category: food technology: food chemistry

Acids, de.: Säure

Acid is a chemical compound which may donate a hydrogen ion to another compound. These ions have the chemical symbol H₊. Where this reaction occurs in water (H2O) oxonium ions (H3O₊) are formed and the pH value goes down. Very generally spoken, an acid is the counterpart to a base.

Properties of acids

In relation to foods and their preparation acids have the following properties:

• Curdle proteins
• Taste sour in watery solution
• Form bases with water and salts
• Citric acid and acetic acid may be identified by their smell
• Acids are corrosive. They especially corrode base metals and limescale. Strong acids also corrode clothes and skin.
• Acids may be diluted with water. This makes them weaker.
• At room temperature acids may be solid (i.e. vitamin C), liquid (i.e. hydrochloric acid) or gaseous (i.e. carbon dioxide).

Vinegar is acetic acid solved in water. It has been known since antiquity. Hydrochloric acid, nitric acid and sulphuric acid among others have been known since Medieval times.