Evaluation and Quality of "Ricotta" Cheese Production from Whey

By:

Aisha Saeed Eljack Higgazey

B.Sc.(Honor) in food Engineering and Technology

University of Gezira (2009)

A Dissertation

Submitted in partial Fulfillment of the Requirement for the Degree of

Master of science

In

Food Engineering

Department of Food Science and Technology

Faculty of Engineering and Technology

University of Gezira

Supervisor: prof. Abdel Moneim Elhadi Sulieman

Co-Supervisor: Dr. Zakaria Ahmed Salih Ahmed

August, 2011

1

Evaluation and Quality of " Ricotta Cheese Production From Whey

By:

Aisha Saeed Eljack Higgazey

Supervision Committee:

Maim Supervisor: Prof. Moneim Elhadi Sulieman ……………………

Co-Supervisor: Dr. Zakaria Ahmed Salih Ahmed ……………………

2

Evaluation and Quality of "Ricotta" Cheese Production from Whey

By:

Aisha Saeed Eljack Higgazey

Examination Committee:

Name Position Signature

Prof. Abdel moneim Elhadi Suliman Chairman …………

Prof. Elnaim Abdalla Ali External Examiner …..…….

Dr.Elzubier Ahmed Salih Internal Examiner …………

Date of Examination: 15/8/2011

3

DEDICCTION

I dedicate this little effort with all my respect and

Deep love to….

My father and mother and brothers and sisters……

My teacher

And all people who searches to knowledge……..

AISHA SAEED….

4

ACKNOWLEDGMENTS

To my parents my steady source of love comfort, thank you for always listening to me and encouraging me. I could have made it where l am today without you

My deepest thanks and appreciation are due my major supervisor prof. Abdel Moneim Elhadi Suleimam. For initating this research, invaluable guidance.assistance and encouragement throughout the course study.

I would like thank to my sincerely my Co-supervisor Dr. Zakaria Ahmad Salih Ahmed. For close supervisor and research guidance.

I would like to thank all people who demonstrated interest in publlshing this research.

I would like to thank all the people who discussed this project.

5

انتاج وتقيم جودة جبن الشرش "الريكوتا"

عائشة سعيد الجاك حجازي

ماجستير هندسة األغذية )اغسطس ,2011(

قسم علوم وتكنولوجيا األغذية- كلية الهندسة والتكنولوجيا- جامعة الجزيرة

ملخص البحث

تصنع جبن الريكوتا من الترسيب الحراري لبروتين الشرش او خليط من الشرش واللبن. هدفت هذه الدراسة لتقيم جودة خصائص جبن الريكوتا المنتجة معمليا . الطرق المستخدمة تحتوى التحاليل الكيمائية, والتحاليل الميكروبيولوجية وكذلك التقييم الحسي. التحاليل الكيمائية لجبن الريكوتا تشمل: الرطوبة%72.89, البروتين %.14, الدهن %6, الرماد %5.37, الرقم الهيدروجيني%5.28, الحموضة %1.38, المواد الصلبة الكلية %18.41,الكالسيوم ملجرام لكل100جرام, البوتاسيوم120ملجرام لكل100 جرام ,الصوديوم 106ملجرام لكل100 جرام.ومن ناحية اخرى التحليل الميكروبيولوجى وضح العد الكلى الميكروبى 1× 102 خلية/جم, الخمائر واالعفان 2×104 خلية/جم, وكذلك كل االحياء الدقيقة الضارة لم توجد فى عينة الجبنة. التقيم الحسى وضح ان جبنة الريكوتا عموما مقبولة. وهذه الدراسة توصى بتشجيع صناعة االلبان محليا الدخال جبنة الريكوتا لمقابلة االحتياج المحلى واستخدام الشر شفى منتجات االلبان االخرى.

6

Evaluation and Quality of "Ricotta" Cheese " Production from whey

Aisha Saeed Eljack Higgazey

M.Sc. in Food Engineering (August, 2011)

Dept. Food Science and Technology

Faculty of Engineering and Technology- University of Gezira

ABSTRACT

Ricotta cheese in med from heat-acid precipitation of protein from whey or whey-milk blend. The study aimed to evaluate the quality characteristics of ricotta cheese produced at laboratory level. The methods used included chemical analyses, microbiological analyses as well as sensory evaluation. The chemical composition of ricotta cheese was as follows: moisture: 72.89%, protein: o.14% ,fat: 0.6%, ash: 5.37%, pH: 5.28%. acidity: 1.38%. total solid:18.41%, Ca: 225mg/100g, K: 120mg/100g. and Na:106mg/100g. On the other hand the microbiological analysis showed that the total viable count was 1 ×10 2 c.f.u/g and yeast and mould count was 2 ×104 c.f.u/g However, all harmful microorganisms were not detected in cheese sample. The sensory evaluation showed that ricotta cheese was generally acceptable. The study recommends encouraging the local dairy industry to introduce of ricotta cheese so as to meet the local need and to use whey in the other dairy products.

7

Total of count

Subject Page no. Dedication i Acknowledgements ii Abstract iii Arabic abstract iv Table of contents v List of table vi CHAPTER ONE: Introduction 1 CHAPTER TWO:LITERATURE REVIEW 2 2.1 The milk 2 2.1.1 Milk and dairy product 2 2.1.2The main composition 2 2.1.2.1Milk fat 2 2.1.2.2 Milk protein 3 2.1.2.3 Acidity 3 2.1.2.4 General nutrients 3 2.1.2.5 Water content of milk 4 2.1.3 Milk microbiology 4 2.2 The cheese 5 2.2.1Definition of cheese 5 2.2.2 Historical of cheese 6 2.2.3 Classification of cheese 6 2.2.4 Cheese technology 7 2.2.5 Types of cheese in sudan 7 2.2.5.1 Gibna Bayda 8 2.2.5.2 Mudeffara cheese 9 2.2.5.3 Mozzarella cheese 10 2.2.6 World cheese types 10 2.2.6.1 Grana-type cheese and parmesan 13 2.2.6.2 Cheddar cheese 13 2.2.6.3 Dutch type cheese 13 2.2.6.4 Swiss cheese 13 2.3 Whey 14 2.3.1 Definition and constituents of whey 15 2.3.2 types of whey 15 2.3.3 Emerging health benefits of whey and uses 15 2.3.4 Nutrition properties of whey 16

8

2.3.5Product produced from whey 17 2.4 Ricotta cheese 17 2.4.1 Definitionof Ricotta cheese 17 2.4.2 Historical of Ricotta cheese 18 2.4.3 Types of Ricotta cheese 18 2.4.3.1 Ricotta infornata 18 2.4.3.2 Ricotta affunicata 19 2.4.3.3 Ricotta scanta 19 2.4.4 Description of Ricotta cheese 19 2.4.5 The basic making of Ricotta cheese 20 CHAPTER THREE: MATERIALS AND METHODS 3.1 Materials 21 3.1.1 Preparation of whey samples 21 3.1.2 Bacteriological media 21 3.1.2.1 Plate Count Agar (PCA) 21 3.1.2.2 Potato Dextrose Agar (PDA) 22 3.1.2.3 Macconkey Agar (MCA) 22 3.1.2.4 E C Broth Agar 22 3.1.2.5 Salmonella Shegilla Agar (SSA) 23 3.2 Methods 23 3.2.1Chemical analysis of whey 23 3.2.1.1PH Measurement 24 3.2.1.2Determination of titratable acidity 24 3.2.1.3 Determination of moisture 24 3.2.1.4 Determination of protein content 25 3.2.1.5 Determination of fat content 25 3.2.1.6 Determination of ash content 26 3.2.1.7 Determination of Solid non content 26 3.2.2Microbiological analysis of whey 27 3.2.2.1 Total viable count 27 3.2.2.2 Yeast and Mould count 27 3.2.2.3 Coliform bacterial count 27 3.2.2.4 E. coli test 27 3.2.2.5 Salmonella detection 28 3.2.3 Preparation of Ricotta cheese laboratory level 28 3.3.1 Cheese yield 28 3.3.2 Assessment of Ricotta cheese 28 3.3.2.1 Chemical analysis of laboratory made Ricotta cheese 28

9

3.3.2.1 Minerals determination 29 3.3.2.1.1 Determination of Calcium 29 3.3.2.1.2 Determination of Sodium 30 3.3.2.1.3 Determination of Potassium 30 3.3.2.2 Microbiological analysis of laboratory made Ricotta cheese 31 3.3.2.3 Sensory evaluation of laboratory made Ricotta cheese 31 Statistical analysis 31 CHAPTER FOUR:RESULTS AND DISCUSSION 31 4.1 Chemical composition of whey sample 32 4.2 Microbiological analysis of whey sample 32 4.3 Chemical composition of laboratory-made Ricotta cheese 35 4.4 Mineral content of laboratory-made Ricotta cheese 37 4.5 Microbiological analysis of laboratory-made Ricotta cheese 37 4.6 Sensory evaluation 41 CHAPTER FIVE: CONCLUSIONS AND RICOMMENDATIONS 43 5.1 Conclusions 43 5.2 Recommendations 43 REFERENCES 44

10

List of tables

Table No. subject Page No. 4.1 Chemical composition of whey 33 4.2 Microbiological analysis of whey 34 4.3 Chemical composition of Ricotta cheese 36 4.4 Mineral content of laboratory-made ricotta cheese 38 4.5 Microbiological analysis of laboratory-made ricotta cheese 40 4.6 The mean scores for sensory attributes of the ricotta 42

11

CHAPTER ONE

INTRODUCTION

Cheese is generic name for group of fermented milk based food products produced throughout the world in great variety of flavors, textures and forms (Fox et al, 2000). Sandine and Elliker (1970) suggest that there are more than 1000 varieties of cheese. Walter and Hargrove (1972) describe about 400 varieties and list the names of a further 400, while Burkhalfer (1981) classifies510 varieties. Cheese making remained a craft until recently with the gradual acquiring of knowledge about the chemistry and microbiology of milk and cheese, it become possible to gain more control over the cheese making process. Few new varieties have evolved as a result of increased knowledge, but existing varieties have become better defined and their quality has become more consistent.The Ricotta cheese is a high moisture soft cheese (Modler and Emmons, 2001). It can be produced from cheese whey or milk or mixture of both (Pizzillo et al, 2005).Ricotta cheese is very mild and it is used in many Italian dishes. Several methods have been developed for utilization of whey; one of these methods is the manufacture of Ricotta cheese (Kosikowski, 1982). Ricotta cheese is a dairy product of Italian origin, which means “re cooked”, it is produced by boiling acidified cheese whey (Maubois and Kosikowski, 1978).Ricotta cheese was manufactured as described by Mahran et al (1999). All whey protein cheese mixture were homogenized and were heated at 90c/15-30 min. The curd was left in the whey for10 min and then scooped in plastic frame lined over a drainage table and allows to achieve complete drainage in 24 hr. The curd was placed in plastic container and stored at 4c.Ricotta cheese is not know or consumed largest in Sudan, and few data is available in this type of cheese, there for the objectives of the present study were:

-To evaluate the chemical and microbiological characteristics of the whey

- To produce of ricotta cheese at laboratory level using whey.

