Routine methods for the determination of solids-not-fat, moisture and fat (by difference) in butter—robustness, bias and precision

Abstract

Abstract Routine methods for the determination of solids-not-fat (SNF) by the Kohman method and moisture by IDF Provisional Standard 137 in butter were tested for robustness, compared for bias with methods described in European Commission Regulation No. 880/98 (EC 880 method) and collaboratively studied. The SNF results were affected by the choice of solvent as well as the cooling technique (marble slab or desiccator) used for the beakers containing the dried SNF, but not by the heating technique (oven or hot plate) used for the empty beakers and the beakers containing the SNF. IDF Provisional Standard 137 was found to be robust with regard to the heating technique (oven or hot plate) and cooling technique (marble slab or desiccator) used for the empty beakers as well as for the cooling technique (marble slab or desiccator) used for the beakers containing the dried butter. IDF Provisional Standard 137 and the Kohman SNF method gave results that were, on average, 0.07 g/100 g higher and 0.08 g/100 g lower, respectively, compared with the EC 880 method. No significant bias was found for fat-by-difference. Estimates for repeatability (2.8sr) and reproducibility (2.8sR), respectively, were: SNF: 0.21 g/100 g and 0.44 g/100 g; moisture: 0.34 g/100 g and 0.40 g/100 g; fat-by-difference: 0.40 g/100 g and 0.57 g/100 g. The precision estimates for moisture were larger than those stated in IDF Provisional Standard 137. This standard should be updated as its precision estimates were not established in accordance with ISO Standard 5725.