1. food and drink

STUDIES ON PROCESSED CHEESE SPREAD
BASED ON SUDANESE CONVENTIONAL CHEESES
By
Rasha Tag Elsir Ibrahim Fazaa
B.Sc. Agric. (Honours)
University of Khartoum
1999
A Thesis Submitted in Partial Fulfillment of the Requirements for
M.Sc. of Science in Agriculture (Food Science and Technology)
Supervisor:
Prof. Abdelhalim Rahama Ahmed
Co-supervisor:
Dr. Hassan Ali Mudawi.
Food Science & Technology Department
Faculty of Agriculture, University of Khartoum
January - 2004
1
DEDICATION
This work is dedicated to
My
father,
mother
and
grandmother OmElHassan
To my brothers, Ibrahim,
Yassir and Faisal
To
my
sisters
Noon,
Leina and Bian
To
my
friends
and
colleagues
With love and respects
Rasha
2
3
Acknowledgement
From the very beginning to the end I thank Allah who provides
me with health and strength and through whom a number of relatives
and friends and many more than I can mention helped me throughout
this study.
I would like to express my sincere gratitude to my supervisor
Prof. Abdelhlaim Rahama for his valuable advice and directions
throughout the study. Also, I would like to express my sincere
gratitude to Dr. Hassan Mudawi, Dr. Mohammed Osman, Dr.
Abdelwahab Hassan, Dr. Gamaa AbdelGadir, Tech Elamin
Abdallah, Ustz. Ibtihag Awad and Eng. M.M. Elfanageeli for their
help and support.
Deepest gratitude and appreciations are also extended to Dr.
Mohammed Osman Mirgani, the Manager of Raira factory and the
Staff member.
Thanks are due to Dr. Isam Eldeen Hassan
Abdelmomen and Ustz Alaa Eddin Ahmed, Kuku Milk Factory, Ustz
Abood Ali Fait, King Abdelaziz City for Science and Technology,
Riyadh and Ustz Sami Mahgoub, Elmarai Company for Dairy Product
KSA., Riyadh for their help and encouragement.
Last but not least Iam greatly indebted to my uncle Abuobida
Taha, and my family for financing this study.
4
ABSTRACT
The effect of certain chemical emulsifiers and gum Arabic as a
natural emulsifier on quality of processed cheese spread was studied.
Processed cheese spread samples were prepared based on
conventional Sudanese cheese; namely white cheese, mozzarella
cheese and shedder cheese.
The results showed that the total solids, fat, ash and
phosphorous content of the processed cheese spread were significantly
(P ≤ 0.05) lower than the conventional market sample, while the total
protein, soluble protein and salt of developed cheese spread were
significantly (P ≤ 0.05) higher than the commercial one.
Processed cheese containing an emulsifier of 3% hydrous
trisodium orthophosphate (TSOP) was significantly (P ≤ 0.05)
superior in taste and after taste compared to other treatments as well as
commercial cheese. An insignificant (P ≤ 0.05) difference was also
observed in flavour, texture and overall preference among cheeses,
however, the processed cheese containing 2.5% unhydrous trisodium
orthrophosphate (TSOP) and 0.5% gum Arabic was significantly (P ≤
0.05) inferior in flavour, taste, texture, and overall preference
compared to other treatments as well as commercial sample. When
samples of processed cheese spread were stored in a refrigerator at
5
4ºC for 45 days and examined intervally (15 days) during storage for
changes in physico-chemicals attributes, significant (P ≤ 0.05)
decrease was observed in pH, total protein and total soluble protein,
against significant (P ≤ 0.05) increase in acidity, total solids, sodium
chloride and phosphorus content of samples.
It is worth mentioning that the pH, total protein and soluble
protein
of
processed
cheese
containing
disodium
hydrogen
orthrophosphate (DSHOP) and gum arabic showed significant (P ≤
0.05) decrease compared to samples containing no gum arabic.
On the other hand, addition of gum arabic to TSOP showed
significant (P ≤ 0.05) increase in pH, total solids, ash and phosphorus
content of the cheeses and significant (P ≤ 0.05) decrease in their total
protein, soluble protein, sodium chloride and acidity. It was concluded
that processed cheese containing 3% hydrous TSOP was found to
match acceptability of commercial cheese known to be patented for
confidential ingredients with respect to emulsifying agents
6
‫ﺑﺴﻢ اﷲ اﻟﺮﺣﻤﻦ اﻟﺮﺣﻴﻢ‬
‫ﺧﻼﺻﺔ اﻷﻃﺮوﺣﺔ‬
‫ﺗﻤﺖ دراﺳﺔ أﺛﺮ اﺳﺘﺨﺪام ﺑﻌﺾ اﻟﻤﺴﺘﺤﻠﺒﺎت اﻟﻜﻴﻤﻴﺎﺋﻴﺔ واﻟﺼﻤﻎ اﻟﻌﺮﺑﻲ آﻤﺴﺘﺤﻠﺐ‬
‫ﻃﺒﻴﻌﻲ ﻋﻠﻰ ﺟﻮدة اﻟﺠﺒﻦ اﻟﻤﻄﺒﻮخ اﻟﻘﺎﺑﻞ ﻟﻠ ّﺪهﻦ )‪.(Spread‬‬
‫ﺗ ﻢ ﺗﺤ ﻀﻴﺮ ﻋﻴﻨ ﺎت اﻟﺠ ﺒﻦ اﻟﻤﻄﺒ ﻮخ اﻟﻤ ﺼﻨﻊ ﺑﺎﺳ ﺘﺨﺪام ﻋﻴﻨ ﺎت ﻣ ﻦ اﻟﺠ ﺒﻦ اﻟﻤﻌﻬ ﻮد‬
‫ﺑﺎﻟﺴﻮدان )اﻟﺒﻴﻀﺎء ‪ ،‬ﻣﻮزرﻳﻼ واﻟ ﺸﺪر(‪ .‬أﻇﻬ ﺮت اﻟﻨﺘ ﺎﺋﺞ اﻧﺨﻔﺎﺿ ًﺎ ﻣﻌﻨﻮﻳ ًﺎ )‪ (P ≤ 0.05‬ﻓ ﻲ‬
‫ﻣﺤﺘﻮي اﻟﻤﻮاد اﻟﺼﻠﺒﺔ ‪ ،‬اﻟ ّﺪهﻦ ‪ ،‬اﻟﺮﻣﺎد واﻟﻔﺴﻔﻮر ﻓﻲ ﻋﻴﻨﺎت اﻟﺠ ﺒﻦ اﻟﻤﻄﺒ ﻮخ اﻟﻤ ﺼﻨﻊ ﻣﻘﺎرﻧ ﺔ‬
‫ﺑﺎﻟﻌﻴﻨﺔ اﻟﺘﺠﺎرﻳﺔ ﺑﻴﻨﻤﺎ آﺎن ﻣﺤﺘﻮي اﻟﺒﺮوﺗﻴﻦ اﻟﻜﻠﻲ ‪ ،‬اﻟﺒﺮوﺗﻴﻦ اﻟﺬاﺋﺐ واﻷﻣ ﻼح ﺑﺎﻟﻨ ﺴﺒﺔ ﻟﻌﻴﻨ ﺎت‬
‫اﻟﺠ ﺒﻦ اﻟﻤﻄﺒ ﻮخ اﻟﻤ ﺼﻨﻊ أﻋﻠ ﻰ ﻣﻌﻨﻮﻳ ًﺎ )‪ (P ≤ 0.05‬ﻣ ﻦ اﻟﻌﻴﻨ ﺔ اﻟﺘﺠﺎرﻳ ﺔ ‪ .‬ﻋﻴﻨ ﺎت اﻟﺠ ﺒﻦ‬
‫اﻟﻤﻄﺒ ﻮخ اﻟﻤﺤﺘﻮﻳ ﺔ ﻋﻠ ﻰ اﻟﻤ ﺴﺘﺤﻠﺐ ‪ %3‬ارﺛﻮﻓﻮﺳ ﻔﺎت ﺛﻼﺛﻴ ﺔ اﻟ ﺼﻮدﻳﻮم ”‪ “TSOP‬اﻟﻤ ﺎﺋﻲ‬
‫أﻇﻬﺮت ﺗﻤﻴﺰًا ﻣﻌﻨﻮﻳًﺎ )‪ (P ≤ 0.05‬ﻓﻲ اﻟﻄﻌ ﻢ وﺗ ﺬوق ﻣ ﺎ ﺑﻌ ﺪ اﻟﻄﻌ ﻢ ﻣﻘﺎرﻧ ﺔ ﺑﺒﻘﻴ ﺔ اﻟﻤﻌ ﺎﻣﻼت‬
‫واﻟﻌﻴﻨﺔ اﻟﺘﺠﺎرﻳﺔ‪ .‬آﺬﻟﻚ ﻓﻘﺪ أﻇﻬﺮت اﻟﻨﺘﺎﺋﺞ ﻋ ﺪم وﺟ ﻮد إﺧ ﺘﻼف ﻣﻌﻨ ﻮي )‪ (P ≤ 0.05‬ﺑﺎﻟﻨ ﺴﺒﺔ‬
‫ﻟﻠﻨﻜﻬ ﺔ ‪ ،‬اﻟﻘ ﻮام )إﺣ ﺴﺎس اﻟﻔ ﻢ( واﻟﻘﺒ ﻮل اﻟﻨﻬ ﺎﺋﻲ ﺑﻴﻨﻤ ﺎ آﺎﻧ ﺖ ﻋﻴﻨ ﺎت اﻟﺠ ﺒﻦ اﻟﻤ ﺼﻨﻊ اﻟﻤﺤﺘﻮﻳ ﺔ‬
‫ﻋﻠ ﻰ )‪ (2.5% DSHOP + 0.5GA‬اﻻ ﻣ ﺎﺋﻲ ﻣﺘﺪﻧﻴ ﺔ ﻣﻌﻨﻮﻳ ًﺎ )‪ (P ≤ 0.05‬ﻓ ﻲ اﻟﻨﻜﻬ ﺔ ‪،‬‬
‫اﻟﻄﻌ ﻢ ‪ ،‬اﻟﻘ ﻮام واﻟﻘﺒ ﻮل اﻟﻨﻬ ﺎﺋﻲ ﻣﻘﺎرﻧ ﺔ ﺑﺎﻟﻌﻴﻨ ﺔ اﻟﺘﺠﺎرﻳ ﺔ ‪ ،‬آ ﺬﻟﻚ ﻓ ﺈن ﻋﻴﻨ ﺎت اﻟﺠ ﺒﻦ اﻟﻤﻄﺒ ﻮخ‬
‫واﻟﻤﺨﺰن ﻋﻨﺪ درﺟ ﺔ ﺣ ﺮارة ‪ °4‬م وﻟﻤ ﺪة ‪ 45‬ﻳﻮﻣ ًﺎ واﻟﺘ ﻲ ﺗ ﻢ اﺧﺘﺒﺎره ﺎ دورﻳ ًﺎ آ ﻞ ‪ 15‬ﻳ ﻮم ﻗ ﺪ‬
‫أﻇﻬﺮت اﻧﺨﻔﺎﺿًﺎ ﻣﻌﻨﻮﻳًﺎ )‪ (P ≤ 0.05‬ﻓﻲ ﻗﻴﻢ اﻟﺮﻗﻢ اﻟﻬﻴﺪروﺟﻴﻨﻲ ‪ ،‬اﻟﺒﺮوﺗﻴﻦ اﻟﻜﻠﻲ واﻟﺒ ﺮوﺗﻴﻦ‬
‫اﻟ ﺬاﺋﺐ ﻣﻘﺎﺑ ﻞ زﻳ ﺎدة ﻣﻌﻨﻮﻳ ﺔ ﻓ ﻲ ﻣﺤﺘ ﻮي اﻟﺤﻤﻮﺿ ﺔ ‪ ،‬اﻟﻤ ﻮاد اﻟ ﺼﻠﺒﺔ ‪ ،‬آﻠﻮرﻳ ﺪ اﻟ ﺼﻮدﻳﻮم‬
‫واﻟﻔﺴﻔﻮر ﻟﻠﻌﻴﻨﺎت‪.‬‬
‫أﻇﻬﺮت ﻧﺘﺎﺋﺞ اﻟ ﺮﻗﻢ اﻟﻬﻴ ﺪروﺟﻴﻨﻲ ‪ ،‬اﻟﺒ ﺮوﺗﻴﻦ اﻟﻜﻠ ﻲ واﻟﺒ ﺮوﺗﻴﻦ اﻟﻜﻠ ﻲ اﻟ ﺬاﺋﺐ ﻟﻌﻴﻨ ﺎت‬
‫اﻟﺠ ﺒﻦ اﻟﻤﻄﺒ ﻮخ اﻟﻤ ﺼﻨﻊ واﻟﻤﺤﺘ ﻮي ﻋﻠ ﻰ اﻻرﺛﻮﻓﻮﺳ ﻔﺎت اﻟﻬﻴﺪروﺟﻴﻨﻴ ﻪ ﺛﻨﺎﺋﻴ ﺔ اﻟ ﺼﻮدﻳﻮم‬
‫‪7‬‬
‫واﻟﺼﻤﻎ اﻟﻌﺮﻳﻰ اﻧﺨﻔﺎﺿًﺎ ﻣﻌﻨﻮﻳًﺎ )‪ (P ≤ 0.05‬ﻣﻘﺎرﻧﺔ ﺑﺎﻟﻌﻴﻨ ﺔ اﻟﺨﺎﻟﻴ ﺔ ﻣ ﻦ اﻟ ﺼﻤﻎ‪ .‬ﻣ ﻦ ﻧﺎﺣﻴ ﺔ‬
‫أﺧﺮي ﻓﺈن إﺿﺎﻓﺔ اﻟﺼﻤﻎ اﻟﻌﺮﺑﻲ ﻟﻠـ"‪ "TSOP‬أﻇﻬﺮت زﻳﺎدة ﻣﻌﻨﻮﻳﺔ )‪ (P ≤ 0.05‬ﻓ ﻲ اﻟ ﺮﻗﻢ‬
‫اﻟﻬﻴﺪروﺟﻴﻨﻲ ‪ ،‬ﻣﺤﺘﻮي اﻟﻤﻮاد اﻟﺼﻠﺒﺔ ‪ ،‬اﻟﺮﻣﺎد واﻟﻔﺴﻔﻮر ﻟﻬﺬﻩ اﻷﺟﺒﺎن‪ .‬واﻧﺨﻔﺎﺿ ًﺎ ﻣﻌﻨﻮﻳ ًﺎ ) ‪P‬‬
‫‪ (≤ 0.05‬ﻓ ﻲ ﺑﺮوﺗﻴﻨﻬ ﺎ اﻟﻜﻠ ﻲ واﻟﺒ ﺮوﺗﻴﻦ اﻟ ﺬاﺋﺐ وزﻳ ﺎدة ﻣﻌﻨﻮﻳ ﺔ )‪ (P ≤ 0.05‬ﻟﻜﻠﻮرﻳ ﺪ‬
‫اﻟﺼﻮدﻳﻮم واﻟﺤﻤﻮﺿﺔ‪.‬‬
‫وﺧﻼﺻ ﺔ اﻟﻘ ﻮل أن ﻋﻴﻨ ﺔ اﻟﺠ ﺒﻦ اﻟﻤﻄﺒ ﻮخ اﻟﻤ ﺼّﻨﻊ ﺑﺈﺳ ﺘﺨﺪام )‪ (3% TSOP‬اﻟﻤ ﺎﺋﻲ‬
‫ﻳﺘﻮاﻓ ﻖ ﻣ ﻦ ﺣﻴ ﺚ ﻣﻌ ﺎﻳﻴﺮ اﻟﻘﺒ ﻮل ﻣ ﻊ اﻟﺠ ﺒﻦ اﻟﺘﺠ ﺎري وﻣ ﻦ ﺣﻴ ﺚ اﺳ ﺘﺨﺪام ‪ TSOP‬آﻤ ﺎدة‬
‫ﻣﺴﺘﺤﻠﺒﺔ ﻣﻮﺛﻮق ﺑﻬﺎ ﻣﻦ ﺿﻤﻦ اﻟﻤﻜﻮﻧﺎت اﻷﺳﺎﺳﻴﺔ‪.‬‬
‫‪8‬‬
LIST OF CONTENTS
Page
Dedication ………………………………………………………………………………………………
i
Acknowledgment ……………………………………………………………………………………
ii
Abstract ……………………………………………………………………………………………….…
iii
Arabic abstract ………………………………………………………………………………………..
v
List of contents ………………………………………………………………………………………
vii
List of tables …………………………………………………………………………………………
ix
List of figures …………………………………………………………………………………………
x
CHAPTER ONE: INTRODUCTION ………………………………………………………
1
CHAPTER TWO: LITERATURE REVIEW……………………………………………
3
2.1 Milk and dairy products………………………………………………………………………
3
2.1.1 Cheese…………………………………………………………………………………………
3
2.1.1.1. Classification of cheese………………………………………………………………
5
2.1.1.2. Cheese technology……………………………………………………………………
6
2.1.1.3. Chemistry of cheese formation……………………………………………………...
8
2.1.1.4. Chemistry of curdling………………………………………………………………….
8
2.1.1.5. Chemistry of stretching……………………………………………………………..
8
2.1.1.6. Processed cheeses……………………………………………………………………….
