AOAC ERP MICRO AUGUST 2018

OMAMAN-44 B: Collaborative Study Protocol Expert Review Panel Use Only August 2018

5.8.5 Calculate repeatability as the standard deviation of replicates at each

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concentration of each matrix for each method:

s r

=

n

∑

2

(

)

1 X X n − − i

1

i

=

5.8.6 Calculate the relative standard deviation:

RSD r

= [s r

/mean cand

] x 100

5.8.7 Calculate the mean difference between the candidate and reference method transformed results with 95% confidence interval for each matrix at each contamination level and each time point using the Least Cost Formulations, Ltd., Paired Method Analysis for Micro Testing Xcel worksheet (7). Use the paired or

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unpaired analysis as appropriate.

6.0 14 15 The purpose of the Collaborative Study (CS) is to estimate the reproducibility and determine the 16 performance of the candidate method among the collaborators. A minimum of eight laboratories 17 reporting valid data is required (12 laboratories will be recruited). NOTE : Laboratories in different 18 locations but belonging to one company or institute are acceptable as different organizations. The CS 19 will be organized by Q Laboratories. Matrix Study – Collaborative Study

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6.1 A relevant matrix (infant formula with probiotics) will be inoculated with a single strain of Enterobacteriaceae ( Cronobacter sakazakii , CCUG 28863) by the expert laboratory. There will be a total of four levels of contamination analyzed by all collaborators: an uninoculated level, low level, intermediate level, and a high level of contamination after

both 24 and 48 h of incubation of the plates. 6.1.1 Level 1: Blank (≤10 CFU/g) 6.1.2 Level 2: Low (100–500 CFU/g)

6.1.3 Level 3: Intermediate (1,000–5,000 CFU/g) 6.1.4 Level 4: High (10,000–50,000 CFU/g) ERP Use Only 6.2 For each contamination level, two test portions are analyzed by the candidate method, and two test portions are analyzed by the reference method in each laboratory. 6.3 All samples will be blind-coded by the expert laboratory. Prior to shipment by the expert laboratory, each set of samples will be packaged into suitable containers with cool packs. Also included in the shipment are samples for collecting data on the shipment

itself, a temperature control sample and a background screen sample.

6.4 For the temperature control sample, each collaborator will measure the temperature of the shipment upon arrival. The objective of the temperature control sample is to verify

the shipment package maintained ≤8° C.

6.5

Upon receipt, each collaborator will test each sample according to the reference method and the alternative method. In addition, the expert laboratory will test a set of samples at the same time as the collaborating laboratories confirm the presence of the