الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Part 1: Behavior and associative growth of probiotic bacteria with yogurt and cheese starter cultures
Growth of probiotic Lactobacilli strains in MRS and skimmilk.
Five Probiotic Lactobacilli were inoculated in MRS broth and Skimmilk (1.0%) and subsequently incubated at 37° for 8h. Samples were taken at 0, 2, 4, 6, and 8 h of incubation for analysis. The data show that:
Lb. casei and Lb. rhamnosus had the highest significant growth rate in the MRS medium, followed by Lb. helveticus and Lb. acidophilus. While Lb. reuteri had the least significant OD600nm growth rate.
Gradual decreases in pH values were observed with the tested probiotic strains as the incubation time increased.
The highest significant pH values were in Lb. reuteri after 8 h of incubation time. On the other hand, the least significant pH values were in Lb. rhamnosus and Lb. helveticus along 8h of incubation.
Total viable count of probiotic Lactobacillus spp. ranged from 6.45 to 6.25 Log10 CFU/ml at zero time of incubation for Lb. rhamnosus and Lb. reuteri, respectively.
Probiotic bacteria counts significantly increased by increasing of incubation time, and the probiotic counts were found more than 8.0 log10 CFU/ml. Lb. casei, followed by Lb. rhamnosus and Lb. helveticus showed the fastest growth of all strains in skimmilk.
At the beginning of incubation, pH values ranged between 6.64 to 6.30, followed by a significant decrease as the incubation time progressed.
The selected five probiotic strains were found able to acidify the skimmilk. with a significant difference (P < 0.05) resulting in values the pH values of milk inoculated with probiotic bacteria decreased to 4.68 pH units.
1.2. Associative growth of probiotic bacteria in skimmilk with cheese and yoghurt starter cultures
The associative growth of probiotic bacteria with cheese starter culture in skimmilk was studied within 8 h of incubation. Results resealed that:
The cheese starter culture count (as Lactococci counts) alone reached 9.52 Log10 CFU/ml after 8 h of incubation.
Lactococci counts significant increased in all treatments as the incubation time progressed.
Probiotic counts ranged from 6.35 to 6.11 Log10 CFU/ml (Lb. acidophilus and Lb. rhamnosus, respectively) at the beginning of incubation.
Probiotic counts significantly increased every 2 h of incubation till the end of incubation at 8h.
The highest significant Probiotic counts were noticed with Lb. helveticus (9.75 Log10 CFU/ml), while the least significant Probiotic counts were observed with Lb. reuteri (8.45 Log10 CFU/ml).
The highest TA % was observed in Lb. casei, followed by Lb. rhamnosus, while the lowest TA% was recorded in Lb. reuteri.
The obtained data also reveal that probiotic strains Lb. casei, Lb. rhamnosus and Lb. helveticus could grow and reach the maximum counts in the presence of Lactococci (cheese starter culture).
The Streptococci counts ranged from 6.98 to 6.65 Log10 CFU/ml at the beginning of incubation.
The highest streptococci counts were in number was with yoghurt starter 9.48 Log10 CFU/ml followed by the presence of Lb. rhamnosus 9.35 Log10 CFU/ml while the least number was in treatment with Lb. reuteri 8.45 Log10 CFU/ml at the end of incubation after 8h.
Probiotic bacterial counts ranged from 6.98 and 6.55 Log10 CFU/ml in yoghurt starter culture with Lb. rhamnosus and Lb. reuteri, respectively.
Probiotic and Lactobacilli counts increased significantly by increasing of incubation time.
After 8h of incubation the highest probiotic counts were with Lb. helveticus 9.38 Log10 CFU/ml, followed with Lb. rhamnosus 9.21 Log10 CFU/ml. While, the least probiotic counts were in Lb. reuteri 8.62 Log10 CFU/ml.
Titratable acidity (TA %) ranged from 0.19 to 0.16% at the beginning of incubation in yoghurt starter culture and Lb. reuteri 0.16% at zero time of incubation.
The highest TA % was in yoghurt starter 1.12 % followed by Lb. casei 1.03% then Lb. helveticus 0.98%, while the least TA% was in lowest was Lb. reuteri 0.75% at the end time of incubation.
It could be recommended, the use of yoghurt starter culture with probiotic lactobacilli which gave the highest growth and viability of probiotics.
Part II: Making and Properties of soft and Bio- soft cheese:
Soft and Bio-soft cheese was made by using buffalo’s retentate with total solids 30.2% and fat 16%. Pasteurization was carried out at 72℃ /15 s, followed by homogenization at 50 °C on 150 – 100 par then cooling at 40℃ .
