A total of 150 samples of raw milk, ice cream and yogurt (50 of each) were collected randomly in their packages from different localities in Beni‐Suef governorate, Egypt, to study the presence of Bacillus cereus in these products. B. cereus could be detected in 30, 48 and 2% of examined raw milk, ice cream and yogurt samples with a mean count of 9.11 × 102 ± 4.87 × 102, 6.37 × 103 ± 2.83 × 103 and 6 ± 5.9 cells/mL or g, respectively. All B. cereus isolates showed hemolytic activity; 95% of isolates showed vero cell toxicity and 27.5% of them killed adult mice. B. cereus could not be detected in artificially inoculated yogurt after 24 and 48 h. B. cereus was sensitive to pefloxacin, gentamycin, chloramphenicol and nalidixic acid, whereas all isolates were resistant to colistin sulfate. Public health significance and suggestive control measures are discussed.
PRACTICAL APPLICATIONS
The incidence of contamination of raw milk and ice cream by Bacillus cereus is fairly high, and nearly all of the isolates showed hemolysin and cytotoxic toxin activities, so the risk of food poisoning caused by B. cereus in such products should not be neglected. B. cereus rapidly dies in yogurt, so acidification is a common method of preservation, and as the acidity of fermented milk increased, B. cereus fails to survive. Pefloxacin, gentamicin and chloramphenicol are effective antibiotics against B. cereus infection. B. cereus is highly resistant to colistin sulfate.
The objectives of this study were to assess the microbiological quality of domiati cheese and to evaluate the capacity of Lactobacillus acidophilus La-5 and Bifidobacterium longum ATCC15707 to inhibit the growth of Staphylococcus aureus and Escherichia coli O157:H7 during manufacture and storage of domiati cheese. The results of the microbial investigation indicated poor microbiological quality of cheese samples, the microbiological parameters recorded higher values than admissible levels. Domiati cheese produced from milk artificially contaminated with S. aureus and E. coli O157:H7 was used as a model for studying the antibacterial activity of L. acidophilus La-5 and B. longum ATCC15707 against these pathogens. The results obtained in this study indicated the remarkable effect of L. acidophilus La-5 and B. longum ATCC15707 in preventing survival of S. aureus and E. coli O157:H7 during cheese storage. The inactivation rate was more pronounced with S. aureus than E. coli O157:H7 and it was dependent on probiotic strain. L. acidophilus inactivation was significantly higher (P value < 0.05) than that attained with B. longum. Survival of probiotic bacteria in domiati cheese was satisfactory.
PRACTICAL APPLICATIONSThe microbial contamination of domiati cheese represents not only spoilage of the product but also constitutes a high risk to human health. The probiotic bacteria have the ability to improve the microbiological quality and safety of domiati cheese. Survival of both Lactobacillus acidophilus La-5 and Bifidobacterium longum ATCC15707 in domiati cheese was satisfactory, which indicate that the domiati cheese would be a suitable vehicle for the delivery of probiotic bacteria.
Aluminium is non-essential element for humans and is considered to be a toxic metal. The present investigation was carried out to determine aluminium concentrations in milk and milk products, to estimate the intake of aluminium via consumption of milk and dairy products and to investigate the leachability of aluminium from utensils into milk products during processing and storage. A total of 85 milk and milk products samples were collected from farms, individual farmers and dairy shops in Beni-Suef governorate, Egypt. Mean aluminium concentrations in farm milk, market milk, kareish cheese, yoghurt and rice pudding were 19.93, 107.32, 52.36, 4.19 and 80.97 ppm, respectively. Aluminium intake through milk and milk products consumption was calculated to be 246.72 mg weekG 1 which corresponds to 205.5% of the PTWI. Processing and storage of milk in aluminium containers also raise aluminium content significantly. The results indicated the advantage of using stainless steel over aluminium utensils for processing and storage of milk products, especially those acidic in nature.
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