الفهرس 
Manufacture of ice cream
Bacteriological control of ice cream productionOnly 14 pages are availabe for public view
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Abstract
Milk is almost a complete food in itself since it contains both energy supplying nutrients (fat and carbohydrates) and body building nutrients (proteins and minerals).
Ice cream is a dairy product, which contain a variety of ingredients in addition to milk, cream and sugar. This is a popular dairy product throughout the world.
Kareish cheese is one of the most popular soft, fresh, lactic acid, low salt type of cheeses in Egypt. It is prepared from low fat or skimmed milk and contains all the skim milk constituents including, proteins, sugar, some of the water soluble vitamins and most of the calcium and phosphorus compounds originally present in the milk.
Cheese and ice cream, can be considered a good medium for bacterial growth due to their nutrient content and long storage duration. Several steps in their production can cause bacteriological hazards. Though pasteurization of milk can destroy most of the pathogens posing risk to public health, however the potential bacteriological hazards can still be found in the final products after pasteurization through the addition of contaminated ingredients or improper handling.
The present study aimed to assess the bacteriological quality of some dairy products (ice cream& kariesh cheese) in different markets in Alexandria, enumeration of the total viable heterotrophic bacteria, determination of the total and fecal coli forms, and E. coli in ice cream and kariesh cheese, detection of Salmonella in ice cream and kariesh cheese, and studying the validity of some rapid methods versus the conventional methods for the detection of Salmonella.
The study was carried out on a total of 160 samples, (80) ice cream and (80) kariesh cheese samples collected from different localities in Alexandria. The ice cream samples were transported to the laboratory in a refrigerated container and maintained in the refrigerator within 6 hours until examined in the laboratory. Kariesh cheese samples were purchased directly transferred to the laboratory with minimum of delay until examined.
All samples were analyzed for enumeration of the total viable heterotrophic bacteria using the standard pour plate method, and for the determination of total, fecal coli forms and E.coli using multiple tube dilution method, and also for the detection of Salmonella using conventional method, CHROMagar. 50 samples were examined for Salmonella by ELISA (TECRA Unique Salmonella test).
1. Out of 80 samples examined for TBC, 54(67.5%) were acceptable.
2. Thirty six, 45 and 34 samples were unacceptable according to total colifoms,fecal coliforms and Ecoli respectively.
3. Unacceptable total bacterial count in ice cream samples was detected in 7 (21.2%) of 33 cup ice cream samples, 5 (35.7%) of 14 stick ice cream samples and in 14 (42.4%) of33 open ice cream samples.
4. The unacceptability of ice cream samples due to total coliforms was 4 (12.1 %) of 33 cup ice cream samples, 7(50.0%) of 14 stick ice cream samples and 25 (75.8%) of 33 open ice cream samples.
5. The unacceptability of ice cream samples due to fecal coli forms was 8(24.2%) of 33cup ice cream samples, 9 (64.3%) of 14 stick ice cream samples and 28(84.8%) of 33 open ice cream samples.
6. The unacceptability of ice cream samples due to Ecoli was 3(9.1 %) of 33 cup ice cream samples, 7 (50.0%) of 14 stick ice cream samples and 24(72.7%) of33 open ice cream samples. ’
7. The difference between the rate of contamination between cup and stick, and between packed and open ice cream samples was statistically significant.
8. The mean bacterial count in all the tested bacterial parameters was higher in the open ice cream samples than the packed category, and this was statistically significant.
9. The mean of total bacterial count, total coliforms , fecal coliforms and E coli in open ice cream samples were 1.7x1Q6 , 7.8x1Q2, 5.4xl02 and 9.5xI01 respectively, while in packed ice cream samples were 9.2xl07 , 1.2xl02, 1.6 xl02 and 0.25 xl01 respectively.
10. Salmonella was detected in one sample only (1.3%).The detection was from cup packed ice cream sample.
11. Salmonella was detected when RV broth was used while not detected when TT broth was used.
12. The sensitivity and specificity of CHROMagar were 100% and 69.0%
respectively.
13. The sensitivity and specificity ofXLD agar were 100% and 77.6% respectively.
14. The sensitivity and specificity of BG agar were 0.0% and 100% respectively.
15. The sensitivity and specificity of ELISA (TECRA unique salmonella test) were 100% and 100% respectively.
16. Fifty four, 64 and 60 samples were unacceptable according to total colifoms,fecal coli forms and Ecoli respectively.
17. Salmonella was not isolated from any of the samples.
18. The unacceptable kariesh cheese samples according to the total coliforms were 3(37.5%) of the 8 known brand packed kariesh cheese samples, 2(20.0%) of the
10 unknown brand packed kariesh cheese samples and 49(79.0%) of the 62 open kariesh cheese samples.
4. The unacceptable kariesh cheese samples according to fecal coliforms were 4(50%) of the 8 known brand packed kariesh cheese samples, 4(40.0%) of the 10 unknown brand packed kariesh cheese samples, and 56(90.3%) of the 62 open kariesh cheese samples.
5. The unacceptable kariesh cheese samples according to E.coli were 4(50%) samples of the 8 known brand packed kariesh cheese samples, 4(40.0%) samples of the 10 known brand packed kariesh cheese samples, and 52(83.9%) samples of the 62 open kariesh cheese samples.
6. The difference between the rate of contamination between known and unknown brands of kariesh samples was statistically non significant while between packed and open kariesh samples was statistically significant.
7. The mean bacterial count in all the tested bacterial parameters was higher in the open kariesh cheese samples than the packed category, and this was statistically significant.
8. The mean for total bacterial count, total coli forms , fecal coliforms and E.coli in open kariesh cheese samples were 1.1xI09, 7.3xl02, 6.9xl02and 3.8x102 respectively, while in packed kariesh cheese samples were 2.4xl08, 1.6x102, 3.2 xl02and 4.4 x101 respectively.
It can be concluded from this study that:
1. Salmonella was detected in only one ice cream sample while not detected in kariesh cheese samples.
2. Open milk products are more contaminated than packed products.
3. RV was found to be highly superior to TT in the isolation of Salmonella from ice cream.
4. ELISA was the most superior in the detection of Salmonella from ice cream as it was found to be sensitive, specific and easy to perform.
5. CHROMagar and XLD were better than BGA in the detection of Salmonella from Ice cream.
6. XLD was better than CHROMagar in the detection of Salmonella from ice cream.