9
2.1.1.6.a. Chemistry of processed cheese…………………………………………………...
11
2.1.1.6.b. Salts as emulsifiers in processed cheese……………………………………….
11
2.1.1.6.c. Role of emulsifiers in processed cheese……………………………………….
13
2.1.1.6.d. Types of emulsifiers used in processed cheese……………………………..
13
2.1.1.6.e. Nutrients of processed cheese………………………………………………….…
18
2.1.1.6.f. Factors affecting quality of processed cheese………………………………
22
2.1.1.6.g. Physico-chemical quality defects of processed cheese……………………
26
2.1.1.6.h Effect of storage on processed cheeses…………………………………….…
27
CHAPTER THREE: MATERIALS AND METHODS……………………………..
28
3.1. Materials………………………………………………………………………………………..…
28
9
3.1.1. Food materials…………………………………………………………………………...…
28
3.1.2. Chemicals and reagents……………………………..……………………………………
28
3.2. Experimental methods………………………………………………………………………
3.2.1. Preparation of processed cheese spread to select types of emulsifies………
29
29
3.2.2. Preparation of processed cheese spread using different levels of
emulsifier ………………………………………………………
3.3. Analytical procedures……………………………………………………….…………………
30
30
3.3.1. Physicochemical attributes of samples……….……..…………………………
30
3.3.1.1. pH……………………………………………………………….……………………………
31
3.3.1.2. Total solids………………………………..………………………………………………
31
3.3.1.3. Titratable acidity…………………………………...……………………………………
31
3.3.1.4. Fat content…………………………………………………………………………………
32
3.3.1.5. Ash content…………………………..……………………………………………………
33
3.3.1.6. Phosphorus determination……………………………………………………………
33
3.3.1.7. Total protein………………………………………………………………………………
34
3.3.1.8. Soluble nitrogen…………………………………….……………………………………
35
3.3.1.9. Chloride (salt) ……………………………………………………………………………
35
3.4. Organoleptic quality of cheese………………………………..……………………………
37
3.5. Statistical analysis ……………………………………………………………………………...
37
CHAPTER FOUR: RESULTS AND DISCUSSIONS………...………………………
38
4.1. Effect of emulsifier on physio-chemical characteristics of processed cheese
38
4.2. Effect of storage on physical properties of processed cheese spread...…….……
39
4.3. Effect of storage on chemical properties of processed cheese spread...…...……
45
4.4. Effect of emulsifier on organoleptic properties of processed cheese spread…
57
CHAPTER FIVE: CONCLUSIONS AND RECOMMENDATIONS......………
69
5.1. Conclusions…………………………………………………………….…………………………
69
5.2. Recommendations…………………………………………..…………………………………
70
REFERENCES…………………………………………………….…………………………………
71
APPENDICES……..………………………………………….………………………………………
77
10
LIST OF TABLES
Table
1.
Page
Effect of type of emulsifier on physico-chemical characteristics of
39
processed cheese spread………………………………………………………………
2.
Changes in pH during storage of processed cheese spread. containing
41
different emulsifiers...…………………………………………………………….……
3.
Changes in total solids (%) of processed cheese spread during storage
45
4.
Changes in total protein (N × 6.38) of processed cheese spread during
46
storage.………………………………..……………………………………………….……
5.
Changes in fat level (%) of processed cheese spread during storage
50
6.
Changes in ash content (%) of processed cheese spread during storage
52
7.
Changes in phosphorus level (mg/100 g) of processed cheese spread
54
during storage.……………….…………………………………………………….……
8.
Changes in NaCl level (%) of processed cheese spread during storage
56
9.
Organoleptic quality of processed soft cheese spread containing
58
different emulsifiers.…………………………………………………………….……
10.
Organoleptic quality of processed mixed cheese spread containing
60
different emulsifiers.……..………………………………………………….……
11.
Organoleptic quality of processed soft mixed cheese spread containing
61
different emulsifiers.………..………………………………………………….……
12.
Organoleptic quality of processed cheese spread containing different
63
of emulsifiers.………………..…………………………………………….……
13.
Organoleptic quality of processed mixed cheese spread containing
64
different levels of hydrous emulsifiers.………………………………….…..…
14.
Organoleptic quality of processed mixed cheese spread containing
66
different levels of hydrous emulsifiers.…………………………………...……
15.
Organoleptic quality of processed cheese mixed spread containing
different levels and types of emulsifiers.………………………………………..
11
68
LIST OF FIGURES
Figure
Page
1.
Simplified procedure for the manufacture of various types of cheese
7
2.
Changes in titratable acidity (% lactic acid) of processed cheese
43
spread during storage………………………………………..…..……………………
3.
Changes in soluble protein of processed cheese spread during storage
12
48
CHAPTER ONE
INTRODUCTION
Mankind has known milk since old times. Cow milk was used
as food since 6000 BC. It is quick to ferment and become sour, when
temperature gets high and start separating the whey and curd is then
formed. Through this simple accidental occurrence that the cheese
industry evolved.
Cheese is one of nature's most interesting and versatile foods,
a staple of worldwide importance and use. Good cheese can be
produced from the milk of most mammals such as cow, sheep, goat,
buffalo and camel and can be preserved for many months.
As a rich source of protein and calcium, cheese has few
nutritional rivals. But, throughout the world, cheese craft and cheese
consuming habits, were dictated by geographic, economic and historic
conditions and consequently have differed radically. These differences
have made their impact on present – day cheese technology.
Processed cheese is made from natural ripened cheese. Cheese
of different age and types were blended together and processed into a
final product with pleasant flavour and smooth body and texture. The
basic aim of processing is to blend natural cheese, water and
emulsifying salts into a homogenous mixture and pasteurize to obtain
an end product which has sufficient fluidity for convenient packing
which possesses long keeping quality.
13
In Sudan, cheeses are consumed widely by the different
socioeconomic classes of Sudanese families. There are no available
data on either of methods of processing or the quantity produced of
cheese, which makes it difficult to estimate the amount of cheese
produced. Generally, cheese produced in Sudan are of two types
namely a soft white cheese (Gibna Beida) and a braided semi-hard
cheese "Mudaffara". Other types of cheese introduced by Sudanese
industry are mozzarella, which is a picklled cheese and a processed
cheese spread which no longer produced by the Sudanese industry.
The objective of this work is to study the effect of certain
chemical emulsifiers and gum arabic as a natural emulsifier on quality
of processed cheese spread based on Sudanese conventional cheeses.
14
CHAPTER TWO
LITERATURE REVIEW
2.1 Milk and dairy products:
Milk and dairy products are good sources of protein, calcium,
phosphorus, potassium and many trace minerals and vitamin A,
thiamin and riboflavin (Kons, 1972; Payne, 1993). Fresh liquid milk is
traditionally used in most of the developing countries and little may 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-life locally accepted products, rather than imitating dairy
products from temperate climates like fresh butter, cream and cheeses
which need expensive refrigeration (Payne, 1993).
2.1.1 Cheese:
Cheese is the generic name for a group of fermented milk –
based food products, produced in a great range of flavours and forms
15
throughout the world from humble beginnings i.e. simply as a means
of conserving milk constituents (Fox, 1993a).