- To evaluate the microbiological, chemical and snsory quality characteristics of the manufactured ricotta cheese.

12

CHAPTER TWO

LITERATURE REVIEW

2.1 The milk:

Milk is defined as the secretion of the mammary glands of mammals. its primary natural function being nutrition of the young . Milk of some animals, especially cow, buffaloes, goat and sheep, is also used for human consumption, either as such or in the form of arrange of dairy products (Walstra etal.2006).

2.1.1 Milk and dairy products:

Milk and dairy products are good sources of protein ,calcium, phosphorus, potassium and trace minerals and vitamin A, thiamin and riboflavin (Kons,1972;payne,1993) fresh liquid milk is traditionally used in most of they developing countries and little be consumed after boiling and usually only in tea and coffee (Dirar,1993).

A great proportion of the milk produced in tropical countries is converted into indigenous products like ghee or some kind of fermented concentrated products that can be kept without artificial cooling. Most of these concentrated products are at present made in the homes but are gradually being made commercially .For most tropical milk processing plants it is a good business to produce these long-live locally accepted product, rather than imitating dairy products from temperature climates like fresh butter, cream and cheese which need expensive refrigeration (Payne, 1993).

2.1.2 The main composition of milk:

2.1.2.1 Milk fat:

Milk fat is the most variable of all milk components .fat content of 3.5 to3.7 mean little when applied to one breed, one animal or one source of supply . the mixture of triglycerides make(98 to 99%) of milk fat. The remaining 1% to 2% of milk fat is composed of phospholipids, sterols, carotenoides, fat soluble, vitamins A, D, E and K and some trace of free fatty acids(Hall and Harper, 1959).

13

2.1.2.2 Milk proteins:

Total milk protein ranges from about 2.5 to 5.5%. The average for regions in which Holstein Frisians predominate is about 3.3kg/hl. There are two major groups of proteins, the caseins (about 2.6 %) which refer to as the cheese proteins’ and the whey proteins (about 0.7 %) which as the name suggests are usually lost in the whey during cheese making. Caseins are not water soluble and so the cow packages them in water dispersible particles called micelles which along with caseins include most of the milk calcium, magnesium, phosphate and citrate. Unlike whey proteins which are very sensitive to heat , caseins are little affected by heating except that they react with heat denatured whey proteins. (http://www.foodsci.uoguelph.ca/cheece/sectionc.htm,2000)

2.1.2.4 Acidity (PH):

Acidity as measured by pH is one of the most critical parameters with respect to both food safety and both process and quality control of fermented foods such as cheese .the titratable acidity of milk typically varies from 0.12 to 0.19% lactic acid depending on composition, especially protein content. The PH of milk is near the physiological PH of 6.8 which, considering the following points, means that milk is a good growth medium with respect to acidity (PH).

Most organisms grow best at PH near physiological PH of 6.8, titratable acidity (AT) is not a good predictor of acid effects on microbial growth and chemical properties such as protein functionality .

The major groups of microorganisms important to food preservation are in order of increasing acid tolerance: bacteria, yeasts and moulds . Natural fermentation of warm raw milk by lactic acid bacteria reduces milk PH to less than 4.0 which prevents the growth of pathogenic bacteria and most spoilage bacteria (http://www.foodssci.uoguelph .ca/cheese/sectionc.htm,2000).

2.1.2.5 General Nutrients:

Milk is good source of all principal nutrient. Such as easily digestible fat, carbohydrate material and contains high percentage of complete easily digestible animal protein in addition of some of the important vitamins: A, B,E and also contains important mineral compound ,like calcium and phosphorus .(Zenb, 2003)

14

2.1.2.5 Water Content of milk:

Milk is a natural liquid food containing a high percentage of water (87%) it is actually a concentrated food meant to produce rapid growth in young mammals . water is a medium in which all other component of milk (total solids) are dissolved or suspended .A small percentage of the water in milk is hydrated to lactose and salt and some is bound to protein.

2.1.3 Milk microbiology:

Organisms with a diameter of 1 mm or less are called microorganisms Microorganisms have a wide taxonomic distribution , they include metazoan animal many algae and fungi, bacteria, and viruses their existence was unknown until the invention of microscopes, optical instruments that serve to magnify small objects that cannot be clearly seen by naked eye . yeast and mold growths are more obvious than bacteria growths (Archer et al. 1996).

Microorganisms themselves may serve as food or feed, may be employed in the preparation of special nutrients, such as organic acid or vitamins to be added to foods, may be used in the production of special foods by fermentation, or may serve as sources of enzyme mixtures or single enzymes for the treatment of food during processing. The appropriate cultures for these various purposes must bemaintained, usually in pure culture, in as table yet active condition, and must be build up to considerable volume for use as mass or bulk cultures for a particular process(Frazier and Westhoff, 1967).

A few year ago a high school biology teacher, trying to impress upon the class the relevancy of microorganisms to illness, stated emphatically that all bacteria were harmful, while this teacher may have been commendable from public health standpoint, since certain bacteria cause disease, the beneficial effects of the great majority of species of microorganisms far outweigh the deleterious aspects of illness caused by relative few pathogenic species (Carls, 1978).

We heat process some food or freeze other to kill or inactivate these life some of microorganisms. But in many of our foods we encourage their growth to reduce our many foods in which fermentation plays an essential role(Anderson,

15

1969). Man’s ability to control the activities of microorganisms has given us a deeper insight into the chemical nature of life. Yeast and bacteria are widely distributed in nature(carls, 1978).

The preparation and preservation of food by fermentation processes are depend upon the production by certain microorganisms of chemical substances that alter the flavor of food and are generally inhibitive to the growth of undesirable microorganisms. Although fermentation is one of the most ancient method of food preservation, an accurate concept of the nature of its change has had to await the development of the science of microbiology that has occurred(Burrows, 1954). Microorganisms necessary in food fermentation may be added as pure cultures or mixed cultures, or, in some instance, no culture may be added if the desired microorganisms are known to be present in sufficient numbers in the original raw material(Farazier and Westhoff, 1967).

Microorganisms carryout their activities by mean of enzyme systems they are catalysts, as such they serve to speed up the chemical reaction that constitute the processes of life, making reaction proceed spontaneously and rapidly. They may be considered manifestation of natures impatience. The kind and amount of enzymes secreted by cells of particular organism are highly specific to the function of that ceel(Wood,1961).

2.2The cheese:

2.2.1 Definition of cheese:

The present word cheese is drived through the old English words (case) and (chiese) from the Latin (causes). This mean clotting or solid curd. The expansion of the numbers of types of cheese makes a simple definition of cheese difficult.

Cheese is defined as the curd of milk produced by enzyme activity and subsequent separation of the whey from the coagulum to give more solid curd (scott, 1986). Another definition of cheese is that it is solid curd with some or all of the whey drained off and further matured during storage (payne 1990). More over, he added that the curd can be formed by the action of lactic acid bacteria, organic acid such as lemon juice or vinegar or rennet and some times in the presence of heat.

16

2.2.2 Historical of cheese:

Cheese is generic name for a group of fermented milk based food products produced throughout the world in a great variety of flavours, textures and forms (Fox et.al, 2000). Throughout the world the names applied to cheese could almost reach 2000 (scott,1981). Sandine and Elliker(1970) suggested that, there are more than 1000 varieties of cheese. Walter and Hargrove(1972) describe about 400 varieties, while in United States of America (USDA,1978) more than 800 cheese varieties have been described, but some of these cheese have different local name and are practically the same. This confirms the view of Davis(1965) that is exact origin of the cheese name could be attributed to the following: region of cheese manufacture, religious institution, type of milk (cow, goat, sheep or buffalo), borrowed or med-up names, shape, and appearance, type of cheese, method of ripening or the addition of additives.

The International Dairy Federation (IDF) (1985) has produced a catalogue in collaboration with its National Committees describing 510 different cheese. Cheese evolved Fertile Crescent between the Tigris and Euphrates rivers in Iraq, some 8000 years ago during so-called Agricultural Revolution , when certain animals and plants were domesticated as source of food (Pederson,1979).

2.2.3 Classification of cheese:

Classification of cheese is very complicated, due to the great range of cheese varieties. Many different method of classification were adopted, considering size, shape packing or coating, as well as place of manufacture, type of milk, moisture content, ripening and preserving agency (Scott,1998). Cheese can be classified according to its texture into very hard (Romano cheese), hard(cheddar cheese), semi- soft(Limburger, whit soft cheese) and soft cheese(cream, cottage). It can also be classified according to manner of ripening, into cheese of bacteria ripening, mold ripening, surface microorganisms and unripened cheese (Morris et al.1954). On the other hand, some of these cheeses subdivided into sub-classes according to many factors; such as moisture fat and the method of ripening (knopf,1976). Lampert (1992) reported that are eighteen kinds of cheese typical of the different processes by which they are made namely, Brick, Camembert, Cheddar, Cottage, Cream, Edam, Gouda, Hand, Limburger, Neufchatel, Parmesan, Provolone, Romano, Roquefort, Sapsago,

17

Swiss, Trappist and whey cheese . Shaw (1994) reported the soft cheese can be classified into soft un-ripened and soft ripened, or into semi soft cheese and other soft/semi soft cheese. The other soft/semi cheese is subdivided into whey cheese (Ricotta), processed cheese (block, food and spreads) and cheese substitute (spread).

