer solution turning the set screw marked pH 4, or whatever method used for your meter.
  4. Add a known amount of grape juice or wine into a beaker (usually 10 milliliters).
    Place the pH meter into the solution. At this point you can take a reading of the pH of the must or wine.
  5. Add 0.1N NaOH (1/10 Normal Sodium Hydroxide) to the solution until the pH meter reads 8.2. In our set-up, we have a stand that supports a 10 ml burette with a stopcock on the bottom of the burette. The burette is calibrated in 0.1 increments. When the stopcock is opened, the solution is allowed to flow into the beaker. Closing the stopcock stops the flow of solution and allows a reading from the burette of how much solution has been dispensed. As the solution pH rises to around a pH of 6.0, changes occur faster so be careful as you pass pH 7.0 on your way to pH 8.2.
  6. Use the following formula to determine the TA of your wine or must. TA = (Number or milliliters of NaOH / Number of milliliters of juice) X 0.75 The units for the TA in this calculation are: Number of grams of tartaric acid per 100 milliliters of juice.
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One Response to Determining Titratable Acidity with Sodium Hydroxide

  1. Gin says:

    A reader has posed a question: Do you find that “TA pH Meter Method Using NaOH 0.1N” on your website to be reliable, or comparable to the Vinmetrica TA method?

    SHW member Don Koehler responds to the inquiry:
    If your pH meters and electrodes are properly maintained and then calibrated using fresh pH buffers at pH 7 and 4, the methods should give comparable results. Use the same meter all the time and do not jump back and forth between meters if you have both.

    I have several friends that use the Vinmetrica and are satisfied with its performance. The Vinmetrica does a lot for you, especially with the SO2 and M-L capabilities, in addition to pH and TA. I have used a Checker Plus for several years and find it works well, too. (always get the “Plus”) It works good for a couple of years and when it starts to fail, I get a new one. (Amazon, $45-$50)

    Always store the probes correctly in electrode storage solution, and cleaning once in a while (esp. the Checker) helps stability in calibrating and reading, too. A stir plate and stirring bar are convenient to have for titrations. I think Vinmetrica supplies that with its instrument. I even use the phenolphthalein method in new wines at crush which are usually not too dark to see the color change, going towards red, greenish, and then finally almost black at the end point (in some red wines). The pH meter method works too, but it is easy to overshoot the end point a bit, but usually not enough to change the TA calculation much. (October 6, 2019)

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