الفهرس 
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Abstract
Probiotic food is defined as a processed product that contains viable probiotic microorganisms in a suitable matrix and in sufficient concentration.
Functional foods are designed to boost human health, more specifically intended for weight management (prevention of obesity), natural defenses (boosting of immunity), bone calcification (prevention of osteoporosis), digestion (prevention of intestinal disorders), cardiovascular health (prevention of heart diseases by lowering the cholesterol level or blood pressure). To combine the beneficial effects of milk, plant extract, and probiotic microorganisms. A portion of functional food has some beneficial effects on health.
The first probiotic definition was rendered in 1908 by Metchnikoff, who proposed that the consumption of fermented milk products prolongs the human life.
The word ‘probiotic’, derived from the Greek language, means ‘for life’ and has had many definitions in the past. Definitions such as ‘substances produced by protozoa that stimulate the growth of another’ or ‘organisms and substances that have a beneficial effect on the host animal by contributing to its intestinal microbial balance’ were used. These general definitions were unsatisfactory because ‘substances’ include chemicals such as antibiotics.
The most common probiotic species in infants are Bifidobacterium infantis, Bifidobacterium breve, and Bifidobacterium longum. As infants mature, B. infantis and B. breve are replaced by Bifidobacterium adolescentis and B. longum. Bifidobacteria produce acetic and lactic acids in a molar ratio of 3:2 from 2 mol of glucose in an ideal synthetic medium. Lactic acid is in the L-(+) form, which is more easily metabolized by infants than is the D-(-) form.
Bifidobacteria may synthesize and produce vitamins like riboflavin, thiamine, vitamin B6, and vitamin K and related bioactive molecules like folic acid, niacin, and pyridoxine. Bifidobacteria containing fermented milk is rich in free amino acids and vitamins.
The aim of this study:
1. This study was carried out in order to investigate and compare The effect of different percentages of growth-promoting substance, i.e., yeast extract (0.1, 0.5, and 1%) on the growth rate of Bifidobacterium breve (ATCC 15700) in some dairy products, i.e., yoghurt, fermented dairy drink (acidophilus milk) and soft cheese (Domiati cheese).
2. Using Bifidobacterium breve (ATCC 15700), and yeast extract in the manufacture of some dairy products i.e., yoghurt, acidophilus milk, and soft cheese.
3. To compare Effect of the percentage of added yeast extract in the manufacture of some dairy products and the effect on chemical composition, bacteriological quality, and organoleptic properties during storage of bio-yoghurt, Acidophilus milk, and Domiati cheese.
4. To compare the chemical composition, bacteriological quality and organoleptic properties of some probiotic dairy products manufactured by using liquid and reconstituted cow’s milk and the effect of adding yeast extract as a growth promoting substance during the manufactured of the products.
Six dairy products were manufactured using liquid and reconstituted cow’s milk: -
1- Bio-yoghurt manufactured from liquid cow’s milk and fortified by yeast extract during storage at 5˚ ± 2˚C for 15 days
Yoghurt is one example of a fermented dairy product that is frequently used to deliver probiotics to consumers. For both preventive and therapeutic purposes, Bifidobacterium breve is frequently utilized as probiotic. The objective of this work was to examine the effect of growth-promoting (yeast extract) at 0.1, 0.5, and 1% and Bifidobacterium breve (Bif. breve) at 1, 3, and 5% on the chemical composition, microbiological quality, organoleptic properties and shelf-life stability of bio-yoghurt during storage at 5˚ ± 2°C for 15 d.
Bio-yoghurt was then stored at 5°± 2˚C until further analysis. Each trial was replicated 3 times. Percentage of moisture, developed titratable acidity, sensory evaluation, LAB count, total bacterial count (TBC), Bif. breve count, and coliform bacteria were examined in the bio-yoghurt at 0, 5, 10, and 15 days.
The obtained results indicated that
1) there was a gradual significant (P < 0.05) increase in the percentage of DTA in all samples during 15 days of storage. After 15 days of storage, the B5c sample recorded 0.91% the highest significant increase compared to the control sample, which recorded 0.78%.
2) there was a gradual significant (P < 0.05) decrease in the percentage of moisture content in all samples during 15 days of storage. After 15 days of storage control sample recorded 82.86% significant decrease compared to B5c sample, it recorded 83.11%.
