pH. A symbol representing the negative logarithm of the concentration of hydrogen ions (q.v.) in gram atoms per liter (q.v.) of a solution or mixture. It expresses active acidity (q.v.) or alkalinity (q.v.) on a scale with a range of values between 0 and 14, whose midpoint at 7 represents true neutrality. pH values below that point indicate higher hydrogen ion (H,) than hydroxyl ion (HO-) concentrations, i.e., an acid condition, whereas values above that point indicate a predominance of hydroxyl ions , or an alkaline condition. pH is an important control factor in biological and biochemical reactions. In baking, it plays a significant role in both yeast-raised and chemically-leavened bakery products, affecting both processing conditions and the quality of the finished products. Under practical conditions, a pH range of 4.7 to 5.3 is normal during the various stages of doughmaking. It may be measured colorimetrically by the use of indicator dyes (q.v.) that show definite color shades for specific pH values, or electrometrically by means of a pH meter (q.v.).