Thesis (Ph.D.) - Cairo University - Faculty of Science - Department of Botany - Microbiology

The present study was performed to determine the incidence of food-borne pathogens in different farm animals{u2019}products as a prerequisite for controlling the spread of those pathogens. Farm animals{u2019} products samples (40 samples) were collected from local markets in Cairo and Giza governorates as follows: Milk (6 samples), Yogurt (5 samples), Meat and Minced meat (8 samples), Eggs (6 samples) and Chicken breast, thigh and liver 15 samples). Detection of some food poisoning bacteria was performed using both microbiological and molecular biology methods using PCR technique. The obtained data revealed that, E. coli, Bacillus cereus, Staphylocoocus spp., Salmonella spp., Yersinia enterocolitica, brucella spp, Campylobacter spp. and Listeria spp. were detected in tested samples in percentages of 25%, 100%, 100%, 50%, 7.5%, 12.5%, 25% and 22.5%, respectively. In a trial to study the effect of different concentrations of essential oils extracts (thyme, Oregano and Menthol) against the isolated gram negative bacteria (Salmonella typhimurium and E. coli) and gram Positive bacteria (Staphylococcus aureus, Bacillus cereus and listeria monocytogens) concentrations ranged from 0.01% to 0.8% v/v were used. Minimum Inhibitory Concentration(MIC) of each essential oil (EO) was determined and the mode of action against salmonella typhimurium was estimated using Transmission Electron Microscope (TEM).The determined MICs were used in processing of Luncheon replacing (either completely or partially sodium nitrite), cheese and yogurt to study the effect of it as food preservatives aiming at increasing its shelf life time. Panel test was performed using the 3 products to examine its acceptance among consumers. It can be concluded from the results obtained in this study that bad handling is the major contributing factor in the spread of food poisoning bacteria complete or partial replacement of chemical preservatives can be applied using natural plant extract which can also be used to increase the shelf life time of food of animal origin

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