الفهرس 
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Abstract
Probiotics are “live microorganisms which when administered inadequate numbers confer a health benefit on the host”. These bacteria beneficially affect human health by improving the balance of intestinal microflora and improving mucosal defenses against pathogens. Prebiotics is defined as “a non-digestible food ingredient that beneficially affects the host by selectively stimulating the growth and/or activity of one or a limited number of bacteria in the colon”; a synbiotic is a combination of probiotics and prebiotics that “beneficially affects the host by improving the survival and the implantation of live microbial dietary supplements in the gastro intestinal tract by selectively stimulating the growth and/or by activating the metabolism of one or a limited number of health promoting bacteria”. Cheese is a dairy product which has a good potential for delivery of probiotic microorganisms into the human intestine due to, its specific chemical and physical characteristics compared to fermented milks.
WSC is the main white cheese normally produced from raw buffalo or cow milk, and sometimes a mixture of both. WSC was frequently used as a part of the human diet, which contains a high amount of protein, calcium, minerals, and vitamins. For few years, the consumption of cheese has significantly increased all across the world. The objectives of this study were to:
1- Manufacture white soft-cheese with probiotic bacteria.
2- Studythechemicalandmicrobiologicalcharacteristicsof probiotics white soft- cheese.
3- Study the effect of salt on the viability of probiotic bacteria and characteristics of probiotic white soft-cheese.
4- Study the effect of storage temperature on the viability of probiotic bacteria and characteristics of probiotic white soft-cheese.
Making WSC with different salt concentrations using Bifidobacterium longum (5%), microbial rennet (0.2%) cultures. Cheese samples were divided into 5 samplestreatments. The control group contains 5% salt, T1 contains 6% salt, T2 contains 7% salt, T3 contains 8% salt andT4 contains 9% salt. Then, the cheese is stored at a temperature of 5 ± 2°C, 15 ± 2°C and 25±2°Cfor 90 days. Chemical andmicrobiological properties were performed when fresh and after 15, 30, 45, 60, 75 and 90 days of storage. Statistical analysis showed significant differences (p < 0.0001) in acidity, moisture, fat, salt, total protein and soluble nitrogen percentages between cheese treatments. A significant difference (p < 0.0001) was also found during 90 days of pickle time. Microbiologicalproperties showed that, there is a negative relationship between salt level andthe number of Bifidobacterium longum in the control samples, which had the lowest salt percent. Whichmaintained a large number of Bifidobacterium longum of 5-7 logCFU/gafter 75 days.
Chemical analysis:
Acidity, moisture, salt, total protein (TP), soluble nitrogen (SN) and fat percentages were measured during the 90 days of storage.
There were highly significant differences (p< 0.01) in acidity, moisture, salt, total protein (TP), soluble nitrogen (SN), and fat of WSC between treatments and during the 90 days of storage period.
Acidity (%):
The acidity (%) of control was the highest value compared to other treatments and this value increased from 0.25 to 1.57% during the 90 days of storage at 5±2°C.
The acidity (%) of T4 was lowest than other treatments and boosted from 0.17 to 0.77% during the 90 days of storage at 5±2°C.
The acidity (%) of control was the highest value compared to other treatments and this value increased from 0.22 to 1.69% during the 90 days of storage at 15±2°C.
The acidity (%) of T4 was lowest than other treatments and boosted from 0.18 to 0.84% during the 90 days of storage at 15±2°C.
The acidity (%) of control was the highest value compared to other treatments and this value increased from 0.27 to 1.35% during the 45 days of storage at 25±2°C.
The acidity (%) of T4 was lowest than other treatments and boosted from 0.25 to 0.84% during the 90 days of storage at 25±2°C.
There is a relation between the increase in the percentage of salt and the decrease in acidity in all treatments.
Moisture (%):
The moisture (%) of control was the lowest and decreased from 67.36 to 57.26% during the storage period of 90 days at 5±2°C.
The moisture (%) of T4 was the highest, and decreased from 68.61 to 63.06% at a storage period of 90 days at 5±2°C.
The moisture (%) of control was the lowest and decreased from 67.28 to 56.25% during the storage period of 90 days at 15±2°C.
