Fish Fillet Application

For fish processing, the main value of X-FOS (phosphate-free additive) lies in improving the retention of water by the protein of fish. X-FOS treatment of fish before freezing often reduces the amount of thaw drip, that is the liquid released when frozen fish is thawed. Good quality fish that is frozen and then stored at too high a temperature may have a high thaw drip loss. Chilled fillets lose water slowly during processing and distribution. The loss is usually small, but it may be increased by high temperature, excessive pressure on the product and by delay in distribution.

X-FOS treatment of the fillets will reduce drip loss. Therefore, there are 2 instances where X-FOS treatment of chilled fillets or portions may have a specific advantage. First, chilled fillets of good quality from thawed sea frozen fish often lose a high amount of drip during distribution; X-FOS treatment after filleting can substantially reduce this loss, and can also dramatically improve the appearance of the fillets by changing the dull, ofter brownish, surface that is typical of sea frozen material to a glossy bluish white. The dull surface of poor quality fillets from stale fish can also be given a gloss by treatment with X-FOS. Secondly, X-FOS treatment can improve the appearance of prepacked chilled fillet by preventing the accumulation of unsightly drip within the pack.

Blocks are also made from minced fish flesh, or a proportion of mince may be incorporated in fillet blocks. X-FOS mixed with the mince acts as a binding agent by swelling protein to give the product an improved texture. A similar binding effect occurs when the treatment is applied to fillets that are particularly liable to break up on thawing.

Apart from the water retention advantage, X-FOS has the better advantage over the polyphosphate by having preservative and chelating action on chilled fish and also giving protection against cold store deterioration.

Proprietary solutions should be prepared at the ratio 3-5% solution considerably to the fish weight. This solution should be chilled to avoid warming the fish and to increase the life of the solution.

The simplest way of applying X-FOS is to immerse a batch of fillets or pieces of fish contained in an open mesh basket, agitating them gently so that all surfaces come into contact with the solution. Alternatively the fish can be conveyed mechanically through a long shallow tank of solution; suitable machines are available that can be incorporated in a continuous processing line. A third possibility is to tumble the fillets gently in a slowly rotating drum containing a small amount of solution, say 5 % of the weight of the fish; most of the liquid is taken up by the fish in a few minutes.