3) there was a gradual significant (P < 0.05) increase in log bacterial count in all samples during 15 days of storage, but by different rates the slower rate was in the control sample reached 14.8 log CFU gm-1 compared with B5c recorded 15.63 log CFU gm-1 the highest significant increase after 15 days of storage.
4) there was a gradual significant (P < 0.05) increase in total log CFU of LAB in all samples during 15 days of storage, but by different rates the slowest rate was in the control sample reached 15.32 log CFU gm-1 compared with B5c recorded 15.9 log CFU gm-1 the highest significant increase after 15 days of storage.
The results showed that B5 sample recorded 14.99 log CFU gm-1 an increase in numbers during the storage period, after adding growth-promoting (YE) B5c sample recorded the highest rates in the number of Bif. breve it reached 15.89 log CFU gm-1, and the increase was significant (p < 0.05).
The coliform bacteria were not detected in all cheese samples.
The addition of yeast extract increased (p <.05) the viability of Bif. breve during storage, as well as, acted as an antimicrobial against molds
Yeast was detected in the control sample after 10 d of storage, while it was detected in Bio-yoghurt supplemented with Bif. breve and Bif. breve+ yeast extract after 15 days of storage. Molds were detected in the control sample after 10 d while Bio-yoghurt supplemented with Bif. breve and Bif. breve+ yeast extract did not detect. Yeast count was 6.6 log CFU gm-1 in the control sample after 10 d. Mold count 6.3 log CFU gm-1 in control sample after 10 d.
The overall acceptability of bio-yoghurt was improved (P < 0.05) by the addition of symbiotic (Bif. breve and YE) as compared with the control. The percentage of 5% Bif. breve + 0.1, 0.5, and 1% yeast extract and the percentage of 3% Bif. breve + 1% YE resulted in significant texture, appearance, flavor, and overall acceptability when compared with the control.
2- Bio-yoghurt manufactured from reconstituted cow’s milk and fortified by yeast extract during storage at 5˚ ± 2˚C for 15 days
The objective of this experiment was to examine the effect of growth-promoting yeast extract (YE) at 0.1, 0.5, and 1% with Bifidobacterium breve (Bif. breve) at 1, 3, and 5% on the chemical composition, microbiological quality, organoleptic properties and shelf-life stability of bio-yoghurt during storage at 5° ± 2°C for 15 d.
Bio-yoghurt was then stored at 5°± 2°C for 15 days. This trial was replicated 3 times. Percentage of moisture, DTA, sensory evaluation, LAB colony count, total bacterial colony count (TBC), Bif. breve colony count, and coliform bacteria were examined in the bio-yoghurt after 0, 5, 10, and 15 days of storage.
The obtained results indicated that
1) there was a gradual significant (P < 0.05) increase in percentage of DTA in all samples during 15 days of storage. After 15 days of storage B5c sample recorded 0.92% the highest significant increase compared to the control sample, which recorded 0.8%.
2) there was a gradual non-significant (P > 0.05) decrease in the percentage of moisture content in all samples during 15 days of storage. After 15 days of storage, the B5c sample recorded 82.63% non-significant decrease compared to the control sample, which recorded 82.86%.
3) that there was a gradual significant (P < 0.05) increase in total bacterial colony count in all samples during 15 days of storage, but by different rates the slower rate was in the control sample reached 14.93 log CFU gm-1 compared with B5c recorded 15.28 log CFU gm-1 the highest significant increase after 15 days of storage.
4) there was a gradual significant (P < 0.05) increase in total log CFU of LAB in all samples during 15 days of storage, but by different rates the slowest rate was in the control sample reached 15.42 log CFU gm-1 compared with B5c recorded 15.70 log CFU gm-1 the highest significant increase after 15 days of storage.
The results showed that B5 sample recorded 15.09 log CFU gm-1 an increase in numbers during the storage period, after adding growth-promoting (YE) B5c sample recorded the highest rates in the number of Bif. breve it reached 16.00 log CFU gm-1, and the increase was significant (p < 0.05).
Coliform bacteria were not detected in all samples up to the end of the storage period.
The addition of yeast extract increased (p <.05) the viability of Bif. breve during storage, as well as, acted as an antimicrobial against molds
Yeast was detected in the control sample after 10 d of storage, while it was detected in Bio-yoghurt supplemented with Bif. breve and Bif. breve+ yeast extract after 15 days of storage. Molds were detected in control sample after 10 d while Bio-yoghurt supplemented with Bif. breve and Bif. breve+ yeast extract did not detect. Yeast count was 6.93 log CFU gm-1 in the control sample after 10 d. The mold counts 6.74 log CFU gm-1 in the control sample after 10 d.
