Citric Acid

It is a natural preservative and is also used to add an acidic (sour) taste to foods and soft drinks.

In biochemistry, it is important as an intermediate in the citric acid cycle and therefore occurs in the metabolism of almost all living things.

It also serves as an environmentally benign cleaning agent and acts as an antioxidant.

Citric acid exists in a variety of fruits and vegetables, but it is most concentrated in lemons and limes, where it can comprise as much as 8 percent of the dry weight of the fruit.