Microbiology-PTM-OMA_Modules_1-5

MPN Replicates – Qualitative methods

• For MPN determination of Material 2 (low level), remove:  • 5 replicate large MPN test portions 2‐5x larger than the reference method test  portions and  • 5 replicate small MPN test portions 2‐5x smaller than the reference method test  portions  • For MPN determination of Material 3 (high level), remove: • 5 replicate medium MPN test portions 2‐5x smaller than the reference method test  portions • 5 replicate small MPN test portions 2‐5x smaller than the medium MPN test portions  • Analyze by the reference method, maintaining normal test portion to  enrichment media ratio. • MPNs not applicable to environmental surfaces, chicken carcasses, whole  cantaloupe, or other “unitized” matrixes.