2.2.4 Cheese technology:

The basic technology for the manufacture of the types of cheese is similar. Relatively small change, In procedures, during manufacture result in large perceived differences in the final cheese. The technology is well established but in recent years has become subjected to a considerable degree of refinement and automation (Varnam and Sutherland.1994).in the manufacture of cheese milk is transformed into a concentrated less perishable food stuff. Most of the protein and fat of the milk are retained by the cheese but the more soluble constitutes, such as milk sugar and much of the mineral matter, are lost in the amount of casein, fat and water in the milk upon coagulation. The casein form the network of curd within the fat and water are held (Lampert, 1992). Shaw (1994) reported that the manufacture of cheese basically a mean of preserving milk over the short to medium term, with the essential characteristics being the lowering of PH and water activity.

The fundamental principle of soft/semi-soft cheese manufacture involves a reduction in PH and water activity brought about by a controlled lactic fermentation, accompanied by subsequent drainage of whey and salting of the curd.

2.2.5 Type of cheese in Sudan :

Cheese making is a major milk preservation method in Sudan (Ibrahim,1971). The major traditional cheese types that are produced in Sudan are Gibna Bayda(Osman,1987a); Gibna Mudaffara (Abdel Razig,2000) and mish cheese (Osman,1987b) . they are varying in composition, texture, color taste and flavor due to compositional of milk ,production method, microbial flora, type of package, microbial activity during ripening and ripening condition. cheese production in Sudan has been started by foreign families migrated to the Sudan, and settled mainly at ELDoeim in the White Nile province (Eltayeb,1986).

In Sudan cheese is produced throughout the country especially in ELDoeim White Nile province, Elobeid, south kordofan, Darfur province and other localities in

18 the country. Gibna Baday is produced in four areas in south and west Darfur states. In Darfur Gibna Baday is produced throughout the year and the highest production is during the ruing season. Milk in rural areas is always converted into other product which with stand longer storage periods such as fermented milk, ghee, cheese and sour milk (Payne,1990). The making of Gibna Baday in Darfur varies from one place to other. The variation is due to the method of processing. Salting before or after renneting or during moulding .also due to way of treating the whey, Sudanese Gibna Baday is unique among cheese varieties in that high concentration of table salt (sodium chloride)is added to milk before processing (Soman,2005) it is manufactured from row or heated milk (Ibrahim,2003). During processing under tropical conditions cheese deteriorates rapidly before it ripens thus salting before renneting become essential for its preservation (Alla Gabo,1986) .

2.2.5.1 Gibna Baday:

Gibna baday (white cheese) is practically the only kind of cheese on the market available to the public at large in the Sudan and is thus normally refered to simply as Gibna (cheese). There is little doubt the technology of making Gibna has been introduced into the Sudan from Egypt, or through Egypt, from the Mediterranean countries, such as Greece. It is not known exactly when Gibna Baday was first introduced into the country but it is most likely that the Sudan has known this cheese for nearly a century. Many Sudanese think that the product is a truly indigenous fermented food in the Sudan, but this contention has no basic. Elawad (1987) suggested that white cheese was introduced into the Sudan from Egypt during colonial times (1898-1956) and that the Sudanese merchants later took up the manufacturing task, adding their own flavor to the product. According to the Ibrahim (1971) the art of making white cheese was first introduced by two Europeans, one of whom was a British professor at the Faculty of Veterinary Sciences of the University of Khartoum by the name of I.A. Gillespie. Other investigators reported that the manufacture of whit cheese was first introduced by Greek family, Katherin and Panaioti maestro, who settled in 1908 the town of Dueim on the white Nile, in 1920 established the first cheese plant intended for commercial production (Ali, 1987). In line with this view, it’s known that until recently ,Gibna Baday was sold in Khartoum in groceries ran primarily by Greeks (Ibrahim,1970b). According to Suleiman (2007) Gibna Baday was prepared using the three type of milk: raw,

19 pasteurized and boiled . the raw milk contained:43.0% moisture, 12.5% ash, 20.16% protein and 56.48% total soluble solids, while the pasteurized milk cheese contained: 50.9% moisture, 10.5% ash, 17.63% protein and 48.76%total soluble solids and the boiled milk cheese contain: 48.5% moisture. 13.4% ash, 15.4% protein and 55.75% total soluble solids.

2.2.5.2 Mudaffara cheese:

Mudaffara cheese is a local braided semi-hard un ripened cheese with close texture and yellowish colour, slightly acid and salty taste .it is known in urban communities of Sudan (Elsheikh,1997).the Sudanese consumer has always shown, since several generation ,particular favoritism to the taste of mudaffara. The relatively high cost of mudaffara cheese is mainly attributed to its complicated technology that includes scolding, slicing, cooling manual working of the curd and finally braiding, preparation of mudaffara cheese. The process needs highly experienced and skilled workers (Abdel Razig,2001). In addition the method of manufacture needs to be improved in order to produce a safe product with good quality (Elsheikh,1997).

The general practice used in Sudan and in the middle East countries is that cheese is made from cow’s and goat’s milk which has a great role in dairy processing although large quantities of milk are produced (Abdel Razig,2001).However ,there was no significant difference between the different types of milk in acidity and pH(Elsheikh,1997).

Ahmed(1987) reported that yield of mudaffara cheese increased with increased added skim milk powder and the quality improved when 5% milk powder was added fresh cow’s milk. For goat’s milk, the addition of 5% milk powder increased yield without significant change in quality.

2.2.5.3 Mozzarella cheese:

Mozzarella is an Italian cheese traditionally made from high fat milk. It melts easily and is used extensively in cooking. it has been manufactured and introduced to the market due to the recent popularity of Italian dishes. the manufacture of mozzarella was first practiced in Khartoum dairy product factory in 1992 (Khateeb,1997).The method of manufacturing Mozzarella cheese slightly. differs from one place to another. In the united state, however the cheese is produced from

20 whole or partially skimmed milk. Small amount of starter culture or organic acid followed by rennet extract are added. Forms is not cooked, but simply cut and the whey is drained off. The matted curds are formed into blocks, drained and at worm temperature undergo mild acid ripening at Ph 4.4- 5.2 at critical ph or acidity the curd is heated in water, stretched and molds, placed in proper forms and slightly salted. Artificial flavor and flavor producing enzymes normally are not added to Mozzarella cheese (Kosikowiski, 1982).

2.2.6 World cheese types: A wide range of cheeses and cheese-like products are produced worldwide but from a very limited range of raw materials. Natural cheese is made from cows, sheep’s, goats, or buffalos milk ,lactic acid bacteria, rennet (in the of rennet- coagulated varieties)and salt ,yet it has been said that there is a cheese for every taste preference and a taste preference for every cheese. Cheese has a long history and the collective heritage of creation varieties has been ensured in Europe by protected designation of origin for certain varieties. No definitive list of cheese varieties exists but it is estimated that there are about 1000-1500 varieties produced worldwide. However , many of these cheese are in fact very similar and attempts have thus been made of classify varieties into relatively homogeneous groups. Based on made of coagulation of the milk and various technological parameters, cheeses can be classified into about 12 major families:

- Acid – coagulated varieties (e.g. cottage cheese, quarg ,cream cheese).

- varieties coagulated by combination of heat and acid (e.g. ricotta).

- Rennet –coagulated cheese (most varieties), which can be subdivided based largely on the technology of their manufacture and ripening into:

- Extra-hard (grana-type) cheeses(e.g. Grana padano).

- Hard cheeses (e.g. Monterey jack).

- Semi-hard cheeses (e.g. Gouda).

- Swiss-type cheeses(e.g. Emmental).

- varieties ripened under brine (e.g. feta).

21

- Pasta-filata varieties (e.g. Mozzarella).

- Surface (white) mould-ripened cheeses (e.g. camembert).

- Blue cheese (e.g. Roquefort).

- Surface(smear)-ripened cheeses (e.g. titlist).

In addition ,rennet- coagulated cheeses can be dried or converted to processed cheese (McSweeney et.al, 2004).

Many of these major families contain varieties that are similar in terms of the technology of their manufacture and microbiology and biochemistry of their ripening but may be made from milk of different species. Imitation cheese products (cheese analogues) and enzyme-modified cheese (which is used as flavouring) is also produced. Family, a minor group of Norwegain whey “cheese” (brunost, brown cheese) are produced by concentration and crystallization of whey to give a product with a smooth, firm body and a caramel-like flavor and long shelf-life (McSweeney ed.al,2004).

2.2.6.1 Grana-type cheeses and parmesan:

The hardest cheeses are the Italian Grana varieties and their industrial counterpart, parmesan. The hard grainy texture of Italian Grana –type cheeses (e.g. parmigiano-reggiano or Grana padano) results from the use of raw semi- skimmed milk for their manufacture and a high cooking temperature (54oC) and evaporation of moisture during their long ripening period (often 2 years or more). Grana-type cheeses are sometimes consumed as a table cheese when they are young and relatively soft but the mature product is often used grated as a condiment on pasta or other dishes (M cSweeney et.al, 2004).

In additions to these traditional Italian cheeses with controlled designation of origin, parmesan-type cheeses are made worldwide. parmesan-type cheeses are often smaller than traditional Italian Grana type varieties and are made from pasteurized milk and cooked to a lower temperature. They are more heavily salted, are ripened for shorter periods and often are made using exogenous lipases, which gives them a strong lipolysed flavor (McSweeney et.al, 2004).

