Citric acid anhydrous or monohydrate, the most widely used acidulant to give a sour taste in food and beverage, also acts as a preservative, PH buffer, antioxidant and chelating agent. The European food additive number for it is E330. China is the biggest manufacturer of citric acid in the world and exported around 1 million tons in 2019.

http://www.chinafooding.com/Citric_acid_anhydrous