The moisture (%) of T4 was the highest and ranged from 68.54 to 61.85% at a storage period of 90 days at 15±2°C.
The moisture (%) of control was the lowest and decreased from 66.23 to 60.44% during the storage period of 45 days at 25±2°C.
The moisture content of T4 was the highest and ranged from 68.58 to 61.53% at a storage period of 90 days at 25±2°C.
Fat (%):
The fat (%) of control was the highest and increased from 14.69 to 17.43% during the storage period of 90 days at 5±2°C.
The fat (%) of T4 was the lowest, and ranged from 13.53 to 15.55 at a storage period of 90 days at 5±2°C.
The fat (%) of control was the highest and increased from 15.49 to 18.08% during the storage period of 90 days at 15±2°C.
The fat(%) of T4 was the lowest and increased from 13.75 to 15.53% at a storage period of 90 days at 15±2°C.
The fat (%) of control was the highest and increased from 15.74 to 17.14% during the storage period of 45 days at 25±2°C.
The fat (%) of T4 was the lowest and increased from 13.19 to 15.39% at a storage period of 90 days at 25±2°C.
Salt (%):
The salt (%) of control was the lowest and increased from 2.69 to 3.66% during the storage period of 90 days at 5±2°C.
The salt (%) of T4 was the highest, and increased from 5.89 to 6.58 at a storage period of 90 days at 5±2°C.
The salt (%) of control was the lowest and increased from 13.12 to 3.85% during the storage period of 90 days at 15±2°C.
The salt (%) of T4 was the highest and increased from 6.04 to 6.78% at a storage period of 90 days at 15±2°C.
The salt (%) of control was the lowest and increased from 3.18 to 3.42% during the storage period of 45 days at 25±2°C.
The salt (%) of T4 was the highest and increased from 6.08 to 6.81% at a storage period of 90 days at 25±2°C.
Total protein (TP):
The TP (%) of control was the lowest and decreased from 14.74 to 11.39% during the 90 days of storage period at 5±2°C.
The TP (%) of T4 was the highest and decreased from 16.22 to 13.77% during the 90 days of ripeningat 5±2°C.
The TP (%) of control was the lowest and decreased from 15.25 to 11.53% during the 90 days of storage period at 15±2°C.
The TP (%) of T4 was the highest and decreased from 16.70 to 13.87% during the 90 days of ripening.
The TP (%) of control was the lowest and decreased from 14.16 to 12.44% during the 45 days of storage period at 25±2°C.
The TP (%) of T4 was the highest and decreased from 16.27 to 14.60% during the 90 days of ripening at 25±2°C.
Soluble nitrogen (SN):
The SN (%) of control was the highestand boosted from 0.225 to 0.389% during the storage period at 5±2°C.
The SN (%) of T4 was the lowest and increased from 0.172 to 0.264% during the 90 days of storage at 5±2°C.
The SN (%) of control was highest and boosted from 0.327 to 0.466% during the storage period at 15±2°C.
The SN (%) of T4 was the lowest and increased from 0.180 to 0.271% during the 90 days of storage at 15 ±2°C.
The SN (%) of control was highest and boosted from 0.305 to 0.450% during the storage period of 45 days at 25±2°C.
The SN (%) of T4 was the lowest and bosted from 0.179 to 0.313% during the 90 days of storage at 25±2°C.
Microbiological properties:
Total bacterial, Bifidobacterium, yeasts& molds and coliform counts were enumerated during the 90 days of storage.
The TBC of control was highest as compared to other treatments, and increased up to 30 days of storage period at 5±2°C, recorded 7.38log CFU/g,then the TBC decreased until the end of storage period, recorded 6.24 log CFU/g after 90 days of storage.
The TBC of T4 was the lowest compared to other treatments, and increased up to 15 days of storageat 5±2°C, recorded 4.63 log CFU/g, then the TBC decreased until the end of storage (90 days), recorded 4.01 log CFU/g.
The TBC of control was high as compared to other treatments, and increased up to 30 days of storage period at 15±2°C, recorded 7.55 log CFU/g, then the TBC decreased until the end of storage period(90 days), recorded 6.58 log CFU/g.
