Microbiological Study of Some Cheese and Milk Powder Samples

Abstract

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 1.2×10 4 ±2.1×10 3 , 2.2×10 3 ±3.3×10 2 , 1.1×10 4 ±6.2×10 3 cfu/gm for Soft, Processed and Hard Cheese, respectively. The mean value of Coliform count were 2.3×10 3 ±0.21×10 3 , 1.2×10 2 ±0.33×10 2 , 3.1x10 2 ±0.56×10 2 cfu/gm for Soft, Processed and Hard Cheese, respectively. The mean value of mould and yeast count were 3.2×10 3 ±0.12×10 3 . 1.1×10 2 ±0.13×10 3 , 1.6×10 2 ±0.75×10 2 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 3.2×10 3 ±0.12×10 3 , 1.1×10 3 ±0.13×10 3 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 2.1×10 3 ±0.12×10 3 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 1.3×10 2 ±0.67×10 2 , 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