Yeasts constitute large groups of microorganisms that are recently attracting attention of industry and scientists. Different biological activities make them favorable candidates for numerous applications not limited to the food sector. The aim of this study was to examine beneficial yeasts associated with some traditional Egyptian dairy products and to evaluate their microbiological and technological properties. One hundred samples of locally produced yoghurt, Kariesh, Domiatti and Mish cheeses were collected from different localities at Sharkia Governorate, Egypt. Seventy-seven (77%) of the examined samples were positive for the presence of yeasts. Kariesh cheese had the highest total yeast count compared with other examined dairy products. From these positive samples, a total of 154 yeast isolates were screened for their antibacterial activities against the common foodborne pathogens (Staphylococcus aureus and Escherichia coli). Yeast isolates showing highest antibacterial activity were identified and then investigated for some technological properties (growth ability at different temperature, low pH and different NaCl conditions). Only 30 strains corresponding to Saccharomyces cerevisiae, Debaryomyces hansenii and Candida zeylanoides were found to be effective against S. aureus and/ or E. coli strains. These strains have also technological properties that allow them attractive for use in food industry and for further evaluation.
A total of 100 samples of raw Buffalo milk including (50 from dairy shops and 50 from dairy farms) were collected randomly at Sharkia Governorate for chemical and microbiological evaluation. Chemical assessment of the milk samples collected from dairy shops revealed that the mean values of Fat, Solid Not Fat (SNF), Protein, Lactose and Salts percentages were 6.06±0.36, 9.08±0.23, 3.54±0.09, 4.73±0.14 and 0.74±0.02 respectively, while dairy farm samples were 6.18±0.31, 9.53±0.44, 3.89±0.09, 5.12±0.15 and 0.78±0.03; correspondingly. Microbiological examination revealed that the mean values of faecal coliforms were 2.03×10 6 ± 0.75×10 6 and 1.8×10 6 ± 0.59×10 6 in dairy shops and farms, respectively. The identified species of isolated coliform organisms in both types of milk were Citrobacter diversus (11.3% vs 11.1%) Citrobacter freundii (9.6% vs 9.6%), Enterobacter aerogenes (12.1% vs 9.6%), Enterobacter agglomerans (11.3 vs 10.4%), Enterobacter cloacae (13% vs 11.1%), Klebsila oxytoca (9.6% vs 11.9%), Klebsila pneumoniae (9.6% vs 10.4%) and E.coli (23.5% vs 25.9%); respectively. Mean values of total staphylococci were 4.29×10 6 ± 0.21×10 6 and 8.08×10 6 ± 2.27×10 6 in milk samples of shops and farms respectively. The identified species in both types were S. aureus, S. epidermidis, S. saprophyticus, S. capitis and S. intermedius with percentages of 28% vs 35%, 48% vs 41%, 10% vs 12%, 8% vs 7% and 6% vs 5%; respectively. It was exposed that 8 strains (28.57%) and 10 strains (28.57%) were identified as methicillin-resistant S. aureus that containing mecA gene. In conclusion, high prevalence of different udder pathogens among dairy animals may attributed to the lack of sanitary conditions that adapted in dairy farm. So, restriction to application of hygienic measures in dairy farms as well as quality control and quality assurance programs should be adopted to get safe and good quality raw milk.
Obtaining healthy food, free from chemical or synthetic additives, is a major challenge. In this study, we developed a preservation method using essential oils and evaluated their effect on multidrug resistant pathogenic Gram-negative bacteria. Different concentrations (1%,0.1%,0.17% and 0.35%) of Thyme oil and black seed oil were employed in this study against pathogenic E. coli and A. hydrophila in soft cheese. The used oils at a concentration of 0.1% through dipping method resulted in accepted color and odor, little effect on flavor and normal texture and appearance, while 0.1% during inoculation had the same effect as in dipping method except moderate odor. Thyme oil had the highest reduction rate in case of 1% dipping and 0.17% inoculation on A. hydrophila, while against E. coli it was found that 0.17% inoculation and 0.35% of the dipping method had the highest reduction effect. Thyme essential oil seems to be a suitable natural food preservative alternative.
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