Production and evaluation of a reference material for moisture, ash, and total fat mass fractions, and titratable acidity in whole milk powder

摘要

Given the importance of reference materials (RM) in the structuring and maintenance of quality management systems for food analysis laboratories, RM were produced for the measurement of moisture, ash, total fat, and titratable acidity in whole milk powder. Two types of packaging and three storage temperatures were evaluated. The RM were considered homogeneous. The materials that were packaged in the pouches and those packaged in the amber glass bottles with screw caps (stored at room temperature) were not stable for moisture. Nevertheless, considering the four measurands, the amber glass bottles under refrigeration and freezing temperatures were the best packaging and storage conditions, respectively. Homogeneity and stability studies were carried out according to the ISO Guide 35, IUPAC harmonized protocol, and ISO 13528, considering the potential applicability of the produced materials as certified reference materials or even as RM for use in proficiency testing schemes. For homogeneity, despite the different criteria, there was agreement between the results. Considering the stability, the agreement depended on the evaluation of the regression assumptions, which is not required by the ISO Guide 35. The contribution of uncertainty associated with homogeneity was greater than that related to stability. The results indicated that the produced materials, i.e., the candidate certified RMs, were suitable for assessing trueness and could be submitted to further inter-laboratory characterization.