Titratable acidity (TA), a.k.a total acidity, measures the total acid concentration in a food. In some food systems, food acids play an essential role in determining the flavour (sourness), colour (pH sensitivity of some compounds e.g. anthocyanin) and microbial stability. Most food acids are usually organic acids. Table 1 lists some common food acids. Nonetheless, some food products do contain inorganic acids such as carbonic acids and phosphoric acid which can serve as the predominant acids in these food products.

 

As food systems are generally very complex, kerb cycle derivatives, fatty acids, and amino acids present can all contribute to the total acidity of the food. Titration lacks the ability to distinguish them and therefore, it is essential to note titratable acidity values in terms of the predominant acid. pH measures the amount of free hydronium ions (H3O+) in the system. Organic acids partially dissociate to form H+ and its conjugate base A-. In aqueous solutions, the hydrogen cation combines with water to give the hydronium ions. Thus, these free hydronium ions are quantified by the pH term (active acidity). 

 

HA ⇌ H+ + A-

H+ + H2O → H3O+

 

The buffering system of foods results in the suppression of the dissociation of food acids. Therefore, it is important to both quantify the titratable acidity and the pH of food systems.