الفهرس 
AcknowledgementOnly 14 pages are availabe for public view
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Abstract
Functional foods are defined in basic terms as “foods that may provide health benefits beyond basic nutrition. Probiotic strains are claimed to confer health benefits to human organisms when consumed in adequate amounts. Thus, over the last decades, there has been an increased interest in the production of functional foods containing probiotic bacteria. Probiotics are “live microorganisms which when administered in adequate 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. Bifi. longum is a probiotic bacteria that has been incorporated into fermented dairy products due to its reported health benefits, Bifidobacterium is one of the most important genera in this field, thus due to its several health benefits such as cholesterol and triglycerides reduction, weight loss, immune stimulation, and cancer prevention especially colon cancer. Prebiotics are supplements or foods that contain nondigestible food ingredients that selectively stimulate the favorable growth and/or enhance the activities of indigenous probiotic bacteria. The symbiotic term is used for the product which contains both the probiotic bacteria and the prebiotics. Symbiotic should be specifically used to explain such products where prebiotic compounds support the growth of probiotic organisms. Synergism can be explained as the ingestion of probiotic bacteria such as Lactobacilli and the growth promotion of intestinal Bifidobacteria. Dairy products like milk and yoghurt have been largely produced on the concept of symbiotics. 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. In this regard the current study includes four main points:
1. To study the viability and growth rate of Bifidobacterium longum (ATCC 15707) in different kinds of milk, i.e., buffalo’s milk, cow’s milk, reconstituted whole milk powder and reconstituted infant formula milk powder.
2. To study and compare the effect of different percentages of some growth promoting substances, oat (1,3 and 5) %, WPC (1,3 and 5) % and AG (0.5,1 and 2) % on the growth rate of Bifidobacterium longum (ATCC 15707), in milk.
3. using Bifidobacterium longum (ATCC 15707), whey protein concentrate and Arabic Gum in the manufacture of some dairy product.
4. To compare the effect of some growth promoting substances in the manufacture of some dairy products and the changes chemical composition, bacteriological quality, and organoleptic properties during storage of bio-yoghurt, Acidophilus milk and Domiati cheese.
The obtained results can be summarized as follow:
1) Effect of different types of milk on the growth rate of Bifi. longum (ATCC 15707) grown at 37 ◦C for 36 hr.
In order to know the effect of milk from different mammals on the growth of Bifi. Longum bacteria, experiments were carried out using buffalo’s milk, cow’s milk, reconstituted whole milk powder and reconstituted infant formula milk powder.
The obtained results showed that the developed titratable acidity was gradually increased until the end of the incubation period and until the completion of curdling. Coagulation had occurred after 24h in Buffalo’s milk, 26 h in cow’s milk, 24h in whole milk powder, and 36 h in infant formula milk powder of incubation.
After milk inoculation the Percentage of DTA was 0.17, 0.22, 0.23, and 0.10% in buffalo’s milk, cow’s milk, whole milk powder, and infant formula milk powder respectively. During storage there was gradual increase in DTA. The increase in percentage of DTA was minimal in the first 8 h but increased significantly thereafter. The initial acidity was from 0.17 to 0.35, from 0.22 to 0.35, from0.23 to 0.48, and from 0.10 to 0.25 Buffalo’s milk, cow’s milk, whole milk powder and infant formula milk powder respectively.
Total colony forming unit of Bifi. longum was dependent on the type of milk used. The highest mean counts were whole milk powder that was 11.41 log cfu/ml followed by Buffalo’s milk, 10.44 log cfu/ml and cows’ milk 9.91 log cfu/ml.
Bifi. longum (ATCC 15707) reached the count of 11.41 log cfu /ml in Whole milk Powder and the lowest growth was noticed in Infant formula milk powder reaching the count of 8.43 log cfu/m.
There was direct relationship between the rate of increase in CFU and percentage of DTA.
The average mean count in infant formula milk powder was lower 8.43 log cfu/ml than that of whole milk powder in which it was reached 11.41 log cfu/ml. In conclusion, this study has shown that whole milk powder could promote the growth of Bifi. longum the most in comparison with cows’ milk and infant formula milk powder followed by Buffalo’s milk.
2) Effect of growth promoting substances on the growth rate of Bifi. longum in sterilized skim Buffalo’s milk.
Effects of different percentages of some growth promoting substances, i.e.; oat, whey protein concentrate, and Arabic Gum on the growth rate and acid production by Bifi. longum in sterilized skim milk at 40˚C was studied.