Sandine and Elliker (1988) mentioned that there are more than
1000 cheese varieties and Walter and Hargrove (1983) described more
than 400 varieties and listed the names of a further 400, while
Burkhalter et al. (1986) classified 510 varieties of cheese. It is
commonly believed that cheese evolved in the "Fertile crescent"
between the Tigris and Euphrates, In Iraq, 8000 years ago (Knopf,
1976).
The first fermented dairy foods were produced by a fortuitous
combination of events which are initiated by the ability of a group of
bacteria, now known as the lactic acid bacteria, to grow in milk and to
produce enough acid to reduce the pH of milk to the isoelectric point
of the caseins, at which these proteins coagulate. Neither the lactic
acid bacteria nor the caseins were designed for this function (Fox,
1993a).
Lampert (1992) defined cheese as the product made from the
curd obtained from whole, partially skimmed or skimmed milk of
animals with or without added cream by coagulating the casein with
rennet, lactic acid or other suitable enzyme or acid, and with or
without further treatments of the separated curd by heat or pressure, or
by means of ripening ferments, special molds or seasoning. The same
16
author stated that, in the United States, the name cheese is un qualified
and is understood to mean cheddar cheese.
2.1.1.1. Classification of cheese:
Classification of cheese is very complicated, due to the great
range of cheese varieties. Many different methods 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, white
soft cheese) and soft cheese (cream, cottage). It can also be classified
according to manner of ripening, into cheese of bacterial ripening,
mold ripening, surface micro-organisms and unripened cheese (Morris
et al, 1945)
On the other hand, some of these cheeses are subdivided into
sub-classes according to many factors; such as moisture fat and the
method of ripening (Knopf, 1976). Lampert (1992) reported that there
are eighteen kinds of cheese typical of the different processes by
which they are made namely, Brick, Camembert, Cheddar, Cottage,
Cream, Edam, Couda, Hand, Limburger, Neufchatel, Parmesan,
Provolone, Romano, Roque fort, Sapsago, Swiss, Trappist and whey
cheese.
Shaw (1994) reported that soft cheese can be classified into soft
un-ripened and soft ripened, or into semi soft cheese and other
17
soft/semi soft cheese. The other soft/semi soft cheese is subdivided
into whey cheese (Ricotta), processed cheese (blocks, food and
spreads) and cheese substitute (Spread).
2.1.1.2. Cheese technology:
The basic technology for the manufacture of all types of cheese
is similar (Figure 1). Relatively small changes, 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 the 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 forms the network of curd within which the
fat and water are held (Lampert, 1992).
Shaw (1994) reported that the manufacture of cheese is
basically a means 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.
18
Cheese technology
Milk
Add starter
Incubate
Add recent
Acid set
Cut
Ripen
Drain
Scald
Pack
Stir
Ripened soft (Camembert)
Drain
Salt
Pack
Texture crud
Unripened soft (Ricotta)
Milk
Salt
Note: Stage in parentheses are not involved in the
manufacture of some varieties. Manufacture may
involve some light cutting and scalding.
Hoop
Press
Bacteria
Pack
Smear ripened semisoft e.g. munster
Internal mould
Pack
Mould ripened semihard e.g. roquefort
Bacteria
Pack
Bacteria ripened hard and
semi-hard e.g. Cheddar
Fig. 1. A Diagram of simplified procedure for the manufacture of various
types of cheese.
19
2.1.1.3. Chemistry of cheese formation:
Conversion of milk from a fluid to a gel (Coagulation) is a basis
step common to all types of cheese. Gel formation is a consequence of
protein destabilization and may be brought about either by acid
proteinases such as chymosin, the active component of rennet,
quiescent, acidified to pH value close to the isoelectric point of the
proteins or by a combination of acidification and heating (Varnam and
Sutherland, 1994).
2.1.1.4. Chemistry of curdling:
The casein complex in milk has been shown to comprise four
moieties α, β, K, γ and it is the K Casein, which exerts stabilising
influence against coagulation. The rennet enzyme, chymosin, cleaves
the phenylalanine methionine bond (105-106) in the K-casein
molecule which effectively destabilizes the casein complex. It is a two
stage process, the first being enzymic:
K – casein
Enzyme
para – K – casein + macropeptide
and the second, non-enzyme stage which occurs concurrently:
Para–K–casein
Ca++
pH 6.0-6.4
di calcium para–K–casein (Shaw, 1994).
2.1.1.5. Chemistry of stretching:
The chemistry of stretching operation involves conversion by
lactic acid, of the di-calcium para caseinate, produced as a result of
20
rennet action to mono-calcium para caseinate which, when held to
54ºC or higher becomes smooth pliable, stringy and retains fat;
pH 6.2
Calcium caseinate + chymosin
dicalcium para caseinate
dicalcium para caseinate + lactic acid
monocalcium paracaseinate + calcium lactate (Shaw, 1994).
2.1.1.6. Processed cheeses:
Processed cheeses are characterized essentially by composition,
water content and consistency; according to these criteria three main
groups may be distinguished as processed cheese blocks, Processed
cheese foods and Processed cheese spreads (Kosikowski, 1982).
Processed cheeses are manufactured by blending and heating
one or more base cheese with a sutitable emulsifying salt until a
homogeneous mass results. Processed cheese spreads may also
contain other dairy ingredients, such as skim – milk, cream butter and
whey powder. Many value added spreads are available containing
such additives as shrimp, pepper, horseradish, nuts, mushroom, garlic
and herbs (Shaw, 1994).
Caric and Kalab (1993) found that the processed cheese spreads
are made by selecting suitable cheese according to age, flavour, body
and texture. Proper selection of natural cheese is of the utmost
importance for the successful production of processed cheese. Meyer
(1973) concluded that the computation of the ingredients is conducted
21
on the basis of established fat and dry matter contents of the natural
cheese components.
The operation of blending the ingredients is strongly influenced
by the desired characteristics of the final products. Grinding (milling)
is an operation which enable better contact between emulsifying agent
and blend ingredients during processing. Addition of emulsifying
agent is the last step in preparing the blend for processing (Caric and
Kalab, 1993).
Thomas (1977) reported that, the processing of cheese means
heat treatment of the blend in a kettle at 70 – 85ºC for 5 – 15 min is
dependent on the product being made. Heating can be indirect, or
direct by steam. After cooling, the blend is discharged either by tilting
the processor or by aseptic pumping to packaging machine (Meyer,
1973). Wwhen continuously processed, the blends are sterilized at
130–140ºC for 2 to 3 seconds in a battery of stainless steel tubes
(Kosikowski, 1982). Zimmermann (1982) Patented a continuous
process for simultaneous melting, homogenization and sterilization in
processed cheese production without the application of pressure.
A Japanese patent (Hayashi et al., 1982) described a method for
the post – processing heat treatment (to 100ºC) of packed processed
cheese, produced in the usual ways. Processed cheese is usually
packed and warapped in lacquered foil, tubes cups, cans, card board or
plastic, cartons and occasionally in glass jars. A recent development is
22
the continuous formation, slicing and packing of the cheese slices,
suitable for sandwiches. The final product should be stored at
temperatures below 10ºC (Caric and Kalab, 1993).
2.1.1.6.a. Chemistry of processed cheese:
The difficulties that occur with processed cheese are directly
related to the natural cheese used as raw material. Natural cheese like
other biological substances is a complicated biological and biochemical
system which cannot be regulated (Meyer, 1973). In turning natural
cheese into processed cheese one of the most important aims is to
achieve a completely stable emulsion. When cheese itself is heated it
does not become fluid, but melts into a gummy mass, and fat and
water are separated. In this way cheese breaks down into its three
main constituent parts. The process is explained as follows: calcium
caseinate undergoes denaturation as a result of heat. Furthermore, salt
and hydrogen bridging bonds are destroyed and the secondary and
tertiary structures of casein are dissolved. As a consequence, fat and
water emerge from the cavities which have been broken up (Bonell,
1970). On the other hand it was reported that when the same cheese is
heated after adding an emulsifying salt, this phenomenon does not
occur (Meyer, 1973).
2.1.1.6.b. Salts as emulsifiers in processed cheese:
In the manufacture of processed cheese, certain salts are used
for the purpose of preventing the separation of fat from the cheese,
23
and at the same time, giving the finished product the desired body and
texture. such salts are known as emulsifiers (Templeton and Sommer,
1936).
Research on emulsifying salts and their role in cheese
processing became quite extensive, as processed cheese products
gained consumer popularty in the mid-thirties (Scharpf, 1971). After a
comprehensive study of salts in processed cheese, emulsifying salt
combines an alkaline monovalent cation with a tri-or quadrivalent
anion. Another old suggestion was made that the hydroxyl groups in
various organic salts directly influence the emulsifying action of the
salt (Taub, 1933).
Habicht (1934) suggested that a partial saponification occurs
between the cation of the salt and the fatty acid and that phosphate
anion combines with casein in such away that there is a film of protein
around each fat globule to prevent escape of fat Palmer and Sly (1944)
described processed cheese as an "oil in water suspension, stabilized
by an emulsion sol consisting of hydrated casein and the emulsifying
salt". Holtstroff et al. (1951) emphasized that satisfactory emulsifiers
must have poly valent anions, for alkaline solutions, and precipitate or
sequester calcium. As the emulsifying agents (milling salts) provide a
uniform structure for the processed cheese, during the melting
process, they are considered of major importance in processed
production (Caric and Kalab, 1993).
24
2.1.1.6.c. Role of emulsifiers in processed cheese:
The essential role of emulsifying agents in the manufacture of
processed cheese is to supplement the emulsifying capacity of cheese
protein. This is accomplished by removing calcium from the protein
system,
peptizingn,
solublizing
and
dispersing
the
proteins,
emulsifying the fat and stabilizing the proteins, emulsifying the fat
and stabilizing the emulsion, controlling pH and stabilizing it and
forming an appropriate structure of the product after cooling (Shimp,
1985). The same author stated that the ability to sequester calcium is
one of the most important function of the emulsifying agents. When
calcium in the Ca paracaseinate complex of natural cheese is removed
during processing by the ion-exchange, with melting salts. Insoluble
paracaseinate is solubilized, usually as Na–caseinate (Caric, 1991).
2.1.1.6.d. Types of emulsifiers used in processed cheese:
• Phosphate emulsifiers:
The largest single use for phosphate in cheese processing is in
the manufacture of pasteurized processed cheese, because of their
versatility and low cost, (Scharpf, 1971). Types of phosphate
emulsifying salts used in processed cheese are;
a) Monophosphates (orthophosphate)
Caric and Kalab (1993) reported that the mono or
orthophosphoric acid forms are in three different types of sodium
25
salts; the mono sodium dihydrogen phosphate (NaH2PO4; E339i), the
disodium hydrogen phosphate (Na2HPO4; E339ii), and the trisodim
orthophosphate (Na3PO4; E339iii). The most commonly used
phosphate emulsifiers for processed cheese have been the alkaline
salts of orthophosphoric acid (Scharpf, 1971).
Sodium orthophosphate was used in commercial manufacture in
the United States (Garstin, 1921). A slight variation in the use of these
phosphates was subsequently patented by Eldredge (1921), Kaufman
and Kaufman (1928), Classey et al. (1935), Siegwart (1936), Palmer
(1935) and others. These patents covered the mono-through trisubstituted sodium slats of orthophosphoric acid and mixture of them
(Scharpf, 1971).
Patent of Mc Collough (1968) covers the composition and use
in cheese of a carefully prepared crystalline di-sodium phosphate
dihydrate which is substantially free of pyrophosphate. The use of tri
sodium orthophosphate in processed cheese has been, also patented by
Kraft (1938), and Parsons (1941), although the great alkaline of this
generally precludes its use as a single emulsifier, small amounts of tri
sodium orthophosphates are used most frequently in combination with
other emulsifiers (i.e. di sodium orthophosphates) when it is desired to
raise the pH of highly acidic cheese stocks.
26
b) Condensed poly phosphates:
There are three types of condensed poly phosphates namely,
poly phosphates, meta phosphates-ring (e.g. Na3P3O4 and Na4P4O2)
and condensed phosphate rings with chains and branches (Caric and
Kalab, 1993). Condensed phosphates have been used with
considerable success in Europe in the manufacture of processed
cheese. Sodium pyrophosphates have been used alone (Benckiser and
Draisbach, 1931b; Draisbach, 1939) and in combination with alkali
orthophosphates (Bohac, 1966), citric, tartaric and adipic acid
(Benckiser and Draisbach, 1931b).
