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International Journal of Dairy Science

Year: 2012  |  Volume: 7  |  Issue: 4  |  Page No.: 103 - 108

Microbial Assessments of Bulk Milk Before and After Pasteurization in Two Different Dairy Farms in Zaria, Nigeria

M.K. Lawan, F.O. Abdulsalawu, A. Suleiman, T. Aluwong and L.S. Yaqub


Milk has high nutritional values and an important source of protein, minerals, vitamins and fat in human diet. It provides excellent medium for growth of both pathogenic and spoilage microorganism. This study was carried out with the aim of assessing the microbial quality of bulk milk before and after pasteurization, in two different dairy farms in Zaria. Bulk milk samples were collected on daily basis for a period of 30 days during which 30 samples each, of pasteurized and raw milk were collected from each of the farms making a total of 120 milk samples. The both samples of raw milk before pasteurization and post-pasteurization of farm A and B were analyze for total aerobic, coliform plates counts and E. coli isolation rates. Mean results of aerobic plate counts of raw milk for farm A and B before pasteurization were; 5.70 and 6.04 log10 CFU mL-1, respectively. These counts decrease to 3.76 and 4.20 log10 CFU mL-1 after pasteurization of the milk. Similarly, the E. coli isolation rate for farm A and B were; 20 and 53.3%, respectively. These also decrease to 6.7 and 13.3% after pasteurization. In addition, coliform counts also follow similarly trend. The coliform count in farm A and B were; 5.32 and 6.49 log10 CFU mL-1, respectively. The counts decrease to 3.16 and 3.74 log10 CFU mL-1 after pasteurization of the milk. Total coliform and aerobic plates counts before bulk pasteurization in both farms were significantly different (p<0.05), with post-pasteurization values when subjected to paired t-test. The coliform and aerobic plates demonstrated poor hygiene practices and inefficient pasteurization methods in both farms. High isolation rate of E. coli in post pasteurization is an indicative of fecal contamination of the bulk milk indicative of serious public health concern. In conclusion, the present study has demonstrated poor method of pasteurization couple with lack of good hygienic practices such as: proper solid waste management, potable water, cleanliness of milking area and absent of milking installation. These are all factors that contributed to production of poor quality milk in both farms with high coliform, aerobic plates and high isolation rate of Escherichia coli post pasteurization.

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