Results of the COOMET 881/RU-a/23 pilot comparisons in the field of measuring the nutritional value of soy flour

To ensure the reliability of measurements of the content of proteins, fats, moisture and ash in food products and food raw materials, it is necessary to use reference materials similar in composition to the analyzed samples and traceable to measurement standards and / or measurement results of national metrology institutes. The equivalence of measurement results from national metrological institutes should be confirmed in key comparisons. The results of the COOMET 881/RU-a/23 pilot comparisons in the field of measurements of the nutritional value of soy flour conducted in 2024 are presented as a preparatory stage before organizing key comparisons in this field. The national metrology institutes of Russia, the Kyrgyz Republic and China took part in the comparisons. Samples of defatted and semi-defatted soy flour composition with preliminarily studied homogeneity and stability were used as samples for comparisons. The measured characteristics were mass fractions of moisture, nitrogen, protein, crude fat and ash. When carrying out measurements, the participants used measurement methods implemented on standard measurement equipment, as well as primary reference measurement procedures. When assessing the uncertainty, the participants took into account the uncertainty components caused by the following: discrepancy between the results of parallel determinations; rounding of measurement results; direct measurements of quantities included in measurement equations; fulfillment of conditions for achieving constant mass after drying, extraction and ashing; deviation of measurement conditions from optimal values. In comparisons, consistent measurement results for mass fraction of moisture, nitrogen, protein and crude fat with expanded uncertainties (at the coverage rate 2) 0.06–0.12 %, 0.034–0.060 %, 0.19–0.40 %, 0.04–0.08 % respectively were obtained. It is two to eight times higher than the accuracy of standard measurement procedures (methods). The observed discrepant measurement result of the ash mass fraction obtained by one participant in the comparisons is due to the empirical nature of the measured value. In the case of measuring the values of empirical quantities, consistency of results can be achieved by strictly establishing the conditions for performing measurements and the permissible limits of their variation. The comparison results are planned to be used in the preparation of proposals for conducting key comparisons in the field of measuring the nutritional value of soy flour.