The retentate was divided into 6 equal portions, then inoculated with probiotic Lactobacillus strains, Cacl2, NaCl and rennet were added.
Retentate mixture was incubated for 1.5 to 2 h, then cutting the curd the cheese treatments were packed in plastic cubes and cold stored at 5 ℃ for 60 days.
Results show that:
DM % content was significantly higher in Bio-soft cheese with Lb. casei. While, the least significant DM% content was in control fresh soft cheese. DM% content increased along the storage period in all soft cheese samples till the end of the storage period (60 days).
DM% content increased and ranged from (34.49 – 33.41 %) in Bio-soft cheese with Lb. casei and control soft cheese, respectively.
F/DM contents were significantly higher in fresh Bio-soft cheese with Lb. casei, followed by Lb. rhamnosus (47.42 %).
F/DM contents gradually increased during of the storage till the end of the storage. F/DM contents reached to 49.01- 48.02 % in Bio-soft cheese with Lb. casei and control, respectively.
Titratable acidity (TA %) was higher in fresh Bio-soft cheese with Lb. casei (0.91 %). On the contrary, the least titratable acidity was in control fresh soft cheese sample (0.63%).
Titratable acidity gradually increased during the storage period till the end of the storage, and TA % ranged from 1.21 to 0.96% in Bio-soft cheese with Lb. casei and control soft cheese treatments, respectively.
The highest significant SWP (%) was detected in Bio-soft cheese with Lb. casei samples (3.58%), and the least significant SWP (%) content was in control fresh soft cheese (3.14%). Gradual increase was recorded in SWP content along the storage period.
SWP (%) content ranged from 4.52 to 4.11% in Bio-soft cheese with Lb. casei and control soft cheese treatments, respectively.
Ash (%) was higher in Bio-soft cheese with Lb. casei (2.52%). The least Ash (%) content was found in control fresh soft cheese (2.11%). Ash (%) slightly increased during the storage period and ranged from 3.35- 2.91%, in Bio-soft cheese with Lb. casei and control soft cheese, respectively.
SN/TN content gradually increased in all cheese treatments throughout the storage for 60 days. Experimented treatment of Bio-soft cheese with Lb. rhamnosus was of the highest SN/TN content, while the least SN/TN was in Bio-soft cheese with Lb. reuteri.
Tyrosine content was higher in Bio-soft cheese with Lb. casei (58.42 mg/100g), while, the least tyrosine content was observed in control fresh soft cheese (41.33 mg/100g). tyrosine content sharply increased along the storage period and ranged from 76.8 to 58.45mg/100g in Bio-soft cheese with Lb. casei and control soft cheese, respectively.
Tryptophan content was higher in Bio-soft cheese with Lb. casei (44.30 mg/100g), meanwhile, the least tryptophan was detected in control fresh soft cheese (29.35 mg/100g).
Tryptophan content reached to (60.83 – 46.20 mg/100g) in Bio-soft cheese with Lb. casei and control soft cheese treatment, respectively at the end of the storage period,
Free amino acids in soft and Bio-soft cheese when fresh and after 60 days increased in all treatments, and the highest FAA contents were observed in Bio-soft cheese with Lb. helveticus.
Aspartic, serine, glycine, histidine, arginine, threonine, alanine, proline, valine, methionine, isoleucine, phenylalanine, lysine and cysteine acids were higher in Bio-soft cheese with Lb. helveticus.
Saturated fatty acids in teasted cheeses were examined, C16 (Palmitic acid) was of the highest value, while the lowest was C20 (Arachidic acid). This trend continued throughout the storage period. saturated fatty acid ratios in all samples, with slightly changed, and they were as C16> C18> C14> C10> C12> C20, respectively.
Total viable count (TVBC) was higher in Bio-soft cheese with Lb. helveticus (9.55 log10 CFU/g). While the least total viable count was in control soft cheese (8.89 log10 CFU/g). Total viable count increased during the first 30 days of the storage, followed by a gradual decrease till the end of storage (60 days).
The viable counts of lactobacilli were higher in Bio-soft cheese with Lb. helveticus and Lb. rhamnosus. Whereas, the least viable count of Lactobacilli was in control soft cheese.
The highest Lactobacilli counts was determined in Bio-soft cheese with Lb. helveticus compared with control soft cheese.
