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3M Petrifilm RYM Collaborative Study
June 2014
OMA-2014-June-XXX
1.
INTRODUCTION
The goal of this collaborative study is to estimate the following performance
parameters of the 3M™
Petrifilm™ Rapid Yeast and Mold (RYM) Count Plate
Method: repeatability (s
r
) and reproducibility (s
R
) standard deviations, relative
standard deviations of repeatability (RSD
r
) and reproducibility (RSD
R
) and
repeatability and reproducibility values (r and R, respectively). Test portions from
4 different contamination levels will be sent to collaborators where they will
perform the 3M Petrifilm RYM Count Plate and parts 1 and 2 of the ISO 21527-
2008
reference method and the
FDA BAM Chapter 18
reference methods. The
following foods will be tested: raw frozen ground beef (80% lean, 20% fat) as a high
moisture product and raw almonds as a low moisture product.
1.1.
Description of the 3M™ Petrifilm™ Rapid Yeast and Mold Count Plate
The 3M™ Petrifilm™ Rapid Yeast and Mold Count (RYM) Plate is a sample-
ready culture medium system which contains nutrients supplemented with
antibiotics, a cold-water-soluble gelling agent, and an indicator system that
facilitates yeast and mold enumeration. 3M Petrifilm RYM Plates are used for the
enumeration of yeast and mold in the food and beverage industries. 3M Petrifilm
RYM Plate components are decontaminated though not sterilized. 3M Food Safety
is certified to ISO (International Organization for Standardization) 9001 for design
and manufacturing.
1.2.
Summary of 3M Petrifilm RYM Count Plate PTM/Precollaborative Study
The results of the PTM study demonstrated the 3M Petrifilm RYM Plate method
to be equivalent to or better than the average log counts of the ISO 21527:2008
parts 1 and 2 and the FDA BAM Chapter 18 reference methods at 48 and 60 hours
for the ten matrices evaluated: yogurt, frozen bread dough, fermented salami, sour
cream, ready-made pie, frozen ground beef patties, raw almonds, sandwiches,
sliced apples, dehydrated soup. In addition, the repeatability of the 3M Petrifilm
RYM method was equivalent to or better than the reference methods at both 48
and 60 hours. In the independent laboratory validation study, there was no
significant difference in detection, enumeration, or repeatability between the 3M
Petrifilm RYM method and ISO 21527:2008 parts 1 and 2 and the FDA BAM
Chapter 18 reference methods for yogurt at 48 and 60 hours. For frozen ground
beef patties there was a significant difference between the 3M Petrifilm RYM
Plate method and the reference methods at 48 and 60 hours with the 3M Petrifilm
RYM method enumerating more organisms that the reference methods(p<0.05).
In strain studies, of the 42 yeast and mold tested, all produced typical colonies on
3M Petrifilm RYM Plate method. Of the 4 bacterial strains that should not have
been detected by the 3M Petrifilm RYM Plate method, all 4 strains did not grow
on the plate. Lot-to-lot study of 3M Petrifilm RYM Plates was evaluated and
showed no differences at time zero. In assay ruggedness studies, there was no
4
DRAFT DOCUMENT
AOAC Research Institute
Expert Review Panel Use Only
OMAMAN-16A/ Collaborative Study Protocol
ERP Use Only - December 2014