The pH of a food is the measure of that product's acidity or alkalinity. The pH-scale ranges from 0 to 14. A pH less than 7 is acidic, a pH of 7 is neutral and a pH greater than 7 is alkaline or basic. Our sense of taste can recognize only major differences in the pH within complex food systems. An acid product would taste sour, while an alkaline product would taste bitter. Some examples of acid foods are citrus fruits (e.g. orange, lemon, grapefruit), juices or yoghurt. Examples of alkaline products are egg white and baking soda.

Acidity regulators are used to alter and control the acidity or alkalinity on a specific level important for processing, taste and food safety. Inadequate control of the pH can result in the growth of undesirable bacteria in the product that could be a potential health hazard.

Examples of acidity regulators in the EU
Citric acid (E330) enhances the activity of many antioxidants, but is no antioxidant by itself. It is mainly used as an acidity regulator as well as aroma compound. In addition it increases gel consistency in marmalades and decreases enzymatic browning in fruits and fruit products.

Calcium acetate (E263) has several functions. It is used in some foods as a thickening agent (cake mixtures, puddings, pie fillings), but can act as a buffer in controlling the pH of food during processing, as a preservative to prevent microbial growth, and as a calcium supplement in pet products.

Fumaric acid (E297) is added to foods as an acidity regulator and flavouring agent. They are used in bread, fruit drinks, pie fillings, poultry, wine, jams, jelly.

Legislation
Acidity regulators are subject, just like any other food additive, to stringent EU legislation governing authorisation, use and labelling, Directive 95/2/EC of the European Parliament and the Council of 20 February 1995 on Food Additives other than Colours and Sweeteners. This legislation requires all added acidity regulators, as all food additives, to be declared on food packaging by their category with either their name or E-number.