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Sodium Tripolyphosphate

Sodium Tripolyphosphate is a phosphate based food additive that is used for food application, especially during freezing Seafood.

Please read our notes on Glaze in this section itself, which details on how freezing causes suction of moisture from the product being frozen.

In order to ensure that the moisture content in the fish is retained, along with glazing and before freezing soaking of the fish is done. Soaking is an industry term and refers to the process of soaking the fish product in a mixture of salt, water, ice and STPP. This mixture causes the pores of the cells of the fish to open and fills the cells with water and salt helps in sealing the pores. Once it is frozen the water remains in the meat.This process results in significant weight gain for the product in the form of water accumulating in the cells. Now two things to remember. 1) Longer the duration of soaking higher the pickup (weight gain) 2) The more the meat (with out skin) is exposed the higher the pickup (weight gain). And a combination of both these factors can create fortunes for the processor and losses for the buyer.

Take this example. A Kg of fillet soaked in STPP mixture for 6 hours can give you a weight gain of about 40 percent increasing the weight to 1400 gms that a buyer may never realise. However the processor will sell all of the 1400 gms as fish meat while actually 40% is pure water.

When this meat is cooked and since by design cooking destroys the cell walls, the water in the cells comes out and gets evaporated in the process of cooking and there by resulting in low net yield as compared to an unsoaked product.

Realising this both US and EU have set limits on the STPP weight gain that a seafood product can have and Japan simply does not buy anything that is soaked.

All though soaking is good for the frozen product, since it retains the moisture in the product and keeps the meat tender, buyers have to be aware of the percentage weight gain before buying, else they will actually end up paying more for water than the meat.

Additional reading http://en.wikipedia.org/wiki/Sodium_triphosphate

The author of this article has actually interacted with the principal scientist of prayon (world leader in phosphate chemicals in food applicationswww.prayon.com) who has confirmed that the net cooked yield of a soaked product is lower to the extent of the weight gain it made before freezing as compared to an unsoaked product.