The TBC of T4 was the lowest compared to other treatments, and increased up to 15 days of storageat 15±2°C, recorded 5.73 log CFU/g, then the TBC decreased until the end of storage, recorded 4.13 log CFU/g after 90 days of storage period.
The TBC of control was highest as compared to other treatments, and increased up to 30 days of storage period at 25±2°C, recorded 7.66 log CFU/g, then the TBC decreased until 45 days of storage period, recorded 7.07 log CFU/g.
The TBC of T4 was the lowest compared to other treatments, and increased up to 15 days of storage at 25±2°C, recorded 5.79 log CFU/g, then the TBC decreased until the end of storage (90 days), recorded 3.75 log CFU/g.
Bifidobacterium count:
The Bifidobacterium count of control was highest as compared to other treatments, and increased up to 30 days of storage period at 5±2°C, recorded 7.60 log CFU/g, then the counts decreased until 75 days of storage period, recorded 6.94 log CFU/g.
The Bifidobacterium count of T4 was the lowest compared to other treatments, and decreased from 4.60 log CFU/g to 4.36 log CFU/g after two weeks of storage at 5±2°C, then the number decreased to 3.94 log CFU/g at 45 days and no colonies were identified up to the end of storage.
The Bifidobacterium count of control was highest as compared to other treatments, and increased up to 30 days of storage period at 15±2°C, recorded 7.71 log CFU/g, then the counts decreased until 75 days of storage period, recorded 7.25 log CFU/g.
The Bifidobacterium count of T4 was the lowest compared to other treatments, and decreased from 4.83 to 4.48 log CFU/g after two weeks of storage at 15±2°C, then the number decreased to 4.12 log CFU/g at 45 days and no colonies were identified up to the end of storage.
The Bifidobacterium count of control was highest as compared to other treatments, and increased up to 30 days of storage period at 25±25°C, recorded 7.91 log CFU/g, then the counts decreased until 45 days of storage period, recorded 7.59 log CFU/g.
The Bifidobacterium count of T4 was the lowest compared to other treatments, and decreased from 5.18 to 4.62 log CFU/g after two weeks of storage at 25±2°C, then the number decreased to 4.15 log CFU/g at 45 days and no colonies were identified up to the end of storage.
Yeast& molds and coliform counts:
The counts of yeasts and molds was not detected in most treatments during the storage period; Whereas, yeasts and molds appeared in control and T1 during 45 days of storage at 25±2°C.
The coliform group was a negative in all treatments during the storage period (90 days).
The control and T1 stored at 25±2°Cwere positive for the test of yeast and molds in 45 days of storage and recorded, 2.38 and 1.88 log CFU/g; respectively, while T2 were positive for the test at 60 days, it containe 1.89 log CFU/g.
T3 and T4 did not show any yeasts and molds during the storage periods, it was noted that there is a relationship between an increase in salt content and a decrease in yeasts and molds.
Sensory evaluation:
Sensory evaluation was done by a regular taste panel of the staff members of the Dairy Science Department, Faculty of Agriculture, Assiut University. Samples were evaluated for flavor (50 points), color and appearance (15 points), and body and texture (35 points) to be 100 points for the total score.
By increasing salt ratio flovor points as well as body and texture decreased in all treatments.
By increasing storage periods, flavor scores as well as body and texture decreased in all treatments.
Cheese samples which stored at 25°C recorded the lowest scores of color and appearance as compared to other treatments, which stored at 5 or 15°C in all treatments.
The highest scoring points were for control stored at 5°C for 90 days (97/100), followed by T1 stored at 5°C for 90 days (95/100), then control stored at 15°C at 90 days (94/100).
For all treatments, as the period of ripening advanced, the total scoring points of the cheese increased since the cheese was kept at refrigerator conditions.
from the foregoing results, it could be concluded that:
1- white soft cheese can be produced from pasteurized milk with good flavor and texture using low salt concentrations and low temperatures.
2- white soft cheese can be stored for 45 days with enough probiotic bacteria (5-7) log CFU/g.