Excellence In Aquaculture THE USE OF STPP IN CATFISH In recent years the use of STPP has become common in the production of catfish fillets. Many questions have risen about what STPP is and its uses. First, let's start with what STPP is. Sodium Tripolyphosphate STPP, sometimes known as STP, is a polyphosphate of sodium. It is the sodium salt of triphosphoric acid. It is used in various applications including use as a preservative for seafood, meats and poultry. The United States FDA lists STPP as "generally recognized as safe", along with salt, vinegar and baking powder. STPP, when used properly, can have some beneficial effects on seafood. One of the more positive effects is the retention of moisture in the seafood. This helps to maintain the fillet's natural texture and appearance when thawing and using. The problem with STPP does not lie with the chemical itself, but in the abuses associated with the use and application of said product. APPLICATION There are many different methods of applying STPP. With the many ways to apply STPP, it would be impossible to list and explain them all. What we will try to do is explain some of the most commonly used forms of application. Generally, a solution is made by mixing the STPP with water, with the percentage of the chemical being between 0.5% and 6% of the solution. Once the solution is prepared, it is applied to the fillets. Once of the methods used is known as a "rinse". Using a higher percentage of solution, usually in the 6% range the fillets are quickly dipped through the solution to accomplish this. A spray technique can also be used to apply the solution. When done in this manner, the result is a pick-up of the solution in the 1 - 2% range. This range is acceptable by most inspection standards. Another method used is the injection of the fillets by an injection machine. This method is used when attempting to have a higher percentage of the solution absorbed into the fillets. Other methods used for achieving high STPP concentration are tumbling and soaking. Tumbling involves the use of a commercial tumbler. The fillets are slowly tumbled in a solution while holding a vacuum. This draws the solution through the fillets for better absorption. The soaking method is simply making a container of solution in which the fillets can be soaked for a period of time. The length of time the fillets are kept in the solution determines the amount of absorption that is to be achieved. The length of time usually associated with this method varies from a few minutes up to as long as 24 hours. This rate of absorption also varies from a 5% rate to as high as a 25% rate. There are some packers that actually combine soaking with tumbling for high levels of absorption. As you can see, the need for knowing what method your packer uses is of the utmost importance. The difference between one method and another can be significant. NET WEIGHT Government guidelines state that the net weight of the product in the box must be equal to or exceed the weight labeled on the box. Additives such as STPP, that are included in that weight, must be stated on the box as far as percentage absorbed. When buying Catfish fillets the sale contract usually states term like 100% with STPP. The problem with this statement is that the majority of the time it is very hard to determine the exactly how much STPP was applied during the processing of the fillets. Special equipment on the market, such as dehydration testers, are made to test the absorption rates. However, this equipment is not common and not very accessible to the everyday seafood buyer. Subsequently, testing and determining the true amount of additives in the product is tricky and at times impossible. Many times products sold as 100% net weight without markings of additives were found to contain STPP. SIGNS OF ABUSE There are a few signs that can be detected when looking for additive abuse in seafood fillets. 1. An appearance of a chalky whit texture or an overly dull look in the fillet. 2. When cooking there is a heavy purge of liquid that comes from the fillet. 3. The cooking time on a treated fillet is far longer than that of a fillet that has not been adulterated with STPP. After adequate time, the fillet still appears raw. 4. A rubbery texture in a finished fillet is also a good sign that the fillets have been heavily treated. IN CONCLUSION We have tried to explain in the preceding text, the methods of packaging and processing Chinese catfish fillets. The process varies widely from packer to packer. Hopefully, these explanations will help you to better understand the different methods used and can assist you in your purchasing decisions. Like most relationships that deal with the purchase of seafood needs, knowing and trusting that your packer has the knowledge, expertise, and honesty to deliver the exact product that you need, and expect, is of vital importance.