How to Determine Acid Levels in Making Your Wine
- 1). Pour a 15-ml sample of must or wine into a test tube. Your titration kit may have come with a plastic syringe for this purpose, which will be marked by milliliters to allow for precise measurements. Wash the syringe after measuring the wine, because you will need it again later.
- 2). Put three drops of phenolphthalein solution into the test tube. Stir or swirl the tube to distribute the phenolphthalein. This phenolphthalein is what will react with the reagent (sodium hydroxide) and cause the color change when you determine the acidity of your wine.
- 3). Draw 10 ml of reagent, or sodium hydroxide, into the clean plastic syringe. If you see air bubbles in the reagent, press the solution out of the syringe and begin again. There should be no bubbles in the liquid. Sodium hydroxide burns on skin and in eyes, so take precautions.
- 4). Drop 0.5 ml of the reagent at a time into the test tube and stir to combine it with the wine and phenolphthalein. As the reagent comes initially into contact with the wine, you will see a momentary color change. White wines will turn pink and red wines will become gray.
- 5). Stir until the color change goes away and the wine returns to its original shade.
- 6). Add another 0.5 ml of reagent and stir until the color subsides again. Repeat until the color change does not subside with continued stirring.
- 7). Look at the syringe and see how much reagent you used to make the color change permanent. Subtract the number of milliliters remaining in the syringe from 10 to determine how many you used.
- 8). Multiply the number of milliliters you used by 0.1 to determine the amount of tartaric acid in the wine. For example, if it took 7 milliliters for your white wine to stay pink after stirring, your wine's titratable acidity is 0.7 percent.
- 9). Perform the titration test three times to ensure accuracy, check precision and perfect your technique. It can be particularly difficult to tell the color change in a red wine, so keep testing until you are certain you have seen the change.
