resentative sample of about 250 to 300 grams was homogenized in a 

 Waring blender prior to removal of a sample for the determination 

 of cholesterol and ether-soluble fat. The value reported for king 

 salmon eggs was determined on a representative sample drawn fron a 

 35-pound lot collected at Astoria, Oregon, during August 19^7. Due 

 to the large size of this species, a 35-pound sample of eggs rep>- 

 resents only 15 to 20 fish. 



Cholesterol Determination 



Numerous methods for the quantitative determination of choles- 

 terol are found in the chemical literature. However, many of these 

 methods are found to be modifications of the Lieberman-Burchard reac- 

 tion, and are designed primarily for the determination of small quanti- 

 ties of cholesterol present in blood. Methods commonly used for the 

 determination of cholesterol in hen egg yolks or in other food products 

 containing egg yolk appeared to be the most logical to use for the 

 analysis of salmon eggs. Accordingly the official method for deter- 

 mination of cholesterol in eggs and egg products included in the A.O.A.C. 

 Methods of Analysis 1/ was used in the initial experiments on salmon eggs. 

 In this method the cholesterol is isolated from a saponified sample as 

 the dibromide and determined by an iodine liberation-titration method 

 using sodium thiosulphate. This method is considered precise and ac- 

 curate but has the disadvantage of being some-ivhat laborious and time- 

 consuming. In order to examine a larger niimber of samples, a simpler 

 method was resorted to after a preliminary check analysis had been 

 made using an aliquot of the same sample in the detennination of chol- 

 esterol by both the A.O.A.C. method and the colorimetric method of 

 Cook and Mehlenbacher (3)» The colorimetric method is based on the 

 Lieberman-Burchard color reaction for cholesterol using the unsaponi- 

 fiable fraction of the ether extract. Lampert (9) found that a Mojon- 

 nier modification of the Rose-Gottlieb method of extraction was useful 

 in work on ice cream mixtvires. Good agreement was observed by Lampert 

 between the results obtained with this modified method and the digit- 

 onin precipitation method when applied to powdered egg samples. Cook 

 and Mehlenbacher (3) suggested the use of a lower temperature d\iring 

 color development and reading and also suggested the use of a spectro- 

 photometer to obtain the transmittance values. In this method the con- 

 centrat ion-transmit tance curve with pure cholesterol standards is de- 

 termined at 64.0 millimicrons, the point of maximum absorption. 



Initially the cholesterol content of dried (lyophilized 2/) chum 

 salmon eggs (see sample chum (deh3ndrated) in Table l) was determined 

 by the A,0,A,C. method. The amount of cholesterol calculated on the 

 basis of the total oil fraction was found to agree within the limits 

 of experimental error with that found for the oil from raw eggs when 

 analyzed by the colorimetric method of Cook and Mehlenbacher (3) • 



1/ Methods of analysis of the Association of Official 

 Agriciiltural Chemists, VI Edition, page 3A9, 194.5. 



2/ The term "lyophilized" is used to designate the process of 

 dehydration in the frozen state ty vacuum sublimation. 



69 