The overall acceptability of probiotic yoghurt was improved (P < 0.05) by the addition of symbiotic (Bif. breve and YE) as compared with the control. The percentage of 5% Bif. breve + 0.1, 0.5, and 1% yeast extract and the percentage of 3% Bif. breve + 1% YE resulted in significant texture, appearance, flavor, and overall acceptability when compared with the control
3- Probiotic acidophilus milk manufactured from liquid cow’s milk and fortified by yeast extract during storage at 5˚ ± 2˚C for 15 days
The impact of adding Lactobacillus acidophilus 3%, Bif. breve (1, 3, and 5%) and yeast extract (YE) (0.1, 0.5, and 1%) on the chemical, microbiological, and organoleptic properties of acidophilus milk during storage.
Probiotic acidophilus milk was then stored at 5°± 2˚C until further analysis. This trial was replicated 3 times. The acidity, sensory evaluation, Lb. acidophilus count, total bacterial count (TBC), Bif. breve count, yeast and mold, and coliform bacteria were examined in the probiotic acidophilus milk at 0, 5, 10 and 15 d.
The obtained results indicated that
1) there was a gradual significant (P < 0.05) increase in percentage of DTA in all samples during 15 days of storage. After 15 days of storage B5c sample recorded 0.76% the highest significant increase compared to control sample, it recorded 0.52%.
2) there was a gradual significant (P < 0.05) increase in total bacterial count in all samples during 15 days of storage, but by different rates the slower rate was in the control sample reached 11.14 log CFU ml-1 compared with B5c recorded 12.75 log CFU ml-1 the highest significant increase after 15 days of storage.
3) there was a gradual significant (P < 0.05) increase in total log CFU of Lb. acidophilus in all samples during 15 days of storage, but by different rates the slower rate was in the control sample reached 11.17 log CFU ml-1 compared with B5c recorded 12.51 log CFU ml-1 the highest significant increase after 15 days of storage.
The results showed that B5 sample recorded 11.6 log CFU ml-1 an increase in count during the storage period, after adding growth-promoting (YE) B5c sample recorded the highest rates in the number of Bif. breve it reached 12.3 log CFU ml-1, and the increase was significant (p < 0.05).
Coliform bacteria were not detected in all samples up to the end of storage period.
The antibacterial effect of Bif. breve prevented yeast, mold and coliform bacteria from growing for up to 15 days.
Molds and yeast were detected only in the control sample after 15 days of storage.
Yeast count reached 5.6 log CFU ml-1 and mold count reached 6.6 log CFU ml-1 after 15 days of storage at 5°± 2˚C.
On the other hand, yeast and molds were not detected in all samples of probiotic acidophilus milk up to the end of the storage period.
All sensory evaluation shows the overall acceptability of AM improved significantly (p<0.05) with adding Bif. breve and yeast extract compared to the control sample.
B5a, B5b, B5c, B5, and B3c samples have recorded the best results in overall acceptance, taste, texture, and appearance
The overall acceptability of acidophilus milk was improved significantly (P<0.05) by the addition of YE and Bif. breve as compared to the control sample.
4- Probiotic acidophilus milk manufactured from reconstituted cow’s milk and fortified by yeast extract during storage at 5˚ ± 2˚C for 15 days.
Dairy products that have been fermented are a great source of a variety of probiotics with many health advantages, which enhance the benefits of milk.
The objective of this work was to examine The effect of growth promoting yeast extract (YE) at 0.1, 0.5, and 1% with Bifidobacterium breve (Bif. breve) at 1, 3, and 5% on the chemical composition, microbiological quality, organoleptic properties and shelf-life stability of probiotic acidophilus milk during storage at 5˚ ± 2°C for 15 d.
Probiotic acidophilus milk was then stored at 5°± 2˚C until further analysis. This trial was replicated 3 times. The acidity, sensory evaluation, Lb. acidophilus count, total bacterial count (TBC), Bif. breve count, yeast and mold, and coliform bacteria were examined in the probiotic acidophilus milk at 0, 5, 10 and 15 d.
The obtained results indicated that
1) there was a gradual significant (P < 0.05) increase in percentage of DTA in all samples during 15 days of storage. After 15 days of storage B5c sample recorded 0.77% the highest significant increase compared to control sample, it recorded 0.53%.
