Determination of butanoic acid in milk fat and fat mixtures containing milk fat: A comparison of methods

Council Regulation (EC) No. 2991/94 has created an urgent need for a reliable method to quantify the milk fat content in spreadable fats containing milk fat. As the butanoic acid concentration is the most promising indicator for the presence of milk fat in a fat blend, a reference method for its determination is required. Three analytical approaches to quantify butanoic acid by gas-liquid chromatography, i.e. determination by free butanoic acid, by methyl butanoate, and by headspace sampling, have been compared. A reference material (anhydrous milk fat) having a certified content of butanoic acid was used to check the accuracy of the methods. All methods tested were well within the uncertainty range of the certified value. The methyl butanoate method had highest precision, followed by the free butanoic acid method and the headspace sampling procedure. Relative standard deviations for repeatability were 0.38, 0.86 and 1.48, respectively. The headspace method had the highest sample throughput (8 samples h(-1)), while the methyl butanoate allowed only one sample h(-1) to be analysed. (C) 1998 Elsevier Science Ltd. All rights reserved.