Polyphosphates and Natural Alkaline Buffers

There has been an interesting discussion on the Seafood HACCP Listserv lately centered on whether any methodology exists to detect the use of non-phosphate additives, such as citrate and carbonate, in seafood. As we know, polyphosphates are used in the seafood industry for many reasons: water holding improvement, cryoprotectant, antioxidant, shell removal (for shrimp), etc. Arguably, the primary use for polyphosphates is to alter muscle protein functionality by raising pH. This causes the protein structure to be more open because it has shifted further away from it’s pI. Addition of salt facilitates polyphosphate action by shifting the pI lower. The result is an improved ability of the muscle protein to hold water through shelf-life and cooking. Unfortunately, this same alteration can be easily abused and result in a tremendous increase in water holding capacity and thus increasing yields to a point where they are fraudulent. Polyphosphates are typically detected in meat by hydrolyzing them to the ortho form and then separated out as quinolinium phophomolybdate, with a reagent called quimociac (QUInoline, MOlybdate, CItrate, and ACetone). Replacement of polyphosphates with more label friendly citrates and carbonates makes it difficult to determine whether abuses in brining are occurring. Seafood protein does have an amazing ability to hold water, and it can hold much more, in my experience, than land animal protein. Addition of water to meat has physical and sensory limitations. When the water holding capacity of “meat” is increased too much (>15-20%), the texture of the product becomes noticeably altered and “ham-like.” Significant changes in appearance (both color and structure) of the fibers also occurs. However, with fish, especially white muscle fish, it is much more difficult to discern these visual and textural changes. I have been astounded with our own experiments to see how easily fish muscle handles >20% added water, acting like a veritable sponge. The result of this addition is also not “unpleasing” from a visual perspective. The fish appears “plumper” and more firm. I can understand the concerns expressed for finding a means to verify the presence and amount of alkaline alternatives in order to insure fair practices.