AOAC ERP MICRO AUGUST 2018

OMAMAN-44 B: Collaborative Study Protocol Expert Review Panel Use Only August 2018

probiotic liquid infant formula, milk based and non-probiotic liquid infant formula, soy based), and dry foods with dried culture (non-fat dry milk, infant without probiotics). Refrigerated foods should be stored for 48– 2 h at 4 ° C prior to testing. Frozen foods should be stored for at least 2 weeks at -20 ° C. Artificially contaminated dried foods or shelf stable foods should be stored for at least 2 weeks at room temperature (20–24 ° C). To inoculate stainless steel, grow the EB target strain and a non-target strain to stationary phase in non-selective broth. Dilute each into 0.1% peptone water so that the contamination levels on the surface correspond to the contamination levels in Table 3 at the time of testing. Mix the strains together and spread 250 µL onto each 100 cm 2 surface portion to allow for even distribution over the entire test surface area without producing excessive accumulation of liquid that may dry unevenly. Allow surfaces to dry 5.5.2 Test five replicate test portions from each contamination level (plus the 0- contamination level, for artificially contaminated samples) in duplicate and marking one the two duplicates with an S to represent a singlet result for each 5.5.3 Liquid food products : Add 11 mL into 99 mL microbiologically suitable dilution blanks. Serially dilute to a countable range of 1–150 CFU/mL. Other automated dilution pipets and dilution schemes are acceptable. NOTE : For milk powders and evaporated milks, reconstitute to normal milk solids with sterile water and 5.5.4 Solid food products : Prepare initial 1:10 dilution* by mixing 25 g test sample with 225 mL 0.1% Peptone Water (PW). Homogenize 1–2 min. Prepare all decimal dilutions by transferring 10 mL of the initial suspension/prior dilution into a tube containing 90 mL of sterile diluent blank (or 11 to 99 mL). Serially ERP Use Only dilute to a countable range of 1–150 CFU/mL. * If 1:10 dilution is not fluid enough to pipet or to wick into the Peel Plate, e.g. cereal, do a 1:50 dilution (25 g product to 1225 mL). For each replicate plate 5 mL onto 5 separate 1 mL Peel Plate EB tests and sum result, or plate 5 mL of homogenate in 1 Peel Plate EBHV plate. Test each replicate in duplicate (10 plates) and mark one set of 5 with an S to denote a singlet result. 5.5.5 Chicken carcass rinse : Add 400 mL of n-BPW to the carcass bag, approximately one-half the volume into the interior cavity and the other half over the skin. Rinse inside and out with a rocking motion for 1 min at a rate of approximately 35 forward and back swings per minute. Prepare all decimal dilutions by mixing 10 mL previous dilution with 90 mL of n-BPW Shake all dilutions 25 times in an approximate a one-foot arc or vortex thoroughly. Use a separate pipette to prepare each dilution. Manufacturer will do same procedure using BPD instead matrix. let settle 3 min. Test as a liquid food. for 16–24 h at room temperature. Peel Plate EB – Method 5.5.1 All steps should be performed as indicated in the Peel Plate EB Operator’s Manual, Attachment 1.

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5.4

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5.5