الفهرس 
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Abstract
Student hostels are important places for student collection, in which food is presented especially “Ready-to- Eat” food. This collection gives a high opportunity for different foodborne outbreaks caused by several microbial pathogens. Milk and dairy products present an important part of food introduced to student hostels. A grand total of 160 random samples of UHT milk, plain yoghurt, feta cheese and processed cheese (40 of each) were used for sensory, microbiological and chemical examination to evaluate their quality. Samples of UHT milk were subjected to some chemical keeping quality tests. All samples were collected from 3 student hostels in Kaliobia Governorate. Regarding organoleptic properties of UHT milk, it was found to be acceptable with an overall score of 16.10±0.547. The microbiological examination of UHT milk samples revealed that the mean Aerobic Plate Count (APC) was found to be 5.0X10±8.6 cfu/ml, while the mean Yeast and Mould Count (YMC) was found to be 3.0X10±5.8cfu/ml. The mean coliform count was 4.3X10±1.2x10 cfu/ml. Only 3 out of 40 UHT milk samples had YMC count and coliform count above normal values stated by EOS (2005). Coliform bacteria isolated from UHT milk were Citrobacter divesous (2.5%), E. coli (2.5%), Klebsiella ozaenae (2.5%) and Klebsiella pneumonia (2.5%). While, moulds isolated from UHT milk were Mucor (2.5%) and Penicillium (5.0%), and the only yeast strains isolated were belonging to Candida Spp. (5.0%).
Summary
85
Listeria or Salmonella Spp. Could not be detected in any of the examined UHT milk samples, however, E. coli O111:K58 strain of the Enterohaemorrhagic E. coli ( EHEC) could be isolated from one sample. The chemical examination of UHT milk samples revealed that the mean pH was found to be 6.59±0.006, which is within the normal range. The mean TVN of the examined UHT milk samples was 6.33± 0.398, while the mean TBA was 0.076 ±0.008 and both were within the acceptable values. The TVN and TBA are significantly correlated to each others as factors or indicators of milk deterioration. Organoleptic examination of the 40 plain yoghurt samples, it was found that the overall score was 11.02±0.694, which is considerd as unacceptable score. The microbiological examination of plain yogurt samples revealed that the mean the mean coliform count was 3.2X10±5.8 cfu/g, while the mean YMC was 3.7X10±5.3 cfu/g. Five out of 40 samples were with higher coliform counts, while 8 out of 40 samples were with higher YMC, when compared to the limits stated by EOS (2005). Coliform bacteria isolated from plain yoghurt samples was Citrobacter diversus (2.5%), Citrobacter freundii (5.0%), Enterobacter agglomerans (2.5%) and Enterobacter cloacae (2.5%). Moulds isolated from plain yoghurt were Alternania (5.0%), Aspergillus (12.5%), Abscidia (2.5%). The isolated yeasts were Candida (10.0%) and Rhodotorula (2.5%). Listeria, Salmonella Spp. or E. coli could not be detected in any of the examined plain yoghurt samples.
Summary
86
The mean pH for plain yogurt samples was found to be 4.79±0.021, which is above the normal range of 3.50-4.50. Regarding the organoleptic properties of the examined cheese samples; feta cheese samples were considered acceptable with an overall score of 17.10±0.458, while processed cheese samples were considered unacceptable with an overall score of 11.54±0.832. The mean coliform count of feta cheese was 2.5x10±5.0 cfu/g, while the mean YMC was 3.5x10±2.9 cfu/g, these figures were within normal limits stated by EOS. Regarding processed cheese samples, the mean coliform count was 3.2x10±5.8 cfu/g. Five out of 40 samples were above the acceptable level. The mean YMC was 4.5x10±9.0 cfu/g with 7 out of 40 samples were above the acceptable limits of EOS. Coliform bacteria isolated from feta cheese was Citrobacter diversus (2.5%), E. coli (5.0%) and Enterobacter aerogenes (2.5%), while in processed cheese was Citrobacter diversus (2.5%), Citrobacter freundii (5.0%), E. coli (2.5%) and Enterobacter hafini (2.5%). Moulds isolated from feta cheese were Alternaria (2.5%), Aspergillus (2.5%), Cladosporium (2.5%), and Penicillium (2.5%). The isolated yeasts were Rhodotorula (5.0%) and Saccharomyces (5.0%). Moulds isolated from processed cheese were Aspergillus (5%), Fusarium (2.5%), Cladosporium (5.0%), Trichoderma (2.5%) and Penicillium (2.5%). The isolated yeasts were Candida (2.5%), and Toruloposis (5.0%).
Summary
87
Listeria, Salmonella Spp. or E. coli could not be detected in any of the examined feta and processed cheese samples. E. coli O86:K62(B7) strain of the EPEC and E. coli O124:K72(B17) strain of the EIEC were isolated from two of feta cheese samples, while E. coli O124:K72 strain of the EIEC was isolated from one processed cheese sample. The pH of both examined feta and processed cheese (4.50±0.030 and 5.30±0.070, respectively) were within normal range stated by EOS. Public health significance of the isolated organisms and possible sources of contamination of UHT milk, plain yoghurt, feta cheese and processed cheese as well as some recommendations to improve the quality of these types of food were discussed.