An accurate and rapid method for the direct determination of fat in butter, butter-margarine blends and milkfat spreads

A simple gravimetric method was developed for the direct determination of fat in butter. The sample was weighed into a plastic centrifuge tube and the fat was extracted using petroleum ether. The petroleum ether/fat phase was allowed to separate from the butter serum phase and was transferred quantitatively to a fat-collecting vessel. Repeated extractions were carried out: to fully recover the fat. The petroleum ether was removed from the combined extracts, and the mass of substances extracted was determined. Validation work showed that the number of extractions and the choice of solvent affected the fat recovery and these were optimised. Sample weight in the range 2-8 g did not affect the fat recovery, Significantly less solvent was used than in the indirect IDF Standard 80 (1977, Butter-Determination of water, solids-non-fat and fat contents on the same test protein. Brussels: International Dairy Federation) method and the revised version thereof, but comparable results were obtained. Peer review and a pilot collaborative study showed the direct method to be robust and precise. Repeatability (2.8*s(r)) estimates for the direct method and IDF Standard 80 (1977) were found to be 0.14 and 0.21 g/100 g, respectively, and reproducibility (2.8*s(R)) estimates were found to be 0.26 and 0.34 g/100 g, respectively. Preliminary work indicated that the direct method is applicable to butter-margarine blends and reduced-fat milkfat spreads for which currently no reference methods are available. The method has the potential to be used as both a reference and a routine method for a wide range of yellow-fat products. (C) 2000 Elsevier Science Ltd. All rights reserved.