The obtained results indicated that each of oat, WPC and AG had increased both of growth rate and acid production of Bifi. longum
The maximum total viable count (log CFU/ml) in samples fortified by oat were 8.95, 10.00 and 10.65 log CFU/ml; in samples contained of 1, 3 and 5% after 16 hours of incubation at 40˚C; respectively.
The maximum total viable count (log CFU/ml) in samples fortified by whey protein concentrate were 10.62, and 9.69 log CFU/ml; in samples contained of 1 and 3% WPC after 12 hours of incubation at 40˚C; respectively.
The maximum total viable count (log CFU/ml) in sample fortified by Arabic Gum were 10.30, 11.20 and 11.25 log CFU/ml; in sample contained of 0.5, 1 and 2% after 12 hours of incubation at 40˚C; respectively.
The highest colony count of Bifi. longum was obtained in milk fortified by good source of nitrogenous compounds such as whey protein concentrate and Arabic Gum which can be explained by the effect of the availability of nitrogenous compounds in milk which can enhance the rate of growth and increase in CFU of Bifi. longum.
The obtained results indicated that whey protein concentrate (WPC) and Arabic Gum (AG) had a much higher effect as growth promoting substances for the growth of Bifi. longum compared with oats.
3) Effect of sodium chloride on the rate of change in (CFU) and developed titratable acidity (DTA) of Bifi. longum (ATCC 15707) cultivated in sterilized skim milk at 40°C.
The effect of 3,5 and 7% sodium chloride on the growth rates and developed titratable acidity of Bifi. longum, when cultivated in sterilized skim milk at 40°C, had been studied.
At the time of inoculate, there was no big difference in percentage of DTA between different samples, it was 0.17, 0.16, 0.15 and 0.15 % in samples contained 0, 3,5 and 7% respectively.
During subsequent incubation there was gradual increase in percentage of DTA, the rate of increase was decreased are the percentage of added NaCl was increased.
After 24 h, the percentage of DTA reached 0.35, 0.33, 0.31 and 0.26 % in samples contained 0, 3, 5 and 7 % NaCl respectively.
The effect of 3,5 and 7% sodium chloride on the population level of Bifi. longum during 32 h of incubation had indicated that in the absence of sodium chloride (control) growth was at an exponential rate up to 20 h reaching a maximum of 10.44 log CFU/ml. After this period, the growth rate declined and reached10.20 log CFU /ml after 32 h incubation. However, in samples contained of 3% sodium chloride, the growth was at a slower rate reaching a maximum of 9.46 log CFU/ml after 20 h of incubation. while in the presence of 5% and 7% of sodium chloride, the growth rate was by very slow rate reaching 9.91 log CFU/ml and 7.70 log CFU/ml respectively after 28 h of incubation.
The rate of increase in colony forming units was decreased as the percentage of sodium chloride was increased, but there was bigger difference in the effect between percentage of 5% and 7% than between 0% and 3% NaCl. Maximum cell population reached 10.44 log CFU/ml, 9.80 log CFU/ml, 8.91 log CFU/ml and 7.70 log CFU/ml when growth was at percentage 0, 3, 5 and 7% sodium chloride respectively. On the other hand, differences in developed titratable acidity as a function of salt concentration in milk. It is still noteworthy that differences between percentage of 5% and 7 was more dramatic than between of 0% and 3% NaCl. This may be no more than the consequence of difference in cell population.
The obtained results indicated that percentage of 7% NaCl would result in a marked decrease in growth rate and in the rate of acid production by B. longum.
This means that sodium chloride has a potential inhibitory effect on the growth of B. longum.
4) Probiotic fermented milk (bio-yoghurt)
In our study we tried to improve the chemical, microbiological and sensory properties of probiotic yogurt, for this aim 1% (WPC) and 2% (AG) were added to the buffalo’s milk. Different yoghurt samples were stored at 5±1°C for 14 days and analyzed fresh and after 7 and 14 days. and all these treatments were tested for chemical, microbiological and sensory properties.
Development titratable acidity (DTA), total solids content (TS), total nitrogen (TN) and soluble nitrogen (SN) were increased with progressing of storage periods at refrigerator temperature up to 14 days, while pH values were decrease in all treatments.
The addition of WPC and AG to yoghurt gave best results of some chemical, microbiological and sensory properties.
During storage there was a gradual increase in DTA, TS, TN and S.N in all samples, on the other hand the rate of increase was faster in YW and YG comparing with YC and YB.
