الفهرس 
REVIEW OF LITERATUREOnly 14 pages are availabe for public view
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Abstract
A total of fifty random samples including 30 raw milk (buffaloes, bulk tank and cow’s) 10 of each, 10 samples of kareish cheese and 10 samples of yoghurt (five in summer and in winter from the same locations). These samples were randomly collected from different farmer’s houses, dairy shops and markets in Mansoura city, Dakahlia governorate during summer and winter of 2006- 2007. All samples were examined for microbiological and chemical for some heavy metals as well as pesticides residues. The experiments were carried out at Dept. of Microbiology, Fac. of Agric., Mansoura Univ., and Central Agricultural Pesticides Laboratory (CAPL), ARC, Giza, Egypt, and obtained results can be summarized as follow: I. Microbiological quality of the tested samples : I.1. Microbial count and incidence: Seven cultivation media either general or specific were used to isolate spoilage and pathogenic microbes (bacteria, mould and yeast) from the tested raw milk and some dairy products samples. Obtained data exhibited high microbial load of the tested raw milk samples appeared on the tryptone glucose extract agar (TGEA) medium either in summer or winter season. The specific cultivation media varying between each other in isolation the spoilage and pathogenic microbes and this had no trend with sampling time. Summer season was illustrated higher count with the seven cultivation media than those of winter season. In case of tryptose agar (TA) medium, some of buffaloes and bulk tank milk samples in winter season showed no count and the same observation was found on SSA medium in four buffaloes milk samples during summer season. Also the high microbial load of kareish cheese (4KC) sample appeared on the MacCA (coliform bacteria) medium in summer season, while the high microbial level of yoghurt (1Yg) sample appeared on TGEA as a general cultivation medium in winter season. Additionally, no results were found in kareish cheese and yoghurt samples of winter 2007 using TA(for Listeria sp., Brucella sp. and other pathogenic microorganisms). I.2. Significance of microbial incidence: Data showed that the high values were 82.03 ± 79.19 x 103, 119.40 ± 62.58 x 103 and 129.03 ± 113.60 x 103 cfu/ml that appeared on tryptone glucose extract agar (TGEA) in examined buffaloes, bulk tank and cow’s milk samples, respectively. On specific cultivation media, the lowest values were found on salmonella shigella agar (SSA), tryptose agar (TA) and potato dextrose agar (PDA), they were 2.10 ± 4.33 x103, 9.30± 18.00 x103 and 5.43 ± 10.5 x103cfu/ml in examined buffaloes, bulk tank milk and cow’s milk samples, respectively. On the level of the sampling season, the high value was in winter season, being 99.05± 81.02 x103, but in summer season it was 95.61± 93.05 x103 cfu/ml on TGEA media. In case of dairy product samples, the high values of microbes appeared on TGEA were 58.67± 54.00 x 103 and 97.53 ± 97.57 x 103 cfu/g in examined kareish cheese and yoghurt samples. In addition, the analysis of variance showed high significant differences between all thetested parameters. I.3. Morphology of isolates Results showed that 37 isolates obtained from five buffaloes milk samples in summer 2006, the highest percent of 77.0% were short rod (G-) bacteria isolated from 5SBM sample. Coccoid-shaped(G+) bacteria represented 63.6% In case of bulk tank milk samples, 38 isolates were obtained during summer season from five samples. The highest percent of isolates to be 98.3% were short rods (G-) bacteria isolated from 1SBTM sample, while 17.1% was sporeformer (G+) that isolated from 2SBTM sample. The highest ( G+) coccoid shaped bacteria of 14.8% was isolated from 4SBTM sample, while big elongated cells represented 19.3% obtained from 4SBTM sample. Six isolates of bulk tank milk samples obtained in winter season. Thirty two isolates obtained from five cow’s milk samples during summer season. The highest percent of 98.8% were short rods(G-) bacteria isolated from 3SCM sample, while 83.4% was coccoid shaped(G+) isolated from 4SCM sample. The highest percent sporeformer (G+) of 52.8% were obtained from 5SCM sample, while big elongated cells represented 3.2% from 2SCM sample. Eighteen isolates in winter season were obtained from five cow’s milk samples. Short rods isolates represented 100% as the highest percent isolates obtained from 4WCM sample, while 94.5% was sporeformer (G+) that isolated from 1WCM sample. In case of kareish cheese samples, twenty six isolates obtained during summer season. The highest percent of 87.7% were big oval cells isolated from 5SKc sample, while big elongated cells represented 75.0% that isolated from 2SKc sample. Also seven isolates obtained in winter season. Big oval cells represented the most incidence to be 100% in 3WKc and 5WKc of the total examined. kareish cheese samples. In case of yoghurt samples collected during summer and winter seasons, 49 isolates were obtained.. Of these isolates, the highest percent of 80.7% was big oval cells from the total examined isolates obtained from 4SYg sample, while sporeformer represented 73.9% from the total examined isolates obtained from 1SYg sample.. Short rods (G-) and sporeformer (G+) bacteria represented the most incidence to be 100% from the total examined isolates obtained from 1WYg and 4WYg samples, respectively. II. Enzymatic activities of some microbial isolates: II.1. Screening for enzymatic production: From raw milk samples, 26 isolates were obtained in summer and winter seasons. Of these isolates, 42.3% were short rod (G-) bacteria, while coccoid shaped (G+) bacteria represented 19.2% of the total count. Spore-forming(G+) bacteria represented 23.1%, while other microbial isolates represented 15.4%. Data showed also that the potent isolates in caseinase activity was strain SBTM165, SCM117, and SBM111, taking into account the value of Hz., respectively. For lipase activity, the best isolates were SBTM52, SBM112, followed by isolate SCM116, and isolate SCM79, respectivly. From dairy products samples, either kareish cheese or yoghurt) 21 isolates were obtained in summer and winter season. The G+ sporeforming bacteria accounted for 28.5%, while the (G-) short rod bacteria isolates represented 23.8% and coccoid-shaped bacterial represented only 4.7%. The potent isolate in caseinase activity isolate SYG145, G- short rod and isolate SYG157, G- short rod bacteria, followed by isolate SYG101, big oval cells shape (yeast) and isolate SYG146, G- short rod bacteria, taking into account the value of Hz. For lipase activity, the productive isolates were SKC16, WYG51, SKC95, and SYG146, respectively. II.2. Incident percent of enzymatic producing microbial isolates: From buffaloes milk during summer season, the G- short rod bacteria represented the most incidence to be 56.8%, from these isolates 14.2% was caseinase producers and 9.5% was lipase producers. In case of winter samples, lipase producers was 14.2% represented from seven (46.6% )short rod bacteria.A total of 38 isolates obtained from bulk tank milk samples during summer season. The most incident isolates was short rod bacteria being 76.3% , 13.8% caseinase producers and lipase producers were 13.8% and 13.8%, respectively. On the other hand, no isolates were found to be caseinase or lipase producers in winter season.Thirty two microbial isolates obtained from cow’s milk samples in summer season. The highest percent were 43.8% for G- short rod bacteria. From these isolates, 14.2%% and 7.14% were caseinase and lipase producers, respectively. Negative results were found for caseinase or lipase producers in winter season.