Sodium Citrate is the sodim salt of Citric acid commonly known as sour salt. Like citric acid, it has a sour taste. Like other salts, it also has a salty taste.
There are three types of sodium citrate: Monosodium, Disodium, Trisodium. Most sodium citrate used for food is the trisodium form.
Sodium citrate is mainly used as a food additive, usually for flavor or as a preservative. It gives club soda both its salty and sour flavors. It reduces the acidity of foods, so it allows spherification with strongly acidic ingredients. Sodium citrate is also used as an antioxidant in food as well as sequestrant. It dissolves easily and acts instantaneously.
Sodium citrate is also used as as emulsifier to make constructed cheese, a smooth and melty cheese but with the flavor of aged cheese.