Concerning the total plate counts (TBC) during the first 7days of storage, there was gradual increase in total log cfu/gm in all treatments.in the same time the higher increase was in YW samples (8.60 log cfu/gm) and the minimum was in YC (7.62 log cfu/gm) at the end of the storage period, there was gradual decrease in log cfu/ml in all treatments, in the same time the highest was in YW.
There was an increase in total count of Lactobacilli after 7 days of storage in all treatments, it is obvious that the increase in YW and YG was higher comparing with YC and YB samples at the end of storage period there was slight decrease in Lactobacilli count in all treatments, in the same time the higher was in YW samples.
Concerning Streptococci count after 7 days of storge, there was increase in Streptococci in all treatment, the higher counts were in YW and YG 7.74 log cfu/gm and 7.32 log cfu/gm. After 14 days of storage, and as a result for the increase in DTA, there was slight decrease in Streptococci count, however, counts were higher 6.90 and 6.63 log cfu/gm in YW and YG and the minimum was 6.17 log cfu/gm in control samples.
For Bifidobacterium longum count after 7 days of cold storage, although there was an increase in Bifi. longum counts in all treatments, the highest count was 9.30 log cfu/gm in YW and the lowest was 8.63 log cfu/gm in YB. These counts were decreased after 14 days of cold storage and still the highest was in YW samples.
The coliform bacteria were not detected in all treatments.
The obtained results indicated that the addition of WPC as a growth promoting substance for probiotic culturing probiotic dairy products improves, flavor, body, texture and Appearance of the product.
5) Probiotic fermented milk drink (Acidophilus milk)
In this part, we conducted to improve the chemical, microbiological and organoleptic properties of probiotic acidophilus milk.1% (WPC) and 2% (AG) were added to buffalo’s milk. Samples were stored at 5±1°C for 14 days and analyzed when fresh and after 7 and 14 days. and all these treatments were tested for chemical, microbiological and sensory properties.
The development titratable Acidity (DTA), total solids content (TS), total nitrogen (TN) and soluble nitrogen (SN) were increase with progressing of storage periods at refrigerator temperature up to 14 days, while pH values were decrease in all treatments.
The addition of WPC and AG in the manufactures of acidophilus milk gave best results of some chemical, microbiological and sensory properties.
During storage there was a gradual increase in DTA, TS, TN and S.N in all samples, on the other hand the rate of increase was faster in YW and YG comparing with YC and YB.
The addition of WPC and AG to acidophilus milk had increased bacterial viability and acid production which was reached 0.24, 0.33, 0.78 and 0.39 % in AC, AB, AW and AG respectively.
Acidophilus milk made with Lb. acidophilus, Bifidobacteria, 1% WPC enriched had the highest value of acidity, TS, TN, and, SN than the other treatments. These results might be due to the stimulating effect of WPC on the growth of lactic acid bacteria.
The total plate counts (TBC) after 7 days of storage, total bacterial counts were increased in all treatments and reached 8.46, 8.53, 9.54 and 8.55 log cfu/gm in AC, AB, AW and AG respectively. Still the higher was in samples fortified by WPC and the lowest was in the control sample. on the other hand, and after 14 days of storage TBC was decreased in all treatment, and the higher was in sample contained WPC comparing with other treatments.
The counts of lactobacilli were higher in Probiotic Acidophilus milk fortified with 1% (WPC) and 2% (AG) compared with controls. Treatment (AW) that was made by adding WPC exhibited the highest lactobacilli counts. at the end of storage period there was slight decrease in Lactobacilli count in all treatments, in the same time the higher was in AW samples.
Streptococci count after 7 days of storage were increase in all treatments, reached 6.56, 6.63, 7.25 and 6.69 log cfu/gm. we can see that the increase in Streptococci count was higher in samples contained WPC and GA compared with control samples.
Bifidobacterium longum count after 7 days of cold storage, although there was an increase in Bifi. longum counts in all treatments, the highest count was 8.39 log cfu/gm in AW and the lowest was 8.23 log cfu/gm in AB. at the end of storage period there was a gradual decrease in the count in all treatments reached 8.23, 8.39 and 8.38 log cfu/gm in AB, AW ana AG respectively some time counts were higher in AW and AG samples compared with control.
Coliform bacteria were not detected in all treatments.
The obtained results indicated that the addition of WPC as a growth promoting agent for probiotic culturing probiotic dairy products improves, flavor, body, texture and appearance of the product. The overall acceptance scores of samples AC, AB, AW, and AG were 61, 66, 73, and 69 respectively.
