The most versatile and widely used organic acid in foodstuffs,
citric acid is a colourless, crystalline organic compound, belonging
to the family of carboxylic acids.
It is present in practically all plants, and in many animal
tissues and fluids, but it is in particularly high concentrations
in lemons and other citrus juices and many ripe fruits.
First isolated in 1784 from lemon juice, by the Swedish chemist
Carl Wilhelm Scheele, citric acid has been used as a food additive
for over 100 years.
It is normally manufactured by fermentation of cane sugar or
molasses in the presence of the fungus Aspergillus niger, but
it can also be obtained from pineapple by-products and low-grade
Its use as a food additive is wide and varied - as a synergist
to enhance the effectiveness of other antioxidants; as a sharp-tasting
flavouring; as a sequestrant in foods it combines with the naturally
occurring trace metals to prevent discolouration and in wine
production it combines with free iron to prevent the formation
of iron-tannin complexes which cause cloudiness; in brewing
to reduce excess losses of sugars from the germinated barley;
to create an acidic environment to discourage the growth of
certain bacteria, yeasts and moulds and in cheese making it
produces a faster and more consistent method of producing the
necessary acidic environment for the enzyme activity than the
traditional souring by lactic acid caused by bacteria.
Because of this versatility it can be found in a wide range
of products, including non-alcoholic drinks, bakery products,
beer, cheese and processed cheese spreads, cider, biscuits,
cake mixes, frozen fish (particularly herrings, shrimps and
crab), ice cream, jams, jellies, frozen croquette potatoes and
potato waffles, preserves, sorbets, packet soups, sweets, tinned
fruits, sauces and vegetables and wine.
Recorded problems are that it can be a local irritant and in
large amounts can cause teeth erosion.
However there have been erroneous reports that it is a major
cause of cancer. It is thought that this has been brought about
by misunderstanding and confusion over the word Krebs.
Citric acid is one of a series of compounds involved in the
physiological oxidation of fats, proteins, and carbohydrates
to carbon dioxide and water.
This series of chemical reactions, which is central to nearly
all metabolic reactions and the source of two-thirds of the
food-derived energy in higher organisms was discovered by the
German-born British biochemist Sir Hans Adolf Krebs. He actually
received the 1953 Nobel Prize for Physiology or Medicine for
the discovery, and as well as being known as the tricarboxylic
acid cycle (its correct name), it is also known as the citric
acid cycle or the Krebs cycle.
Hence, citric acid is fundamental to the Krebs cycle and Krebs
is the German word for cancer!