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Title: Preliminary chemical and nutritional characterization of liver from longnose skates (Raja rhina)

Author
item Wu, Ted
item Stine, Jesse
item Bechtel, Peter

Submitted to: Journal of Food Composition and Analysis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/8/2010
Publication Date: 5/1/2011
Citation: Wu, T.H., Stine, J.J., Bechtel, P.J. 2011. Preliminary chemical and nutritional characterization of liver from longnose skates (Raja rhina). Journal of Food Composition and Analysis. 24(3):356-361.

Interpretive Summary: Skate livers were collected from a commercial fishery plant in Kodiak, AK for examination of nutritional and chemical properties to add value to the byproduct. The majority of the liver consisted of lipids at 49.6%. Nutritional analysis showed the skate livers are a good source of vitamin E, lipids and proteins. Results suggest skate liver can be used as a unique source of marine oil and protein feed.

Technical Abstract: Skates have recently become a small commercial fishery in Alaska and along the western United States coast. Most of the skate byproduct is discarded or made into meal; therefore, there is opportunity to enhance the utilization for skate byproducts. The objective of this research project was to chemically characterize the longnose skate (Raja rhina) livers. Livers from five long nose skates, caught off the coast of Kodiak were obtained immediately after the wings had been removed by a commercial processor. Each liver was subjected to the following analysis: proximate composition, minerals, amino acids, fat soluble vitamins, protein gel electrophoresis, fatty acid profiles, thiobarbituric acid reactive substances (TBARS) and biogenic amines (BA). Livers were comprised of lipid (49.6%) and protein (10.9%). High levels of alpha-tocopherol were found in the livers (142 ug/ g oil). Fatty acid profile indicated that the lipids extracted from livers contained high concentrations of eicosapentaenoic acid (16.0 %) and docosahexaenoic acid (17.7 %). Average TBARS values were low at 1.5 ug malondialdehyde / g oil, indicating low levels of lipid oxidation. The lysine content as percent of total amino acids on a weight basis was 6.1 % and methionine content was 2.8%. Analysis of BA found putrescine (31 mg/kg liver) and spermine (85 mg/kg liver) present. Results suggest skate liver can be used as a unique source of marine oil with high levels of DHA, EPA and vitamin E.