6) Probiotic Domiati Cheese (PDC)
In this part of investigation, it was conducted to improve the chemical, microbiological and sensory properties of probiotic Domiati Cheese,1% (WPC) and 2% (AG) were added to buffalo’s milk. Samples were stored for 60 days at room temperature and analyzed when fresh and after 15,30,45 and 60 days. And all these treatments were tested for chemical, microbiological and sensory properties.
Our results showed that the development titratable Acidity (DTA), total solids content (TS), total nitrogen (TN), soluble nitrogen (SN) and salt were increase with progressing of storage periods at room temperature up to 60 days, while pH values were decrease in all treatments.
During storage there was a gradual increase in DTA, TS, TN and S.N in all samples, on the other hand the rate of increase was faster in YW and YG comparing with YC and YB.
After 60 days of storage still DW and DG had higher DTA, TS, TN, TS and salt content compared with DC and DG treatments.
Percentage of salt in control cheese and other treatments ranged from 3.46% to 3.97 % in fresh cheese and it ranged from 5.40 % to 5.98 % after 60 days of ripening. The percentage of salt (%) content in control (DC) was the lowest as compared to other treatments and increased from 3.97 % to 5.40% after the 60 day of storage period at room temperature.
Total bacterial count was gradually increased in all treatments up to 45 days of storage and it was reached the maximum count, in the same time it was higher in DW and DG compared with DC and DB. The maximum TBC reached 9.91, 9.98, 10.34 and 10.11 log cfu/gm in DC, DB, DW and DG respectively, which indicate the effect of WPC and AG as a growth promoting substance for the bacterial growth in cheese during storage.
lactobacilli counts were gradually increased in all treatments during storage reached the maximum of 8.62, 8.78, 9.89 and 9.55 log cfu/gm after 45 days of storage, which indicate the effect of WPC and AG as a growth promoting substance for the growth of Lactobacilli, also, the effect of WPC was more than AG. After 45 days Lactobacilli counts were decreased reached after 60 days of storage 6.61, 7.67, 8.25 and 7.97 log cfu/gm in DC, DB, DW and DG respectively.
Counts of Streptococci were gradually increased in all treatments up to 45 days of storage reached 8.51, 8.92, 9.76 and 9.11 log cfu/gm in DC, DB, DW and DG respectively. at the end of the storage period there was some decrease in Streptococci count in all treatments reached 6.20, 6.68, 7.98 and 7.81 log cfu/gm in DC, DB, DW and DG respectively.
For Bifidobacterium longum count during storage there was gradual increase in the total CFU of Bifi. longum in all treatment up to 45 days of storage and it was reached 8.66, 9.79 and 8.75 log cfu/gm. The minimum count was in DB sample and the maximum was in DW sample.
Coliform bacteria were not detected in all treatments
There were some differences in all sensory characteristics i.e., flavor, body & texture, appearance and overall acceptability between different treatments and controls.
Generally, the overall acceptability scores of samples significantly increased during storage at room temperature for up to 60 days. This could be associated with the development of acidity and ripening indices.
from the foregoing results, it could be concluded that:
1. The total cfu Bifi. longum was dependent on the type of milk used. For milks, the highest mean counts were whole milk powder that was 11.41 log cfu/ml followed by Buffalo’s milk, 10.44 log cfu/ml and cows’ milk 9.91 log cfu/ml, the minimum was 7.71in infant formula milk powder after 24 h of incubate.
2. from the obtained results presented it could be seen that whey protein concentrate (WPC) and Arabic Gum (AG) had a much higher effect as growth promoting substances for the growth of Bifi. longum than oats.
3. The results show that 7% NaCl has a potential inhibitory effect on the growth of Bifi. longum.
4. Our results showed that the addition of WPC and AG in the manufacture of probiotic yoghurt, acidophilus milk and Domati cheese improved the chemical composition and bacteriological quality of the product. and although the addition of WPC had increased the organoleptic properties of the yoghurt and acidophilus milk, the addition of AG did not.
5. However, using whey protein concentrate in the manufacture of Domati cheese resulted in which can adversely affect the cheese body and texture, While the addition of Arabic Gum improved the sensory characteristics of Domiati cheese at the end of the storage period.
6. The addition of both WPC and AG improved the bacteriological quality of probiotic yoghurt, acidophilus milk and Domiati cheese agreed with the world requirements and regulations, which means that the product contains at least 106 cfu/ml or 6 log cfu/ml at the end of date of validity.
7. Finally, this study recommends that it can use of probiotic bacteria with Growth Promoting Substances such as whey protein concentrate or Arabic Gum to make good functional dairy foods.