Streptococci counts were higher in Bio-soft cheese with Lb. helveticus while the least viable count of Streptococci was detected in Bio-soft cheese with Lb. reuteri. Viable count of Streptococci slightly increased by increasing of the storage period till 15 days followed by significant decrease as the storage period progressed (60 days).
Viable Streptococci count reached to (8.28– 7.76 log10 CFU/g) in Bio-soft cheese with Lb. helveticus and Lb. reuteri, respectively after 60 days of storage.
Yeasts and moulds counts were only detected at the 30 day of the storage period and increased till the end of 60 days. Yeasts and moulds counts appeared in control soft cheese after 15 days (1.0 log10 CFU/g). At the end of the storage period, Yeasts and moulds counts reached (2.43 – 1.31 log10 CFU/g) in control soft cheese and Bio-soft cheese with Lb. reuteri, respectively.
Hardness values were higher in Bio-soft cheese with Lb. acidophilus (6.24 N), and the least hardness was recorded in Bio-soft cheese with Lb. reuteri (5.82 N). Hardness sharply increased along the storage period till the end of the storage period 60 days. Hardness ranged from 12.12 to 10.58N in Bio-soft cheese with Lb. casei and Lb. reuteri, respectively.
Organoleptically, flavor scores were higher in fresh Bio-soft cheese with Lb. rhamnosus (42.7 points). Although, the least flavor was scored in Bio-soft cheese with Lb. reuteri (40.9 points). Flavor scores gradually increased along the storage period for 60 days and ranged from 46.7 to 41.7 points in Bio-soft cheese with Lb. helveticus and Lb. reuteri, respectively.
Body & Texture were high in fresh Bio-soft cheese with Lb. helveticus (34.2 points). While, the least body & texture was in Bio-soft cheese with Lb. reuteri (32.7 points). Body & Texture gradually increased along the storage till 60 days and ranged from 39.1 to 37.4 points in Bio-soft cheese with Lb. helveticus and Lb. reuteri, respectively.
Appearance scores was higher in Bio-soft cheese with Lb. helveticus (8.9 points), and the least appearance scores was found in Bio-soft cheese with Lb. acidophilus (8.2 points).
It could be recommended that, Bio-soft cheese with high chemical, microbiological and organoleptic properties could be produced by using Lb. helveticus, Lb. rhamnosus and yoghurt starter culture.
Part III: Making and Properties of Ras and Bio- Ras cheese during ripening period:
Cow’s milk (216 liters) was heated momentarily to 75℃ and then equally divided into 6 portions to make the tested treatments. Activated yoghurt starter (2%) was added at 37℃, mixed well and left for a half-hour for acid development, then calcium chloride (0.02%) and rennet were added.
Control Ras cheese treatment was inoculated with yoghurt starter culture (2%). All Bio-Ras cheese treatments were inoculated with (1:1) yoghurt starter with one of examined probiotic lactobacilli.
After coagulation within 40 minutes, the curd was cut into small cubes and the temperature was raised to 45℃ in 15 minutes. The curd was held at this temperature for 50 minutes. The whey was then drained down to the level of the curd (acidity of whey 0.14%). Then, the salt was added (2% of used milk) and mixing for 15 minutes then the curd was cooled, molded and pressed with 160 lbs for the first 2 hours. Overnight pressing was done by increasing the weight up to 1000 lbs.
The cheese mold dried and salted on both sides with ten grams of dry salt each other day. Cheese then plastic coted and ripened for 3 months at 15± 2℃ and about 85% relative humidity. The detained results resealed that:
Fresh Bio-Ras cheese with Lb. casei was higher in dry matter content (P ≤ 0.05), followed by the ones belonging to Bio-Ras cheese with Lb. rhamnosus, and Lb. acidophilus, (58.72 and 58.70%), respectively.
DM content increased gradually as the ripening period progressed in all treatments.
Bio-Ras cheese with Lb. reuteri treatment and Bio-Ras cheese with Lb. rhamnosus were of the highest Fat/DM content, followed by the control Ras cheese, (56.10 to 55.52).
The titratable acidity in fresh Ras and Bio-Ras cheese treatments ranged from 0.69% to 0.61% in Bio-Ras cheese with Lb. casei and Bio-Ras cheese with Lb. reuteri, respectively.
However, titratable acidity increased by increasing of the ripening period and ranged from 0.91 % to 0.82% in Bio-Ras cheese with Lb. casei and Bio-Ras cheese with Lb. reuteri after 90 days of ripening period.
