Five Ras cheese treatments were made by replacing normal cheese starter with Lactobacillus rhamnosus. Cheese treatments were microbiologically, chemically and organoleptically evaluated when fresh and after 1,2,3 and 4 months. Moisture content decreased, while total nitrogen, fat, ash, titratable acidity, soluble nitrogen, total volatile fatty acids (TVFA), Shilovich number and score of organoleptic properties increased by replacing the normal cheese starter with Lactobacillus rhamnosus, and the increases were proportional to the rate of replacing. Moisture content of all cheese treatments decreased during ripening period, while fat, total nitrogen, water soluble nitrogen, Shilovich number, TVFA and scores of organoleptic properties increased. Lactobacillus rhamnosus counts increased during the first month of ripening period then decreased. Cheese treatment (T4) being made, with adding 1.0% Lactobacillus rhamnosus exhibited the highest count, and even after the ripening period, it contained higher count of probiotic bacteria than that should be present to achieve the therapeutic effect. Also this cheese treatment was the most acceptable cheese treatment.

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Fifteen batches of stirred yoghurt were made to study the effect of microentrapment on the viability of bifidobacteria and their ability to inhibit the growth of E. coli and Staph. aureus. Entrapped cells of Bifidobacterium bifidum and Bifidobacterium infantis were able to produce antimicrobial agents which inhibited E. coli and Staph. aureus used as test organisms. Viable counts of unentrapped bifidobacteria decreased sharply, while entrapped cells of bifidobacteria were quite stable during refrigerated storage of stirred yoghurt. Bif. infantis was more tolerant to storage conditions than Bif. bifidum. Microentrapment of bifidobacteria improved their survival during storage of stirred yoghurt, especially Bif. bifidum, whose viability was not significantly (P>0.05) different from entrapped Bif. infantis. Viable counts of E. coli decreased during storage of stirred yoghurt. Addition of bifidobacteria caused a sharp decrease in the viability of E. coli. E. coli growth was not dectected at the 5th day, when entrapped cells of bifidobacteria were added to stirred yoghurt, while E. coli growth was not detected at the 7th day of storage in yoghurt containing unentrapped bifidobacteria. Addition of Bif. bifidum inhibited the growth of E. coli more effectively than Bif. infantis. Staph. aureus showed similar patterns to E. coli, except that Staph. aureus was more tolerant to storage conditions. The counts of total bacteria, lactobacilli and Streptococcus salivarius subsp. thermophilus increased up to the third day then declined till the end of storage. Titratable acidity increased gradually during the first 3 days of storage then increased slightly up to the end of storage, while pH values dropped during storage. Adding of bifidobacteria, E. coli and Staph. aureus did not affect significantly (P>0.05) the counts of lactobacilli and Str. salivarius subsp. thermophilus, acidity and pH value.

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Quality attributes of yoghurt made from cow's milk fortified with whey protein hydrolysate were studied. Six yoghurt treatments were made, control yoghurt was made by adding 3% non-fat dry milk to cow's milk while the other five treatments were made by fortifying cow's milk by 0.5, 1.0, 1.5, 2.0 and 2.5% whey protein hydrolysate respectively and 3.0% nonfat dry milk to each treatment. All yoghurt treatment was stored in refrigerator for 12 days and was sampled when fresh and at 3, 6, 9 and 12 days for chemical, rheological, microbiological analysis and sensory evaluation. The obtained results indicated that adding whey protein hydrolysate to cow's milk caused a significant increase of total solids, total protein and ash contents, titratable acidity, while decreased pH values and whey syneresis of yoghurt treatments and these effects were proportional to the rate of adding whey protein hydrolysate. Also, adding whey protein hydrolysate up to 2.0% increased the scores of organoleptic properties and treatment T4 that made with adding 2.0% whey protein hydrolysate was the most acceptable yoghurt treatments. Total solids, total protein, ash and fat contents of all yoghurt treatments did not change significantly, (P > 0.05) during storage period, while titratable acidity increased. Whey separation decreased during storage period up to the sixth day of storage period then increased up to the end of storage period, while the scores of organoleptic properties were almost stable up to the ninth day of storage period.

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