METHOD OF DETERMINING CAROTENOID CONTENTS OF 

 ALASKA PINK SHRIMP AND REPRESENTATIVE VALUES FOR 



SEVERAL SHRIMP PRODUCTS 



Carolyn E. Kelley' and Anthony W. Harmon^ 



ABSTRACT 



An extraction method is described for estimating the amount of carotenoids in pink shrimp. The carot- 

 enoid index is useful as a measure of quality and as an indicator of changes during storage. Values for 

 several shrimp products are reported. 



The carotenoid content of Alaska pink shrimp 

 is affected by many conditions and can be used 

 as an index of the general quality of canned 

 shrimp and of the changes in quality of frozen 

 shrimp during storage. It has been also used as 

 a factor in determining optimum peeling charac- 

 teristics of shrimp (Collins and Kelley, 1969) 

 and in selecting desirable retorting conditions 

 (Kelley, 1971'). Color differences in shrimp at 

 different seasons and in different areas may be 

 important in harvesting and marketingpractices. 

 The carotenoid in Alaska pink shrimp is pri- 

 marily astaxanthin. Both total astaxanthin and 

 astacin, its oxidation product, are measured by 

 the method to be described, which wa'fe developed 

 for use with frozen Alaska king crab (Ravesi, 

 1965') and adapted to Alaska pink shrimp which 

 contain more interfering protein and moisture 

 than crab. 



' National Marine Fisheries Service, Fishery Products 

 Technology Laboratory, Kodiak, AK; present address: 

 609 Schoenbar, Ketchikan, AK 99916. 



^ Formerly, National Marine Fisheries Service, PMsh- 

 ery Products Technology Laboratory, Kodiak, AK; pre- 

 sent address: Department of Chemistry, Oklahoma State 

 University, Stillwater, OK 74074. 



\ Kelley, C. E. 1971. Carotenoid content of pink 

 shrimp: Effect of retorting conditions. National Ma- 

 rine Fisheries Service, Fishery Products Technology Lab- 

 oratory, Kodiak, Alaska. (Unpublished manuscript.) 



* Elinor Ravesi. 1965. Effect of processing and fro- 

 zen storage on the carotenoid pigments of Alaska king 

 crab. Unpublished manuscript filed at NMFS, Kodiak, 

 Alaska. 



Manuscript accepted August 1971. 



FISHERY BULLETIN: VOL. 70, NO. I, 1972. 



METHOD OF DETERMINING 

 CAROTENOID CONTENTS 



To 50 g of blended meat add approximately 

 10 g of silica gel and 100 ml of the proper ace- 

 tone solution: 



1. 759r acetone for canned shrimp with liquor. 



2. 65% acetone for frozen cooked or raw 

 meats. 



3. 50 ^r acetone for raw shrimp with shells on. 

 The silica gel, which serves as a filter aid, is not 

 essential but makes subsequent extraction and 

 filtration easier. Blend just enough to ensure 

 complete mixing and filter through a medium 

 porosity fritted glass funnel, maintaining suc- 

 tion until dripping ceases. Rinse container and 

 filter as needed with 50 "^r acetone. Discard 

 colorless filtrate and blend residue about 2 min 

 with 15 to 20 g anhydrous sodium sulfate and 

 100 ml of 1:1 2-propanol: chloroform. Filter 

 and re-extract with 50 ml solvent one or two 

 times as needed to get a colorless meat. Use 2- 

 propanol: chloroform as rinse solution during 

 these extractions. Transfer filtrate to 500 ml 

 round bottom flask and strip the solvent, using 

 a rotating vacuum evaporator. Add 5 to 10 ml 

 chloroform and evaporate to dryness. Dissolve 

 residue in enough pure cyclohexane to wash sides 

 of flask and add 10 to 15 g aniiydrous sodium 

 sulfate. Let set for a few minutes and filter 

 through sodium sulfate on a fine porosity fritted 



111 



