Trisodium Citrate European food additive number E331. This ingredient is usually added together with citric acid to enhance flavor or reduce the PH level in food and drinks. Also, it can act as an emulsifier in cheese making. It is used as an antioxidant in food as well as to improve the effects of other antioxidants. It commonly refers to trisodium citrate (E331iii) when we talk about sodium citrate.