الفهرس 
Introduction
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Abstract
To determine the hygienic aspects, chemical and microbiological quality of some traditional Egyptian cheese, a total of 200 samples of white soft cheese represented by Tallaga, Feta, Baramily and Istambuli (50 samples each) were collected randomly from supermarkets, dairy shops and street-vendors in Giza Governorate, Egypt.
Tallaga cheese was prepared from buffalo milk containing 3% sodium chloride. Native lysozyme (250 and 500 ppm) and combined lysozyme 250 ppm with EDTA and with catechin were added. Cheese batches were refrigerated (4 ± 1 °C) and examined at zero time (within 2 hours), 1, 3, 5 day then weekly till spoilage of the cheese.
The obtained results showed that:
1. Chemical Examination:
The averages of pH value and NaCl% in the examined cheese were 6.354, 3.732%; 5.018, 7.0%; 3.441, 6.702% and 4.465, 5.94% for Tallaga, Feta, Baramily and Istambuli cheese, respectively.
2. Microbiological Examination:
The aerobic plate count (APC) and psychotropic count were detected in all examined samples with average values of 1.5×10⁵, 4.8×10⁴; 2.1×10⁴, 7.4×10³; 1.2×10⁵, 3.5×10⁴ and 4.7×10⁴, 2.0×10⁴ cfu/g in Tallaga, Feta, Baramily and Istambuli, respectively.
Coliforms, fecal Coliforms and E. coli bacteria were detected in 86, 76 and 60% of Tallaga cheese, 64, 54 and 32% of Feta cheese, 88, 68 and 50% of Baramily cheese and 78, 64 and 54% of Istambuli cheese, respectively. E. coli averages waere 2.7x10², 1.8x10², 2.9x10² and 1.2x10² cfu/g for the concerning samples, respectively.
Serological identifications of the isolated E. coli revealed that 14, 6, 12 and 8% out of all examined cheese samples were pathogenic. Most relevant detected serotypes in cheese were related to enterohemorrhagic (EHEC) and enterotoxoginc (ETEC) strains. Also, Enteoinvasive (EIEC) and enteropathogenic (EPEC) related serotypes have been detected in some examined cheese samples.
S. aureus count ranged between >10² and 8.0×10², 1.5×10³, 9.0×10³ and 9.0×10² cfu/g, and were detected in 46, 60, 58 and 56% of the examined cheese samples, respectively. Moreover, 58, 24, 48 and 40% of tested samples were contaminated with anaerobic bacteria. And the averages values of the total moulds and yeast count were 3.6×10², 8.3×10², 1.4×10³ and 6.0×10² cfu/g in the examined cheese samples, respectively.
Evaluation of antimicrobial potential of lysozyme in Tallaga cheese:
3.1. Organoleptic evaluation:
Appearance scores were reduced to spoiled, 5, 5, 6 and 6 out of 10 points; body and texture scores out of 40 points were reduced to spoiled, 17, 20, 23 and 24; flavor out of 50 points were reached spoiled, 20, 25, 25 and 28 and overall organoleptic scores were spoiled, 42, 50, 54 and 58 at the 14th day of storage for control, Lz250, Lz500, LzE and LzC; respectively.
The control samples couldn’t be evaluated at 14th day of storage, while both native lysozyme treated samples spoiled before 21st day of storage and the other combined lysozyme samples maintained for the end of the experiment.
3.2. Microbiological evaluation:
The reduction % of total bacterial count at 14th day were 27.12, 32.28, 20.9 and 36.87 log cfu/g for Lz250, Lz500, LzE and LzCc, respectively. The aerobic bacterial count reached a maximum of growth at 14th day in C and Lz250 samples, while Lz500 showed reduction from 4.83 to 4.72 log cfu/g at 14th day. Also, LzE showed reduction in TBC for first 7 days then started to elevate to reach 5.87log cfu/g at 21st day. LzC showed significant reduction in TBC from 4.83 log cfu/g at zero time and reached 4.32 log cfu/g at 21st day compared with other Tallaga cheese samples.
All treated samples showed reduction in Psychrotrophs count from 3.86 log at zero time to 2.91, 2.79, 2.61 and 1.56 log cfu/g at 14th day of storage, with reduction% 43.822, 46.14, 49.61 and 69.88% for Lz250, Lz500, LzE and LzC, respectively.
The Coliforms count were 3.56 log for zero time and reached 3.43, 3.3, 2.87 and 1.04log cfu/g at 14th day of storage while, the reduction % were 29.42, 32.1, 40.95 and 78.6% in lysozyme treated cheese batches.
Fecal Coliforms count started with 2.92 log at zero time and reached 3.18, 3.28, 2.79 and 1.04 log cfu/g with reduction% of 20.5, 18, 30.25 and 74% at 14th day for Lz250, Lz500, LzE and LzC, respectively. Furthermore; neither Coliforms nor fecal Coliforms were detected at 21st day of storage in Tallaga cheese treated with lysozyme and catechin.
E. coli count were 2.7 log at zero time and turned to 3.88, 3.11, 3.15, 2.77 and undetectable log cfu/g in C, Lz250, Lz500, LzE and LzC, respectively. That translated to 19.85, 18.81, 28.61 and 100 % reduction. E. coli was undetectable in cheese with lysozyme and catechin by 14th day of storage.
At zero time S. aureus count was 2.62 in all cheese batches and reached 3.7, 3.57, 2, 1 and undetectable log cfu/g in C, Lz250, Lz500, LzE and LzC samples, respectively at 7th day. As well as, the reduction % were 3.51, 45.96, 72.97 and 100% for Lz250, Lz500, LzE and LzC, respectively. The viability of S. aureus was lost in cheese with LzC by 5th day and with LzE by 14th day as it was undetectable.
The reduction % of total yeast and molds were 20.85, 28.39, 33.29 and 43.21% at 14th day of storage, while it started with 2.48 log cfu/g at zero time then had been 3.98, 3.15, 2.85, 2.63 and 2.26 log cfu/g by 14th day of storage for C, Lz250, Lz500, LzE and LzC, respectively.