Comparative Analysis of Microbial Populations in Raw and Pasteurized Cow Milk Collected from Dairy Farms in Jos, Plateau State

Milk is a highly perishable food matrix susceptible to contamination from multiple sources including the animal, environment, and handling practices. This study compared microbial populations in raw and pasteurized cow milk collected from selected dairy farms and mini-dairies in Jos, Plateau State, North Central Nigeria. A total of 60 samples (30 raw, 30 pasteurized) were collected and analyzed for total viable count, coliform count, thermoduric count, somatic cell count, and isolation of Listeria monocytogenes, Brucella species, and Mycobacterium bovis using selective enrichment and culture methods. Results showed that raw milk samples had significantly higher total viable counts (mean: 7.2 × 10^6 CFU/mL) compared to pasteurized samples (mean: 4.1 × 10^3 CFU/mL). Listeria monocytogenes was detected in 26.7 percent of raw milk samples and was absent in pasteurized samples, confirming adequate pasteurization efficacy. However, 16.7 percent of pasteurized samples showed evidence of post-pasteurization contamination with coliforms, attributed to recontamination during bottling. Brucella-positive samples were identified in 6.7 percent of raw milk, posing occupational and zoonotic risk. These findings emphasize the importance of strict pasteurization compliance, hygienic bottling practices, and surveillance for zoonotic pathogens in the Plateau State dairy industry. Keywords: raw milk, pasteurized milk, Listeria monocytogenes, dairy farms, Jos.