Acids

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Acids are substances which release hydrogen ions (positively charged hydrogen atoms, i.e. H+) when they dissolve in water, or release hydrogen gas when dissolving metals, or react with bases to form salts. From a theoretical standpoint, pH is the logarithm to base 10 of the reciprocal concentration of hydrogen ions, or single positively charged atoms. In practice, it is measured on a scale from 0 to 10, based on standard solutions. Common acidic foods include lemon juice (citric acid) with pH of 2.1, weak wine vinegar (acetic acid) a pH of 2.5 and yoghurt (lactic acid) a pH of 4.0. Most foods are acidic or neutral; they are usually used in their natural form, but sometimes are used as pure chemicals, e.g. citric acid or tartaric acid.

Acids are vital to human bodily functions. For food biology, acidic foods are important for:

In flavouring, adjusting the level of sourness is a crucial last minute task of cooking, so adding a twist of lemon or a dash of vinegar enlivens a meal. On the other hand, sugar does not neutralize acidity, so you get a pleasing sweet and sour flavour in your mouths, so essential to Chinese cuisine.

Associated Pages

Further Reading

  • Davidson, A. (1999) The Oxford Companion to Food, Oxford University Press. ISBN 0192115790.
  • Stobart, T. (1981) The Cook's Encyclopedia: ingredients & processes, Harper & Row. ISBN 0060141271.