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 f at 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 quanti tatively to a fat-collecting vessel. Repeated extractions were carried out: to fully recover the fat. The petroleum ether was removed from the combine d extracts, and the mass of substances extracted was determined. Validation work showed that the number of extractions and the choice of solvent affec ted 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 t han in the indirect IDF Standard 80 (1977, Butter-Determination of water, s olids-non-fat and fat contents on the same test protein. Brussels: Internat ional Dairy Federation) method and the revised version thereof, but compara ble results were obtained. Peer review and a pilot collaborative study show ed the direct method to be robust and precise. Repeatability (2.8*s(r)) est imates 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 ind icated that the direct method is applicable to butter-margarine blends and reduced-fat milkfat spreads for which currently no reference methods are av ailable. 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 S cience Ltd. All rights reserved.