Variation in Food Microbiological Tests Used to Evaluate Analyst Performance.

Area of Science:

• Food Science
• Analytical Chemistry
• Quality Assurance

Background:

• Laboratory quality assurance programs rely on accurate method variation estimates for analyst performance evaluation.
• Understanding variance components (replicate error, analyst, and analyst-sample interaction) is crucial for method validation.

Purpose of the Study:

• To estimate the total variance for eleven milk and food analytical methods.
• To assess the satisfactory performance of current analyst levels in state and federal laboratory quality assurance programs.

Main Methods:

• Evaluated eleven analytical methods for milk and food testing.
• Calculated total variance estimates for each method, including Standard Plate Count, coliform counts, and various Most Probable Number (MPN) tests.

Main Results:

• Total variance estimates for milk methods ranged from 0.00504 (electronic somatic cell count) to 4.06 (Wisconsin mastitis test).
• Logarithmic total variance estimates for food methods ranged from 0.00853 (aerobic plate count) to 0.24245 (Staphylococcus aureus MPN).

Conclusions:

• The study concludes that current analyst performance within state and federal laboratory quality assurance programs is satisfactory.
• Variance estimates provide a basis for ongoing method evaluation and performance monitoring.