What is Sodium Tripolyphosphate Doing in Your Fish?
By Marie Logan
Seafood lovers beware: there’s a chemical that threatens to deceive you about the freshness of your flaky fillets of fish. You might be paying more for seafood that contains this chemical, because it can increase the weight of the products to which it’s applied. Worse, you might not even know it’s there, because labeling of this potentially toxic chemical is not mandatory in the U.S.
So what is it? It’s an additive—called sodium tripolyphosphate, or STPP for short—and it is used to make your seafood appear firmer, smoother and glossier. Seafood manufacturers may soak your seafood in a quick chemical bath of STPP in order to achieve these effects. Some of the more commonly “soaked” seafood items include scallops, shrimp and anything filleted that’s very flaky—like hake, sole or imitation crab meat. (For those of you following food safety news, this is similar to the spraying of carbon monoxide on red meat, which can make older meat appear fresher than it is.)
If seafood is soaked for too long in an STPP bath, it may absorb more water, which means you’ll pay more for the product by the pound because the excess water makes it weigh more. A product may have been “soaked” with STPP if a milky white liquid oozes from the fish as you cook it, and it may also deflate in size a bit.
In large quantities, STPP is a suspected neurotoxin, as well as a registered pesticide and known air contaminant in the state of California.
How can one steer clear of STPP? Ask at your market or fish shop if the scallops or shrimp you’re being sold are “dry.” You can ask the same thing of waiters at seafood restaurants—they should have an understanding of the topic. (In industry-speak, “wet” fish means a product has been soaked in phosphates.) You can also check labels of packaged products, which may list STPP as an ingredient. Unfortunately, it’s not mandatory for companies and sellers to do so.
Remember, consumers have the power. Start wielding yours today! Find out where the fish you’re ordering comes from, and how it’s produced, to help influence your local food system.
Read up more on STPP in our fact sheet, “What’s on Your Fish?” As always, if you have any questions, please post them here in our comments section and we’ll do our best to respond in a timely manner.