The next higher homolog tripoly phosphate has been suggested
as a possible emulsifier for processed cheese manufacture (Hoermann
and Firgau, 1937; Knapsack-Griesheim, 1958). The preparation and
use of emulsifier mixtures containing high- and low- temperature
modifications of sodium tripoly phosphate are described by Knapsach
– Griesheim (1958).
The manufacture and use of the higher condensed phosphates in
processed cheese have been pioneered by German workers, the well –
known German Joha process is a patented method based on the use of
polymeric phosphate emulsifying salts (Benckiser, 1955). French
(Benckiser and Draisbach 1931a) and U.S. patents (Draisbach, 1933)
covered generically the use of sodium metaphosphates, wherein
solutions of this compound are added to finely ground cheese at
27
temperatures below 100ºC. The emulsifying properties of a novel
composition based on mixtures of insoluble alkali condensed
phosphates and soluble alkali-meta, calcium and magnesium salts
have been demonstrated (Ronald, 1951). In this system long-chain
crystalline poly phosphates (Kurrol's or Maddrell's salts) are
solubilized in situ by the presence of the soluble alkali-metal salts. In
a mixture containing both Maddrell's and Kurrol's salts in which either
amounts to 20 – 80% of the total weight of both, no additional
solubilizing salt is needed because they will mutually solubilize each
other (Scharpf, 1971).
All condensed polyphosphates hydrolyse in aqueous solutions;
hydrolysis also occurs during melting and afterwards. The degradation
of polyphosphate increases with the duration of processing,
irrespective of the rate of stirring and the temperature used (Caric and
Kalab, 1993). About 50% of the polyphosphates added are hydrolysed
during the melting procedure and the remainder is hydrolysed after 7
to 10 weeks of storage (Roesler, 1966).
• Citrate emulsifiers:
Citric acid is a tribasic acid and forms three sets of sodium salts,
monosodium citrate (NaH2C6H5O7), di sodium citrate (Na2HC6H5O7)
and tri sodium citrate (Na3C6H5O7). From many citrates available,
only tri sodium citrate alone or in combination with other salts, is used
as an emulsifying agent in processed cheese production, although
28
citric acid may be used to correct the pH of the cheese. Potassium
citrate imparts a bitter taste to the finished product (Caric and Kalab,
1993), also monosodium citrate was reported to cause emulsion
breakdown during cheese melting, because of its high acidity, while
disodium citrate leads to water separation during solidification of the
melt also because of high acidity (Thomas, 1977).
Addition of citrate, orthophosphate, pyrophosphate all at 3% to
curds obtained from concentrated milk, led to products with poor
sensory attributes, although citrate at 2% gave satisfactory results
(Caric and Kalab, 1993).
• Natural emulsifiers:
Different types of natural emulsifiers could be used in
processed cheese manufacture such as yolk, guar gum and gum arabic.
The commercial exploitation of gum arabic for stabilizing
emulsions has been established over many years, but the sterochemical basis for this application was only elucidated in 1980. The
emulsifying properties of gum arabic are related to its nitrogen
(protein) content (Dickinson et al., 1988). Recently work has shown
the emulsifying properties of gum. The arabino galactan protein
complex (AGP) contains only about half the protein associated with
gum arabic, but is nevertheless responsible for most of its emulsifying
properties (Randall et al., 1989).
29
Dickinson et al. (1988) studied the emulsifying behaviour of
gum arabic and concluded that there is a strong correlation between
the proportion of protein in the gum and its surface properties at the
water interface (emulsifying property).
The relatively low protein content of gum arabic requires high
concentration of gum in most emulsification systems (Imeson, 1997).
2.1.1.6.e. Nutrients of processed cheese:
Cheese is a food of high nutritive value, rich in protein, fat and
minerals, such as calcium and phosphorus. Various cheeses differ
considerably in their composition and therefore in their energy values
(Atherton et al., 1977).
• Fat:
Scott (1998) reported that cheese from whole milk is known to
contain most of the fatty acids (saturated or unsaturated), but the extra
unsaturated fats in the milk quickly cause rancidity problem unless
antioxidants are added immediately as the milk is produced.
Fresh cheese have an absolute fat content of up to 12%,
while
ripened
one
Consumers generally
contains
between
and
30 %
fat.
prefer high fat cheese, because a high fat
content contributes significantly
Renner (1993) stated
20
to
flavour
quality. Moreover,
that the typical aroma of some types of
cheese, for instance cheddar, developed only when the fat in
30
dry matter content is at least 40 – 50%, because the aroma is due
mainly to the break down products of fat formed during cheese
ripening. However, the production of low- fat cheese offers great
opportunities to market new products which are perceived as "healthy"
due to their low fat content. On the other hand, Jamesson (1990) found
that low-fat cheese are organoleptically acceptable than high-fat one.
The concentration of free fatty acids in cheese is usually 15g/kg. There is a close link between the content of free volatile fatty
acids in a number of cheese varieties and their flavour (Renner, 1993).
• Protein:
The nutritional importance of cheese arises from its content of
biological proteins. The protein content of different varieties of cheese
varies between 20 and 30%. Within any one type of cheese, the
protein content varies inversely with the fat content (Renner, 1993).
The protein content of food for man must also contain those
amino acids essential for nutrition. Animal proteins are more likely to
contain these essential amino acids than vegetable proteins and
therefore, have a better biological value (Scott, 1998). Cheese can
contribute significantly to the supply of essential amino acids. Renner
(1993) reported that, when the amino acid composition of milk and
cheese proteins are compared to the reference protein, which indicates
the ideal concentration of essential amino acids in a dietary protein, it
31
can be seen that cheese protein meets the requirements to the same
extent as milk protein except those for methionine plus cystine.
• Minerals:
a) Phosphorus and calcium:
The phosphorus and calcium contents of cheese are important
as those of milk (Scott, 1998). Since hundred grammes of soft cheese
will supply 30 – 40% of the daily calcium requirement and 12 – 20%
of the daily phosphorus requirement then hundred gram of a hard
cheese will meet the daily calcium requirement completely, and
contribute 40 – 50% of the phosphorus requirement (Renner, 1993).
In the USA, the serving of cheese is said to contribute on
average about 25% and up to 42% of the recommended dietary
allowance of calcium (Tunick, 1987). It should be noted that where
one variety of cheese is made with different fat contents, the higher fat
cheese contains less calcium and phosphorus. The nutrient density for
calcium in different types of cheese is 1.3–7.0 and for phosphorus
2.0–5.7 (Renner, 1993).
The
physicochemical
changes
occurring
during
cheese
manufacture and ripening, do not affect calcium bioavailability,
calcium absorption rate from cheddar cheese averaged 76.8%
(Buchowski, and Miller, 1990) while the phosphorus absorption by
human subjects was 64% from milk and 62% from cheese (Renner,
1993).
32
The ratio of calcium to phosphorus in cheese was also thought
to be desirable nutritionally (Andlow, 1977).
b) Sodium:
The wide range of the sodium contents is due to the different
amounts of sodium chloride added to cheese; the following are
average values for the NaCl content (%) of different cheeses, namely
fresh cheese 0.1, processed cheese 2.5, feta 3.7, Camembert 2.4;
Edam/Gouda 1.9; Mozzarella 1.6 and Cheddar 1.7 (Kindstedt and
Kosikowski, 1984).
A minimum intake of less than 500 mg and maximum of four
gram sodium per caput per day was suggested by the German
Nutrition Association (Renner, 1993). Cheese contributes to the total
sodium intake only to small extent, even in countries with a high
cheese consumption, e.g. 0.12 – 0.23 gram sodium per caput per day
in Australia, Switzerland and the United Kingdom (Edwards et al.,
1989). Although cheese contributes only about 5% to the total sodium
intake, the manufacture of low- sodium cheese is recommended by
using a brine containing potassium or magnesium chloride (Renner,
1993).
Attempts to produce a low- sodium cheese by simply reducing
the quantity of sodium chloride added during manufacture, have been
unsuccessful and result in a cheese of poor body which is prone to
microbiological spoilage during ripening.
33
Equally, attempts to replace sodium chloride with "salt
substitutes", such as KCl have met limited success. Suitable low Na+
cheese has been made by blending a cheese base made from directly
acidified milk (tri-acetyl glycerol cheese) with a ripened cheese of
normal Na+ content (Varnam and Sutherland, 1994).
2.1.1.6.f. Factors affecting quality of processed cheese:
• Types of natural cheese used:
Raw material for processing of processed cheese is used to refer
exclusively to rennet cheese i.e. the hard, soft and sliceable cheese.
Beside the usual analytical variables, such as pH value, dry matter and
food content, every raw material for processing is characterized above
all by a certain level of protein and by the nature of its structure. The
absolute protein content includes all existing, nitrogen containing
components, the relative casein content describes the level of protein
available for the formation of a stable protein structure. Due to long
time experience in practice it was confirmed that the intact casein
content level in the final product must not fall below 12% (Anis and
Ernstrom, 1984). Beside these chemical influence, cheese structure
can be changed through mechanical and thermal treatment.
A young cheese is stable against thermal and mechanical
treatment therefore processed cheese with long, sliceable and elastic
structure is achieved when young raw materials are taken for the
production of processed cheese (Almarai, 2003).
34
Under heavy mechanical and thermal forces the long structure
of processed cheese can be shortened without any chemical
degradation. If the process goes beyond the optimum creaming state
the originally slightly viscous system turns to a highly viscous
pudding – like solid. The specialist refers to this state of affairs as over
creaming (Anis and Ernstrom, 1984).
The production of the different processed cheese types
(sliceable, spreadable, block processed cheese, toasting slices …etc)
requires the correct selection and composition of raw materials to be
processed. Abou Donia et al., (1983) reported that in some countries,
processed cheese is manufactured from only one variety of cheese of
different degrees of maturity e.g. processed cheddar cheese in UK and
Australian, cheddar, Gruyere and Mozzarella in the USA and Canada.
More frequently, processed cheeses are produced from a mix of
various natural cheese types. This results in easier processing and a
better flavour balance. Since it is possible to correct certain physical
properties, some defective cheese can be used in processed cheese
manufacture. Natural cheeses with microbial defects should not be
selected for processing. However, proper selection of good quality
natural cheese is not by itself a guarantee that the processed cheese
will be of the high quality desired (Fox, 1993b; Kosikowski, 1982).
35
• Emulsifiers:
The most important ingredients in processed cheese are the
emulsifying salts and natural cheeses, with considerable work having
been reported on the effect of emulsifying salts on the physical and
chemical changes, keeping quality and sensory evaluation of
processed cheese (Thomas et al., 1980).
Dickinson (1999) found that the stability and rheology of
emulsion made with sodium caseinate depend on two factors; the
structure and composition of the adsorbed protein layer at the oil –
water interface, and the state of self – assembly – and aggregation of
the protein in the aqueous phase.
Mayer (2001) describe the bitterness in processed cheese
probably, because of an overdose of a specific emulsifying agent (of
light phosphorus content).
• Milk addition:
In addition to natural cheeses, various other dairy products for
prepared of processed cheese spreads used which are classified into:
a) Skim milk powder:
Skim milk powder improves the spreadability and stability of
processed cheese, but if used in quantities exceeding 12% of the total
mass, it may adversely affect the consistency or may remain
undissolved. However, skim milk powder may be reconstituted first,
36
its casein precipitated by citric acid or proteolytic enzymes and the
resulting crud added to the blend (Thomas, 1977).
b) Milk fat ingredients:
Caric and Kalab (1987) mentioned that the milk fat ingredients
used to adjust the fat content of processed cheese to the desired level
must be of high quality and be free from off-flavours.
c) Pre-cooked cheese:
Another dairy – based product commonly used as an ingredient
in processed cheese spreads is pre-cooked cheese or "rework", which
intensifies the creaming properties of the blend (Berger et al., 1989;
Caric, 1991).
• Non-Dairy ingredients:
In certain countries non diary ingredients used in processed
cheese dried vegetables, garlic and caraway or mayonnaise in certain
countries, some sweet non-dairy ingredients are used in processed
cheese as non-dairy additives e.g. fruit syrup cocoa, vanilla and coffee
extract. Some attempts have been made to incorporate cotton seed
flour (Caric, 1991).