22

2.2.6.2 Cheddar cheese: Shedder is a hard cheese that originated from the village of the same name in the south-west of Britain and is now among the most important cheeses made worldwide, particularly in English-speaking countries. Cheddar cheese is made from pasteurized, standardized cow’s milk . Mesophilic starter cultures are used and, in large cheese factories, defined-strain starter systems are common. The milk is rennetet at 30oC and the curd/whey mixture is cooked to 37-39oC and the curds are cheddared (M cSweeney et.al, 2004). Traditionally , cheddaring involved the repeated piling and repilling of curds which fused together and were cut into blocks. During cheddaring , starter activity countries to reduce the PH , solubilises colloidal calcium phosphate and causes physicochemical changes to the curd which changes from being soft and friable to being tough and pliable. Modern continuous cheddaring systems have dispensed with this Traditional piling and repiling of curd blocks and simply provide time for acidification of the curd at it passes though a tower or belt systems. When sufficient acidity has developed (pH 5.4), the curd is milled (cut) into small pieces and dry – salted. Dry-salting cause a rapid increase in the salt-in moisture content of the curd and starter activity stops abruptly. After salting , the curd pieces are pressed into the from of a block before ripening at 6-8oC for 4 months to>2 years depending on the degree of maturity desired. Cheddar is an internal , bacterially ripened variety and it maturation is characterized by the rapid decline in starter activity and the growth of non – starter lactic acid bacteria. Metabolism of lactate is usually restricted to restricted to racemisation, and citrate metabolism can cause undesirable openness in the cheese . proteolysis and amino acid catabolism are important to flavor , while lipolysis is usually limited (McSweeney et.al, 2004).

2.2.6.3 Dutch-type cheeses: Gouda and related cheese (e.g. Edam) are the most common Dutch-type cheese . they belong to the group of semi-hard cheese and have undergone maturation for at least 4 weeks when brought to the market (dusterhoft and van den berge2004). The majority of Dutch-type cheese have a fat-in dry-matter (FDM) content of at least 40% and a moisture-in-non-fat-solids (MNFS) content below 63%. Gouda-type cheeses are usually made from pasteurized, partly skimmed milk, clotting is by calf or microbial rennet and mesophilic mixed-starters comprising lactococci and

23 leuconostoc are used. The curd undergoes only a mild scalding (36o C) to control the moisture content and it washed to control the extent of acidification. The cheeses are pressed and brine –salted. Acidification occurs during pressing until the first hours of brining . Gouda-type cheeses, typically in the from of 12-15 kg wheels or blocks, are characterized by a limited number of rather small round eyes they have a smooth texture when young to medium matured, are easily sliced and have good melting properties. A 4-weeks-old 12 kg cheese should show 10-20 eyes per cross-section that are regularly distributed and have a diameter between 2 and 10 mm. about 75% of the dutch production is naturally ripened at around 13C and 25% is foil ripened at a lower temperature.

Within this general description , a large variation in ripening times (4 weeks to 1 year) and fat contents (50% FDM to 20% FDM) exists. The use of adjunct cultures has brought a relatively large Variation in flavors and has been beneficial for the production of low fat varieties. The volume of low fat cheeses production in the Netherlands (34% FDM and below) is around 1% but is increasing steeply (product chap, 2005). Outside the Netherlands, Germany is the largest producer of Dutch-type cheeses. In 2004 46% of all hard and semi- hard cheeses produced in Germany was Gouda- or edam- type (dusterho ft and van den berg 2004).

1.2.6.4 Swiss cheeses: Swiss type cheeses were originally manufactured I themmenvalley (emmental) in Switzerland their precursors were various mountain cheeses. Emmental cheeses is probably the best –known Swiss type cheeses and it frequently referred to simply as Swiss cheeses Swiss type cheeses have around regular cherry-sized eyes which vary in size from medium to large (1-3 cm) (Bachmann et.al,2002). The propioinc acid fermentation leads to characteristic eyes and nutty flavours and can either occur spontaneously or be achieved by a culture of selected propionibacteria. A spontaneous fermentation leads to irregular eye formation ,because of great strain diversity of the natural propionibacteria flora in milk .the number and size of the eyes vary markedly and cracks or splits are quite comman. comte and beaufort are typical examples of cheese varieties with spontaneous propioinc acid fermentation . the use of a culture of selected propionibacteria allows a more regular eye formation as a result of controlled propioinc acid fermentation. All

24 these cheese varieties are referred to as Swiss type cheeses, the boady of Swiss cheeses are typical of hard or semi-hard cheeses, the characteristics of Swiss manufactured emmental cheeses are: -high PH of 5.2 at whey drainage . -cooking to53oC (inactivation of much chymosin activity). -maturation in a warm room (23o C) to promote propioinc acid fermentation followed by maturation at 13oC . -cylindrical shape . -firm and rind. -weight: 60-130 kg. -1000-2000 round eyes diameter 1-4 cm . -flavor: mild , nutty ,slightly sweet becoming more aromatic with increasing age. -cheese boady- ivory to light-yellow, slightly elastic. -ripened for 4-8 months (up to 15 months ). Today emmental- type cheese is producted in many countries and a great variety of other Swiss type cheeses are also available on the market including jarlsberg massdammer leerdammer and many other products denoted as Swiss type cheeses they are manufactured by methods differing from traditional Swiss production in termtment of milk, extent of mechanization, the starters used and the weight and shape (Bachmann et.al,2002). 2.3 Whey:

Few years ago , whey was treated as an significant by-product of cheese making used mainly in animal feed or discarded (McBean, 2003). Formerly , whey was regarded as waste product of little or no value, and often returned to farmers with charge. Although mainly water (about 93%)the solid represent a valuable food, and today practically all whey is separated, concentrated and converted to paste or powder (Davis, 1968).

2.3.1 Definition and constituents of whey:

Whey is a by product of cheese making. It contain high quality protein, lactose, minerals(calcium, phosphorus, magnesium, and zinc), vitamins and traces of milk fat. Whey protein isolated is higher in protein and contains little, if any, lactose or fat

25

(McBean, 2003). Whey is high of biological value compared to most other protein; has a high content of sulfur containing amino acid important for the biosynthesis of glutathione, a tripeptide with antioxidant, anticarcinogenic, and immune stimulating properties, and is the highest natural source of branched chain amino acid which may stimulate muscle protein synthesis (McBean. 2003).

Petersen (1939) reported that whey is only direct by-product from the making of cheese. Whey from rennet coagulated milk averages from 6.5-7.5% dry mater, 4.5- 5.2% lactose’s, 0.8-0.9% protein, 0.3-0.5% fat and 0.6-0.7% ash and also contains all of the riboflavin of milk (Petersen, 1939).

2.3.2Types of whey:

The main types of whey are sweet whey and acid whey .acid whey is produced from cheese that is directly acidified with mineral acid or lactic acid. Where as sweet whey is result of starter culture acidification of cheese (Bordenave-Juchereau et al; 2005). Sweet whey generally has titratable acidity between 0.1-0.2%, a PH of 5.8-6.6 and is derived from rennt coagulated cheese like cheddar (coagulation of milk casein by rennet). Acid whet has titratable acidity of 0.4%, a PH less than 5.0 and is derived from fresh cheese (acid coagulation of milk casein).

2.3.3 Emerging health benefits of whey and uses:

Whey still used mostly for livestock feeding and the production of primost, both of which have been noted previously (Petersen, 1939). He reported that, whey is also used for the production of whey powder, condensed whey milk sugar and riboflavin or vitamin G. the cream so produced is known as whey cream (Petersen, 1939). Whey powder and condensed whey are used in candy making and in various baked and other product (Petersen, 1939), also he reported that milk sugar is used extensively as a food and for medical preparation. Davis(1968) reported that spray dried whey is a good and useful product for many purposes, e.g. processed cheese (Ricotta cheese), humanized milks, dietetic preparation and animal feed.

Today , as a result of recent discoveries of its function and bioactive roles, the whey and whey component (particularly protein) are viewed as value added ingredient in infant formulas, sports nutrition foods and beverages, and other food products(McBean,2003).Whey and whey components have potential health benefits

26 beyond their nutrient content. Suggesting that whey derived bioactive component have antimicrobial and antiviral properties; enhance immune defense; possess anti- oxidant effect; may help protect against cancer and cardiovascular disease; and enhance the performance of physically active individuals (International Dairy Federation, 1997and Dairy Export Council, 2003).

Several whey protein, including lactoferrin and its peptide derivative, lactoferricin, have been shown to inhibit the activity of a diverse range of microorganisms and some harmful food borne pathogen (McBean, 2003). Also exhibit antiviral activity against human immunodeficiency virus (H I V), stimulate the immune response

2.3.4 Nutrition properties of whey:

There are many advantage of using whey protein instead of other protein to enhance foods. Whey protein actually consists of several component proteins including beta-lactoglobulin, alph-lactoalbumin, glycomacropepted, bovine serum albumin, immunoglobulins,noglobulins and lactoferrin (Canning, 2004). They are also rich in calcium, phosphorous, magnesium and zinc (Hazen, 2005). Whey protein concentrates and whey protein isolates typically contains 500-700mg calcium per 100g powder (Dirienzo, 2004). The amino acid profile of sweet whey is very blanced, and each amino acid present exceeds the intake recommendations for both children age 2-5 and adults as set by the Food and Agricultural Organization and World Health Organization (Walzen, 2004).

There is more recent research indicating that whey as used in a high protein. low carbohydrate diet could contribute to weigh loss and a reduction in body fact (Dahm, 2005) this may result from the ability of proteins moderate energy intake and increase the feeling of fullness (Holihan, 2005). Glycomacrppeptide (GMP) a component of whey protein, has been found to stimulate production of the hormone cholecystokinin, which sends a signal to the brain that the stomach is full (Canning, 2004).

Whey protein could contribute many other health benefits to human. Peptides in hydrolyzed whey may lower blood pressure and reduce blood cholesterol levels (Dahm, 2005; Canning, 2004). Whey protein may have a positive effect on blood glucose and insulin levels (Dahm, 2005).

