pH and Titratable Acidity

Abstract

Titratable acidity and pH are two interrelated concepts in food analysis that deal with acidity. Each of these quantities is analytically determined in separate ways and each provides its own particular insights on food quality. For example, while pH is important to assess the ability of a microorganism to grow in a specific food, titratable acidity is a better predictor than pH of how organic acids in the food impact flavor. Unlike strong acids that are fully dissociated, food acids are only partially ionized. Some properties of foods are affected only by this ionized fraction of acid molecules while other properties are affected by the total acid content. This chapter focuses on the principles and procedures involved in measuring pH and titratable acidity. pH, which is the negative log (base 10) of the hydrogen ion concentration, is measured with a pH meter and the millivolt is converted to pH using the Nernst equation. Titratable acidity, which measures the total acid concentration in a food, is determined by titration of intrinsic acids with a standard base. The concept of Brix/acid ratio is covered in this chapter, since the perception of a tart flavor caused by organic acids is strongly influenced by the presence of sugars.