Excipient (pharmacologically inactive substance)
What is it?
Sodium tripolyphosphate, STPP, is a chemical often used to soak seafood so that it will appear more firm and glossy. It is also known as pentasodium salt or triphosphoric acid. STPP is also an ingredient in detergents and soaps. Most gel, liquid, tablet, and powder forms of both laundry and dishwasher detergent contain STPP. As a food, it is generally regarded as safe, but large ingested amounts of the product can be toxic.
 FDA. Database of Select Committee on GRAS Substances (SCOGS) Reviews. Sodium tripolyphosphate. Accessed March 3, 2015 at http://www.accessdata.fda.gov/scripts/fcn/fcnDetailNavigation.cfm?rpt=scogsListing&id=323