الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
The number of bacteria in milk has a decisive effect on the quality and safety of dairy products (White 2011). Milk products provide a highly favorable media for multiplication of different types of food poisoning microorganisms from different sources. Thus, effective cleaning procedures and good manufacturing practices during cheese making process can reduce the risk (Sanaa et al., 2004). White soft cheese is one of the common delicious cheeses consumed in Egypt. There are many varieties of white soft cheese depending on the technique of manufacture, salt percentage and many other factors. Production and handling of locally manufactured Egyptian white soft cheeses, is still under-way especially those produced by cheese maker in most villages distributed all-over the country. Therefore, such cheese is mostly contaminated with different types of organisms gaining access to the product from various sources. Cheese could be contaminated by different types of microorganisms during its production, handling, distribution and storage under unhygienic conditions. Contamination with different microorganism’s causes cheese spoilage and/or foodborne illnesses.
Aim of investigation:
First part: evaluate chemical composition, organoleptic and microbiological quality of some dairy products collected from different areas of New Valley governorate. The samples were divided as:
- 40 samples of cow`s milk - 40 samples of Kareish cheese - 40 samples of Domiati cheeses and 40 samples of plain yoghurt.
Results could be summarized as follows:
first part:
chemical properties
I- Cow’s milk was high in moisture (88.69%) & acidity (0.23%) and low in fat 2.41%, other components were normal.
II- Total solids, salt and acidity in Kareish and Domiati cheeses were within the normal limits.
III- Plain yoghurt was normal in TS% and low in fat than legal standards, while the acidity was quite high (0.95%) in most areas.
microbiological properties
1- Total bacterial counts were; 6.56, 5.65, 3.70 and 6.25 log CFU.g-1 for raw milk, Kareish cheese, Domiati cheese and yoghurt, respectively.
2- Psychrotrphic bacterial counts were high in milk (4.20 log CFU.g-1) and low in Domiati cheese (3.49 log CFU.g-1).
3- Lactic acid bacterial counts were high in raw milk & Kareish cheese (6.46 & 6.05 log CFU.g-1) and low in Domiati cheese (2.45 log CFU.g-1).
4- Staphylococcus aureus was detected in Kareish cheese in El-Dakhla and Paris. It also detected in Domiati cheese in all regions except in Paris area and was found in yoghurt in El-Dakhla only.
5- Coliform bacteria were detected in all samples; the highest count was in raw milk (3.64 log CFU.g-1).
6- Yeast and molds were detected in all samples and were high in Kareish and Domiati cheeses.
7- The microbiological analyses revealed the presence of some pathogenic bacteria in raw milk and some dairy product samples, as well as a higher total bacterial count and yeasts & molds than the Egyptian standard (ES) recommendation.
Organoleptic properties
1. Organoleptic quality revealed normal colour for all samples. Flavour and taste were to some extend accepted with salty taste in Domiati cheese and yeasty in Kareish cheese.
2. Yoghurt was sour in taste; the overall quality was just accepted for all products.
Second part:
Traditional dairy products in rural areas could be an excellent source of beneficial natural bacteria. Lactic acid bacteria would be the right choice to represent these indigenous isolates with probiotic characteristics. Therefore, the purpose of this study was to
• Isolating and identification of some strains of lactic acid bacteria from these dairy products for use as starters in the manufacture of some dairy products.
• improve nonstarter Egyptian soft cheese, “Tallaga cheese” by using probiotic indigenous strain isolated from the New Valley region.
Results could be summarized as follows:
1. The results showed that the selected isolate, Lacticaseibacillus rhamnosus, showed high tolerance to low pH, pepsin, bile salts and was non-hemolytic.
2. L. rhamnosus also contributed to a reduction in the ripening period and improved taste, and flavor of Tallaga cheese. In addition, their promising characteristics as prospective probiotics may cause improvements in the gastrointestinal microbiota.
3. the strain did not contain any of the tested antibiotic resistant genes. and the selected probiotic strain, Lacticaseibacillus rhamnosus, succeeded in developing the quality of “Tallaga cheese” with synergistic health benefits as probiotic supplements.
4. the selected strain showed the ability to be viable throughout the tested shelf life with high counts, which enhanced their efficacy as a technological probiotic supplement
Recommendation
1. In conclusion it is recommended to improve the safety of raw milk and dairy products, hygiene barriers and raw milk quality must be raised, as well as proper decontamination of processing equipment must be ensured.
2. that the results of the present study indicate that using indigenous strain L. rhamnosus isolated from New Valley is considered a good strategy to improve sensory properties and add potential health benefits as a probiotic supplement in non-starter Tallaga cheese.
3. the use of the strain L. rhamnosus proved their ability not only to manufacture probiotic Tallaga cheese but also to approach its sensorial properties in a microbiologically safe way. Therefore, this culture proved that it can be a viable strategy to improve its acceptance significantly.