الفهرس 
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Abstract
A total of 210 Ras cheese samples of homogeneous size, without surface lesions or abnormality signs, were collected from different four groceries categorized as brand (A, B, C and D) and three different local super-markets categorized as (I, II and III) in Alexandria Governorate (30 of each individual sample) for determination compositional quality, microbiological status and biogenic amines formation. In addition, studying the effect of Ras cheese ripening at refrigeration temperature (4±1 oC) for 10 weeks on the previous parameters.
The obtained results summarized in the following items:
7.1. Compositional quality of examined Ras cheese:
7.1.1. Moisture content:
Mean values of moisture content in Ras cheese samples collected from different groceries A, B, C and D were 46.28 ± 0.07, 43.65 ± 0.11, 42.94 ± 0.06, and 43.66 ± 0.21, respectively. While, in Ras cheese samples collected from hypermarkets I, II and III were 47.83 ± 0.48, 47.58 ± 0.15 and 47.97 ± 0.81, respectively.
7.1.2. Salt content:
Mean value of salt content in examined Ras cheese samples collected from groceries A, B, C and D were 5.39 ± 0.03, 5.26 ± 0.02, 5.44 ± 0.03 and 5.29 ± 0.03, respectively. As well as, the mean values of salt content in examined Ras cheese samples collected from hypermarket I, II and III were 4.86 ± 0.03, 4.86 ± 0.03 and 5.59 ± 0.03, respectively
7.1.3. pH values:
Mean values of pH value in examined Ras cheese samples collected from different groceries A, B, C and D were 6.51 ± 0.12, 6.55 ± 0.05, 6.91 ± 0.12, and 6.66 ± 0.04 respectively. While, in examined Ras cheese samples collected from hypermarkets I, II and III were 6.68 ± 0.05, 6.57 ± 0.06 and 6.65 ± 0.05, respectively.
7.2. Microbiological evaluation of Ras cheese during ripening:
Mean values of enterobacteriaceae in examined Ras cheese samples collected from different groceries A, B, C and D were 4.83 × 105 ± 0.07 × 105, 4.41 × 105 ± 0.05 × 105 , 6.75×104 ±0.02×105 and 4.87 × 105 ± 0.22 × 105 cfu/g, respectively. While, in samples collected from different hypermarkets I, II and III were 3.76 × 105 ± 0.08 × 105, 2.79 × 105 ± 0.36 × 105, and 1.15 × 105 ± 0.39 × 105 cfu/g, respectively.
Incidence of identified enterobacteriaceae and histamine producing enterobacteriaceae species isolated from examined Ras cheese samples were determined.
Mean values of Enterococcus in examined Ras cheese samples collected from different groceries A, B, C and D were 3.22 × 104 ± 0.02 × 104, 2.83 × 104± 0.09× 104 , 3.47 × 104 ± 0.05 × 104 and 3.59 × 104 ± 0.03 × 104 cfu/g, respectively. While, in samples collected from different hypermarkets I, II and III were 1.41 × 104 ± 0.04 × 104, 1.90 × 104 ± 0.07 × 104, and 3.45 × 104 ± 0.06 × 104 cfu/g, respectively.
Incidence of identified enterococcus and histamine producing enterococcus species isolated from examined Ras cheese samples were determined.
Mean values of lactobacilli in examined Ras cheese samples collected from different groceries A, B, C and D were 5.02×105±0.08×105, 1.49×106±0.44×106, 2.31×106±0.48×106 and 4.11×106±0.19×106 cfu/g, respectively. While, in samples collected from different hypermarkets I, II and III were 3.90 × 105 ± 0.08× 105, 4.04 × 105 ± 0.04 × 105, and 3.99 × 105 ± 0.08 × 105 cfu/g, respectively.
Incidence of identified lactobacilli and histamine producing lactobacilli species isolated from examined Ras cheese samples were determined.
7.3. Biogenic amines level in examined Ras cheese samples using HPLC:
Mean values of different biogenic amines in examined Ras cheese collected from groceries (A, B, C, D) and hypermarkets (I,II,III) using HPLC were (134.0±12.5, 109.0±9.2, 278.2±33.2, 114.0±14.2) and (24.0±1.8, 131.0±11.8, 89.0±6.5 ppm), respectively for Cadaverine; (91.0±5.5, 42.0±3.3, 78.0±4.5, 2.6±0.1) and (11.4±2.5, 88.0±6.3, 2.5±0.2 mg/100g), respectively for histamine; (21.0±1.8, 32.0±2.1, 18.0±2.2, 8.0±0.74 ppm) and (22.0±2.2, 5.8±0.3, 7.2±0.4 ppm), respectively for Putrescine and (85.0±8.5, 124.0±15.5, 194.0±17.5, 154.0±12.5 ppm) and (187.0±16.5, 69.0±5.5, 111.0±9.5 ppm), respectively for Tyramine.
7.4. Experimental works:
7.4.1. Compositional quality of Ras cheese during ripening
Mean levels of moisture percent of Ras cheese stored at refrigerator temperature decrease gradually from 55.21 ± 2.02 at zero day reach to 43.37 ± 1.59 at week 10 of storage
Salt percent gradually increase from 4.41 ± 0.05 at zero day of storage until reach 5.81 ± 0.06 at week 10 of experiment.
PH gradually decrease along storage period from 6.85 ± 0.03 at zero day until reach 6.01 ± 0.9 at 10th week of storage.
7.4.2. Microbiological evaluation of Ras cheese during ripening:
Enterobacteriaceae count significantly decrease gradually from 5.0x108 ±7.02x106 at zero day until reach 4.60x10± 0.24x10 CFU/g at week 10 with reduction percent reach to 99.99%.
Enterococci count significantly decrease from 3.46 x 105 ± 3.17 x 104 at day zero until reach to 2.20 x 10 ± 0.23 x 10 CFU/g at week 10 with reduction percent reach to 99.99%.
Lactobacilli count; there was a fluctuation in the mean values of lactobacilli during ripening period where the highest count recorded at 2nd and 10th week 4.40 x 105 ± 0.25 x 105 and 4.40 x 105 ± 0.15 x 105 CFU/g, respectively.
7.5.3. Histamine producing bacteria during ripening of Ras cheese:
Incidence of histamine producing enterobacteriaceae, enterococci and lactobacillus were determined.
7.4.4. Biogenic amine pattern during ripening of Ras cheese:
Cadaverine significantly decrease from 119.8 ± 8.19 at zero day until reach 48.78 ± 6.82 mg/100g at week 10 of storage with reduction percent reach to 59.28%.
Histamine content decrease from 8.45 ± 2.59 at zero day until reach 3.00 ± 0.61 mg/100g at week 10 of storage.
Putrescine gradually decrease from 2.26 ± 1.58 at zero day until reach 2.01 ± 0.58 mg/100g at week 10 with reduction percent reach to 11.06%.
Tyramine significantly decrease from 133.48 ± 9.87 at zero day until reach 39.22 ± 6.39 mg/100g at week 10 with reduction percent reach to 70.61%.