27

Several whey protein component, such as lactoferrin, may even be able to protect the body from infection by inhibiting the activity of certain microorganisms including some food borne pathogens (Canning, 2004;Walzen, 2004).

2.3.5 Products produced from whey:

There are several products can be obtained through the processing of liquid whey including concentrated whey, whey powder , lactose, lactoalbumin, whey proteins, and whey protein concentrated and isolates. Whey powder is the product of dried fresh whey, containing all of the components found in the whey except the water. Reduced lactose whey is whey in which the lactose is reduced to less than 6o% (USDEC, 2004). Whey protein concentrated (WPC) result from removing non-protein components in order to achieve a certain protein content. They can vary in protein content depending on the processing method. But can content no less than the percentage including in its name. for example WPC34 must contain no less than 34% protein. The most common types are WPC34, WPC50, WPC60, WPC75, and WPC80.whey protein isolate(WPI) results from removing non-protein components in order to achieve a 90% protein content.

2.4 Ricotta cheese:

2.4.1 Definition of Ricotta cheese:

Thericootacheese is ahigh moisture soft cheese (Modler and Emmons,2001). it can be produced from whey or milk or mixtureof both (Pizzillo etal, 2005). Ricotta cheese is very mild it isused in many Italian dishes. Several methods have beendeveloped for utilization of whey one of these methodis the manufacture of Ricotta cheese.(Kosikowski, 1982) Ricotta cheese is dairy product of Italian origin, which means"re cooked". It is produced by boiling acidified whey (Maubois and Kosikowski,1978).

2.4.2 History of Ricotta cheese:

Cheese was historically a large export product for Sicilym, along with grai. It was also a main part of their diet and was usually made from goat's or cheap's milk . Many dessert featuring ricotta originated in Sicily. (http://www.ehow.com./about- 4575931-history-ricotta-cheese htm.2000) Ricotta cheese is not acheesebut acreamy

28 curd is literally cooked twice hence the name "re-cooked. Ricotta is known as an albumin or serum a cheese made as a by- product of cheese from the re-cooked whey The foam of the whey when it is being recooked is called zabbina in Sicillain. which comes from the Arabic word zarb, though also to be the root of the custard dessert zabaionne. The best ricotta is mamd with sheep's milk. tow of earliest mention or depiction of ricotta is related to Sicily. Professor Santi Correnti, chairman of the history department of the Univesity of Catania and a preeminent historian of Sisily, write that during the reignof the Sicilian King Frederick11, in the earlt thirteenth century the kig and his hunting party come across the hut of a dairy farmer making ricotta and, being ravenous, asked for some theof depiction of the Tacuium sanitatis, the latin translation of Arab physician ibn Butlan's eleventh century Taqwim al-sihha. Mention ricotta cheese and the first thing to come to mind is probably classic Italian lasagna ricotta works well in many dessert as well as savory dishes.

(http://www. Fading ad com fading ad blog/?p=5123 2001).

2.4.3 Types of ricotta cheese:

Whil Italian ricotta is typically made from the whey of sheep, cow, goat or water buffalo milk ,the American product is almosst always made of cow,s milk whey. while both types are low in fat and sodium.

2.4.3.1 Ricotta infornata:

Is produced by placing a large lamp of soft ricotta in the oven until it develops brown, lightly charred crust, sometimes even until it decome sandy brown all the way through.

2.4.3.2 Ricotta affuniccata:

Is similer to ricotta infornata. it is produced by placing of soft ricotta in a smoker until it develops agrey curt and aquire charred wood scent.

2.4.3.3 ricota scanta:

is the process of letting the ricotta go sour in a controlled manner, for about a week ,then stirring it every 2-3 days, salting occasionally and allowing the liquid

29 flow a way. after about 100 days, the ricotta has the consistency of cream cheese, with a distinct and piquant aroma, much like dlue cheese but muchricher.

(http:www.amaltheia dairy, com/AD.2005).

2.4.4 Description of ricotta cheese:

Ricotta is an Italian sheep milk or cow milk whey cheese. Ricotta 'recooked' uses the whey, a limpid, low- fat nutritious liquid that is aby product of cheeseproduction. Ricotta from whey; the liquid separated out form the curds when cheese is made. most of the milk protein (aspecially casein) is removed when cheese ismade, but some protein remains in the whey. mostly albumins this remainin protein can be harvested if the whey is first allowed to become more acidic by letting it sit for 12-24 hours at room temperature.Then the acidified whey is heated. the combination of low pH and high temperture causes additional protein to precipitate out, forming afine curd. Once cooled the curd is separated by passing though afine cloth. Ricotta is fresh cheese creamy white in appearance, slighty sweet in tasta, and contains around 5% fat.

(http://www.tarladalal. Com/glossaryse -ricotta cheese-318i 2010).

Technically, ricotta is not a cheese at all, but a cheese by-product. its name, ricotta, means cooked again, an obvious referne to the production method used to male it. Ricotta is made frm the whey drained from such cheese as mazzarell, provolone, andother cheese. American ricotta is generally made with acombination of whey and whole low-fat or skim cow'smilk. Ricotta is a fresh soft, snowy white cheese with arich but mild, slightly sweet flavor. the textuure is much like agrainy thich sour cream. ricotta is naturally low infat, with a fat content ranging from 4 to 10 percent. it is also low in salt, even lower than cottage cheese. Since ricotta is made primarily from lactose-rich whey, it should be avoided by those who are lactose-intolerant. Unrelated to soft ricotta, ricotta salada made of sheep's milk The liquid is presssed out and the solids are compacted into rounds, enabling it to be cut with aknife. its texture is a crumbly but firm .(http://www.Wikipedia/ wiki/Ricotta 2008).

2.4.5 The basic steps making of ricotta:

30

1- Save the whey from making cheese in anon-reactive pot. Filter as much of curd parties out, cansince they would other wise from tough in the final ricotta.Cover andlet sit12-24 hours at romm temperature to develop sufficient acidity.

2- The next morning, heat the acidified whey with stirring

3- Continue heating with stirring until its temperature is near boiling (93O%). Remove from heat and added lemon juice.thencover avd allow the "cooked

" whey to coo undisturbed until comfortable to touch.

4- Gently scoop out the curd. Because the curd are very fine and delicate they can stop up the cloth easily.

5- After all of the wet curd have been transferred to the cheese cloth, allow the whey to drain throughout the clot (it can take 2-3 hours).

6- Remove the ricotta from the cheese cloth, pack into acontainer, cover and stoer in the refrigerator. cooking about. Com/cs/ cheese information/a/ ricotta

31

CHAPTRE THREE

MATERIALS AND METHODS

3.1 Material:

All the glassware's, media and other material used were aither wet sterilized or dry sterilized. The hot sterilization was done at 160OC for 2 hours, while wet sterilization was carried out at 120OC for 15 minutes. All bacteriological media used were those of dehydrated media.The media were prepared according to manufacturer's instruction.

3.1.1 preparation of whey samples:

the whey sample were collected from local market in Wad Medni, Gazira state during April-May 2011. Whey samples were placed in plastc container in refrigerator at 6OC. And then transported to Department of Food science and Technology Laboratory, Faculty of Engineering and Technology, University og Gazira.

3.1.2 Bacteriological mdia:

The following media were used in the present work.

3.1.2.1Plate Count Agar:

The medium composition was as follows (g/l)

Casein enzyme hydrolysate 5

Yeast extract 2.5

Dextrose 1

Agar 12

Final pH 7.2+0.2

The requisite quantity deydrated medium was dissolved in water by boiling, dispensed in approprite amount in Erlenmeyer conical flask and autoclaved at 15 psi (121OC) for 15 min and then cooled to room temperature befor use.

3.1.2.2 Potato Dextrose Agar:

The medium composition was as follws (g/l)

Potato infusion 200

Dextrose 20

Agar 15

Finl pH 5.1+0.2

32

The requisite quantity deydrated medium wasdissolved in water by boiling, dispensed in approprite amount in Erlenmeyer conical flask and autoclaved at 15 psi (121OC) for 15 min and then cooled to room temperature befor use.

3.1.2.3 Macconkey Agar(MCA):

Pancreatic digest gelatin 12

Peptic digest of animal tissue 1.5

Casein enzymic hydrolyte 1.5

Lactose 10

Bile salt 1.5

Sodium chlorid 5

Neutral red 5

Finl pH 7.0 +0.2

3.1.2.4.E C Broth Agar:

The medium composition was as follows (g/l)

Casein enzyme 20

Lactose 5

Bile salt mixture 1.5

Di potassium phosphate 4

Final pH 6.9+0.26

The requisite quantity deydrated medium wasdissolved in water by boiling, dispensed in approprite amount in Erlenmeyer conical flask and autoclaved at 15 psi (121OC) for 15 min and then cooled to room temperature befor use.

3.1.2.5 Salmonella Shegilla Agar (SSA):

The medium composition was as follows (g/l)

Beef extract 5.0

Balanced peptone 5.0

Sodium citrate 8.5

Sodium thiosulphate 8.5

33

Agare 13.5

Lactose 10

Bile salt 8.5

Ferric citrate 1.0

Brilliant green 0.0003

Neutral red 0.025

Final pH 7.2+0.2

The requisite quantity deydrated medium wasdissolved in water by boiling, dispensed in approprite amount in Erlenmeyer conical flask and autoclaved at 15 psi (121OC) for 15 min and then cooled to room temperature befor use.

3.2 Methods:

3.2.1 Chemical analyses of whey: chemical analyses were conducted for the collected whey sample, these analyses included:

3.2.1.1 PH Measurement:

The pH of whey was measured using digital pH meter (PN9410.GL. Britain). The pH meter was calibrated with buffers of pH 4and 7. The PH values was recorded according to AOAC (1990).

