Direct determination of fat using ISO/CD 17189.2—an international collaborative study of spreadable fats and a meta-analysis

Abstract

A method for the direct determination of the total fat content in spreadable fats, including low fat and regular fat margarines, reduced fat butter, blended spreads and a sterol-fortified spread, was studied collaboratively using 12 laboratories and eight samples (fat range: 23–82 g fat/100 g product). The method involved mixing 1–2 g of sample with petroleum ether solvent to extract the fat. The solvent of pooled lots of 3–4 extractions (the number of extractions depended on the phase separation technique used) was evaporated, and the extract was dried to constant mass and weighed. Estimates of repeatability (2.8sr) and reproducibility (2.8sR) were 0.24 g fat/100 g product and 0.44 g fat/100 g product, respectively. A meta-analysis of five international collaborative studies yielded grand estimates of repeatability and reproducibility of 0.26 g fat/100 g product and 0.45 g fat/100 g product, respectively (95% confidence intervals: 0.24–0.28 g fat/100 g product and 0.41–0.49 g fat/100 g product, respectively). These estimates apply to the full scope of draft ISO standard 17189.2, i.e. butter, edible oil emulsions and spreadable fats. The work reported in this paper completes the validation of this standard, which may now be progressed for final adoption as an international reference method.