Microbiological Study of Some Cheese and Milk Powder Samples

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Dalia E. El-Etriby
Infection Control Unit, Specialized Internal Medicine Hospital, Mansoura University


Background: Milk is a nutritious food for human, but it is also a suitable medium for
growth of microorganisms and can spoil easily. Objective: The aim of this study was to
establish the microbidogical quality of cheese and powdered milk in order to prevent
potential risks of dairy products for consumer health and to ensure its quality.
Methodology: A total of seventy five samples of different cheese types (Soft Cheese,
Processed cheese and Hard cheese, 25 each) and fifty samples of milk powder were
collected from different supermarkets in Mansoura City, Dakahlia Governorate. All
samples were evaluated microbiologically for the quality of this products through
determination of total bacterial count, coliforms count and Moulds and Yeasts count.
Isolation and identification of E.Coli, Staphylococcus aureus, Salmonella spp., moulds
and yeasts were also carried out. Results: In Cheese Samples, the mean value of total
aerobic count were 1.2×104±2.1×103, 2.2×103±3.3×102, 1.1×104±6.2×103 cfu/gm for
Soft, Processed and Hard Cheese, respectively. The mean value of Coliform count were
2.3×103±0.21×103, 1.2×102±0.33×102 , 3.1x102±0.56×102 cfu/gm for Soft, Processed and
Hard Cheese, respectively. The mean value of mould and yeast count were
3.2×103±0.12×103. 1.1×102±0.13×103, 1.6×102±0.75×102 cfu/gm for Soft, Processed and
Hard cheese, respectively. Salmonella spp. appeared only in 20% of Soft cheese samples,
while it was absent in Processed and Hard cheese samples. Staphylococcus aureus were
absent in Hard cheese, while it was detected in 60% and 32% of Soft and Processed
cheese, respectively. The mean value of E.coli were 3.2×103±0.12×103,
1.1×103±0.13×103 cfu/gm for Soft and Processed cheese, respectively. While it was not
detected in Hard Cheese samples. In milk powder samples, the mean value of total
aerobic count was 2.1×103±0.12×103 cfu/g. Total coliforms count of examined samples
was 12-55 cfu/gm in 4(8%) samples, while coliforms were not found in 46 (92% ) of milk
powder samples. The mean value of moulds and yeasts count was 1.3×102±0.67×102,
which was insignificant. Salmonella spp. and E.coli were not detected in all milk powder
samples, while Staphylococcus aureus was found in 18% of the examined samples.
Conclusions: From the results of this study, it could conclude that the unhygienic
conditions prevailing during handling, processing, distribution or sale should be
reviewed and controlled by respective authority in order to prevent contamination of
cheese and powdered milk for the safety of consumers

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