Bio-Ras cheese with Lb. rhamnosus followed by Lb. helveticus were of the highest SWP content throughout the ripening period (P ≤ 0.05).
Ash content in all Ras and Bio-Ras cheese treatments slightly increased by ripening period advanced and increased with high concentration in Bio-Ras cheese with Lb. casei.
Bio-Ras cheese with Lb. casei followed by Bio-Ras cheese with Lb. helveticus then Lb. rhamnosus were of the highest ash content during the ripening period.
It is clear that Bio-Ras cheese samples containing Lb. casei was of the highest SN/TN (P ≤ 0.05) during the ripening process, followed by Lb. rhamnosus and Lb. helveticus.
Bio-Ras cheese with Lb. helveticus was of higher TVFA (P ≤ 0.05) than all other treatments and control Ras cheese.
TVFA increased significantly (P ≤ 0.05) in all Ras and Bio-Ras cheese, reaching maximum values at the end of the period, (22.80 to 29.80).
Bio-Ras cheese with Lb. helveticus was of higher Shilovich ripening index (P ≤ 0.05) than all other cheese treatments.
Shilovich ripening index increased and ranged from 146.10 to 90.23 in Bio-Ras cheese with Lb. helveticus and Lb. reuteri. While the least significant Shilovich ripening index was recorded in Bio-Ras cheese with Lb. reuteri and control Ras cheese, (90.23 and 100.10).
The Formal ripening index was ripening period and strain type dependent. In fresh Ras cheese Formol ripening index ranged from 22.6 to 31.2 (Lb. helveticus and Lb. reuteri, respectively), followed by increase in all treatments as the ripening progressed to be ranged from 87.2 to 121.1 (Lb. reuteri and Lb. rhamnosus, respectively).
Bio-Ras cheese treatment with Lb. rhamnosus was of the highest content of soluble tyrosine, while the treatment with Lb. helveticus was of the highest amount of soluble tryptophan (with a significance level of P ≤ 0.05).
Bio-Ras cheese with Lb. helveticus, followed by Lb. casei, and Lb. rhamnosus were of the highest free amino acids compared with control Ras cheese. Whereas, the least free amino acids contents were completely low in Bio-Ras cheese with Lb. acidophilus and Lb. reuteri.
FFA increased gradually with increasing of ripening period. Ras cheese with added probiotic lactobacilli cultures contained higher FFA values during ripening. However, cheeses containing Lb. casei, Lb. rhamnosus and Lb. helveticus exhibited higher FFA contents than did those with other probiotics.
During the first 30 days of ripening, all types of cheese showed a gradual increase in Total Viable Bacterial (TVB) counts. Slight decrease in the TVB counts towards the end of the ripening period. The Bio-Ras cheese with Lb. helveticus was of the highest TVB count, followed by Lb. rhamnosus and control Ras cheese.
Bio-Ras cheese with Lb. rhamnosus treatment had the highest TVB count, followed by treatment with Lb. helveticus treatment by the end of the ripening period.
Lactobacilli count in Bio-Ras cheese with Lb. helveticus was of the highest counts 8.24 log10 CFU/g by the end of ripening, followed by Lb. rhamnosus. The Lactobacilli and Streptococci counts were consistently higher than 7 log10 CFU/g, indicating that Bio-Ras cheese has probiotic properties for humans. Throughout the ripening period.
The highest number of yeasts and molds count were found in the control and Bio-Ras cheese with Lb. reuteri at the end of the ripening.
Flavor was significantly higher in Lb. helveticus (34.8 points) and the least flavor was in control (26.0 points). Flavor gradually increased during the ripening, flavor reached to (46.0– 37.5 points) for in Lb. helveticus and Lb. casei at the end of ripening period (90 days), respectively.
Body & Texture was (22 points) in control Ras cheese. Body & Texture gradually increased along ripening Body & texture reached to (37.1 – 34.0 point) for Lb. helveticus and control, respectively at the end of the ripening.
Appearance scores were higher in Bio-Ras cheese treated with Lb. rhamnosus (8.7 points). While, the least appearance was in control (7.5 points). Appearance scores gradually increased along the ripening period till the end of ripening period (90 days). Appearance scores ranged from 10.0 to 9.0 points in Ras-cheese treated with Lb. rhamnosus and control, respectively.
Bio-soft cheese, as well as Bio-Ras cheese, could be made in presence of high numbers of probiotics:
Lb. helveticus, Lb. rhamnosus and Lb. casei with high microbiological, and sensory characteristics.