3.2.1.2 Determination of terrible acidity:

The titer metric determination acidity of whey was accomplished according to the AOAC(1980) method. The sample taken for determination of whey acidity was10 ml then diluted in 100ml distilled water, then taken 10ml was pipetted into two a 100ml conical flask. The pipettes were washed with distilled water, and then six drops of phenolphthalein indicator were then added. The samples were then titrated with 0.1 N. NaoH until a stable pink color was formed. The titrable acidity was expressed as % lactic acid from the following formula.

Whey and cheese titrable acidity % = ml of NaOH × 0.1× 90× 100

Weight of the sample ×100

Where 90 is the amount of lactic acid reacted with 1.0ml of o.1 N NaOH.

34

3.2.1.3 Determination of moisture:

The moisture content of whey sample was determined according to AOAC Official Method (1980). Three of porcelain dishes were taken, washed and dried for 1 hr at 100oC by the oven, then cooled down to room temperature in a desiccator for 30 min. and weighted. Weighting balance (Mettler H33 A.R type) was used to weight samples before and after drying. 10 ml was taken from whey and placed in porcelain dish. The dish with a samples were then dried for 2 hr at 105oC and cooled down in desiccators and weight. This procedure was repeated until a constant weight was reached. The loss in weight equals the grams of moisture.

% moisture was calculated as follows:

Moisture % = Wi –Wf

Wi

Where:

Wi is initial weight of samples.

Wf is the final weight of the samples.

3.2.1.4 Determination of protein:

Protein content was determined by kjeldahel produce according to AOAC(1980) one ml from whey and 3g from cheese were placed in digestion flask; copper catalyst and antibumping granules were added. Then 25ml of concentrated sulfuric acid was added and the content was digested within two-three hours. After digestion, the contents were cooled and diluted to 100ml by addition of distilled water. 20ml of diluted digested was poured into the distillation unit and 10ml of 40% sodium hydroxid was added. Twenty five ml of boric acid with2-3 drops of methyl red were added to the digest and placed in a conical flask. Distillation of the reaction mixture librated ammonia and reacted with boric acid, changing the colour from red to light greenish blue. Excess alkali was then titratedusing (0.1) hydrochloric acid, until color changed to light purple. The titration reading was reported. The protein content was determined by multiplying the percentage of nitrogen by the empirical factor 6.36 as follow:

%N = Volume of HCL × T × 14 × dilution factor×100

1000 ×volume of sample

Then % protein =% N ×6.36

Where:

14 = the molecular weight of nitrogen.

35

T = Normality of acid, HCL

N = Nitrogen content

3.2.1.5 Determination of fat content:

Gerber tub was used to determine fat content of whey samples according to the method by AOCA (1990). The butyrometer was filled with 10ml H2SO4. 11ml samples (whey and cheese) were pipette in to the butyrometer. The 2 ml amylalcohol was added and the butyrometer was closed with astopper.The contents were shaken vigorously until all protein particles were dissolved.The butyrometer was then placed in a water bath at 65oC for 5 minutes (fat column under the water surface). Moving the stopper regulated the fat column. The butyrometer was then placed in a centrifuge for 5 minutes, the fat content was read directly on the butyrometer scale g/100 g sample.

3.2.1.6Determination of ash content:

The ash content of whey and cheese samples were determined according to AOAC Official Methods (1980), 10ML from whey and two grams from ricotta cheese were wrighted ina muffle furnace at 550oC until ash carb-free (2-4 hours), cooled in desiccators and weighed. then ash was calculated:

W1× 100

W2

3.2.1.7Determination of Solid non fat content:

Solid non fat in whey and cheese were determined by using the following formula:

Total solid% - fat%

Total solid in whey and cheese samples were determined according to AOAC(1980) modified method. In that 1ml from whey and 3 gram were weighted into a dry clean crucible dish, then heated on water bath for 10-15min. the dish was then placed in an oven at 80oC overnight cooled down in a deisccator and weighted.The total solids (TS)content was calculated from the following equation:

TS% =W1×100

W2

Where:

W1 = weight of the sample after drying.

W2 = weight of the sample

36

3.2.2 Microbiologicalanalyses:

Ten ml of whey was homogenized with 90 ml of distilled water by shaking for several minutes, from this suspension; 1 ml was taken rrom the dilution and transrerre to another tube to make seril dilution up to 106.

3.2.2.1 Tatal viable count:

Tatal viable count per ml of the sample was carried out by pour plating of suitable dilution on melted nutrient agar, and incubated aerobically after solidification at 37oC for 72 hour(Dirar, 1976).

3.2.2.2 Yeast and Mould count:

Yeast and Mould were enumerated acccording to Marshall (1993) using potato dextrose agar (PDA).The plates were incubated at 25o C for 3-5 days, plates containing betweem 300 colonies were count as colony forming units(C.F.U).

3.2.2.3 Coliform bacterial count:

Coliform bacterial count was determind according toMarshall (1993) using Macconkey broth. The tubes were incubated at37O C for 48 hours. positive tubes gave gas in Durham tubes. Then the positive tubes were sub culturedinto EC broh medium and then incubated at 44OC for 24 hours, to determined coli form bacteria, the tubes showing any amount of gas production were considered positive.

3.2.2.4 E.coli test:

Plates showing positive coliform were subjected to confirmed test using Brilliant green bile broth in test tubes with Durham tube. The test tubes were then incubated at 45OC for48 hours. each confirmed positive tube was sub culured into EC broth midia and then incubated at 45OC for48 hours. Tubes showing any amount of gas production were considered to be positive (Kreger and VanRij,1984).

3.2.2.5 Salmonella detection:

Hundred ml of sample incubated at 37OC for 24 hours. then10 ml were drawm asepticlly and added to 100 ml selenited broth. The broth was incubated at 37OC for 24 hours. Then with a loopful streaking was done on dried Bismuth sulphite agar plates. the plates were then incubated at 37OC for 72 hours. Black metallic sheen discrete colonies indicated the presece of salmonella. a confimator test was carried out by taking a discreete black.

3.3 Preparation of Ricotta cheese of laporatory level:

Ricotta cheese wae made from heated acid precipitation of protein from whey. During heating by using a heater (at 79OC),7 liters of whey protein was coagulate. the rate of coagulation increasea as temperature is raised to 93OC and thick layer of curd

37 wasformed on thesurface of the whey. When coagulation was completed and the curd was firm (after 10-20 min. at 93OC ) the curd was removed from the heater withperfoated by ordnary plastic mesh. 10 ml of lemon juice was immediately added to the resulted curd. after about 10 minute the mixture was placed in cheese cloth for 2-3 hours. The ricotta cheese was then kept in small plastic container.

3.3.1 cheese yield:

The resulting cheese was weighted immediately after using aweighting balance, the weights of cheese sample was recorded.The yield of cheese was calculated as follows:

Yield= Weight of cheese×100

Weigh of cheese

3.3.2 Assessment of Ricotta cheese:

The quality of laporatory made Ricotta cheese was determined using chemical, microbiological and sensory method.

3.3.2.1chemical analysis of laboratory made Ricotta cheese:

The chemica analysis pH, Acidity,total solid,solid non fat, moisture, protein, fat and ash were deteermined as desribed in 3.1.1.

3.3.2.1.2 Minerals determination:

Three gram from the cheese sample was weighted at 600OC over night then wetted using water and transferred through filter paper into a100 ml conical flask. 10ml of conc. Hcl were added to the conical flask, and lastly the volume was completed usimg distilled water. for stock solution preparation, grams of metal salt was weighted and dissolved in one liter of distilld water to obtained 1000 ppm concentration. Standard solution were prepared by taking difference volume using distilled water. then readings were taken andstandard curve was formed.

Mineral content was calculated as follow:

Ca, Na, K( ) = Concentration×100

Sample wt.

3.3.2.1.1 Determination of Calcium:

Calcium was determined by using the flame photometer apparatus

I. Ca stock solution

(caco3) was dissolved and dilute in 1 liter distilled water to obtained(1000 ppm Ca).

38

Ca stander solution

5,10, 15, 20, 25 ml were taken from Ca stock solution into 100 ml vol.flasks and completed to the mark with distilled water, then the emissions for standers and sample were read using the flame photometer.

Concentration ppm Emieeion

0.0 0.0

50 20

100 40

150 63

200 80

250 100

The calibration curve (E Vs C) was plotted, and then form the curve the quantity of Ca in the sample was calculated.

3.3.2.1.2.2 Determination of sodium

Sodium was detemined by using the flame photometer apparatus.

Sodium stock solution (Nacl) was dissolved and dilute in 1 liter distilled water to obtained(1000 ppm Na).

Sodium stander solution

2, 4, 6,8,10 ml from Na stock solution into 100 ml vol.flasks and completed to the mark with distilled water, then the emissions for standers and sample were read using the flame photometer apparayus.

Standard conc. Ppm Emission

0.0 0.0

10 35

20 57

30 78

40 92

50 100

39

The calibration curve (E Vs C) was plotted, and then form the curve the quantity of Na in the sample was calculated.

3.3.2.1.2.3 Determination of potassium:

Potassium was detemined by using the flame photometer apparatus. Potassium stock solution

(KCK)was dissolved and dilute in 1 liter distilled water to obtained(1000 ppm K).

Potassium stander solution

Stander solution of K was prepared in range of (0-20 ppm) in 100 vol. flasks stock solution.The emissions for standers and sample were read using the flame photometer.

Standard conc. Ppm Emission

0.0 0.0

4 38

8 62

12 72

16 92

20 100

The calibration curve (E Vs C) was plotted, and then form the curve the quantity of k in the sample was calculated.

3.3.2.2 Microbiological analyses of laboratory made Ricotta cheese:

The microbiological analyses total viable count, yeast and mould count, coli form count, E. coli and salmonella were determined as described in 3.2.2.

3.3.2.3 Sensory evaluationof laboratory made Ricotta cheese:

The Ricotta cheese was subjected to sensory evaluation using 10 panelists. The panelists were asked to rate or judge samples to be tasted under 9 scales, about the appearance, texture, color, flavor and the overall acceptability. Each panelist was provided with water for rinsing The sample was given codes before being tested.

