Microsoft Word - 3M Petrifilm REC Plate OMA Manuscript 09121

ERP Methods Book

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Results were compared using a paired statistical analysis (8). Inoculating strains are listed in  1

2

Table 10. 

In addition, 12 of the 31 food matrices (fresh raw ground beef, raw frozen chicken wings,  3

raw milk, whole liquid egg, tuna sushi, smoked salmon, bunched spinach, pasteurized carrot  4

juice, ready‐made sandwiches, raw vegetable with salad dressing, chicken feed and soybean  5

meal) and both environmental surfaces were compared to ISO 4832:2006 and ISO 16649‐ 6

2:2001 reference methods as part of a harmonized validation study with MicroVal. As such, the  7

comparison to the ISO methods was conducted per ISO 16140‐2:2106 validation guidelines (9).  8

The same inoculated lots of material were used for all comparisons. Five replicate portions for  9

each level of each matrix were prepared and diluted in PSS, as directed in the ISO methods, and  10

then tested by the 3M Petrifilm Rapid E. coli /Coliform Count Plate, ISO 4832:2006 and ISO  11

16649‐2:2001. Results were compared using a paired statistical analysis. An uncontaminated  12

level was not tested in this comparison, as it is not required by ISO 16140‐2: 2016.  13

To prepare the artificially contaminated foods, an isolated colony from each inoculating  14 strain was transferred from trypticase soy agar with 5% sheep blood (SBA) into ISO‐BPW and  15

incubated at 35 ± 1 o C for 16–24 h. Following incubation, the culture was diluted to a desired  16

target level using ISO‐BPW as the diluent and a bulk lot of each matrix was inoculated and  17

homogenized by hand. Refrigerated foods were held for 48–72 h at 2–8°C and frozen foods  18

were held for 2 weeks at ‐20°C or less prior to analysis. For all low moisture, shelf‐stable foods,  19

a lyophilized inoculum was used to spike a bulk lot of each matrix and then homogenized. Low  20

moisture foods were held at ambient temperature (20–25°C) for two weeks.  21

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December 6, 2018