All non-dairy ingredients intended for blending (muscle foods,
vegetables, spices) must be sterile and of the highest quality, with
typical flavour. The quantities of these must be properly prescribed for
blending (Caric and Kalab, 1993).
37
Also, for bacterial growth inhibition, some preservaties are
used, such as sorbic acid, sorbic acid salts, boric acid and natural
compound such as niacin. In addition to some antioxidant such as
tocopherols, natural or artificial, butyl hydroxy toluene and bytyl
hydroxy anisole (Caric, 1991).
2.1.1.6.g. Physico-chemical quality defects of processed cheese:
Many defects of natural cheese are carried over to the processed
offspring but a number of defects are completely remedied by
processing. But in natural cheese with putrid, unclean and chemical
flavours should not be used. (Kosikowski, 1982).
Fox (1993b) defined a good processed cheese as cheese that
should have a smooth, homogenous structure, uniform colour and free
from fermentation gas holes. The same author stated that various
factors can cause physico-chemical defects. The most important
factors are the unsuitable blend, arising from the use of poor-quality or
contaminated natural cheese, a bad relationship of blend components,
improper protein/fat ratio in cheese, irregular quality or quantity of
emulsifying agent, incorrect values of pH, moisture content, or
quantity of reworked cheese and inadequate processing, e.g.
unsuitable time, temperature regimens, inadequate agitation, improper
cooling and unsuitable storage condition.
38
2.1.1.6.h. Effect of storage on processed cheeses:
The changes that occurred in the processed cheese during
storage depend on the composition and properties of the fresh product
and the storage conditions.
Fresh samples from different brands of processed cheese were
stored by Hamed et al. (1997) at room temperature for 4 months, and
analyzed for moisture, fat, salt, total and soluble protein contents,
inorganic phosphorus, pH and organoleptic properties. During storage
moisture, fat, total and soluble protein and pH slightly decreased,
while sodium chloride increased. The scores for flavour, texture,
colour and general appearance of fresh and stored processed cheese
showed a general tendency to decrease throughout the storage period.
Shehata et al. (1982) reported that the total scores of the organoleptic
properties of processed cheese decreased with advanced storage.
Storage at room temperature for 4 months of market processed
cheeses had a slight effect on its chemical composition, however
storage has a more pronounced effect on the quality and rheological
properties of processed cheeses (Hamed et al. 1997).
Singh and Kanawjia (1989) reported that the sensory
characteristis of flavour and texture of processed cheese decreased
during storage at 37C° but biochemical changes in pH, soluble
nitrogen and titratable acidity increased at the same storage
temperature.
39
CHAPTER THREE
MATERIALS AND METHODS
3.1. Materials:
3.1.1. Food materials:
Three types of Sudanese cheese (cheddar cheese, white cheese
and mozzarella cheese) were obtained from Butana Factory,
Khartoum North. Five types of emulsifiers (anhydrous disodium
hydrogen ortho-phosphate, hydrous disodium hydrogen ortho
phosphate, hydrous trisodium ortho-phosphate, Sodium dihydrogen
ortho-phosphate and trisodium citrate) were obtained from the Food
Research Centre, Shambat, and The Department of Food Science and
Technology, Faculty of Agriculture, University of Khartoum.
A preservative (potassium sorbate) was obtained from Crystal
Industrial Co. LTD, an antioxidant (Butyl hydroxy toluene) was
obtained from Elsheikh Mustafa Alamin Group Companies and gum
arabic was obtained from the Gum Arabic Company.
3.1.2. Chemicals and reagents:
All chemicals and reagents used were of technical grade
donated by the Food Research Centres store, Shambat and the
Department of Food Science and Technology, Faculty of Agriculture,
University of Khartoum.
40
3.2. Experimental methods:
3.2.1. Preparation of processed cheese spread to select types of
emulsifiers:
For the selection of the best emulsifiers, the preparation of the
processed cheese spread was done according to Meyer, (1973) with
some modification. Processed cheese was prepared by addition of the
five emulsifiers mentioned earlier to white cheese alone and to a
mixture of white cheese, cheddar cheese and mozzarella cheese using
stainless kettle.
One hundred grammes of blended white cheese (24.3% fat,
52.73%
moisture),
3%
of
anhydrous
disodium
hydrogen
orthophosphate and 9.68% of butter were mixed thoroughly by "Billy
bar blender HR 1340" for 2 minutes under direct water bath steam, 6%
of water were then added, continous for 8 minutes. Other four
experiments were carried out following the same procedure using
hydrous
disodium
orthophosphate,
hydrous
tri-sodium
orthophosphate, hydrous sodium dihydrogen orthophosphate and
anhydrous
tri-sodium
citrate,
instead
of
disodium
hydrogen
orthophosphate as emulsifiers. Manual packing was followed for all
samples using 250gm glass containers. Packed materials were then
examined for initial acceptability tests.
Also, five experiments were carried out following the same
procedure, using a mixture of blends (of cheddar cheese containing
41
33.7% fat, 32.1% moisture, white cheese and mozzarella cheese of
22.3% fat, 45.95% moisture, instead of white cheese alone. The three
most acceptable samples were then selected in addition to the above
two samples. The five selected samples were then subjected to
acceptability tests for screening of the best emulsifiers to be used in
processed cheese preparation.
3.2.2. Preparation of processed cheese spread using different
levels of emulsifier:
Five levels (2% emulsifier, 2% emulsifier + 1% gum arabic,
2.5% emulsifier, 2.5% emulsifier + 0.5 gum arabic and 3% emulsifier)
of the two best emulsifiers, selected from earlier acceptability test (disodium hydrogen orthophosphate anhydrous and tri disodium ortho
phosphate dodecahydrate) were used as optimum emulsifier for
production of processed cheese spread following the same procedure
mentioned earlier.
These four types of formulations are stored for 45 days under
refrigeration (temperature 4°C). The analysis was carried out at 0.0,
15, 30 and 45 days intervals of storage and they were analyzed for
physical, chemical and organoleptic quality.
42
3.3. Analytical procedures:
3.3.1. Physicochemical attributes of samples
The physiochemical properties of cheese samples were assessed
by the following procedures.
3.3.1.1. pH:
The pH was determined in 10% solution of sample as described
by Newlander and Atherton method (1964) using a glass electrode pH
meter (KARL KOIB, D-6072 Dreieich) at room temperature (38ºC).
3.3.1.2. Total solids:
The total solids content was determined according to the AOAC
method (1990). Two grammes of cheese were placed into a clean
dried flat-bottom aluminum dish, heated in a steam bath for 10-15
minutes, and transferred to an air oven for 3 hours at 103 + 2ºC. After
drying, the dishes were placed in a desiccator to cool and weighed.
Drying and weighing were repeated several times until constant
weight was obtained.
The total solids content was calculated from the following equation:
% Total solids =
w1
×100
w2
where:
w1 = weight of sample after drying.
W2 = weight of sample before drying.
43
3.3.1.3. Titratable acidity:
The acidity of cheese was determined according to the AOAC
method (1990). Ten grammes of cheese were weighed and placed in a
conical flask and distilled water at 40ºC was added until the volume in
the flask was 105 ml. The sample was then vigorously agitated and
filtered. Twenty five milliliters of the filtrate were pipetted into a
porcelain dish and 5 drops of phenolphthalein indicator were added.
The sample was titrated against 0.1N NaOH till a faint pink colour
that lasted for at least 30 seconds was obtained. The acidity was
calculated from the following equation:
% Acidity =
T×4
w
Where:
T = titre value
W = weight of sample.
3.3.1.4. Fat content:
The fat content was determined by the Gerber method (AOAC,
1990). A 10 ml sulphuric acid (density 1.815 gm/ml) were poured into
clean dry Gerber tubes. About 3 grammes of cheese was weighed into
a preweighed 50ml beaker, 3-4 ml of warm (50-55ºC) distilled water
were added and mixed with the glass rod until a uniform slurry was
formed. The slurry was transferred quantitively to a Gerber tube, then
44
1 ml of amyl alcohol was added to the tube followed by addition of
distilled water. The contents in the tube were thoroughly mixed till
white particles were seen. The tubes were centrifuged at 1100 rpm for
5 minutes. The fat column separated was read and taken as percent fat
in sample.
3.3.1.5. Ash content:
Ash content was determined according to the AOAC method
(1990). Two grammes of cheese were weighed into clean and dry
crucible and evaporated to dryness on steam bath. The crucibles were
placed in a muffle furnace of 550ºC for 1.5-2 hrs, cooled in a
desiccator and weighed, the ash content was calculated as follows:
% Ash =
w1
×100
w0
where:
w1 : weight of ash
w0 : weight of sample.
3.3.1.6. Phosphorus determination:
The phosphorus was determined by the method of Chapman
and Pratt (1982). One gram of sample was weighed in a crucible and
ignited at 550ºC in a muffle furnace till a light grey ash was formed.
Then 5ml of 5 N HCl was added to the ashed sample, it was then put
in a sand bath for 10 minutes, then filtered into a 50 ml volumetric
45
flask. The filter paper was washed with H2O; washings were collected
in the same flask, then diluted to volume with H2O. Five ml of the ash
extract was transferred into 50 ml volumetric flask, 10 ml ammonium
molybdate vanadate reagent (22.5 g NH4Mo7O.2H2O in 400 ml H2O +
1.25 g ammonium vanadate in 300 ml boiling distilled water) and 250
ml conc. HNO3 was added, mixed and completed to one litre, then
mixed again after 30 minutes. The density of colour was read at 470
nm wavelength UV. 120-02 Spectrophotometer.
3.3.1.7. Total protein:
The method recommended by the AOAC (1965) Analytical for
the determination of total nitrogen in cheese, with the use of Kjeldahl
systems, was applied. A 2 grammes of cheese sample were placed in
Kjeldahl flask, 25 ml of concentrated sulphuric acid were added to the
sample in the flask and Kjeldahl tablets were added as catalyst. The
flask was heated for digestion in the fumes room for 3 hours till a
clear solution was obtained and the contents were allowed to cool to
room temperature.
The contents of Kjeldahl flask were rinsed and transferred to the
distillation apparatus and then distilled with 10 ml of NaOH solution
(40%). The distillate was received in 10 ml of boric acid (2%) with
added indicator (methyl red and bromocresol green) and then titrated
against 0.02N HCl where the total nitrogen was calculated according
to the equation:
46
% total nitrogen =
T × N ×1.4
wt. of sample
where:
T = volume of titration
N = Normality of HCl.
% total protein = total nitrogen × 6.38.
3.3.1.8. Soluble nitrogen:
The soluble nitrogen was determined by the Kjeldahl method
according to Ling (1963). A 2 gram cheese was weighed into small
beaker, 25 ml of warm distilled water were added, the contents were
gently and transferred into a 100 ml graduated flask. Distilled water
was added until 100 ml of the extract was obtained, the contents were
mixed well, filtered and 5ml of the filtrate was transferred with a
pipette into a Kjeldahl flask. The procedure for measuring total
nitrogen was then used to estimate soluble nitrogen in cheese as
follows:
% Soluble nitrogen =
T × N × 1 . 4 × 6 . 38 × 20
wt . of sample
where:
T = volume of titration
N = Normality of HCl.
47
3.3.1.9. Chloride (salt):
The method used for the determination of chloride and sodium
chloride (salt) in processed cheese was recommended by the AOAC
(1990). A 2g sample was weighed into a preweighed 50ml beaker,
20ml of warm (50º to 55ºC) distilled water was added, mixed until a
uniform slurry was formed by using glass road. The mixture was then
transferred to 250ml flask, 10ml of distilled water (50º to 55ºC) was
added to the flask after rinsing the beaker, then 25ml of 0.1N silver
nitrate, 10ml of con. nitric acid, 50ml of distilled water were added to
the sample, while boiling the 5ml of 5% potassium permanganate
were added 3 times, until the colour of the solution turns brown for at
least 5 minutes. The solution was heated until the brown colour
disappeared, then the solution was filtered by using filter paper
thoroughly with hot distilled water in a clean 250ml flask, then the
solution was cooled to room temperature. A 2ml of ferric ammonium
sulphate (indicator) was added, the excess silver nitrate was titrated
against 0-1N potassium thiocyanates until the pale red brown colour
appeared. A 2ml of distilled water was used instead of 2 grammes
sample to get the blank value.
calculation:
% Sodium chloride =
[T1 × N1 (AgNO 3 ) − T2 × N 2 ( NKSCN )] × 0.0585 × 100
g sample taken
where:
48
T1: ml of silver nitrate (AgNO3)
N1: Normality of AgNO3.
