Results of pilot comparisons in the field of measuring the nutritional value of milk powder COOMET 880/RU-a/23

A necessary condition for obtaining high-quality food products that satisfy human physiological needs for essential nutrients and energy is continuous monitoring of the macronutrient content. The correctness of measurements in the process of such monitoring is verified by analyzing, in parallel with working samples reference materials of the composition of food products and food raw materials. The certified values of these reference materials shall be traceable to measurement standards and/or measurement results of national metrology institutes. For mutual recognition of the calibration and measurement capabilities of national metrology institutes, they must obtain equivalent results in key comparisons. The possibility of organizing key comparisons is assessed during pilot comparisons. The article presents the results of pilot comparisons in the field of measuring the nutritional value of milk powder COOMET 880/RU-а/23 with the participation of national metrology institutes of the Russian Federation, Republic of Belarus, Kyrgyz Republic and China. Samples of skim and whole milk powder were selected as the objects of comparison. The measured characteristics are mass fraction of moisture, nitrogen, protein, fat, ash, carbohydrates (lactose). Each participant in the comparison used measurement procedures, measurement instruments and equipment that ensure the highest accuracy. When assessing the uncertainty of the values of the specified measured characteristics, the participants took into account the standard deviation of the results of parallel determinations, uncertainties from the quantities included in the measurement equations, and methodological factors. The comparisons demonstrated the consistency of most of the measurement results presented by the participants. Some deviating measurement results of operationally determined quantities (mass fraction of ash, mass fraction of moisture) are due to the empirical nature of the methods used, i.e. the dependence of the measurement results on the applied drying or ashing conditions. For rational values (mass fraction of nitrogen), the discrepancies are probably due to incomplete extraction of the component from the test sample, as well as the lack of established traceability of the sample used to standardize the titrant. The results of the comparisons will be used in preparing proposals for conducting key comparisons for the purpose of mutual recognition of national standards and calibration and measurement certificates in the field of measuring the nutritional value of milk powder.