BS EN ISO 19036:2019 pdf free.Microbiology of the food chain — Estimation of measurement uncertainty for quantitative determinations.
This document specifies requirements and gives guidance for the estimation and expression of
measurement uncertainty (MU) associated with quantitative results in microbiology of the food chain.
It is applicable to the quantitative analysis of:
— products intended for human consumption or the feeding of animals;
— environmental samples in the area of food production and food handling;
— samples at the stage of primary production.
The quantitative analysis is typically carried out by enumeration of microorganEsms using a colony- count technique. This document is also generally applicable to other quantitative analyses, including:
— most probable number (MPN) techniques;
— instrumental methods, such as impediometry, adenosine triphosphate (ATP) and flow cytometry;
— molecular methods, such as methods based on quantitative polymerase chain reaction (qPCR).
The uncertainty estimated by this document does not include systematic effects (bias).
2 Normative references
There are no normative references in this document.
3 Terms, definitions and symbols
3.1 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https://www.iso.org/obp
— IEC Electropedia: available at http://www.electropedia.org/
4 General considerations
MU associated with any measurement value includes multiple components.
As indicated in the Scope (see Clause 1), the uncertainty estimated by this document does not include contributions from systematic effects (bias). In food chain quantitative microbiology, assigned values or reference quantity values are usually not available so bias cannot be reliably estimated.
This document considers three distinct types of uncertainty component:
— technical uncertainty;
— matrix uncertainty;
— distributional uncertainty.
Technical uncertainty arises from operational variability and is estimated, using a global approach, from a reproducibility standard deviation of the final result of the measurement process (see Clause 5). This global approach means that the technical uncertainty estimate comes from final test results rather than by calculation using estimates of uncertainty at every individual stage of the test.
Matrix uncertainty arises from imperfect mixing of the laboratory sample, resulting in poor reproducibility of microbial levels between test portions, which can be large for solid matrices, and especially for composite food products. Matrix uncertainty is estimated for each kind of matrix (see Clause 6).
Even for homogeneous materials, the random distribution of microorganisms leads to distributional uncertainty (see Clause 7), of which three potential kinds are considered in this document. The relevance of each depends on the method used:
— for colony-count techniques:
— Poisson uncertainty (see 22);
— confirmation uncertainty (see 2.3);
— for MPN techniques: MPN uncertainty (seeZ4).
The uncertainty for each distributional uncertainty source is estimated mathematically.BS EN ISO 19036 pdf free download.