Objectives:A recent process to produce fish protein isolates free of most insoluble components such as oil, cellular membranes, skin, bones, and low molecular weight soluble impurities has been proposed based on the solubility properties of fish muscle proteins. This project will examine the problem caused by proteins of the fish tissues used that may not be easily separable from the desired proteins. These include the heme proteins and proteolytic enzymes. Due to density considerations, some insoluble pigment components are also difficult to remove. Specific objectives of this proposal are:1. To determine the effect of processing conditions, especially low pH, on the changes induced in the heme proteins as well as in their ability to catalyze lipid oxidation.2. To remove heme proteins from the fish protein isolates, either chemically or physically, with minimum oxidative damage to the lipids and proteins and with the minimum protein loss.3. To remove melanoidin pigments to maintain good color with minimum protein loss when tissues other than muscles are included in the process, e.g. headed and gutted fish4. To develop ways of removing cellular membranes more compatible with an industrial process than the high speed centrifuging procedure used in the laboratory Methodology:The research in this proposal is directed towards producing or improving fish protein isolates produced from major species on the Atlantic, the Gulf, and the Northwest Pacific coasts. Fatty pelagic fish like makerel, menhaden and herring will be examined on the Atlantic coast, mehaden on the Gulf coast, with Pacific whiting the focus of the Oregon component. The research will be directed at overcoming characteristics currently considered to be major problems in allowing a new processing procedure with improved yields and an ability to produce quality protein isolates from species which has been traditionally difficult to handle. The acid-solubilization process will be applied to all of these species, and the specific problems with each will be targeted by one of the participating laboratories. The Massachusetts laboratory will concentrate on color and flavor problems associated with the heme proteins, hemoglobin and myoglobin, and the color problems associated with the melanoidin pigments. Removal or destruction of heme proteins will be by selective solubilization/precipitation as a function of pH and concentration of salts, by chemically destroying the heme pigments by oxidation as with hydrogen peroxide, or removing the heme by adsorbing to polymers that can be separated from other components of the mixture. This work will be done both in the presence of all of the muscle proteins or after separating the hemoglobin and myoglobin with the soluble sarcoplasmic protein fraction. Melanoidin pigments will be removed by control of tissue disruption to separate the melanoidin containing pigments from the tissue in a proper size to be removed by differential centrifugation. The efficacy of using an alkali solubilization process will be added to the project at no extra cost. In addition, we shall also add an investigation into ways to remove cellular membranes that are compatible with an industrial scale operation.Rationale:A process has been developed to separate protein isolates from fish muscle free of insoluble contaminants. This offers the opportunity to use resources directly for human food that currently are wasted or go to lower value products. To maximize quality, it is necessary to develop ways to control the effect of soluble proteins that lead to a lowering of quality. Successful conclusions of the research will allow a greater variety of raw materials to be used and will produced higher quality products that will greatly expand marketing possibilities.