Knowledge on the initial bioburden (H0) in raw milk intended for pasteurization is a useful tool to enable risk assessments for both product... Show moreKnowledge on the initial bioburden (H0) in raw milk intended for pasteurization is a useful tool to enable risk assessments for both product and process safety. In a nationwide survey, a total of 214 comingled raw milk samples were collected from unique silos in different regions of United States. The samples were analyzed for prevalence and levels of Salmonella spp. and Escherichia coli O157:H7 using the VIDAS® (bioMerièux) SLM and ECPT assays and cultural methods. Total Viable Count (TVC), Coliforms (CC), Enterobacteriaceae (EB), E. coli (EC) and Staphylococcus aureus (STA) counts in raw silo milk were analyzed using the TEMPO® Automated System (bioMerièux). Aerobic spore counts (ASC) in raw milk were analyzed by a modified Standard Method. Raw milk samples were directly streaked on to Methicillin-resistant Staphylococcus aureus (MRSA) agar. Forty seven out of 214 samples (21.96%) were positive for Salmonella spp. at an average level of 0.973 MPN/ml. Nineteen out of 214 samples (9.05%) were positive for E. coli O157:H7 at an average level of 0.069 MPN/ml. Presumptive MRSA was detected in 8 out of 206 (3.88%) raw milk samples; however biochemical analysis did not result in positive confirmation. The average counts for TVC, CC, EB, EC STA and ASC were found to be 4.62, 3.23, 3.56, 3.23, 2.36 and 1.42 log CFU/ml, respectively. There was no correlation observed between the quality indicating microorganisms (TVC, CC, EB, EC and ASC) and the presence of Salmonella spp. or E. coli O157:H7. Based on the literature studies, occurrences of these pathogens in raw milk were at low prevalence rates when the sampling was done at bulk milk tank levels. Higher volume samples taken from commingled silos resulted in higher prevalence rates of pathogens. The results obtained in this study can be used for establishment of Food Safety Objective (FSO) in raw milk intended for pasteurization. M.S. in Food Safety and Technology, May 2011 Show less
