A Rapid Technique for Extraction of Yolk Cholesterol

Modifications were made in the Folch (1956) procedure of extraction of cholesterol to obtain a simpler, more rapid extraction of egg yolk cholesterol with no loss of accuracy and repeatability. In the modified extraction procedure 15 ml. of 2:1 chloroform-methanol was added to 1 gm. egg yolk, the sample shaken by hand, 5 ml. of H2O added and the sample again shaken by hand. After centrifugation, the removal of the aqueous-methanol layer and filteration of the chloroform layer, the cholesterol content of samples was determined. The amount of cholesterol extracted and recovered by the modified technique was significantly higher than when the original extraction procedure was used. The increased extraction was due both to the smaller volume of chloroform-methanol used in emulsification and to the method of shaking. Substitution of KCl solution for water, or addition of sodium sulfate appeared to have no effect on the cholesterol extracted. The coefficient of variability for extractions obtained by the modified method was 9.8% compared to 29.9% for extractions obtained by the original procedure.