2) there was a gradual significant (P < 0.05) increase in total bacterial count in all samples during 15 days of storage, but by different rates the slower rate was in the control sample reached 11.18 log CFU ml-1 compared with B5c recorded 12.84 log CFU ml-1 the highest significant increase after 15 days of storage.
3) that there was a gradual significant (P < 0.05) increase in total log CFU of Lb. acidophilus in all samples during 15 days of storage, but by different rates the slower rate was in the control sample reached 11.24 log CFU ml-1 compared with B5c recorded 12.6 log CFU ml-1 the highest significant increase after 15 days of storage.
The results showed that B5 sample recorded 11.72 log CFU ml-1 an increase in numbers during the storage period, after adding growth-promoting (YE) B5c sample recorded the highest rates in the number of Bif. breve it reached 12.59 log CFU ml-1, and the increase was significant (p < 0.05).
Coliform bacteria were not detected in all samples up to the end of storage period.
The antibacterial effect of Bif. breve prevented yeast, mold, and coliform bacteria from growing for up to 15 days.
Molds and yeast were detected only in the control sample after 15 days of storage.
Yeast count reached 5.6 log CFU ml-1 and mold count reached 6.6 log CFU ml-1 after 15 days of storage at 5°± 2˚C.
On the other hand, yeast and molds were not detected in all samples of probiotic acidophilus milk up to the end of the storage period.
All sensory evaluation showed the overall acceptability of AM improved significantly (p<0.05) with adding Bif. breve and yeast extract compared to the control sample.
B5a, B5b, B5c, and B3c samples have recorded the best results in overall acceptance, taste, texture, and appearance.
The overall acceptability of AM was improved significantly (P<0.05) by the addition of YE and Bif. breve as compared to the control sample.
5- Probiotic soft cheese manufactured from liquid cow’s milk and fortified by yeast extract during storage at 5˚ ± 2˚C for 60 days
Cheese has recently been the focus of a number of marketing and scientific investigations, due to its effectiveness in delivering probiotics to the digestive tract. The objective of this experiment was to examine the effect of yeast extract (YE) 0.1, 0.5, and 1% with cheese cultures on the chemical composition, microbiological quality, organoleptic properties, and shelf-life stability of probiotic soft cheese (PSC) during storage at 5˚ ± 2˚C for 60 days.
The acidity, moisture, salt, Lactic acid bacteria (LAB) colony count, total bacterial colony count (TBC), Bif. breve colony count, yeasts and molds, coliform count, and organoleptic properties were examined in the PSC after 0, 15, 30, 45, and 60 days of storage. The addition of YE had increased the total log CFU of Bif. breve, LAB, TBC, percentage of salt, and development titratable acidity (DTA) were significantly (P < 0.05) increased during storage on the other side, the percentage of moisture was decreased (P < 0.05) during storage.
The results obtained for the percentage of DTA during storage of PSC showed that gradual significant (P < 0.05) increase in the percentage of DTA in all samples during 60 days of storage. After 60 days of storage, the B5c sample recorded 1.51% the highest significant increase compared to a control sample, which recorded 1.32%.
Also, the obtained results indicated that there was a gradual significant (P<0.05) decrease in percentage of moisture content in all samples during 60 days of storage. After 60 days of storage B5c sample recorded 57.32% significant decrease compared to control sample, it recorded 58.91%.
The results obtained for the percentage of salt content during storage of PSC showed that gradual non-significant (P > 0.05) increase in percentage of salt content in all samples during 60 days of storage. After 60 days of storage B5c sample recorded 4.23% compared to control sample, it recorded 4.1%.
The obtained results indicated that there was a gradual significant (P < 0.05) increase in total log bacterial colony count in all samples during 60 days of storage, but by different rates the slower rate was in the control sample reached 14.15 log CFU gm-1 compared with B5c recorded 14.57 log CFU gm-1 the highest significant increase after 60 days of storage.
The obtained results indicated that there was a gradual significant (P < 0.05) increase in total log CFU of LAB in all samples during 60 days of storage, but by different rates the slowest rate was in the control sample reached 14.64 log CFU gm-1 compared with B5c recorded 14.89 log CFU gm-1 the highest significant increase after 60 days of storage.
The results showed that B5 sample recorded 14.24 log CFU gm-1 an increase in count during the storage period, after adding growth-promoting (YE) B5c sample recorded the highest rates in the number of Bif. breve it reached 14.74 log CFU gm-1, and the increase was significant (p < 0.05) after 60 days of storage.
