engleski

Validation and Measurement Uncertainty in Food Microbiology: Differences between Qualitative and Quantitative Determinations in Practice

Accreditation according to the standard ISO 17 025: General requirements for the competence of testing and calibration laboratories, which guarantees the compliance with standard operating procedures and the technical competence of the staff involved in the tests, recently are widely introduced in food microbiology laboratories in Croatia. In addition to introducing quality manual, and lot of general documents, some of the most demanding procedures in routine microbiology laboratories are establishing measurement uncertainty (MU) procedures and validation experiment design. Those procedures are not standardized yet, and it required practical microbiological knowledge, altogether with statistical competence. Differences between validation experiments design for quantitative and qualitative food microbiology analysis are discussed in this work, and practical solutions are shortly described. MU for quantitative determinations are more demanding issue than qualitative MU calculation. The concepts of repeatability (r) and reproducibility (R) are widely used in the analysis of data from collaborative trials in quantitative microbiology. Repeatability provides a measure of the variability between analyses conducted on identical test materials by the same technician in the same laboratory, under conditions as similar as possible (e.g. by using the same apparatus and reagents within the shortest possible interval of time), whilst the R measures the variability when the analyses are conducted by different technicians at different laboratories. In qualitative food microbiology, the usual measures of R and r are inapplicable. Analysis is based on the probability of finding the same test results for identical test materials within and between laboratories, respectively. MU calculations are based on external proficiency testing data and internal validation data. In this work practical schematic description for both of those procedures are made.

measurement uncertainty; validation; food microbiology laboratory; qualitative andquantitative measurement

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