Date of Award
Master of Science in Food and Resource Chemistry
Food and Resource Chemistry
Charles E. Olney
The meat of sharks and other members of the family Elasmobranchii contains urea. Urease, present in fish muscle or released by microbes grown during storage, catalyzes the decomposition of urea to ammonia, which is responsible for off-flavor and odor in products from fish containing urea. Therefore, it is necessary to r~move urea in the preparation of FPC (fish protein concentrate) from shark meat, if the FPC is to be utilized as a highly nutritive animal protein supplement in food to combat human malnutrition in developing and underdeveloped countries.
For the production of urea-free FPC, multistage cross-current solvent extraction, multistage countercurrent solvent extraction and an aqueous phosphate process in combination with multistage countercurrent solvent extraction were tried , Ethanol (95%) and commercial hexane were used as solvents to remove urea, moisture and lipids in the crosscurrent and countercurrent methods. In the aqueous phosphate process, hexametaphosphate at pH 4.0 was used to precipitate protein from an aqueous medium while urea was removed with the water phase. Subsequent solvent extraction reduced the moisture and lipid levels to below the FDA limits of 10% and 0.5%, respectively.
In all stages the solvent was added in the ratio of one ml per gram of ground raw fish. Starting with shark meat containing 1.1% urea and 13.4% lipids, the urea and lipid levels in the FPC were 0.16 and 0.61%, respectively, following countercurrent solvent extraction using three ethanol stages followed by three hexane stages with 15 minute extraction periods. Six crosscurrent ethanol extractions with 60 minute extraction periods reduced the urea level in the FPC to a trace, while the lipid was 0.41%. The FPC produced by these methods was white or light cream colored with no or slight amine and fishy odor and good functional properties.
The FPC produced by the aqueous phosphate process followed by countercurrent solvent extraction was better in color, odor, flavor and texture than FPC produced by the solvent extraction alone. The urea and lipid levels in the FPC were 0,07 and 0.56%, respectively.
Ali, Moshin, "Preparation of Fish Protein Concentrate (FPC) from Shark" (1972). Open Access Master's Theses. Paper 979.