This sheen is usually caused by bacterial decay, but not always. The chemical additive tripolyphosphate (nickname "tripoly" in the trade) is sometimes the culprit, especially when it's used excessively by overzealous fishermen and seafood processors. The method is simple: The seafood is soaked for several hours in a tripoly solution. The resulting chemical reaction retards the water loss that occurs naturally in protein tissue when a life form dies. Protein tissue loses water during the postdeath stage because its molecular structure contracts, decreasing its water retention ability. Tripoly raises the tissue's PH factor, causing the protein's molecular structure to unfold, thereby increasing its ability to bind water.
Money is the obvious reason the fish industry wants to curtail water loss. If a product weighed 10 percent more when the merchants caught or bought it then when they sell it, a lot of potential profits go down the drain, literally.
The less obvious reason is also money-related. Tripoly not only does its job in eliminating water loss but gives the industry a generous bonus. The chemical actually increases the net amount of water in the seafood by 5 to 10 percent. The tripoly user can therefore increase the amount of seafood he has to sell without catching or buying more seafood. In essence, the seafood merchants are selling water.
Seafood advertisers argue that the tripoly process makes frozen seafood more succulent that it would other wise be. That's true, to some degree. What they don't tell you is that the tripoly treatment can give shrimp a mushy texture, soapy flavor, and - as mentioned earlier - a slimy coating when overused.
The use of these additives has raised at least two health questions. Sodium watchers are concerned because tripoly sometimes comes in forms like sodium tripolyphosphate. Moreover, phosphates can decrease the ability of bones to acquire essential calcium, a condition that can lead to osteoporosis.
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