The antimicrobial activity of Bif. breve delayed the growth of yeast, molds, and coliform bacteria during storage.
Coliform bacteria was not detected in all cheese samples.
Yeast and mold were not detected in any cheese sample
All sensory evaluation shows the overall acceptability of PSC improved (p<0.05) with adding Bif. breve and yeast extract compared to the control. B5a, B5b, B5c, and B3c samples have recorded the best results in overall acceptance, flavor, texture, and appearance during storage.
6- Probiotic soft cheese manufactured from reconstituted milk and fortified by yeast extract during storage at 5˚ ± 2˚C for 60 days
Cheese has a better potential for delivering probiotic microorganisms to the human digestive tract in comparison to fermented milk. The objective of this study was to examine The effect of yeast extract (YE) 0.1, 0.5, and 1% with cheese cultures on the chemical composition, microbiological quality, organoleptic properties, and shelf-life stability of probiotic soft cheese (PSC) during storage at 5˚ ± 2˚C for 60 days.
Percentage of DTA, moisture, salt, Lactic acid bacteria (LAB) colony count, total bacterial colony count (TBC), Bif. breve colony count, yeasts and molds, coliform bacteria, and organoleptic properties were examined in the PSC after 0, 15, 30, 45, and 60 days of storage. The addition of YE increased the total log CFU of Bif. breve, LAB, TBC, percentage of salt, and development titratable acidity (DTA) were significantly (P < 0.05) increased during storage on the other side, the percentage of moisture was decreased (P < 0.05) during storage.
The results obtained for the percentage of DTA during storage of PSC showed that gradual significant (P < 0.05) increase in the percentage of DTA in all samples during 60 days of storage. After 60 days of storage, the B5c sample recorded 1.52% the highest significant increase compared to the control sample, which recorded 1.33%.
The obtained results indicated that there was a gradual significant (P < 0.05) decrease in percentage of moisture content in all samples during 60 days of storage. After 60 days of storage B5c sample recorded 57.25% significant decrease compared to control sample, it recorded 58.90%.
The results obtained for the percentage of salt content during storage of PSC showed that gradual non-significant (P > 0.05) increase in percentage of salt content in all samples during 60 days of storage. After 60 days of storage B5c sample recorded 4.14% compared to control sample, it recorded 4.11%.
The obtained results indicated that there was a gradual significant (P < 0.05) increase in total bacterial count in all samples during 60 days of storage, but by different rates the slower rate was in the control sample reached 14.25 log CFU gm-1 compared with B5c recorded 14.97 log CFU gm-1 the highest significant increase after 60 days of storage.
Also, the obtained results indicated that there was a gradual significant (P < 0.05) increase in total log CFU of LAB in all samples during 60 days of storage, but by different rates the slowest rate was in the control sample reached 14.74 log CFU gm-1 compared with B5c recorded 15.01 log CFU gm-1 the highest significant increase after 60 days of storage.
The results showed that B5 sample recorded 15.16 log CFU gm-1 an increase in numbers during the storage period, after adding growth-promoting (YE) B5c sample recorded the highest rates in the number of Bif. breve it reached 15.51 log CFU gm-1, and the increase was significant (p < 0.05) after 60 days of storage.
The antimicrobial activity of Bif. breve delayed the growth of yeast, molds, and coliform bacteria during storage.
Coliform bacteria were not detected in all cheese samples.
Yeast and mold were not detected in any cheese sample
All sensory evaluation shows the overall acceptability of PSC improved (p<0.05) with adding Bif. breve and yeast extract compared to the control. B5a, B5b, B5c, and B3c samples have recorded the best results in overall acceptance, flavor, texture, and appearance during storage.
Conclusion
from the foregoing results, it could be concluded that:
Our results showed that the addition of yeast extract in the manufacture of yoghurt, acidophilus milk, and soft cheese improved the chemical composition and microbiological quality of the product.
Also, using Bif. breve in the manufacture of probiotic soft cheese, bio-yoghurt, and acidophilus milk can improve the sensory characteristics at the end of the storage period.
The addition of yeast extract improved the bacteriological quality of bio-yoghurt, probiotic acidophilus milk, and probiotic soft cheese agreed with the world requirements and regulations, which means that the product contains at least 106 CFU (ml-1 or gm-1) or 6 log CFU (ml-1 or gm-1) at the end of date of validity.
Finally, this study recommends that it can use probiotic bacteria with growth-promoting substances such as yeast extract to make good functional dairy products.