FISHERY BULLETIN; VOL. 70, NO. I 



glass funnel, washing: sodium sulfate with cyclo- 

 hexane to remove all traces of color. If filtrate 

 is clear, dilute to 100 ml. If it appears hazy, 

 repeat the filtration, allowing solution to remain 

 in fresh sodium sulfate for a brief time. Read 

 at 474 nm on spectrophotometer, using cyclo- 

 hexane as a blank. 



The precision of the method was determined 

 by analyzing 11 identical samples in quadrupli- 

 cate on 11 different days. Twenty-two cans of 

 the same code of canned shrimp were blended 

 in a Waring blendor, and the homogeneous mix- 

 ture was sealed in cans and frozen at — 60° F. 

 For each day's sampling, two cans of the frozen 

 mixture were thawed and blended together. 



Different lots of solvents were used at inter- 

 vals to determine the sensitivity to slight vari- 

 ations in solvents. The solvent lot was not criti- 

 cal but the cyclohexane used in the spectropho- 

 tometer should be carefully distilled within a few 

 days of use. We used a Gilford modification 

 of a Beckman DU spectrophotometer' which 

 gives readings with three place accuracy. The 

 range of absorbance readings was 0.420 to 0.452, 

 the average was 0.436, and the standard devi- 

 ation was 0.008. 



The carotenoid content, expressed as the carot- 

 enoid index, is a calculated value based on dry 

 weight. The solids content of the shrimp was 

 determined by the Association of Official Agri- 

 cultural Chemists method (Horwitz, 1965: 346), 

 using 5 to 10 g of the blended meat sample and 

 heating at 105° C for 18 to 24 hr. The carotenoid 

 index represents the absorbance (A) in 100 ml 

 of solvent of the carotenoids from 1 g of dry 

 sample, measured in a 1-cm cell. It is calculated 

 as follows: 



C, = 



(A^ 474 nm in 100 ml cyclohe xane ) (100) 

 (50-g wet sample) {% dry weight) 



The absorbance reading of a shrimp sami)le 

 with average moisture content is roughly 10 

 times larger than the carotenoid index; there- 

 fore the carotenoid index equivalent of the stan- 

 dard deviation is slightly less than 0.001. 



The amount of carotenoid can also be ex- 

 pressed as grams of pigTnent/gram tissue by 

 using the extinction coefficient of 2150, as re- 

 ported by Kanemitsu and Aoe (1958). The 

 amount of astacin present in fresh shrimp is 

 small and since the extinction coefficients of 

 astacin and astaxanthin for calculation purposes 

 do not introduce significant error for routine 

 analytical work, the calculation would be: 



grams pigment/1 g tissue = 



(A aj^47^nm) (100 ml) 

 100 (50 g) (d) (2150) 



wiiere d is the cell width in centimeters. This 

 could be converted to dry tissue weight by multi- 

 plying by the percent of solids in the sample. 



CAROTENOID CONTENTS OF 



VARIOUS TYPES OF 



SHRIMP SAMPLES 



Table 1 gives carotenoid values of various 

 types of shrimp samples described. Most of the 

 data were collected as part of some other project 

 so these samples are from several lots of shrimp 

 caught at different times of the year. Only those 

 grouped together in the table can be accurately 

 compared with each other. All data, however, 

 represent an average figure for the given sample 

 and may be used to compare types of sample 

 products or processing methods. 



Tablk 1. — Carotenoid values for 11 shrimp samples. 



Sampling conditions 



Carotenoid 

 index 



Cause of color 



differences indicated 



by data 



° The use of trade names is merely to facilitate de- 

 scription and does not imply endorsement of a product. 



112 



