A weak tricarboxylic acid, citric acid is a naturally occurring organic substance. It is primarily used as an acidifier in biochemistry, and as a flavoring and chelating agent when added to foods and beverages. Citric acid is produced on an industrial scale at a rate of more than 1 million tons per year, and has been produced industrially for use in the food and pharmaceutical industry since the early 20th century. As a food additive, citric acid prevents sucrose from crystallizing in suspensions such as caramel or caramel syrup, and in frozen substances such as ice cream to emulsify fats and prevent lipid separation. Citric acid also makes an excellent cleanser due to its function as a chelating agent, and it is the cleanser of choice when descaling lime deposits in boilers and evaporators. Furthermore, citric acid is also used in lower concentrations in cosmetic products such as facial skin peels.