Food additives are introduced to a range of foods in order to improve their nutritional value, their colour, flavour or texture, or to aid in their preservation. A system of labelling known as E numbers is used to classify food additives. Food additives with E numbers between E330 and E340 represent a group of antioxidants that also have the ability to act as buffers.
Buffers in Food
Buffers are chemicals that maintain the acidity of the food at the appropriate level. This allows flavour and appearance to be maintained and is also critical to the preservation of a number of processed foods. The acidity of food is a measure of the concentration of hydrogen ions within the food product. Additives that act as buffers usually comprise metal salts corresponding to a weak acid found naturally within the food to be preserved. For example, the addition of sodium citrate to a food containing citric acid will create a buffer solution. In the buffer solution, the weak acid and its salt exist in equilibrium, and this allows them to resist changes in acidity by reacting with any extra hydrogen ions to remove them, or by generating new hydrogen ions when needed. This maintains a constant acidity within the food product.
Sodium, Calcium and Potassium Citrate
The citrate additives are widely used antioxidants and buffers that have a range of applications. They are all capable of reducing the chemical reaction that causes the discolouration of fruit, so a member of this group of chemicals is often the additive of choice in fruit products. Sodium citrate (E331) is a versatile food additive used as a buffer principally in jams and jellies. Potassium citrate (E332) is another antioxidant and buffering additive that is found in a number of food products including cakes and biscuits, cheese and jam. Calcium citrate (E333) is an important acidity regulator that is often used in carbonated drinks.
Monopotassium phosphate (E340) is principally used as an antioxidant, but it also has buffering capabilities. It is used in pudding products such as custard and milk powder and jelly mixes, and may be added to cooked meat. Monopotassium phosphate is an important ingredient in many sports drinks, as it provides potassium as an electrolyte, as well as offering a buffering action.
Potassium tartrate (E336) is obtained from grapes during the winemaking process. In addition to its buffering action, potassium tartrate also helps bread to rise consistently. It is used as a buffer in wine and bread production, and may also be added to fruit pie mixes.