What is pH
pH is the measurement of the concentration of free hydrogen ions in a liquid. The pH of pure water is 7. Liquids with a larger concentration of hydrogen ions than water are acid and have a pH value less than 7. Liquids with a lower concentration of hydrogen ions on the other hand, are base and have a pH value higher than 7. The pH scale runs from 1 to 14.

Can I measure the pH instead of the acidity of the must
No! In winemaking, the acidity is the representation of the amount of grams of acid in your wine/juice, usually expressed in grams of tartaric acid per litre. This can only be measured with a special indicating solution like Vinoferm blue indicator. You can, however, use a pH-meter in combination with the blue indicator: instead of adding blue indicator until the colour turns blue, add blue indicator until a pH of 7.00 is obtained. This method is more accurate and gives better readings for, amongst other things, red juices! The combination pH-meter, blue indicator and an automatic burette is a professional set-up for accurately measuring acidity.