1. A modification of the A. O. A. C. method for complete butter analysis is described. The method is considered applicable for use in control laboratories, in which eight or more samples are analyzed at a time.
2. This method, together with the Kohman and Mojonnier analyses for butter, was compared with the A. O. A. C. method as a standard. The modified official and the Kohman methods check closely with the A. O. A. C. method for all constituents of butter. With the 50 samples analyzed in duplicate the fat content was 0.22 percent lower by the Mojonnier method (abnormal values not included-see table I ) than by the A. O. A. C. method. About 10 percent of the Mojonnier analyses varied widely from the duplicates and from the A. O. A. C. method.
3. The variation between duplicates is attributed (a) to peculiarities in the emulsification of the fat in the extraction flasks, which caused incomplete extraction, and (b) to a blowing out of ether-fat solution around the stoppers when these were removed or to both.
4. Data are presented which show that the value by which normal Mojonnier fat determinations are lower than the A. O. A. C. method is equivalent to the fatty acids, which are not extracted in the Mojonnier procedure but which appear as fat with the A. O. A. C. analysis. It is further shown that this difference was larger, as the rancidity of the butter increased.
5. The modified official method is a rapid method and is considered sufficiently accurate for the analysis of good quality butter in control laboratory work. Likewise the A. O. A. C. method is considered to be accurate as an analytical standard for the analysis of good quality butter. The Kohman method as outlined is a rapid method sufficiently accurate for plant use. All three methods give values for fat which are too high by an appreciable amount for the analysis of rancid butter.
6. The Mojonnier and the "la-gram" extraction methods give a closer approximation of the true fat value of rancid butter than do the dry extraction methods (A. O. A. C., modified official and Kohman).
Bird, E. W. and Breazeale, D. F.
"Chemistry of butter and butter making I. A comparison of four methods for the analysis of butter with an explanation of a discrepancy found to exist in the fat determinations,"
Research Bulletin (Iowa Agriculture and Home Economics Experiment Station): Vol. 11
, Article 1.
Available at: https://lib.dr.iastate.edu/researchbulletin/vol11/iss144/1