الفهرس 
REVIEW OF LITERATUREOnly 14 pages are availabe for public view
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Abstract
SUMMARY AND CONCLUSIONS
Objectively, because of the conventional heating whether pasteurization, boiling or rather sterilization is the common procedure applied to control the load of microbes in milk. In spite of its very straightforward and efficient, but may lead to several sensory acceptability and nutritional losses in the resultant product, particularly when heat treatment is implemented in poor quality milk, which possesses a high load of microbes and hence more heating process (temperature degree and/ or time) is needed. Accurate thermal treatment methods such as pasteurization may not be available in small cheese manufacturers, as it increases the clotting time and weakens both of the milk rennetability and the strength of the hardness of cheese curd. Therefore, many small cheese manufacturers resort to using unauthorized preservatives or illegal proportions instead of pasteurization innovative, easy to implement, and rapid technologies are required for the modern food industry to meet the never ending demands of consumers (e.g. fresh and safe ready – to – eat products. Microwave and magnetic field have several merits that make there a technology to be considered in the food industry; they are the most powerful sanitizer; cheaper than pasteurization and traditional models, they acts strongly against extended spectrum of microorganisms, i.e. bacteria, fungi and bacterial as well as fungal spores. In addition, it may be considered a promising way because its reduced cost, which makes it affordable for small food producers, mini dairies especially small cheese manufacturers. Therefore, this research aims to assess the effect of microwave and magnetic field versus heat treatment on some chemical and microbiological properties including pathogens of raw milk, from which of the most common white soft cheeses in Egypt namely Domiati cheese.
Technically, to achieve these purposes the study was conducted into two parts as following:
Part I: Production of low-salt Domiati cheese from raw, heated, microwave and magnetic treated milk
In this part of study, low-salt Domiati cheese was produced using raw milk (control), heated milk, microwave and magnetic treated milk. Resultant cheeses were analyzed for compositional, microbiological, rheological and sensory properties when fresh and during pickling period up to 3 months. The obtained results can be summarized as follows:
1- Low-salt Domiati cheese with control had lower moisture content compared to cheese made from heated milk, microwave treated milk and magnetic treated milk. During pickling, the moisture content showed a decrease in all treatments including control.
2- There were slight difference in fat content between control and all other low salt Domiati cheese treatments. Fat content increased gradually with increasing of pickling period for control and all other treatments.
3- Low-salt Domiati cheese with control had higher content of protein than other treatments. All Domiati cheese samples showed slight increase in protein with increasing of pickling period.
4- T1 (cheese made from heated milk) had the highest content of salt. There were significant differences between {control samples & T3 (cheese made from magnetic milk} and {T1 & T2 (cheese made from microwave milk)}. There was slight decrease in salt contents of all low-salt Domiati cheese with increasing of pickling period.
5- Ash content was lower in control than that of all other cheese treatments. T1 made from heat treated milk had the highest ash content among all treatments. There was a decrease in ash content of all low-salt Domiati cheese treatments with increasing of pickling period.
6- Control cheese samples from raw milk exhibited significantly higher acidity values than that of all other treatments. The titratable acidity of all cheese samples increased as the pickling period progressed to reach maximum values at the end of pickling period.
7- The trend of changes in pH values of all cheese treatments were opposite to that of titratable acidity.
8- There were significant differences in the yield between cheese made from (heat treated milk & microwave milk) and cheese made from (raw milk & magnetic field milk). The yield of cheese made from raw milk was lower than that of other treatments. Along pickling period, the yield decreased gradually with increasing of pickling period in all treatments.
9- Control and T3 samples had the highest SN content compared to other treatments. Moreover, T1 and T2 treatments had the lowest SN content. During pickling, SN content gradually increased being significant for all low-salt Domiati cheeses with extending of pickling period in all treatments.
10- Among treatments, control cheese possessed the highest value of TVFA while, T1 had the lowest. There was a gradual increase in TVFA of all treatments during pickling period.
11- Domiati cheese made with control cheese exhibited higher formol number than that in other treatments, while T1 had the lowest number. Moreover, the formol number increased along pickling period in all treatments.
12- Control with raw milk cheese also showed the highest schilovich index among all treatments. Moreover, the schilovich values increased along pickling period in all treatments.
13- Control samples had the highest count of total viable bacterial count (TVBC), while T2 had the lowest when fresh and along pickling period. Through progression of pickling, TVBC of all cheese samples was increased until the first month and then sharply declined up to the end of pickling period.
14- Control samples had the highest lactic acid bacteria (LABC), while all treatments possessed lower counts. During the pickling, LABC of all cheese samples gradually increased with the prolonging of pickling period till the end of first month of pickling, and gradually decreased till the end of pickling period.
15- Staphylococci could not be detected in all cheese samples including control when fresh and along the pickling period.
16- Coliform bacterial counts were not detected in all fresh samples, except cheese made from raw milk. During ripening period, the coliform bacterial counts in fresh control cheese samples were decreased reaching their minimum at the end of ripening period.
17- Control cheese had the highest viable spore forming bacterial count when fresh and along pickling period. Spore forming bacteria gradually decreased with prolonging the pickling period (3 months) in all treatments.
18- Cheese made from pasteurized milk (T1) and from microwave treated milk (T2) had lower yeasts and molds counts than that of control samples and T3 (from magnetic field treated milk). Yeasts and molds count increased rapidly in all low-salt Domiati cheeses with increasing of pickling period.
