Estimation of Measurement Uncertainty in Food Quantitative Microbiological Techniques
Estimation of Measurement Uncertainty in Food Microbiological Techniques
Keywords:
Measurement uncertainty in food microbiological tests, Technical measurement uncertainty, Combined standard uncertainty, Intra-laboratory reproducibilityAbstract
Accredited laboratories, as per ISO/IEC 17025:2017, must estimate measurement uncertainty under the requirements of clause 7.6 to report measurement uncertainty values alongside test results, when requested by clients or when test results overlap within the acceptance range. The Bureau of Quality and Safety of Food, Department of Medical Sciences, Thailand, has collected intra-laboratory reproducibility of food microbiological test results from 2021 to 2024 to derive technical uncertainty (Utech) of microbiological tests according to ISO 19036:2019. A total of 203 samples covering 11 test items were analyzed, including aerobic plate count (APHA 2015, Chapter 6&8), aerobic plate count (BAM 2001, Chapter 3), yeasts and molds (BAM 2001, Chapter 18), yeasts and molds (AOAC 2019; 997.02), lactic acid bacteria (ISO 15214:1998), Coliforms (BAM 2020, Chapter 4), Bacillus cereus (BAM 2020, Chapter 14), Clostridium perfringens (BAM 2001, Chapter 16), Staphylococcus aureus (BAM 2016, Chapter 12), of which the units of measurement are CFU per gram, except Coliforms (BAM 2020, Chapter 4) and Escherichia coli (BAM 2020, Chapter 4) are MPN per gram. The results of the measurement uncertainty estimation were 0.0620, 0.0647, 0.1041, 0.0677, 0.0988, 0.0517, 0.0919, 0.9210, 0.0794, 0.1412, and 0.1412, respectively. Therefore, the laboratories can use these values to calculate the combined standard uncertainty in reporting, along with the test results, which can be compared with the standard criteria to assess the test results confidently.
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