2918.15 - Salts and esters of citric acid:

Category 2918.15 encompasses salts and esters derived from citric acid. Citric acid is a weak organic acid found naturally in citrus fruits, widely used as a food additive (acidulant, flavoring, preservative) and in industrial applications. Therefore, this classification covers various chemical compounds formed when citric acid reacts with bases (salts) or alcohols (esters). Examples include trisodium citrate, dipotassium citrate, and various citrate esters, all of which retain the fundamental citric acid structure but possess altered chemical properties due to the presence of the salt or ester group.

This category is distinct from its siblings, such as lactic acid (2918.11) or tartaric acid (2918.12 and 2918.13), by virtue of its specific chemical origin. While all fall under the broader heading of carboxylic acids with an alcohol function, the defining characteristic here is the citric acid backbone. For instance, while 2918.14.00.00 covers citric acid itself, 2918.15.00.00 specifically covers its derived salts and esters.

Within 2918.15, the subcategories provide for further refinement. The most prominent subdivision is often dedicated to specific, commonly traded salts like sodium citrate (2918.15.10.00), which has extensive use in food and beverage industries. The "Other" category (2918.15.50.00) serves as a residual category for any remaining salts or esters of citric acid not specifically enumerated, ensuring comprehensive coverage for all such derivatives.