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Bird et al.: J ournal of AOAC International Vol. 98, No. 3, 2015 767
Evaluation of the 3M™ Petrifilm ™ Rapid Yeast and Mold
Count Plate for the Enumeration of Yeast and Mold in Food:
Collaborative Study, First Action 2014.05
Patrick Bird, Jonathan Flannery, Erin Crowley, James Agin, and David Goins
Q Laboratories, Inc., 1400 Harrison Ave, Cincinnati, OH 45214
Robert Jechorek1
3M Food Safety Department, 3M Center – Bldg. 260-6B-01, St. Paul, MN 55144
Collaborators: K. Beers, J. Blumfield, R. Brooks, B. Brown, A. Calle, R. Dermer, B. Dieckleman, C. Fagundes, P. Fatemi,
A. Gaydos, K. Gonzales, A. Hankins, T. Hirsch, W. Lee, A. Mastalerz , J. Medellin, D. Metzger, A. Morris, J. Pickett, K. Powers,
J. Reed, J. Reynolds, N. Shipley, S. Spencer, J. Williams
Received January 21, 2015.
The method was approved by the Expert Review Panel for
Microbiology for Food and Environmental Surfaces as First Action.
The Expert Review Panel for Microbiology for Food and
Environmental Surfaces invites method users to provide feedback on
the First Action methods. Feedback from method users will help verify
that the methods are fit for purpose and are critical to gaining global
recognition and acceptance of the methods. Comments can be sent
directly to the corresponding author or
1 Corresponding author’s e-mail:
DOI: 10.5740/jaoacint.15-006
FOOD BIOLOGICAL CONTAMINANTS
The 3M™ Petrifilm™ Rapid Yeast and Mold (RYM)
Count Plate is a simple, ready-to-use chromogenic
culture method for the rapid detection and
enumeration of yeast and mold in food products.
The 3M Petrifilm RYM Count Plate method was
compared to the U.S. Food and Drug Administration
Bacteriological Analytical Manual (FDA BAM) Chapter
18, Yeasts, Molds and Mycotoxins and the ISO
21527:2008 Microbiology of Food and Animal Feeding
Stuffs—Horizontal Method for the Enumeration for
Yeast and Molds – Part 1: Colony Count Technique
in Products with Water Activity Greater Than 0.95
and Part 2: Colony Count Technique in Products with
Water Activity Less Than or Equal to 0.95 reference
methods for raw almonds and raw frozen ground beef
patties (77% lean). The 3M Petrifilm RYM Count Plate
method was evaluated using a paired study design
in a multi-laboratory collaborative study following
the current AOAC Validation Guidelines. Three target
contamination levels (low, 10–100 CFU/g; medium,
100–1000 CFU/g; high 1000–10000 CFU/g) as well
as an uninoculated control level (0 CFU/g) were
evaluated for each matrix. Samples evaluated by the
3M Petrifilm RYM Count Plate method were prepared
in duplicate and incubated at both 25°C and 28°C.
Plates at both temperatures were enumerated after 48
and 60 h of incubation. No significant difference was
observed between the 3M Petrifilm RYM Count Plate
method and the FDA BAM or ISO 21527 reference
methods for each contamination level. No statistical
differences were observed between samples analyzed
by the 3M Petrifilm RYM Count Plate method (at
either 25°C or 28°C) and the reference methods. No
statistical significant differences were observed
between enumeration of colonies at 48 and 60 h on
the 3M Petrifilm RYM Count Plate method and the
reference methods.
Foodborne yeasts and mold constitute a large and diverse
group of microorganisms. Due to their heterotrophic
nature, these microorganisms are able to adapt and survive
in a wide range of environmental conditions including acidic
and alkaline conditions, temperatures ranging from 5°C to 35°C
and in low moisture (<0.85Aw) products (1, 2). Many of these
species cause varying degrees of food decomposition leading
to substantial economic loses (2). Several foodborne molds,
and possibly some yeasts, may also be hazardous to human
health due to their ability to produce toxic metabolites (1).
The presence of these microorganisms in food commodities
can indicate contamination of the product, inadequately
cleaned food processing equipment, or inadequate food storage
facilities (2). Cultural enumeration of yeasts and molds can take
5 to 7 days and the need for rapid enumeration is critical to
the food industry. The 3MTM PetrifilmTM Rapid Yeast and Mold
Count (RYM) Plate uses a cold-water-soluble gelling agent and
an indicator system to facilitate the enumeration of yeast and
molds after 48 h of incubation.
The 3M Petrifilm RYM Count Plate allows for the simple and
rapid enumeration of yeasts and molds in the food and beverage
industries. Samples are diluted in 0.1% peptone water and
a sample aliquot is plated onto the 3M Petrifilm RYM Count
Plate. The sample aliquot is dispersed throughout the growth
area and the plates can be incubated at 25–28°C. Enumeration
of colonies occurs in as little as 48 h of incubation. If colonies
appear faint, the plates can be incubated up to an additional 12 h
for enhanced interpretation. The 3M Petrifilm RYM Count Plate
provides gridlines to assist with the enumeration.
Prior to the collaborative study, the 3M Petrifilm RYM Count
Plate method was validated according to AOAC Validation
Guidelines (3) in a harmonized AOAC Performance Tested
MethodSM (PTM) study. The objective of the PTM study was to
demonstrate that the 3M Petrifilm RYM Count Plate accurately
detected and enumerated yeasts and molds in selected foods
as claimed by the manufacturer and that no difference in