The pH is a measure of how strong the acids are in relation to all of the other compounds in a wine or must. The lower the value, the more strongly acidic the sample will be; i.e: a pH of 3.3 will be more acidic than 3.9. In winemaking, most pH values will be between the 3.0 and 4.0 ranges, with most of the focus happening in the range of tenths between these two ends ("3._pH"). While the TA will tell you how much physical acid there is in the wine or must, the pH tell you how this acidity will be perceived.
How To Test pH:
You test the pH using a specialized tool called a pH meter
. The pH meter should be calibrated using a set of pH buffer solutions. Once calibrated, all that is needed to test the pH of wine or must is to insert the probe into the sample and slowly stir until the reading on the meter stabilizes. That's it!
Some Useful Info About pH:
- Unlike TA testing and adjusting, pH adjustments are not linear; if you add 1 g/L of acid to a wine or must you now have exactly 1 more g/L of acid in solution and a TA test will confirm this. However, if you add 1 g/L of Potassium Carbonate to a wine or must the reaction will vary from wine to wine and the pH will not shift in a linear, predictable fashion. This is why any attempt to adjust the pH should start with a bench trial!
- pH units are logarithmic; a pH of 3.0 is ten times more acidic than a pH of 4.0. So beware, a little shift goes a long way.
- The effectiveness and amount of free SO2 needed to protect our wines is directly tied to wine pH: lower pHs require less free SO2, and higher pHs require more free SO2 to achieve the same amount of protection. Note: at pH 3.8 and higher, it is not chemically possible to maintain the amount of free SO2 in the wine that is technically required to protect it. So, if your wine has a high pH, then we highly recommend adjusting the pH down (using tartaric acid).
Everything you need to know to get the most out of your pH meter can be found in MoreWine!s Use and Care of a pH Meter Manual
. In addition, complete information on adjusting pHs, conducting bench trials, and pH/SO2 management can be found in our Red Winemaking Manual
and our White Winemaking Manual