Determination of moisture, solids-not-fat and fat-by-difference in butter using routine methods according to ISO 8851/IDF 191—an international collaborative study and a meta-analysis

Abstract

An international collaborative study of routine methods for the determination of moisture, solids-not-fat (SNF) and fat-by-difference (i.e. fat (g 100 g –1 product) =100−moisture (g 100 g –1 product)−SNF (g 100 g –1 product)) in butter was carried out to obtain estimates of the precision parameters repeatability (2.8 s r ) and reproducibility (2.8 s R ). Ten laboratories tested blind duplicate samples of eight different butters according to standard operating procedures jointly drafted by the International Standards Organisation (ISO) and the International Dairy Federation (IDF) (draft ISO standard 8851, parts 1–3; draft IDF standard 191, parts 1–3). Estimates of repeatability and reproducibility respectively were: moisture, 0.28 g 100 g –1 product and 0.44 g 100 g –1 product; SNF, 0.20 g 100 g –1 product and 0.34 g 100 g –1 product; fat-by-difference, 0.30 g 100 g –1 product and 0.51 g 100 g –1 product. These estimates are similar to those found previously in a New Zealand study. A meta-analysis, pooling the results of the present study and the New Zealand study, yielded overall estimates of repeatability and reproducibility as follows: moisture, 0.31 g 100 g –1 product and 0.42 g 100 g –1 product; SNF, 0.20 g 100 g –1 product and 0.39 g 100 g –1 product; fat-by-difference, 0.35 g 100 g –1 product and 0.54 g 100 g –1 product, and these are recommended for adoption in the respective methods. This study completes the validation work for the respective methods, which may now be progressed for final adoption as international standard routine methods. A protocol is proposed for dealing with situations where multiple precision estimates are available.