Studies on Beneficial Yeasts Isolated from Some Egyptian Dairy Products

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.