Sodium tripolyphosphate (STPP) is a chemical that has many uses in industry, ranging from an ingredient in cleaning products to a food preservative. Also known by alternate names like pentasodium salt or
triphosphoric acid, the substance falls into the classification Generally Regarded As Safe (GRAS), which means that past use of the chemical has presented no risk to health. It can also be found in some paints and ceramic products, among other uses.
One of the common usages of STPP is as an ingredient in detergents and soaps. Most gel, liquid, tablet, and powder forms of both laundry and dishwasher detergent contain it. Its key function is that it allows surfactants, which are molecules that help dissolve surface dirt, to work at their full potential. The
chemical can also soften hard water for easier foaming and cleaning, and it helps prevent dirt from sticking to the surfaces of the object being cleaned. Many general household cleaning products, including surface and toilet cleaners, contain STPP.
Sodium tripolyphosphate is also used to preserve foods such as red meats, poultry, and seafood, helping them to retain their tenderness and moisture during storage and transport. Pet food and animal feed can also be treated with it, serving the same general purpose as it does in human food. STPP also has been used to help preserve the quality of drinks such as milk and fruit juices.
Because sodium tripolyphosphate can improve the appearance of seafood like shrimp and scallops, there is some concern that unscrupulous salespeople may sell products that are not fresh to consumers who cannot see the signs that the items have started to go bad. Although it cannot be used specifically for this purpose, this chemical also holds in water, making the seafood heavier and therefore more expensive. Some food quality experts recommend asking a fishmonger or other salesperson for seafood that has not been
treated with this chemical. Some stores will mark products that have not been exposed to STPP as "dry."
Sadly, there is FDA requirements to label foods with sodium tripolyphosphate, but several manufacturers have begun to do so. Even though deemed safe for ingestion, this is one chemical you want to avoid if you've experienced reactions due to eating frozen fish. Check for seafood products labeled as "dry" which means they have not been contaminated with the chemical. Food products labeled as "wet" have usually been treated with sodium tripolyphosphate.
STPP, is a suspected neurotoxin according to the National Institute for Occupational Safety and Health’s (NIOSH) Registry of Toxic Effects of Chemical Substances. Food-grade STPP may cause acute
skin irritation, and prolonged contact with skin should be avoided. STPP is listed on the U.S. Environmental
Protection Agency’s Federal Insecticide, Fungicide and Rodenticide Act as a registered pesticide and it is also registered as an air contaminant under California’s Occupational and Safety Health Act. The material safety data sheet lists STPP as toxic to the lungs with prolonged exposure having the potential to produce organ damage. This neurotoxin also has the ability to cause internal inflammation from those suffering from autoimmune diseases. Inflammation leads to painful flare-ups.