Propylene glycol alginate (PGA) E 405 is an emulsifier, stabilizer, and thickener. Chemically, propylene glycol alginate is an ester of alginic acid, which is derived from kelp. PGA is commonly used in beverages including alcohol to provide a creamy taste. It is also a primary emulsifier in salad dressings. PGA is cold water soluble and it helps to stabilize foam.