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 How do I use an acid testing kit?

How do I use an acid testing kit?

Acid testing kits can help you know how much acid you are dealing with in your wine. Specifically, these kits are testing for tartaric acid. By testing the acid level in your wine, you are able to adjust it as you need to, but you can only adjust the wine so much otherwise you end up with a chalky flavor in your wine.

Be aware that these kits are only able to test acid up to 1%. Anything above that and the reading will be inaccurate. Unfortunately, the hot, dry summers in the past few years have caused the acid levels to rise significantly. The commercial wine makers in Minnesota are reporting acid levels around 1.25%.

If you question the results, call a local university’s agricultural department. A lot of schools test wine grapes and might be able to tell you what the level of acid is for you area.

We’ll tell you the procedure for taking a reading, how to adjust, and what are ideal acid levels for most wines made. Again, you are only able to adjust so much, so your wine might end up with a bite to it because of the poor growing conditions.

How to measure

  1. Using a plastic syringe, measure 15 cc of wine or juice into the test bottle. Note: Red wine samples may be measured into a larger clear glass vessel and sufficient distilled water added to the sample to dilute the color to a rose.
  2. Add three (3) drops of Phenolphthalein Color Solution to the test sample.
  3. Wash out the syringe and draw in 10 cc Sodium Hydroxide neutralizer.
  4. Add the Sodium Hydroxide slowly to the wine or juice sample. As the neutralizer is being added to the sample of wine or juice, agitate the cup until a slight color change is noted and remains.
  5. Continue adding the Sodium Hydroxide a very small amount at a time, agitating the cup with each addition, until a deep, dark color change is noted and an additional drop of neutralizer does not cause or affect the darker color.
  6. This indicates the end point has been reached.
  7. White wines will change to pink/red, red wine will change to a blue/grey/black.
  8. Each 1 cc of Sodium Hydroxide neutralizer required to attain the color change indicates 0.1% of acid expressed as Tartaric. If 5 cc of neutralizer is needed to attain the end point color change, the acid is 0.5%.
  9. Adjust the acid content of the wine to the desired level on the basis that 1 teaspoon of Acid Blend will raise the acid level of 1 U.S. gallon of must by 0.15%.
  10. Make certain that the Sodium Hydroxide and Phenolphthalein bottles are always kept tightly capped when not in use because both solutions will deteriorate through exposure to air.
  11. Wash and dry syringe and test cup after each use.

Adjustment

To adjust the acid levels in your wine follow these directions:

Increase:

  • 1/3 oz. (9.5 g) Acid Blend to 1 gallon of must raises the acid by 0.3%.
  • 1 oz. (28.3 g) Acid Blend to 6 gallons of must raises acid content by 0.15%
  • 4 oz. (113.4 g) Acid Blend to 36 gallons of must raises acid content by 0.1%

Decrease:

This is much more common for wine makers to have to do in America.

Use 2.5 g per gallon of Calcium Carbonate (precip. chalk) will lower acidity approximately 0.1%

Do not reduce acidity by more than 0.3 – 0.4% because your wine will end up with a chalky taste to it.

You are better off leaving the wine a little acidic then using a lot of calcium carbonate to reduce the acid.

Acid Levels

Listed below are the ideal acid levels for most types of wines.

  • Fruit Wines 0.60%
  • Red Grape Wines 0.65%
  • White Grape Wines 0.75%
  • Sherries 0.50%

The acid testing kit comes with everything you need to take several tests a year. It is best to take a test just before or just after you pitch your yeast. It is better to make the adjustment before the wine has a chance to ferment then later on in the process. However, if you forget, you can make adjustments all the way until bottling time. Chances are the adjustments won’t be as beneficial, but it can still help the wine.

How do I use an acid testing kit? PDF

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