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3M Petrifilm RYM Collaborative Study
June 2014
OMA-2014-June-XXX
5.2.1.
Cat. #6475 3M Petrifilm Rapid Yeast & Mold Plates 25/pouch, 2
pouches/box
5.2.2. Cat. # 6477 3M Petrifilm Rapid Yeast & Mold Plates 25/ pouch, 20
pouches /case
5.3.
Additional Reagents - 3M Petrifilm RYM Count Plate
5.3.1.
Sterile diluent –
0.1% peptone water
5.4.
Additional media
5.4.1.
Dichloran-rose bengal chloramphenicol (DRBC) agar
5.4.2.
Dichloran 18% glycerol (DG18) agar
5.5.
Apparatus
5.5.1.
Pipettes
. –
capable of pipetting 1,000µL or sterile serological pipette
5.5.2.
Sterile pipette tips.
–
capable of 1,000µL
5.5.3.
Stomacher®
. –
Seward or equivalent
5.5.4.
Filter Stomacher®
bags
. - Seward or equivalent
5.5.5.
3M™
Petrifilm™
Flat Spreader (6425)
5.5.6.
Incubators
. –
Incubator capable of maintaining 25 ±
1°C and 28 ±
1°C, and having a solid front so as to maintain a dark interior.
5.5.7.
Refrigerator
. –
capable of maintaining 2-8°C, for storing the 3M
Petrifilm RYM Count Plates
5.5.8.
L shaped spreaders (hockey sticks)
5.6.
Determination
5.7.
Sample Preparation
5.7.1. Prepare a 1:10 dilution of each test portion –
25g plus 225 mL of 0.1%
Peptone Water (10
-1
)
5.7.2. Stomach for 2 minutes in the stomacher bag.
5.7.3. Prepare an additional 3 dilutions (10
-2
to 10
-4
) using 0.1% Peptone Water.
5.8.
3M Petrifilm Rapid Yeast and Mold Count Plate Method
(please refer to the
IFU for additional details)
5.8.1.
Place two 3M Petrifilm RYM Plates on a flat, level surface for each
dilution to be tested.
5.8.2.
Lift the top film and with the pipette perpendicular dispense 1 mL of each
dilution onto the center of bottom film of each plate.
5.8.3.
Drop the top film down onto the sample.
5.8.4.
Place the 3M Petrifilm Flat Spreader (6425) on the center of the plate.
Press gently on the center of the spreader to distribute the sample evenly.
Spread the inoculum over the entire 3M Petrifilm RYM Plate growth area
before the gel is formed. Do not slide the spreader across the film.
5.8.5.
Remove the spreader and leave the plate undisturbed for at least one
minute to permit the gel to form.
5.8.6.
Incubate 3M Petrifilm RYM Plates at 25 and 28°C
in a horizontal position
with the clear side up in stacks of no more than 40. Enumerate plates at
48
8
DRAFT DOCUMENT
AOAC Research Institute
Expert Review Panel Use Only
OMAMAN-16A/ Collaborative Study Protocol
ERP Use Only - December 2014