Collaborative Studies of the Rapid Detergent Method for Butterfat in Raw Milk

Abstract

Abstract The AOAC Roese-Gottlieb, Babcock, and Rapid Detergent (TeSa) Methods for the determination of butterfat in raw milk were compared in three separate collaborative studies, two involving identical samples sent to six laboratories (Studies I and 2) and one in which the laboratories collected their own samples (Study 3). Only in the case of the TeSa method in Study 3 was there a significant difference in the average butterfat content as found by the three methods. The TeSa test showed the highest standard deviation in Studies 1 and 2 and intermediate in Study 3. Significantly lower results were obtained by the TeSa and Roese- Gottlieb methods when analyses were repeated on successive days (—0.11 and —0.03%, respectively) in Study 2. The slope of the regression line of the TeSa test versus Roese-Gottlieb differed significantly from a 1:1 relationship in Studies 1 and 3. The TeSa test is recommended only as a rapid field test for use with raw milk less than 24 hours old.