AOAC-RI ERP Book MICRO.pdf

3M Petrifilm RYM Collaborative Study

June 2014

OMA-2014-June-XXX

Collaborators will receive eight 25g test portions to test each matrix using the 3M Petrifilm

RYM and reference methods. Please review the reference methods carefully before initiating

analysis.

One additional 60 g control (negative) test portion will be provided to each collaborator for each

matrix to determine the total plate count on the day of analysis. One temperature control sample

will also be included in the shipment to document the temperature of the sample upon receipt.

Record all results on the data sheets provided.

Food Type

Reference Methods

Diluent

3M Petrifilm

RYM plates

Raw frozen

ground beef

(80% lean/20%

fat)

ISO 21527-2008 &

FDA-BAM Ch. 18

0.1% Peptone

2 at 25°C

2 at 28°C

Raw almonds

ISO 21527-2008 &

FDA-BAM Ch. 18

0.1% Peptone

2 at 25°C

2 at 28°C

1.1.

Sample Preparation

1.1.1.

Prepare a 1:10 dilution of each test portion –

25g plus 225 mL of 0.1% Peptone

Water (10

-1

)

1.1.2.

Stomach for 2 minutes in the stomacher bag.

1.1.3.

Prepare an additional 4 dilutions (10

-2

to 10

-4

) using 0.1% Peptone Water.

1.2.

3M Petrifilm Rapid Yeast and Mold Count Plate Method

(please refer to the IFU for

additional details and Appendix 8.4 for flow diagram)

1.2.1 Place

four

3M Petrifilm RYM Plates on a flat, level surface for each dilution to be

tested.

1.2.2 Lift the top film and with the pipette perpendicular dispense 1 mL of each dilution

onto the center of bottom film of each plate.

1.2.3 Drop the top film down onto the sample.

1.2.4 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.

1.2.5 Remove the spreader and leave the plate undisturbed for at least one minute to

permit the gel to form.

1.2.6 Incubate

two

3M Petrifilm RYM Plates of each dilution at 25°C and

two

Petrifilm RYM Plates at 28°C

in a horizontal position with the clear side up in stacks of

no more than 40. Enumerate plates at

48 ±

2 hours and 60 hours, keeping the time the

plates are out of the incubator to a minimum

DRAFT DOCUMENT

AO C Research Institute

Expert Review Panel Use Only

OMAMAN-16A/ Collaborative Study Protocol

ERP Use Only - December 2014