الفهرس 
Acknowledgement
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Abstract
Cheese can easily become molded by a large number of fungi and a group of unicellular fungal organisms (yeasts) during ripening, after cutting and slicing and during storage in shops or at home. Mold growth discolors the cheese surface and is responsible for certain flavor defects. Furthermore, molds produce toxic metabolites (mycotoxins) which may penetrate the cheese and the polishing of its surface might not sufficiently remove them and affect the health of the consumer.
This work aimed to study the incidence of mycoflora and some mycotoxins which may contaminate 5 types of locally manufactured cheese (hard, fresh Kareish, pickled Kareish, Damietta and processed cheese).
The dilution plate method was used for isolation of fungi from cheese samples. The growing fungi were then purified by its isolation and sub culturing on Czapek’ s agar medium and were identified macroscopically and microscopically. The multimycotoxins analysis method according to Van Egmond et al. (1979) was used for the detection of aflatoxin B1, B2, G1, G2 and M1, Sterigmntocystin, Ochratoxin A and Zearalenone in the 5 types
of cheese samples.
56.66 % of the examined hard cheese samples were found containing molds and yeasts with an average count reached to 279.4 colony /g cheese. Eight species of mycoflora were isolated from the examined hard cheese samples. Aspergillus and Penicilliun species were the most prevalent fungi encountered in 35 and 28.30/0 of the examined samples respectively. Aspergillus species included, A. niger, A. cromonium, A, flavus and A. flavipes, however Penicillium species included P. funiculosum, P. monoverticillata, P. ch rysogenium, P. corylophilum and P. citrinum. Mucor
speCIes including M. circinelloides and M. racemosus were isolated in low frequency (6.660/0 of the examined samples). Botryotrichum atrogrieseum (3.3%), Scopulareopsis brevicoulis (1.70/0), Cladosporium cladosporoides (1.7%) and Geotrichum candidum (3.3%) were frequently encountered only in one or two of the examined hard cheese samples. On the other hand yeasts were found to be present in 8.30/0 of the examined hard cheese samples.
48 % of the examined fresh Kareish cheese samples were found to be contaminated with molds and yeasts with an average count of 318.75 colony/g cheese. Four species of mycoflora could be isolated from the examined fresh Kareish cheese. Aspergillus species (A. niger and A. terreus) was the most prevalent and existed in 40% of the examined samples. Penicllium species was found in 10% of the samples however Mucor racemosus and yeasts were found to be existed in 8 and 30 % of the examined fresh Kareish samples respectively.
36% of the examined pickled Kareish cheese samples were found to be contaminated by molds with an average count of 91.67 colony/g. Three species of molds (Aspergillus, Penicilium and Fusarium) were found to be existed in the examined cheese samples. Aspergillus species (represented by A. niger and A. flavus) was the most prevalent genus, recovered in 30 % of the examined pickled Kareish samples. Penicillium and Fusarium moniliformin species were found in low percentages (40/0 each).
Molds and yeast were isolated from 54 % of the examined samples of fresh Damietta cheese. The total count of the isolated molds and yeasts reached 450 colony / g cheese. Only Aspergillus species (A. niger and A. flavus) and yeasts were the isolated mycoflora from the examined fresh Damietta cheese. Asperigillus species was found existed in 16 % of the
examined cheese samples, while yeasts were ranked the most prevalent genus, contaminating 48 % of the Damietta cheese samples.
Mycological examination of the processed cheese samples revealed that 36 % of the samples were containing molds and yeasts. The average count ofmolds and yeast was 252.8 colony/g processed cheese. Aspergillus species (A. niger and A. flavus), Geotrichum candidum and yeasts were the isolated mycoflora from the examined processed cheese samples. They were found in low percentages (16, 6 and 20 % of the examined samples respectively) .
Evaluation of the results of the mycological examination of the different cheese samples in general could be concluded that Aspergillus, Penicillium and Yeasts were the most prevalent species. Other species were found in rare frequencies.
Multimycotoxin analysis for screening the incidence of the mycotoxins in the locally manufactured hard cheese revealed the presence of aflatoxins B1, B2, G1 & G2 in two samples (13.3%) and aflatoxin M1 in three samples (20%) out of 15 hard cheese samples. The average means ofaflatoxins B1, B2, G1, G2 and M1 in hard cheese samples were 4.33, 4.33, 2.58, 2.58 and 4.59 ~g/kg cheese, respectively.
Only two out of 15 fresh Kareish cheese samples (13.3%) were found containing aflatoxin M1 in a concentration of 2.61 ~g/kg cheese. Aflatoxins B1, B2, G1 and G2 were not detected in any of the examined fresh Kareish samples.
Aflatoxin B1, B2, G1, G2 and M1 were detected in 73.3, 53.3,60,40 and 26.7% of the examined pickled Kareish cheese samples, respectively, the average concentrations of the toxins were 12.67,9.24,6.49, 7.45 and
6.03 ~g!kg pickled Kareish cheese respectively. These results were considered very high specially when it is compared with the percentage and concentrations of the toxins in the other types of cheeses. Fungal spores contamination, long duration storage and the presence of salt (Nacl) which may be stimulate the production of the mycotoxin were the main causes of the elevated levels of afiatoxins in the old Kareish cheese.
80% of the analyzed Damieta cheese samples were found containing aflatoxin M} and 20% of the samples contained aflatoxin B} and no sample contained afiatoxin B2, G} & G2. The average concentrations of afiatoxins B} and M} were 8.03 ~g!kg Damietta cheese.
Aflatoxins B}, B2, G}, G2 and M} were detected in 20% of the examined processed cheese samples. The average concentrations of the afiatoxins B}, B2, G}, G2and M} were 8.02, 6.85, 2.86, 4.0 and 5.73 ~g!kg
processed cheese respectively.
Sterigmatocystin, Ochratoxin A and Zearalenone were not detected in any of the examined 5 types of cheese samples (hard, fresh Kreish, pickled
Kareish, Damieta and processed cheese).
Finally it could be concluded that pickled Kareish cheese contained the highest concentrations and incidence of afiatoxins B}, B2, G}, G2 and Mt. Damieta cheese contains high incidence and concentration of aflatoxin Mt. Although the incidence of contamination of processed cheese with afiatoxins were relatively low, the concentration of the toxins in the positive samples
were high.