Which compound is the main acid in lemons and limes?

Citric acid is the main acid responsible for the tart taste of lemons and limes.

Citric acid is an organic compound with the formula C₆H₈O₇. It occurs naturally in citrus fruits and participates in the citric acid cycle, a central series of reactions that helps cells release energy from nutrients. The compound is also produced commercially through fermentation, commonly using the fungus Aspergillus niger.

Food manufacturers use citric acid as an acidity regulator, flavoring agent, and preservative. It can also bind certain metal ions, a property called chelation, which helps explain its use in cleaning products and industrial processes.

Citric acid is sometimes confused with vitamin C, or ascorbic acid, because both occur in fruit. They are different compounds: citric acid mainly contributes sourness, while vitamin C is an essential nutrient involved in collagen formation and other biological functions.