T2: ml of potassium thiocyanate (KSCN)
N2: Normality of (KSCN)
3.4. Organoleptic quality of cheese:
The organoleptic quality of processed cheese spread was
evaluated by the ranking method described by Ihekoronye and
Ngoddy (1985). Fourteen judges from Food Research Center
(Shambat) and from University of Khartoum were asked to examine
and evaluate the cheese samples by giving ranks for attributes stated
to them on evaluation forms. The sample with best attributes was
given the rank No. 1, and the total number of samples was taken as
least rank in quality (Appendices 1 and 2). Sum of ranks were
statistically analysed and interpreted according to Ihekoronye and
Ngoddy (1985).
3.5. Statistical analysis:
Analysis of variance was carried out according to SAS (1997)
system using 5% level of significance.
49
CHAPTER FOUR
RESULTS AND DISCUSSIONS
4.1. Effect of emulsifier on physio-chemical characteristics of
processed cheese:
Table 1 shows the pH, acidity total solids, total protein, soluble
protein, fat, ash, salt and phosphorus of cheese containing 3.6%
disodium hydrogen orthophosphate (anhydrous DSHOP), cheese
containing 2.5% DSHOP + 0.5%
gum Arabic (GA), cheese
containing 3% trisodium orthophosphate (hydrous TSOP) and cheese
containing 2.5% TSOP + 0.5% (GA) as emulsifier compared to the
commercial cheese.
The results indicated that there was a significant (P ≤ 0.05)
increase in the pH of cheese containing different types of emulsifiers,
compared to commercial cheese, except for cheese containing DSHOP
+ GA which showed significant (P ≤ 0.05) decrease compared to other
samples.
The results also revealed that, there was insignificant (P ≤ 0.05)
decrease in the acidity, total solids, fat and phosphorus of the
commercial product and the samples made by the different types of
emulsifiers used.
50
Table 1.
Effect of type of emulsifier on physico-chemical characteristics* of processed cheese spread
Type of emulsifier in cheese**
*
**
***
PH
Soluble
Acidity (%
T.S
Total
lactic acid)
(%)
protein (%)
Protein
(%)
Fat
Ash
Salt
Phosphorous
(%)
(%)
(%)
(mg/100gm)
Commercial***
5.6c
1.810 a
51.53 a
24.56 c
23.59 d
31.10 a
4.7 ab
1.88 c
663.155 a
(3%) DSHOP
6.4 a
0.947 c
36.33 c
32.30 a
30.34 a
20.00 ab
3.8 d
2.58 a
427.000 bc
(2.5%) DSHOP + (0.5%)GA
5.3 d
1.680 ab
40.10 b
31.11 ab
28.14 b
19.50 c
4.9 a
2.47 ab
420.300 bc
(3%) TSOP
6.1 b
1.640 ab
37.2 c
31.46 ab
29.29 ab
18.80 d
4.0 bc
2.36 b
585.000 c
(2.5%) TSOP + (0.5%) GA
6.2 b
1.520 b
40.15 b
29.47 b
26.79 c
19.00 c
4.4 b
2.21 b
637.100 b
Mean values having different superscript letters in each column differ significantly (P≤0.05)
DSHOP:
Cheese containing 3.0% (unhydrous) disodium hydrogen orthophosphate as emulsifier.
DSHOP + GA:
Cheese containing 2.5% (unhydrous) disodium hydrogen orthophosphate + 0.5 gum Arabic as
emulsifier.
TSOP:
Cheese containing 3.0% (hydrous) trisodium orthophosphate as emulsifier.
TSOP+GA:
Cheese containing 2.5% (hydrous) trisodium orthophosphate + 0.5% gum Arabic as emulsifier.
Commercial: Processed cheese purchased from the market (made in Australia), cheese containing diosodium hydrogen
orthophosphate + trisodium diphosphate as emulsifiers..
51
There was also insignificant (P < 0.05) increase in the total
protein, soluble protein and salt of sample treated with emulsifiers
compared to the commercial one. On the other hand, there was
insignificant difference (P ≤ 0.05) in the ash content between
commercial cheese and the cheese containing different types of
emulsifiers, with the exception of the sample containing 3% DSHOP.
4.2. Effect of storage on physical properties of processed cheese
spread:
Table 2 shows changes in pH during storage of processed
cheese spread containing different emulsifiers. There was significant
(P ≤ 0.05) decrease in the pH of samples treated with different
emulsifiers and stored for different times, except for cheese containing
2.5% DSHOP + 0.5% GA as emulsifier which at 15 and 30 days of
storage showed insignificant difference (P ≤ 0.05) in pH compared to
other treatments.
Addition of gum Arabic to sample containing DSHOP has
significantly (P ≤ 0.05) decreased the pH of the processed cheese
spread as the storage period progressed, however, addition of gum
Arabic to cheese containing 2.5% TSOP as an emulsifier increased
the pH significantly (P ≤ 0.05) for the different storage times.
52
Table 2.
Changes in pH* during storage of processed cheese
spread. containing different emulsifiers
Storage period (days)
Type of emulsifier in cheese**
1
15
30
45
7.7a
6.6d
6.7c
6.4e
7.4b
6.0h
5.9h
5.3i
3% TSOP
7.4b
6.2f
6.4e
6.1g
2.5% TSOP + 0.5% GA
7.4b
6.4e
6.6cd
6.2f
3% DSHOP
2.5% DSHOP + 0.5% GA
*
Mean values having different superscript letters in columns
and rows differ significantly (P ≤ 0.05)
**
DSHOP:
Cheese containing 3.0% (anhydrous)
disodium hydrogen orthophosphate as
emulsifier.
DSHOP + GA:
Cheese containing 2.5% (anhydrous)
disodium hydrogen orthophosphate + 0.5 gum
Arabic as emulsifier.
TSOP:
Cheese containing 3.0% (hydrous) trisodium
orthophosphate as emulsifier.
TSOP+GA:
Cheese containing 2.5% (hydrous) trisodium
orthophosphate + 0.5% gum Arabic as
emulsifier.
53
The decrease in pH of processed cheese observed here is similar
to that observed by Hamed et al. (1997) using similar treatments.
Fig. 2. illustrates the effect of different emulsifiers on the
titratable acidity of processed cheese spread stored for different times.
Prolonging the storage period to 45 days, significantly (P ≤ 0.05)
increased the acidity of the processed cheese spread, except in
samples treated with the DSHOP at 15–30 storage days which showed
insignificant (P ≤ 0.05) decrease while cheese containing TSOP at 1530 storage days showed insignificant (P ≤ 0.05) increase. Addition of
gum Arabic to samples containing DSHOP or TSOP affected
significantly (P ≤ 0.05) the acidity of the processed cheese spread as
the storage period progressed. There was significant (P ≤ 0.05)
increase in the acidity of samples containing DSHOP for different
times of storage. Addition of gum Arabic to samples containing TSOP
caused significant (P ≤ 0.05) decrease in the acidity value, at all
storage periods except at zero hour storage, which showed
insignificant (P ≤ 0.05) difference between samples containing TSOP
and sample containing TSOP + GA. These values are in agreement
with those reported by Shehata et al., (1982) and Singh and Kanawjia
(1989) who showed increase in acidity of processed cheese spread
with storage time.
54
1.8
titratable acidity (% lactic acid)
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0
0
5
10
15
20
25
30
35
40
45
50
Storage period (days)
Fig. 2. Changes in titratable acidity (% lactic acid) of processed
cheese spread during storage
Samples containing 3% DSHOP
Samples containing 3% TSOP
Samples containing 2.5% DSHOP + 0.5 GA
Samples containing 2.5% TSOP + 0.5% GA
55
Table 3 shows the effect of different types of emulsifier in
cheese samples stored at different times on the total solids of the
processed cheese spread. There was significant (P ≤ 0.05) increase in
the total solids of most of the sample containing different emulsifiers
stored for 30 days, except for samples containing DSHOP which at
15-30 days of storage showed insignificant difference (P ≤ 0.05).
Combining gum Arabic with DSHOP or TSOP increased significantly
(P ≤ 0.05) the total solids of the processed cheese spread as the storage
period increased. Templeton and Sommer (1936) found that the
moisture of processed cheese decreased during storage. Hamed et al.,
(1997) reported that the moisture contents of processed cheese slightly
decreased throughout the storage period probably due to evaporation.
4.3. Effect of storage on chemical properties of processed cheese
spread:
Table 4 shows changes in total protein of processed cheese
spread containing different types of emulsifiers during storage.
Significant decrease (P ≤ 0.05) was observed in total protein
content of cheese spread during storage as a result of using
different emulsifiers, however, samples containing DSHOP, TSOP
56
and TSOP+GA stored for 30-45 days showed a slight, yet
insignificant
57
Table 3.
Changes in total solids* (%) of processed cheese
spread during storage
Type of emulsifier in
Storage period (days)
cheese**
1
15
30
45
35.57i
36.27h
36.60gh
36.33h
39.10c
40.02b
40.60a
40.10b
3% TSOP
35.78i
36.88fg
37.57e
37.20ef
2.5% TSOP + 0.5% GA
38.37d
39.13c
40.02b
40.15ab
3% DSHOP
2.5% DSHOP + 0.5%
GA
*
Mean values having different superscript letters in columns
and rows differ significantly (P≤0.05)
**
DSHOP:
Cheese containing 3.0% (anhydrous)
disodium hydrogen orthophosphate as
emulsifier.
DSHOP + GA:
Cheese containing 2.5% (anhydrous)
disodium hydrogen orthophosphate + 0.5 gum
Arabic as emulsifier.
TSOP:
Cheese containing 3.0% (hydrous) trisodium
orthophosphate as emulsifier.
TSOP+GA:
Cheese containing 2.5% (hydrous) trisodium
orthophosphate + 0.5% gum Arabic as
emulsifier.
58
Table 4.
Changes in total protein* (N × 6.38) of processed
cheese spread during storage
Type of emulsifier in
Storage period (days)
cheese**
1
15
30
45
37.49c
35.32d
32.63f
32.30f
35.58d
33.42e
32.13fg
31.11h
3% TSOP
40.05a
35.25d
31.52gh
31.46gh
2.5% TSOP + 0.5% GA
38.75b
33.59e
29.55i
29.47i
3% DSHOP
2.5% DSHOP + 0.5% GA
*
Mean values having different superscript letters in columns
and rows differ significantly (P ≤ 0.05)
**
DSHOP:
Cheese containing 3.0% (anhydrous)
disodium hydrogen orthophosphate as
emulsifier.
DSHOP + GA:
Cheese containing 2.5% (anhydrous)
disodium hydrogen orthophosphate + 0.5 gum
Arabic as emulsifier.
TSOP:
Cheese containing 3.0% (hydrous) trisodium
orthophosphate as emulsifier.
TSOP+GA:
Cheese containing 2.5% (hydrous) trisodium
orthophosphate + 0.5% gum Arabic as
emulsifier.
59
decrease in protein content. The highest protein content (40.05%) was
recorded in samples containing TSOP and the lowest level of protein
(29.47%) was recorded for samples containing TSOP+GA.
Addition of gum Arabic to samples containing DSHOP or to
samples containing TSOP decreased the total protein significantly (P
≤ 0.05) as the storage period increased. Hamed et al., (1997) reported
that the total protein of the processed cheese decreased by storage
time. He attributed this to the limited degradation or assimilation of
protein in cheese.
Fig. 3 illustrates changes in soluble protein of processed cheese
spread during storage as affected by different emulsifiers used. There
was a decrease in the soluble proteins of the samples during the
storage with most emulsifiers used except with samples containing
DSHOP or TSOP+GA stored for 1 – 15 days. Addition of gum
Arabic to samples containing DSHOP or to TSOP affects significantly
(P ≤ 0.05) the level of soluble protein of the processed cheese as the
storage period increased.
60
34
33
32
% soluble protein
31
30
29
28
27
26
25
24
0
5
10
15
20
25
30
35
40
45
50
Storage period (days)
Fig. 3. Changes in soluble protein of processed
cheese spread during storage
Samples containing 3% DSHOP
Samples containing 3% TSOP
Samples containing 2.5% DSHOP + 0.5 GA
Samples containing 2.5% TSOP + 0.5% GA
61
Similar values were also observed between soluble proteins of
samples containing TSOP and TSOP + GA at 1 storage time. Singh and
Kanawjia (1989) reported that the soluble nitrogen of processed cheese
increased during storage.
