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United States Department of Agriculture

Agricultural Research Service

Research Project: CONVERTING ALASKA FISH BY-PRODUCTS INTO VALUE ADDED INGREDIENTS AND PRODUCTS Title: Protein and Lipid Composition of Walleye Pollock (Theragra Chalcogramma) Livers

Authors
item Oliveira, A - UAF
item Bechtel, Peter

Submitted to: Journal of Aquatic Food Product Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 7, 2006
Publication Date: October 3, 2006
Citation: Oliveira, A.C., Bechtel, P.J. 2006. Protein and lipid composition of Walleye Pollock (Theragra chalcogramma) livers. Journal of Aquatic Food Product Technology Vol.15(3):5-19.

Interpretive Summary: Liver is a major component of pollock viscera and the amount of liver and its lipid content is affected by the season, sexual maturity and nutritional status of the animal among other factors. Liver can be easily separated from other viscera tissues and used in the manufacturing of food and feed products. There is growing interest for feed ingredients with distinct nutritional characteristics that are better suited to the dietary requirements of different aquaculture fish species. The objective of this study was to chemically evaluate the lipid and protein from pollock male and female livers. Livers from both female and male pollock contained high levels of lipids in excess of 50%. Over 98% of the lipid was triacylglycerides and only small gender differences were detected. 'Extracted oil from pollock livers was a good source of the omega-3 fatty acids EPA and DHA and had an EPA/DHA ratio of 1.95. Protein from pollock liver was of high quality and a good source of lysine and methionine. Results indicated that ingredients with a high nutritional value could be made from males and female pollock livers.

Technical Abstract: The objective of this study was to chemically evaluate the lipid and protein from pollock male and female livers. Pollock livers, regardless of gender, had lipid contents over 50% of which about 98% were in the form of triacylglycerides. Protein content of male and female livers were similar at approximately 7%. The content of most fatty acids were not significantly different between male and females. The abundance of saturated, monounsaturated, and polyunsaturated fatty acids in all extracted oils averaged about 20%, 55%, and 24%, respectively. The omega-3 and omega-6 fatty acid levels of all livers were approximately 22% and 2.0%, respectively. Only small gender differences were detected between pollock liver lipids and protein. Pollock liver protein is of high quality and extracted oil is a valuable source of omega-3 fatty acids. The contents of most amino acids in the samples were similar for both males and females and samples had high levels of methionine (3.2 and 3.6%), lysine (6.8 and 7.6%) and other essential amino acids.

Last Modified: 10/22/2014