19- Cheese made from heat and microwave treated milk were higher hardness than that of cheese made from raw and magnetic field treated milk, and they increased significantly by increasing the storage period.
20. T1, T2 were slightly preferable in appearance than that of control samples and T3. Body and texture scores increased slightly for all treatments including control with increasing of pickling period.
21- Control cheese and T3 gained the highest acceptability among all fresh samples. At the end of pickling period after 3 months control and treatment T3 was the best while T1, T2 become the worst among all samples.
Part II: Production of high-salt Domiati cheese from raw, heated, microwave and magnetic treated milk
In this part of study, high-salt Domiati cheese was produced using raw milk (control), heated milk (T1), microwave treated milk (T2) and magnetic treated milk (T3). Resultant cheeses were analyzed for compositional, microbiological, rheological and sensory properties when fresh and during pickling period up to 6 months. The obtained results can be summarized as follows:
1- Moisture contents was higher in T1 than that of all treatments. Domiati cheese made with control had the lowest moisture content when fresh and along pickling period. Pickling high-salt Domiati cheese for up to 6 months reduced the moisture content of all cheese samples.
2- The fat content of control samples and T3 with magnetic field was higher than that of treatments T1 and T2. Fat content of high-salt Domiati cheese samples showed a gradual and significant increase during pickling periods in all treatments. Fat contents of high-salt Domiati cheese were lower than that obtained in low salt Domiati cheese up to 30 days.
3- Protein content of control samples is higher than that of all treatments. During pickling, the protein content of all high-salt Domiati cheese samples increased as the pickling period progressed.
4- Control samples had the lowest salt content among all samples while, T1 had the highest. Salt/moisture ratio of high-salt Domiati cheese was higher than that of low salt cheese.
5- Control samples had the lowest ash content, while T1 cheese had the highest. There were decreases of salt contents up to end of 6th month. Ash/DM ratio showed similar trend as that of ash content even more clear. Ash content and ash/DM percentage of cheese increased by increasing the amount of salt added to cheese milk.
6- Control samples had significantly highest values of acidity, while T1 and T2 showed significantly lower values. Titratable acidity of all high-salt Domiati cheese samples was increased by increasing the pickling periods, the rate of increase was higher at the early pickling period, then slightly increased or remained nearly constant at the latter stage of pickling. Cheeses made with 5% salt showed higher acidity than that of cheese made with 10% salted in milk.
7- Cheese treated with heated milk produced highest yield among all other Domiati cheeses. Cheese yield increased with increasing the amount of salt added. As the pickling progressed, a gradual and marked decrease was occurred in the cheese yield.
8- There were noticeable and significant increase in SN content as well as SN/TN percentage in control and T3 than that of other treatments. While, T1 had the lower SN and SN confident than that of other treatments. SN markedly increased in all cheese samples as the pickling period advanced.
9- Control samples had higher TVFA than that of other treatments when fresh or throughout the pickling period. TVFA gradually increased in all cheese samples with extending the ripening period. TVFA were higher in cheeses salted at 5% than corresponding values recorded in cheeses with 10%.
10- Cheese made from heated milk showed the lowest formol number either when fresh or throughout the pickling period. During pickling period, formol number gradually and significantly increased in all treatments. As the pickling progressed, a gradual and significant increase was occurred in schilovich value for all cheese samples. Formol number and schilovich index of high-salt Domiati cheeses were generally lower than those of low salt Domiati cheeses when compared at certain period of pickling in most treatments.
11- Control samples had higher TVBC than that of other treatments. TVBC of all cheese samples was increased until the first month and then sharply declined up to the end of pickling period. The counts is lower in high-salt Domiati cheese than that of low salt Domiati cheese.
12- Control samples showed the highest of LABC. During ripening, LABC appreciably increased in all cheese samples up to the end of first month and then progressively decreased up to the end of maturing period.
13- Staphylococci count could not be detected in all high-salt Domiati cheese samples either fresh or along the pickling period.
14- Coliform bacteria were not detected in all fresh samples of high-salt Domiati cheese treatments, except cheese made from raw milk. During ripening period, the numbers of coliform bacterial counts in control cheese sample were decreased reaching their minimum at the first month. Coliform counts in high salt Domiati cheese markedly lower than that of low salt.
15- The counts of aerobic spore forming bacteria appreciably decreased with increasing the salt content in cheese milk. The counts were not detected after 3 and 2 months in control and T3 cheeses; respectively.
16- Yeasts & molds counts were high in control samples compared with other treatments. Increasing the amount of salt added to cheese milk caused a pronounced decrease in yeasts and molds counts in resultant cheese.
17- Cheese made from heat and microwave treated milk were higher hardness value than that of cheese made from raw and magnetic field treated milk. Hardness values increased significantly by increasing the storage period in all treatments.
18- Domiati cheese made from raw and magnetic field milk possessed gumminess values higher than that exhibited from microwave and heat-treated milk cheese.
19- The appearance of cheese scored close values in all treatments being slightly more preferable in T1 and T2 cheeses.
20- Fresh Domiati cheese treatments with control and magnetic field treatment showed significantly better body & texture than that of T1, T2.
21- There were no significant differences in flavor score among all fresh cheese treatments. Control cheese was faster to reach high score in flavor, while cheese made from heated milk and microwave milk are the lowest.