Milk decontamination and an effective pasteurizing method for household dairies.
Authors:
OLAJUYIGBE Olufunmiso
Publication Type: Journal article
Journal: Journal Of Pure And Applied Microbiology
ISSN Number:
0
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Abstract
This study investigated the bacteriological and the hygienic properties of some
commonly sold canned milk and determined the effectiveness of pasteurization of milk
contaminated with bacterial isolates spectrophotometrically. In this study, Escherichia coli,
Streptococcus spp., Enterococcus aerogenes, Proteus spp., Clostridium spp., Lactobacillus spp.
and Staphylococcus aureus were isolated from the milk samples. The bacterial load of the milk
samples ranged from 5 x 105 to 22 x 105 cfu/ml. The methylene reduction time indicating the
hygienic quality of each milk sample varied from one milk to the other. While NNM and VSM
samples not decolourized after 8 h were considered excellent and PNM and OFM decolourized
methylene blue after 6 and 7 h respectively were considered good milk samples, CFM and
TCM that decolourized methylene blue after 4 and 5 h respectively were considered fair milk
samples. None of them was considered poor as they were not decolourized in less than 2 h.
Pasteurizing milk contaminated with indigenous microflora (IMF), E. coli and Strep. pyogenes
at 40oC, 50oC, 60oC and 70oC over a period of 30 min showed a varied degree of reduction in
the absorbances and its effectiveness. A 10oC increase in temperature resulted in significant
reduction in the absorbances obtained at different time intervals for all the milk samples. This
investigation shows that pasteurizing milk with low heating would reduce the microbial loads
of the milk samples. The method of pasteurizing milk in this study would be applicable in the
household dairies where sophisticated equipment are not required to control microbial loads
in milk.