Table 5 shows the effect of different emulsifiers used on the fat
content of the processed cheese spread stored for different periods of
time. There was a significant (P ≤ 0.05) increase in the fat of cheese
spread containing different emulsifiers stored for 0-15 days, however,
there was a significant (P ≤ 0.05) decrease in the fat of samples stored
for 15-30 days. Similar significant differences (P ≤ 0.05) were also
observed in the fat content of cheese spread containing different
emulsifiers stored for 30 – 45 days.
Addition of gum Arabic to samples containing DSHOP or to
samples containing TSOP as shown in table 5 had insignificant (P ≤
0.05) effect on fat content levels, except values of 15 days of storage
time, which showed significant (P ≤ 0.05) increase in fat content of
processed cheese containing DSHOP.
62
Table 5.
Changes in fat* level (%) of processed cheese spread
during storage
Storage period (days)
Type of emulsifier in cheese**
1
15
30
45
20.00cd
21.33b
20.00cd
20.00cd
20.33c
22.67a
20.33c
19.50cde
3% TSOP
19.33cdef
21.33b
19.33cdef
18.83ef
2.5% TSOP + 0.5% GA
19.33cdef
21.67b
18.33f
19.00def
3% DSHOP
2.5% DSHOP + 0.5% GA
*
Mean values having different superscript letters in columns
and rows differ significantly (P ≤ 0.05)
**
DSHOP:
Cheese containing 3.0% (anhydrous)
disodium hydrogen orthophosphate as
emulsifier.
DSHOP + GA:
Cheese containing 2.5% (anhydrous)
disodium hydrogen orthophosphate + 0.5 gum
Arabic as emulsifier.
TSOP:
Cheese containing 3.0% (hydrous) trisodium
orthophosphate as emulsifier.
TSOP+GA:
Cheese containing 2.5% (hydrous) trisodium
orthophosphate + 0.5% gum Arabic as
emulsifier.
63
Shehata et al. (1982) found no significant change in the fat content
of processed cheese spread during storage whereas Hamed et al.
(1997) reported that the fat content of the processed cheese spread
slightly decreased during storage.
Table 6 shows the effect of different emulsifiers on the ash content
of the processed cheese spread stored for different period of time. The
results indicated that there was insignificant (P ≤ 0.05) decrease in the
ash of samples containing DSHOP and samples containing DSHOP+GA
stored for 1-15 days, however, samples containing either TSOP or
TSOP+GA showed significant (P < 0.05) increase at the same time of
storage. In 15-30 days of storage the results indicated that there was
insignificant difference (P ≤ 0.05) in the ash levels of samples containing
DSHOP and samples containing TSOP + GA showed that there was
significant decrease in the ash.
During the period of 30 – 45 days of storage the results showed
that there was significant (P ≤ 0.05) increase in the ash content of
samples treated with different emulsifiers, except for the one containing
DSHOP+GA which at 30 – 45 days of storage period showed
insignificant difference (P ≤ 0.05) compared to those containing
DSHOP, TSOP and TSOP+GA.
64
Table 6.
Changes in ash* content (%) of processed cheese spread
during storage
Type of emulsifier in cheese**
Storage period (days)
1
15
30
45
3.23f
3.13f
3.27f
3.80de
5.07a
4.90ab
4.80b
4.93ab
3% TSOP
3.23f
3.93d
3.60e
4.03d
2.5% TSOP + 0.5% GA
4.00d
4.35c
3.68e
4.40c
3% DSHOP
2.5% DSHOP + 0.5% GA
*
Mean values having different superscript letters in columns
and rows differ significantly (P≤0.05)
**
DSHOP:
Cheese containing 3.0% (anhydrous)
disodium hydrogen orthophosphate as
emulsifier.
DSHOP + GA:
Cheese containing 2.5% (anhydrous)
disodium hydrogen orthophosphate + 0.5 gum
Arabic as emulsifier.
TSOP:
Cheese containing 3.0% (hydrous) trisodium
orthophosphate as emulsifier.
TSOP+GA:
Cheese containing 2.5% (hydrous) trisodium
orthophosphate + 0.5% gum Arabic as
emulsifier.
65
Addition of gum Arabic to samples containing either DSHOP or
TSOP increased significantly (P ≤ 0.05) the ash content of the processed
cheese spread as the storage period progressed, except the samples of 30
storage days, which showed insignificant (P ≤ 0.05) difference.
Table 7 shows the effect of different emulsifiers on the
phosphorus content of the processed cheese spread stored for different
periods of time. The results indicated that, as the storage period
increased the phosphorus content of processed cheese spread increased,
except for samples containing DSHOP + GA 15 – 30 days stored for 1530 days which showed significant decrease (P ≤ 0.05) in the phosphorus
content as time of storage progressed.
Addition of gum Arabic to samples of cheese containing
DSHOP or TSOP increased phosphorus content value at all storage
times. Addition of gum Arabic to sample of cheese containing
DSHOP lead to significant (P ≤ 0.05) increase in phosphorus content
for samples stored for 0 and 15 days, while samples stored for 30
and 45 days show insignificant (P ≤ 0.05) difference between samples
of cheese containing DSHOP and DSHOP + GA were observed.
Addition of gum Arabic to samples of cheese containing TSOP lead
to
66
Table 7.
Changes in phosphorus* level (mg/100 g) of processed
cheese spread during storage
Type of emulsifier in cheese**
Storage period (days)
1
15
155.5j
344.6h
369.8gh 427.0ef
284.9i
404.3fg
371.5gh
420.3f
3% TSOP
266.4i
440.4ef
495.1cd
585.0b
2.5% TSOP + 0.5% GA
455.5ef
468.2de
527.8c
637.1a
3% DSHOP
2.5% DSHOP + 0.5% GA
*
30
45
Mean values having different superscript letters in columns
and rows differ significantly (P ≤ 0.05)
**
DSHOP:
Cheese containing 3.0% (anhydrous)
disodium hydrogen orthophosphate as
emulsifier.
DSHOP + GA:
Cheese containing 2.5% (anhydrous)
disodium hydrogen orthophosphate + 0.5 gum
Arabic as emulsifier.
TSOP:
Cheese containing 3.0% (hydrous) trisodium
orthophosphate as emulsifier.
TSOP+GA:
Cheese containing 2.5% (hydrous) trisodium
orthophosphate + 0.5% gum Arabic as
emulsifier.
67
significant (P ≤ 0.05) increase in phosphorus content stored for 0 and 45
days, and insignificant (P ≤ 0.05) difference stored for 15 and 30 days.
Hamed et al., (1997) stated that the storage time had no effect on the
inorganic phosphorus content of processed cheese.
Table 8 shows changes in sodium chloride (NaCl) of processed
cheese spread containing different emulsifiers during storage. Significant
increase (P ≤ 0.05) was observed in NaCl content of cheese spread at
different periods of storage, except for samples containing TSOP stored
for 30 – 45 days and sample containing TSOP + GA stored for 15 – 30
days, where insignificant (P ≤ 0.05) decrease was observed.
Addition of gum Arabic to samples containing DSHOP or TSOP
decreased significantly (P ≤ 0.05) the NaCl of the processed cheese
spread as the storage period increased, except the one containing
DSHOP stored for 15 storage days, which was increased significantly (P
≤ 0.05) after addition of gum Arabic. Hamed et al., (1997) found similar
effect on NaCl content, which might be attributed to both losses in
moisture as well as increase in other cheese solids.
68
Table 8. Changes in NaCl* level (%) of processed cheese spread during
storage
Storage period (days)
Type of emulsifier in cheese**
15
30
45
2.21e
2.47b
2.58a
2.33d
2.40c
2.47b
3% TSOP
2.19e
2.40c
2.36cd
2.5% TSOP + 0.5% GA
2.13f
2.13f
2.21e
3% DSHOP
2.5% DSHOP + 0.5% GA
*
Mean values having different superscript letters in columns
and rows differ significantly (P ≤ 0.05)
**
DSHOP:
Cheese containing 3.0% (anhydrous)
disodium hydrogen orthophosphate as
emulsifier.
DSHOP + GA:
Cheese containing 2.5% (anhydrous)
disodium hydrogen orthophosphate + 0.5 gum
Arabic as emulsifier.
TSOP:
Cheese containing 3.0% (hydrous) trisodium
orthoph-osphate as emulsifier.
TSOP+GA:
Cheese containing 2.5% (hydrous) trisodium
orthopho-sphate + 0.5% gum Arabic as
emulsifier.
69
4.4. Effect of emulsifier on organoleptic properties of processed
cheese spread
Table 9 shows the organoleptic quality of processed cheeses
prepared from white cheese containing emulsifiers found suitable for
making processed cheese (cheese containing 3.0% (un hydrous)
disodium hydrogen orthophosphate (DSHOP), cheese containing 3.0%
(hydrous) disodium hydrogen orthophosphate (DSHOP), cheese
containing 3.0% (hydrous) tri-sodium orthophosphate (TSOP), cheese
containing 3.0% sodium dihyrogen orthophosphate (SDHOP) and cheese
containing 3.0% tri sodium citrate (TSC).
Samples of cheese containing anhydrous DSHOP, hydrous
DSHOP, SDHOP or TSC were significantly (P ≤ 0.05) superior to
samples containing hydrous TSOP in flavour. However, insignificant (P
≤ 0.05) differences were observed among all treatments with respect to
taste, texture and total preference of the samples. On the other hand,
samples of cheese containing hydrous DSHOP were significantly (P ≤
0.05) superior to samples containing hydrous DSHOP, samples
containing hydrous TSOP, samples containing DSHOP and those
containing TSC in after taste.
70
Table 9: Organoleptic* quality of processed white cheese spread
containing different types of emulsifiers
Sum of ranks
Type of
emulsifier in
After
Texture &
Overall
taste
consistency preference
Flavour
Taste
32a
35a
35a
34a
37a
31a
32a
23b
31a
31a
57c
47a
44a
43a
51a
SDHOP
48a
52a
54a
52a
48a
TSC
42a
44a
49a
50a
43a
**
cheese
DSHOP
(unhydrus)
DSHOP
(hydrous)
TSOP
(hydrous)
*: means in each column having different superscript letter differ significantly
(P ≤ 0.05).
**: DSHOP: Cheese containing 3.0% (anhydrous) disodium hydrogen
orthophosphate as emulsifier.
DSHOP: Cheese containing 3.0% (hydrous) disodium hydrogen
orthophosphate (hydrate).
TSOP: Cheese containing 3.0% (hydrous) trisodium hydrogen
orthophosphate .
SDHOP: Cheese containing 3.0% sodium di hydrogen orthophosphate
TSC: Cheese containing 3.0% tri sodium citrate
71
Table 10 shows organoleptic quality of processed cheese prepared
from white, chedder and mozzarella cheeses containing different
emulsifiers. Samples of cheese containing anhydrous DSHOP were
significantly (P ≤ 0.05) superior in all quality attributes to cheese
containing hydrous DSHOP and those containing hydrous TSOP or
TSC. Samples of cheese containing SDHOP were obviously inferior to
samples of cheese containing anhydrous DSHOP, hydrous DSHOP,
hydrous TSOP or TSC in all quality attributes tested.
Table 11 shows organoleptic quality of processed cheese spread
containing emulsifiers proved to be optimum and hence selected from
the previous two tests mentioned earlier. It was observed that in flavour,
taste, after taste and overall performance, the samples of cheese
containing
anhydrous
DSHOP-1
and
hydrous
TSOP-1.
Were
significantly (P ≤ 0.05) superior to samples of cheese containing hydrous
DSHOP-2, hydrous DSHOP-1 and anhydrous DSHOP-2. However, in
texture and consistency, the sample containing hydrous TSOP-1 was
superior to those samples.
72
Table 10: Organoleptic* quality of processed mixed cheese spread**
containing different types of emulsifiers
Sum of ranks
Type of
emulsifier in
After
Texture
Overall
Flavour
Taste
28b
25b
28b
25b
23b
30a
33a
36a
37a
33a
46a
42a
37a
37a
40a
SDHOP
57c
68c
65c
70c
70c
TSC
50a
42a
44a
41a
44a
cheese
***
DSHOP
(anhydrous)
DSHOP
(hydrous)
TSOP
(hydrous)
taste
consistency preference
*: means in each column having different superscript letter differ significantly
(P ≤ 0.05).
