The sensitivity of cold water fish to Lipid oxidation has been a major impediment in the production of protein isolates such as surimi.

The sensitivity of cold water fish to lipid oxidation has been a major impediment in the production of protein isolates such as surimi. Recent evidence suggests that major contributors to this oxidation are the heme proteins. Fish hemoglobins are unstable and readily de-oxygenate. They dissociate into monomers and release their heme groups as the pH declines below neutrality. Scientists have developed processing methods for isolating functional proteins from fish muscle tissue. They first solubilized the proteins at low pH (3) or high pH (10.8). This was followed by the isoelectric precipitation of the proteins at pH 5.3 to pH 5.5. The hemoglobins in the fish tissue in either the acidic or akaline process would be subjected to pH values in which increased pro-oxidative activity could be expected. Various approaches to reducing lipid oxidation have included pH control, hemoglobin removal, limited exposure to low pH, selective solubilization and the removal of cellular membranes. Exposure to pH values below neutrality for as short a time as possible has given promising results. One of the advantages of the solubilization process for isolating fish muscle proteins is the potential for removing the oxidative-prone membrane lipids by centrifugation. Contact: Hebert Hutlin, Department of Food Science, University of Massachusetts-Amherst, Room 432, Chenoweth Laboratory, 100 Holdsworth Way, Amherst, MA 01003. Phone: [phone]. Fax: [phone]. Email: [e-mail].