AOAC ERP MICRO AUGUST 2018

OMAMAN-31 E: AOAC RI PTM Report 091501 ERP Use Only - March 2016

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The level of Salmonella in the high level inoculum for all 25 g test portions was determined by Most Probable Number (MPN) on the day of analysis by evaluating 5 x 50 g, 5 x 25 g (reference method test portions), and 5 x 10 g inoculated test samples. The level of Salmonella in the high level inoculum for all 100 g test portions was determined by MPN by evaluating 5 x 200 g, 5 x 100 g (reference method test portions), and 5 x 50 g inoculated test samples. The level of Salmonella in the high level inoculum for all 325 g test portions was determined by MPN by evaluating 5 x 650 g, 5 x 325 g (reference method test portions), and 5 x 160 g inoculated test samples. The level of Salmonella in the high level inoculum for all 375 g test portions was determined by MPN by evaluating 5 x 750 g, 5 x 375 g (reference method test portions), and 5 x 180 g inoculated test samples. Each test portion size for the MPN of each matrix is present below in Table A. The number of positives from the 3 test levels was used to calculate the MPN using

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the LCF MPN calculator (version 1.6) provided by AOAC RI. [7] (http://www.lcfltd.com/customer/LCFMPNCalculator.exe)

Table A: MPN Test Portion Sizes

Reference Method Test Portion

Inoculation Level

MPN Test Portions

Low High Low High Low High Low High

5 x 50 g 5 x 50 g 5 x 200 g 5 x 200 g 5 x 650 g 5 x 650 g 5 x 750 g 5 x 750 g

20 x 25 g* 5 x 25 g* 20 x 100 g* 5 x 100 g* 20 x 325 g* 5 x 325 g* 20 x 375 g* 5 x 375 g*

5 x 10 g 5 x 10 g 5 x 50 g 5 x 50 g 5 x 160 g 5 x 160 g 5 x 180 g 5 x 180 g

25 g

100 g

325 g

375 g

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* Test portions from reference method

USDA/FSIS-MLG Method 4.08 Isolation and Identification of Salmonella from Meat, Poultry, Pasteurized Egg, and Catfish Products and Carcass and Environmental Sponges For the USDA/FSIS reference method, the 25 gram raw ground beef test portions were enriched with 75 mL of modified tryptic soy broth (mTSB) and incubated for 15-24 hours at 42 ±1 °C. The 25 gram raw ground chicken test portions were combined with 225 mL of BPW and incubated for 20-24 hours at 35 ± 2 °C. The 325 g test portions of cooked breaded chicken were combined with 2925 mL of BPW, and then incubated for 18-24 hours at 35 ±2 °C. For chicken carcass rinse test portions, 30 ± 0.6 mL of rinse fluid was combined with 30 ± 0.6 mL of BPW and incubated for 20-24 hours at 35 ± 2 °C. Chicken carcass sponges were combined with 50 ± 1 mL of BPW and incubated for 20-24 hours at 35 ±2 °C. For 100 g test portions of pasteurized liquid whole egg, 900 mL of BPW was combined with the 100 g test portion and incubated for 18-24 hours at 35 ±2 °C. All test portions were stomached for 2 minutes prior to incubation. After incubation, 0.1 ± 0.02 mL of each sample was transferred to 10 mL of mRV broth and 0.5 ± 0.05 mL into 10 mL of TT Hajna broth. The broths were incubated in a circulating water bath at 42 ± 0.5°C for 18-24 hours. Following incubation, a loop full from each broth replicate was

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