**: White , cheddar and mozzarella cheese were used for making processed
cheese.
***: DSHOP: Cheese containing 3.0% (anhydrous) disodium hydrogen
orthophosphate as emulsifier.
DSHOP: Cheese containing 3.0% (hydrous) disodium hydrogen
orthophosphate .
TSOP: Cheese containing 3.0% (hydrous) trisodium hydrogen
orthophosphate.
SDHOP: Cheese containing 3.0% sodium dihydrogen orthophosphate
TSC: Cheese containing 3.0% tri sodium citrate
73
Table 11: Organoleptic* quality of processed white and mixed cheese
spread** containing different types of emulsifiers
Sum of ranks
Type of
emulsifier in
cheese
***
DSHOP-1
(anhydrous)
DSHOP-2
(hydrous)
DSHOP-1
(hydrous)
DSHOP-2
(hydrous)
TSOP-1
(hydrous)
After
Texture
Overall
Flavour
Taste
28b
27b
29b
40a
27b
57c
56c
60c
52a
58c
33a
37a
43a
45a
37a
64c
61c
59c
47a
62c
25b
27b
21b
26b
26b
taste
consistency preference
*: means in each column having different superscript letter differ significantly
(P ≤ 0.05).
**
1. Containing cheddar, white and mozzarella cheese.
2. Containing white cheese only.
***: DSHOP: Cheese containing 3.0% (anhydrous) disodium hydrogen
orthophosphate as emulsifier.
DSHOP: Cheese containing 3.0% (hydrous) disodium hydrogen
orthophosphate.
TSOP: Cheese containing 3.0% (anhydrous) trisodium hydrogen
orthophosphate.
74
The results of organoleptic quality of processed cheese containing
the emulsifiers of anhydrous DSHOP, hydrous DSHOP and hydrous
TSOP were selected as optimum emulsifiers with best performance from
the preceding test (Table 12). The results indicated that the cheese
containing emulsifiers of anhydrous DSHOP and cheese containing
hydrous TSOP were significantly (P ≤ 0.05) superior in all quality
attributes compared to cheese containing hydrous DSHOP-2.
Table 13 shows the organoleptic quality of processed cheese
spread containing screened emulsifiers of anhydrous DSHOP and
hydrous TSOP used at different level of treatments (e.g. 2% anhydrous
DSHOP, 2% anhydrous DSHOP + 1% GA, 2.5% anhydrous DSHOP,
2.5% anhydrous DSHOP + 0.5 GA and 3% anhydrous DSHOP.
Addition of 2% anhydrous DSHOP to processed cheese showed
lower acceptability of flavour and taste compared to other emulsifiers,
although the difference was insignificant (P ≤ 0.05) with after taste,
samples of cheese containing 2% anhydrous DSHOP +1% GA were
inferior to cheeses containing other emulsifiers coupled with gum arabic
with respect to texture and consistency, sample of cheese
Table 12: Organoleptic* quality of processed mixed cheese spread**
containing different types of emulsifiers
75
Sum of ranks
Type of
emulsifier in
cheese
***
After
Texture
Overall
Flavour
Taste
7b
7b
7b
6a
7b
13b
15c
14c
15c
14c
10b
8b
9b
9b
9b
DSHOP
(anhydrous)
DSHOP
(hydrous)
TSOP
(hydrous)
taste
consistency preference
*: means in each column having different superscript letter differ significantly
(P ≤ 0.05).
**: Cheddar, White and mozzarella cheese were used for making
processed cheese
***: DSHOP: Cheese containing 3.0% (anhydrous) disodium hydrogen
orthophosphate as emulsifier.
DSHOP: Cheese containing 3.0% (anhydrous) di sodium hydrogen
orthophosphate.
TSOP: Cheese containing 3.0% (hydrous) tri sodium hydrogen
orthophosphate.
76
Table 13: Organoleptic* quality of processed mixed cheese spread**
containing different level of anhydrous of emulsifiers
Sum of ranks
Type of
emulsifier in
cheese
***
2% DSHOP
(anhydrous)
After
Texture
Overall
Flavour
Taste
34a
36a
40a
57c
41a
52a
48a
55c
59c
51a
49a
45a
38a
40a
44a
39a
40a
38a
28b
37a
36a
41a
39a
26b
37a
taste
consistency preference
2% DSHOP +
1%GA
(anhydrous)
2.5% DSHOP
(anhydrous)
2.5% DSHOP +
0.5% GA
(anhydrous)
3% DSHOP
(anhydrous)
*: means in each column having different superscript letter differ significantly
(P ≤ 0.05).
**: White, cheddar and mozzarella cheese were used for making processed
cheese.
***:
DSHOP:
Cheese
containing
(anhydrous)
disodium
hydrogen
orthophosphate as emulsifier.
DSHOP + GA Cheese containing (anhydrous) disodium hydrogen
orthophosphate + gum Arabic as emulsifier
77
containing 2.5% anhydrous DSHOP + 0.5% GA and cheese containing
3% anhydrous DSHOP were significantly (P ≤ 0.05) superior to cheeses
containing other levels of emulsifiers and gum arabic.
Table 14 shows the organoleptic quality of processed cheese
spread containing different levels of TSOP emulsifier. It was observed
that, the samples of cheese containing 2% hydrous TSOP + 1% GA were
inferior significantly (P ≤ 0.05) in flavour to these samples containing
2% (hydrous) TSOP, 2.5% (hydrous) TSOP, 2.5% (hydrous) TSOP +
0.5% GA and 3% (hydrous) TSOP.
However, in taste the samples containing 2.5% (hydrous) TSOP +
0.5% GA were superior significantly (P ≤ 0.05) to samples containing
2% (hydrous) TSOP, 2.5% (hydrous) TSOP and 3% (hydrous) TSOP
while the sample containing 2% (hydrous) TSOP + 1% GA were
inferior. On the other hand in the aftertaste and texture (consistency)
attributes, all samples of cheese showed insignificant different (P ≤
0.05). while in overall preference the samples of cheese containing 2.5%
(hydrous) TSOP +0.5% GA and samples of cheese containing 3%
(hydrous) TSOP were superior significantly to samples
78
Table 14: Organoleptic* quality of processed mixed cheese spread**
containing different levels of hydrous emulsifiers
Sum of ranks
Type of
emulsifier in
cheese
***
2% TSOP
(hydrous)
2% TSOP + 1%
GA (hydrous)
2.5% TSOP
(hydrous)
After
Texture
Overall
Flavour
Taste
41a
47a
46a
43a
57c
57c
56c
51a
48a
50a
41a
37a
42a
40a
46a
31a
28b
31a
40a
29b
39a
42a
40a
39a
28b
taste
consistency preference
2.5% TSOP +
0.5% GA
(hydrous)
3% TSOP
(hydrous)
*: means in each columns having different superscript letter differ
significantly (P ≤ 0.05).
**: White, cheddar and mozzarella cheeses were used for making processed
cheese.
***: TSOP :Cheese containing (anhydrous) trisodium hydrogen
orthophosphate as emulsifier.
TSOP + GA: Cheese containing (hydrous) trisodium orthophosphate + gum
Arabic as emulsifier.
79
of cheese containing 2.5% (hydrous) TSOP, cheese containing 2%
(hydrous) TSOP + 1%GA and cheese containing 2% (hydrous) TSOP.
The result obtained from the organoliptic quality of processed
cheese spread are more or less in agreement with those reported by
Thomas et al. (1980) who observed insignificant difference in general
acceptability of processed cheese when several emulsifying salts were
used.
Table 15 shows the organoleptic quality of processed cheese
spread containing emulsifiers screened as best ones compared to
commercial cheese. The flavour, texture and total preference of cheese
containing 3% hydrous TSOP and the commercial cheese (control) were
significantly (P ≤ 0.05) superior to those cheeses containing other
emulsifying agents. However, in taste and after taste , the cheese
containing 3% hydrous TSOP was superior to those samples. This may
be attributed to the fact that commercial cheese was fully matured due to
long storage period and also it may contain some other additives beside
its methods of manufacturing that characterizes such type of cheeses.
80
Table 15: Organoleptic* quality of processed cheese spread** compared
to commercial one
Sum of ranks
Type of
emulsifier in
cheese***
Flavour
Taste
After
taste
Texture
Overall
consistency preference
3% TSOP
(hydrous)
27b
24b
27b
29b
24b
2.5% TSOP
(hydrous) + 0.5%
GA
36a
36a
43a
34a
39a
3% DSHOP
(anhydrous)
48a
46a
43a
47a
47a
2.5% DSHOP
(anhydrous) +
0.5% GA
59c
59c
52a
58c
60c
Commercial**
25b
30a
30a
27b
25b
*: means in each columns having different superscript letter differ
significantly (P ≤ 0.05).
**: Processed cheese purchased from the market (Made in Australia)
cheddar and mozzarella cheese, Cheese containing disodium hydrogen
orthophosphate + trisodium emulsifiers
***:
TSOP:
Cheese
containing
(anhydrous)
trisodium
hydrogen
orthophosphate as emulsifier.
TSOP + GA: Cheese containing (hydrous) trisodium orthophosphate as
emulsifier + gum Arabic as emulsifiers.
DSHOP: Cheese containing (anhydrous) disodium hydrogen orthophosphate
as emulsifier.
DSHOP + GA Cheese containing (anhydrous) disodium hydrogen
orthophosphate as emulsifier + gum Arabic
81
CHAPTER FIVE
CONCLUSIONS AND RECOMMENDATIONS
5.1. Conclusions:
From the results found in this study one can conclude the
following:
1.
Sudanese cheese (white, chedder and mozzarella) can act as
excellent raw materials for preparation of processed cheese
spread.
2.
An emulsifiers such as hydrous tri-sodium orthrophosphate
(TSOP) can act as an ideal emulsifying agent in processed
cheese industry.
3.
Addition of gum arabic to the chemical emulsifiers was found
to improve some of the physico-chemical attributes of
processed cheese but not necessarily organoleptic properties of
the end product.
4.
Emulsifiers based on phosphate salts were found more
effective in processed cheese preparation compared to
emulsifiers based on citrate salts.
5.
Finally, processed cheese spread based on hydrous TSOP as an
emulsifying agent was found to match more or less
commercial processed cheese in most acceptability attributes.
82
5.2. Recommendations:
From the conclusions drawn before, the following points can be
recommended:
1.
Conventional Sudanese cheese can be used as raw materials
for making processed cheese spread.
2.
Chemical emulsifiers based on hydrous phosphate salts are
recommended as ideal emulsifiers compared to emulsifying
agents based on citrate salt.
3.
Gum arabic is considered a good natural emulsifier if coupled
with phosphate salts.
4.
Further work is recommended on effect of combination of
chemical or natural emulsifiers on acceptability and storage
quality of processed cheese spread.
83
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Appendix 1.
Ranking used for organoleptic quality of processed cheese spread
Sample No……………….
Date:…………………..
90
Name: ………………………………………………………………….
Please, kindly examine samples of processed cheese spread
presented to you, and rank them for quality attributes mentioned on form
giving I to best rank and 4 to least rank in quality.
No.
sample
Flavour
Taste
After taste
Texture
Overall
(consistency) preference
A
B
C
D
Comments:
……………………………………………………………………………………………………………
……………………………….………………………………………………………………….………
……………………………………………………………………………………………………………
……………………….………………………………………………………………….
……………………………………………………………………………………………………………
……………………………….………………………………………………………………….
91
Appendix 2.
Ranking used for organoleptic quality of processed cheese spread
Sample No……………….
Date:…………………..
Name: ………………………………………………………………….
Please, kindly examine samples of processed cheese spread
presented to you, and rank them for quality attributes mentioned on form
giving I to best rank and 5 to least rank in quality.
No.
sample
Flavour
Taste
After taste
Texture
Overall
(consistency) preference
A
B
C
D
E
Comments:
……………………………………………………………………………………………………………
……………………………….………………………………………………………………….………
……………………………………………………………………………………………………………
……………………….………………………………………………………………….
……………………………………………………………………………………………………………
……………………………….………………………………………………………………….
92