3.3. Statistical analyses:

40

All scores of sensory evaluation were analyzed by the analyseis of variance according to SAS,(1982). To determine there were significant differences between means for each variable; least significant difference (LSD) test was used.

41

CHAPTER FOUR

RESULT AND DISCUSSION

4.1 Chemical composition of whey sample and pH:

Table (4.1) shows the Chemical composition of whey sample. The moisture content 92.20+o.23%. This value was slightly lower than that found by Kosikowski (1979), which was 93.7%. The protein content of liquid whey was 0.15+0.74% This value was lower than that reported by Abozaid (2007), which was 0.9%. The fat content of liquid whey was 0.7+0.1% which was higher than that reported by Kosikowski (1979), which was 0.3%. The ash content of whey is 5.37+0.19%. This value was higher than that found by Kosikowski (1979), which was0.52%. pH value of whey was 5.1+0.30%. This value was higher than that by DTU National Food institute (2009), which was 5.00%. The titratable acidity (expressed as% lactic acid ) of whey was 2.35+0.3%. This result value was higher than that found by htt://www. Dairy forall. com (2005), which was0.4%. The total solid of whey was 17.9+0.06%This value was higher than that found by Dairy forall. com(2011), which was 10.5%.

4.2 Microbiological analysis of whey samples:

Table (4.2) shows Microbiological analysis of whey samples. The total viable count was 9×104 cfu/ml this result was higher than that reported by htt://www.wolframalph.com/entities 2011. which was 4×104 .The yeast and mould of whey samples was 6×104 .cfu/mlcfu/ml this result was higher than that reported by htt://www.wolframalph.com/entities 2011. which was 3×104 . Coliform, E.coli and salmonela were notdetected in whey samples.

Table (4.1) Chemical composition of whey sample and pH:

Parameter Value

Moisture% 920+0.23

Protein% 0.15+0.5

Fat% 0.7+0.1

Ash% 5.37+0.19

pH% 5.1+0.30

Acidity% 2.35+0.30

Total solid% 17.9+0.06

42

Table (4.2) Microbiological analysis of whey samples:

Parameter Value(cfu/ml)

Total viable count 9×104

Yeast and mould 6×104

E.coli 0.0

Salmonella 0.0

4.3 Chemiccal composition 0f laboratory-made ricotta cheese:

The Chemiccal composition 0f laboratory-made ricotta cheese was presented in table(4.3). The moisture content of laboratory-made ricotta cheese was 72.89+2.6% while it was 92.20+0.23% in whey. This may probaly due to effect of high heat treatment which evaporated part of watre. However, the result obtained in present study was lower than that reported by Dairy forall.com (2011), which was 93% for ricotta cheese. The protein content of laboratory-made ricotta cheese was 0.14+0.6% while it was 0.15+0.74% in whey.

The result was lower than that reported by DTU National Food institute (2009), 0.15% which was for ricotta cheese. The fat content of laboratory-made ricotta cheese was 0.6+0.1% while it was 0.7+0.1% in whey. the defference did not exceed 0.1. The result was lower than that reported by DTU National Food institute (2009), 0.8% for ricotta cheese . The ach content of laboratory-made ricotta cheese was 5.37+0.19% while it was 6.9+1.4% in whey.

pH value of laboratory-made ricotta cheese was 5.28+0.23, while it was 5.1+0.3%in whey, and this difference could be attributed tothe effect of heat treatment which eliminated the microbial load. The result was similar to that reported by DTU National Food institute (2009), who found value of 5.00% for ricotta cheese.

The titratable acidity of laboratory-made ricotta cheese was 1.38+0.6%, whil it was 2.35+0.06% in whey. The variation in acidity of whey and ricotta cheese may be attributed to storage of whey at room temperature for 12-24 hoursbefore production of ricotta cheese. The result was lower than that reported by DTU National Food institute (2009), who found value of 1.03% for ricotta cheese. The total solid of laboratory-made ricotta cheese was 18.41+1.5%, whil it was 17.5+0.06% in whey.The defference did not exceed 0.51. The result was lower than that reported by DTU National Food institute (2009), who found value of 17.5% for ricotta cheese.

43

Table (4.3)Chemical composition of ricotta cheese and pH:

Parameter Value

Moisture% 72.89+2.3

Protein% 0.14+0.6

Fat% 1.4+0.6

Ash% 6.9+01.4

pH% 5.3+0.23

Acidity% 1.38+0.06

Total solid% 18.4+1.5 Yield 19.66

4.4 mineral content of laboratory-made ricotta cheese:

Table (4.4) chows the mineral content of laboratory-made ricotta cheese. The calcium concentration was 225mg/100g. This result was lower than that reported by DTU National Food institute (2009), which was 340mg/100g. The potassium concentration of laboratory-made ricotta cheese was120mg/100g. This result was higher than that reported by http://www.wolframalph.com/entities 2011, which was 110mg/100g. The sodium concentration of laboratory-made ricotta cheese is 106mg/100g.This result was higher than that found by http://www.wolframalph.com/entities 2011, which was 100mg/100g. However, the concentration of calcium, potassium and sodium investigated in this study were higher than those reported by http://www.wolframalpha.com/entities 2011.

44

Table (4.4): Mineral contents of laboratory-made ricotta cheese:

Mineral Value(mg/100g)

Ca 225

K 120

Na 160

4.5 Microbiological charactersties of laboratory-made ricotta cheese:

Microbiological analyses of laboratory-made ricotta cheese, in Table (4.6) revealed presence of 1×104 cfu/ml oftotal vaible count. This result was lower than that found by Rossetti(2008), which was 2.8 ×106 cfu/ml. The lower levels of total bacterial count in laboratory-made ricotta cheese were probably due to the effect of heat treatment which suppress the growth of micro organisms and also could be attributed to the excellenthygienic condition of cheese production. The yeasts and moulds count of laboratory-made ricotta cheese was 2×102 cfu/ml. this result was lower than that found by Rossetti (2008), which was 8.0×103 cfu/ml. The lower levels of yeast and mould count of laboratory-made ricotta cheese were probably due to the effect of higher heat. Coliform, E.coli and salmonella were not found in laboratory-made ricotta cheese.

The absence of Coliform, E.coli and salmonella were not found in laboratory- made ricotta cheese, were probably due to the effect of heat treatment of whey used for the production of ricotta cheese which suppressed the growth of those microorganisms (pathogenic bacteria).

45

Table (4.5): Micrbiological analysis of laboratory-made ricotta cheese:

parameter Value(cfu/g)

Total viable count 10×1

Yeast and mould

Coli form 0.0

E.coli 0.0

Salmonella 0.0

4.6 Sensory evaluation:

Table (4.6) summarizes the meam scores forsensory attributes of the ricotta cheese, Gibna Bayd lavachquirit. the result indicated slight differences of the various sensory parameters of cheese samples. There were significant differences p>(0.05) of ricotta cheese color and flavour when compared with those of Gibna Bayd lavachquirit. The low scores of flavour may be attributed to the distraction of certain LAB responsible for generation flavour compound as a result of heat treatment. Generally, the panelist highly accepted ricotta cheese when compared to Gibna Bayd lavachquirit. Howaver, there were no significant difference in appearance, texture and over of the various cheese types.

46

CHAPTER FIVE CONCLUSION AND RECOMMENDATION

5.1 Conclusion:

In the present study the ricotta cheese was prepared at laboratory level using whey which was collected as a by product of Gibna Bayd industry. the man ufactured ricotta cheese wasvanalyzed chemically, microbiologically and sudjected to sensory analysis, and compared to Gibna Bayd lavachquirit cheese types. Chemical analysis of the mamufactured ricotta cheese showed that its main component were 72.89% moisture, 0.6% protein, 0.7% fat and 6.9% ash. Microbial analysis showed that ricotta cheese is free from pathogenic bacteria.

The sensory analysis indecated that the ricotta cheese made from whey was highly acceptable by panelist.

5.2 Recommendations:

From the result of this study we can draw some recommendations, these recommendationsinclud:

1. Encouraging the local industry to increase the production of ricotta cheese so as to meet the local need.

2. Iintroduce whey in other food industries.

47

REFERENCE

Abdel Razig A.K, 2000.Quality Attributes of Braided Cheese "Mudaffara" as affected by the level salt and storage temperature pH. D. thesis, University of Khartoum, Sudan.

Ali M.Z, 1987. The technology of Cheese- Making in Sudan. paper present at the UNFSCO Regional Training Course on Fermented Food of the Arab World; 1-15 Feb. 1986, Food Research Center, Shambat, Sudan.

Alla Gabo, H.I, 1986. Studies on Composition and Qulity of Gibna Bada. M.Sc. thesis,University of Khartoum, Sudan

Abozaid, N. A. 2007. Dairy Industry Waste and soya Bean Milk. PHD thesis,University of Khartoum, Sudan

Anderon, 1969. Carbohydrate Metabolim in Microorganisms.

AOAC 1980. Official Method of analysis, 13 ed. Associoation of Official Analysis Chemists. Washington D.C. 376-384.

AOAC 1990. Official Method of analysis, Helrich K(Ed). 15th end. Associoation of Analysis Chemists, Inc. USAP777.

Archer, M.H., Dilon, V.M., Campell, G. and Owens, J.D., 1996. Effect of Dacty on Growth Rat Salmonella typhrmurium Determined From Detection Times. Measured in amicor well plate photometer, food control 7:63-67.

Bachmann, H.P., Bue tikofer, Vm and Isolini, D, 2002. Swiss- Type Cheese in Encyclopedia of Dairy Science Volume 1, H. Roginski, j.w. Fuquay and P.F. Fox (eds.), academic Press, Amsterdam, pp.363-371.

Bordenave- Juchereau. S., B. Almeida, J. Piot and F. Sannier. 2005.Effect of protein concentration, pH lactose content and pasturization on thermal gelation acid carprine whey protein concentrates, J, of Dairy Research. 72:34-38.

Burkhalter,G, 1981. Catalogaeof cheese (Bulletin 141). Russele: International Dairy Federation.

