RI-ERP-FINALACTION-Recommendations

OMA 2015.13: Collaborative Study Protocol Expert Review Panel Use Only September, 2017

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 RAC Plate growth area before the gel is formed. Do not slide the spreader across the film. 2.5. Remove the spreader and leave the plate undisturbed for at least one minute to permit the gel to form. 2.5.1. Incubate 3M Petrifilm RAC Plates at 32°C (and at 35 °C for raw easy peelshrimp)in a horizontal position with the clear side up in stacks of no more than 40for raw easy peel shrimp and no more than 20 for pasteurized skim milk and instant non-fat dried milk to ensure all plates reach the appropriate temperature. Enumerate plates after 24 ±2 hours for raw easy-peel shrimp and skim milk and after 48 ±3 hours for instant non-fat dried milk. 2.5.2. Count the 3M Petrifilm RAC Plates using a standard colony counter or other illuminated magnifier. Count all colonies regardless of color, size or intensity. 2.5.3. The circular growth area is approximately 30 cm 2 . Gridlines are visible with the use of a backlight to assist with estimated enumeration. Estimates can be made on 3M Petrifilm RAC Plates containing greater than 300 colonies by counting the number of colonies in two or more representative squares and determining the average number per square. Multiply the average number by 30 to determine the estimated count per plate. 2.5.4. High concentrations of colonies on the 3M Petrifilm RAC Plates will cause the entire growth area to become blue or red. Occasionally, on overcrowded 3M Petrifilm RAC Plates, the center may lack visible colonies, but many small colonies can be seen on the edges. When any of these occurs, record results as too numerous to count (TNTC). When an actual count is required, plate at a higher dilution. 2.5.5. Where necessary, colonies may be isolated for further identification. Lift the top film and pick the colony from the gel. Test using standard procedures. 2.6.2. Incubate at 35 ± 1°C for 48 ± 2 hr. 2.6.3. Count and record typical colonies. 2.6.4. Record results from the plates with 30-300 colonies and report average results in colony forming units (CFU) per gram. 2.7. SMEDPChapter 6 2.7.1. Using the diluted sample (prepared in section 1.1) add 1 mL of each dilution into (duplicate) Petri dishes. Add Standard Methods Agar (SMA) and swirl. 2.7.2. Incubate at 32 ± 1°C for 48 ± 3hr for skim milk and 72 ± 3 hr for instant non-fat dried milk. 2.7.3. Count and record typical colonies. 2.6. FDA-BAM Chapter 3 (January 2001) 1 2.6.1. Using the diluted sample (prepared in section 1.1) add 1 mLof each dilution into (duplicate) Petri dishes. Add Plate Count Agar (PCA) and swirl.

AOAC Research Institute Expert Review Pane Use Only

1 http://www.fda.gov/Food/FoodScienceResearch/LaboratoryMethods/ucm063346.htm