30 / 596
3M MDA 2
Listeria
species and
L. monocytogenes
Collaborative Study
OMA-2016-MONTH-XXX
5/4/16
performed starting with the secondary enrichment steps. The recovered isolates
will be identified by the API Listeria Identification System or the VITEK 2 GP
(AOAC OMA 2012.02).
One additional control (negative) test portion will be provided to each
collaborator for each matrix to determine the total plate count on the day of
analysis.
3.6
Most Probable Number (MPN) Analysis.
To determine the level of
Listeria
spp. in the inoculated food test portions on the day of initiation of analysis, a 5-
tube MPN determination is performed by the coordinating laboratory following
the appropriate reference method. The level of
Listeria
will be determined by
Most Probable Number (MPN) on the day of analysis by analyzing 5 x 50 g, 20 x
25 g (reference method test portions) and 5 x 10 g inoculated test samples for raw
chicken breast. For the 125 g deli turkey test portion analysis, 5 x 250 g, 20 x 125
g (reference method test portions) and 5 x 60 g test portions will be analyzed.
Each test portion will be enriched with the appropriate reference method
enrichment broth at a 1:10 dilution and analyzed by the reference method
procedure. The number of positives from the three test levels will be used to
calculate the MPN using the MPN calculator.
( http://www.lcfltd.com/customer/LCFMPNCalculator.exe)[1 ].
Report MPN as MPN/test portion.
4.0
3M MDA2 -
Listeria
species
4.1
Applicability
For the detection of
Listeria
species from:
4.1.1
Beef hot dogs
(25 g and 125 g): 24-30 hours of enrichment in Demi Fraser
broth at 37°C
4.1.2
Cold smoked salmon
(25 g): 24-30 hours of enrichment in Demi Fraser
broth at 37°C
4.1.3
Deli turkey
(25 g and 125 g): 24-30 hours of enrichment in Demi Fraser
broth at 37°C
4.1.4
Full fat cottage cheese
(25 g): 24-30 hours of enrichment in Demi Fraser
broth at 37°C
4.1.5
Queso fresco
(25 g): 24-30 hours of enrichment in Demi Fraser broth at
37°C
4.1.6
Vanilla ice cream
(25 g): 24-30 hours of enrichment in Demi Fraser broth
at 37°C
4.1.7
Bagged raw spinach
(25 g): 24-30 hours of enrichment in Demi Fraser
broth at 37°C
4.1.8
Cantaloupe
(whole melon): 24-30 hours of enrichment in Demi Fraser
broth at 37°C
4.1.9
Raw chicken leg pieces
(25 g): 28-32 hours of enrichment in Demi Fraser
broth at 37°C
AOAC Research Institute
Expert Review Panel Use Only
OMAMAN-29/OMAMAN-30 Combined Collaborative Study Protocol
OMA ERP - June 2016
ERP Use Only