Burrows, W.,1954. Text book of microbiology. W. B. Saunders Co., philadel- pia.

Canning, K. 2004.Wondrous whey.Dairy Field. 187(90:55-62.

Carls, P., 1978. Microbiology Food Fermentation. Cornell University of New York State.

Dahm,L. 2005. Smoothie Soiree. Diary Field. 188(9):81-87.

48

Davis, J.G, 1965. In: Cheese, Vol. I,J. and A. Churchill Ltd., London

Davis, J.G, 1968. Dairy products. Quality Control in the food industry. Volume 2- page 146. Edited by Herschoefer, M.S Academic Press London.

Dirar.H.A., 1976. Optimum temperature for the plate count of milk. Sudan J. Fs. Sci. Technology 8:55-60

Dirar.H.A., 1993. The Indigenous Fermented Food of Sudan In Cheese: Africa Food and nutrition. CAB. International. London.

DUT National Food Institute (2009). Cheese, whey, Myscost, 33% fidm. Department of Nutrition, Technical University of Denmark/

Dusterhoft, E.M. and Van Den Berge, 2004. Gouda Related Cheese In Ceese: Chemistry, Physics and Microbiology Volume2 Major Cheese Group, 3rd end, P.F. Fox, P.L,H. MeSweeney, T.M. Cogan and T.P. Guinee(eds.) Elsevier Academic press, Amsterdam, PP.103-140.

Elteyeb,G. D, 1986. The Cheese Industry and Under developmentin the White Nile. in Rural Development In White Nile Province, Sudan. United Nation University Press, Tokyo 150, Japan.

Elawad, F.A, 1987. Story of Raira Yoghart.Paper Presented at the UNESCO Regional Trainig Course on Fermented Food of the Arab World. Food Research Center, Shambat, Sudan, 1-15 Feb. 1987.

Elsheikh, A.N. 1997. Prroduction of Mudaffara cheese fromD Cow's and Goat's mik. M.Sc. University of khartoum, Sudan.

Fox, P.F, Timothy, M.G, and Mcsweeney, P.L.H ,2000. Fundamentals of cheese science an aspen publication. Aspen Publishers, In Gaithersburg, Maryland.

Frazier, W.C. and Westhoff, D.C, 1967. Food Microbiology. Mc. Graw-Hill Book Company, London.

Hall W. and J. Harper, 1959. Dairy Technology and Engineering. Avi publishing New York.

Hazen. C. 2005. Packing that protein punch. Food product Design. 15(4):32-55.

Henning, D.R; R.J. Baer, A.N. Hassan, R.Dave; 2006.Major advances in Concentrated and Dairy Milk Product, Cheese, and milk fat spreads. J. Dairy Sci. 89:1179-1188.

Ibrahim, A.A, 2004. Effect of Processing and Storage Condition on the Chemical Composition and Microbial Quality of White Soft Cheese. M.Sc. Thesis University of Khartoum, Sudan.

49

Ibrahim, A.E, 1970b. Chemical Preservation of Milk In Sudan. Sudan journal of food science and technology 2, 31-32.

Ibrahim, A.E, 1971. Studies on some Characteristies of Sudan White Cheese J, Vet. Sci. and Anim. Hab. 12(1):31-39.

International Dairy Federation (IDF), 1985. Milk and Milk Products. Method of Sampling (standard 50B). Brussel: Author.

Khateeb, H.A. 1997. In Attempt to Standardize the Manufacturing productive for Sudanese White Cheese (jibna Bayda). M.Sc. Thesis, University of Khartoum, Sudan.

Knopf, A.A,1976. The World of Cheese. Evan Jones, New York.

Kons, S.N 1972. Milk and Milk Products in Human Nutrition. Food and Agriculture Organization of the United Nation, Rome.

Kosikowski, F.V, 1982. Cheese and Fermented Milk Food 3rd edition F.V. kosikowski and Associates. New York.

Kosikowski, F.V, and V.V Mistry 1997. Cheese and Fermented Milk Food. Volume 1:origins and principles.3rd ed. Wesport. conn.

Kreger, M. and K urman-van-Rij, N. J. W. (Ed).1984. The yeasts a taxonomic study 3rd efn. Elsevier, amestrdam.

Lampert L.M, 1992. Modern Dairy Products Eurasia Publishing House (P) Let New Delhi.

Mahran, G.A.; Hammad, Y.A.; Nawal S. Ahmed; Saged, A.F and Abd El- Aziz, M. 1999. Manufacture of Ricotta Cheese from fortifier with skim milk powder using different acidulant. Egyotion J. Dairy Sci., 27:191.

Marshall, R.T. 1993. Standard Method for the Examination of Dairy product, 16th ed. American public Health Assn Washhington D.C.

Maubois, J.L and Kosikowski. F.V. 1987. Aking Ricotta Cheese by ultra filtration. J. Dairy Sci. 61:881-884.

MeBean, L.D. 2003. Emergin Health Benrfits of whey. National Dairy Council Dairy Council Digest, Volume 74(6).

Maubois, P. L. h., Ottogalli, G. and Fwx, P. F, 2004. Diversity of cheese Varieties: an overview, in Cheese; Chemistry, physics and Microbiology Vloume 2Major Cheese Group, 3rd edn, P.F.Fox, P.L. H. McSweeney, T. M.Cogan and T.P. Guinee(eds), Elsevier Academic Press, Amsterdam, pp.1-22.

50

Modler, H.W.and Emmons, D. B. 2001. The Use of Continouus Ricotta cheese Processing to reduce ingredient cost in futher processed cheese products. international Dairy Journal 11:517-523.

Morriss, H.A., Jezeski, J.J,a d Combos, W.B, 1954. The Use of Whute Mutants of penicillum Roquefort in cheese Making, J Dairy Sci. 37:711.

National Dairy Council, 2003. Health Enhancing Properties of Driry Ingredients. Dairy Council Digest. 73(2).

Osman, A. O, 1987a. The Technology of Sudanese Withe Cheese "Gibna Bayda". In: Bulletin of the Int. Dairy Federation, pp:1133-115.

Osman, A. O, 1987b. Mish Production- a Traditional Product Commercialized FAO Regional Seminar, Nairobi, Kenya, 2-7 March 1987.

Osman E .H .E, 2005.The Effect of Packaging on the Quality of Sudanese Withe Cheese. M.Sc. University of Science and Technology, Sudan Pak. J of Nutr. 1(3):123-136.

Pederson, C. S, 1979. In: Microbiology of Food Fermentation. 2nd ed., AVI Publishing Co., Connecticut, and USA.

Peterse, W. H. 1939. Cheses page 601. Dairy Science Miss, Expperiment Station Library, State College, Miss Chicago, edited by R.W. Gregory Copy right 1939 by J. B Lippin COH Company. professor Douglas Goff, dairy Science abd Technology Edcuation Unversity og Guelph, Canada.

Pizzilo, M, Claps; Cifunj, G. F.; Fedel, V and Rubion, R. 2005. Effect of Goat Breed on the Sensory, Chemical and Nutritional Characteristies of Ricotta Cheese Live Stock Production Science 94:33-40

Rossetti, L.; Fornasari, M. E.: Gatti, M.: Lazzi, C.: Neviani, E.: and Giraffa, G.(2008). Grana padano cheese whey starter: microbial composition and strain distribution. Int. J. Food Microbial., 127(1-2):169-171.

Sandine.; W.E and Elliker, P. R, 1970. Microbiology Induced Flavours and Fermented Foods: Flavvour in Fermented Dairy Products. Journal of Agriculture and Food Chemistry, 18:557-556.

SAS. 1982. SAS user' Guid: Statistics analysis system. Institute ine.Carry, North Carolina pp.3-13.

Scott, R. 1981. Cheese-Making Practice(2nd ed.) London: Elsevier Applied Science.

Scott, R. 1986. Cheese-Making Practice ,second edition Elsevier Applied Science publisher, London.

Scott, R. 1998. Cheese-Making Practice, Applied Science publisher, Ltd. London.

51

Shaw, M. B.1994. Modern Cheese Making: soft cheese in modern dairy technology, advanccea in milk products Vlume 2, edited by Robinson, R. K. Elsevier. Applied science publisher. London and New York.

USDA, 1978. IN Cheese Varieties and Description, revised ed., Handbook No. 54, United States Department of Agricultuer, Washington, DC.

USDEC, 2004. Products Definition, Composition, function. Reference Manual for U.S. Whey Lactose products. p 27-40.

Varnum, A. H. and Sutherland, J. P.(1994). Milk and M ilk Products. Chapman & Hall New York, NY. P159-189.

Walster, P.; Wouters, T. M., and Tom, J. G. (2006).Dairy Science and Technology: Second Edition. Taylor and Franeis Group, LLC.

Walter, H. E. and Hargrove, R.C, 1972. Cheese of the world. New York: Dover.

Walzem, R. L. 2004. Nutritional Properties of whey products. Reference Manual for U.S. Whey and Lactose products. section 6.1. USDEC. Arllington, VA. P53-58.

Wood, W. A., 1961. Fermentation of Carbohydrates and related Compounds. In the Bacteria Vol.21.C. Academic press, New York.

Zenb, M. C. 2003. A study of the Isolation and Identification of Lactic Acid Bacteria and Yeast From Raw Milk. M.Sc. Thesis. University of Khartoum Sudan.

http://en Wikipedia/ wiki/ Ricotta, 2008.

http:// www.fading ad. Com fading ad blog? p= 5123, 2001.

http:// www.foodsci. Uoguelph. Ca/cheese/section.2000.

http:// www.tarladal. Com/glossart-ricotta cheese-318i,2010.

http:// www.ehow.com about-4575931- history-ricotta-cheesehtm.2000.

http:// www. Amaltheiaa dairy. com/AD, 2005.

http://home cooking about. Com /es/ cheese information/a/ ricotta: htm 2009.

http://www.dairyforall.com/whey.php,2011.

http://www.wolframalpha.com/entities 2011.

52