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The 10th Egyptian Conference for Dairy Science & Technology, Cairo, Egypt, 415-432, 2007
Manufacture of Mozzarella cheese using Glucono-Delta-Lactone
By
Ismail, M. M.*1, Ayyad, K. M.* and Hamad, M. N.**
* Dairy Technology Department, Animal Production Research Institute, Agriculture Research Center. Egypt
**Food science and Dairy Department, Faculty of Agriculture "Qena", South Vally University. Egypt
1Corresponding author email: magdy250@yahoo.com
ABSTRACT
The impact of milk preacidification with glucono- δ-lactone (GDL) on the yield, composition and
rheological properties of Mozzarella cheese was determined. Cheese were made from buffalo’s, cow’s or
goat’s milk using 0.5% yoghurt starter (control), 0.75% GDL or admixture of 0.25% yoghurt starter and
0.37% GDL. Resultant cheese was examined for chemical, rheological and organoleptic properties when
fresh and during storage period at -18°C for 60 days. Whey of GDL cheese had higher acidity, TS, fat and
TN values than that cheese made without adding GDL. Preacidification of milk with GDL decreased the
yield, TS, fat, TN, ash, salt, calcium and oiling off values of resultant cheese while increased WSN,TVFA
and meltability values of the cheese. Buffalo’s milk Mozzarella cheese had the highest yield, TS, fat,TN,
calcium and also oiling off values, whereas goat’s or cow’s milk cheese showed the highest values of
acidity, ash, salt, WSN, TVFA and also exhibited the greatest meltability. The contents of acidity, TS, ash,
salt, calcium, fat, TN, WSN, TVFA, meltability and oiling off increased with age for all cheese treatments.
Sensory evaluation showed that Mozzarella cheese made using a mixture of 0.25% yoghurt starter and 0.37%
GDL gained the highest scores points for all types of milk treatments.
Key word: Mozzarella cheese- starter- GDL- buffalo’s, cow’s or goat’s milk
INTRODUCTION
Direct acidification (DA) technique had gained considerable commercial interest, as it does not rely on
starter performance which is unpredictable and there is risk of phage infections as well as contamination of
milk supply with antibiotics and helps towards mechanization of production (Fox 1978). The method of
manufacture of Mozzarella cheese by (DA) involves the lowering of pH by different acids to have better
control over pH variations, and to reduce manufacturing time. The different types of acids employed in these
techniques include hydrochloric, phosphoric, lactic, acetic, malic or citric acid. Metzger et al., (2001)
reported that preacidification of milk with organic acids to a pH of 5.8-5.6, in combination with a starter
culture, resulted in a reduction in calcium level of low-fat (6% w/w) low moisture part skim Mozzarella
cheese but did not significantly affect the levels of moisture; the experimental cheeses generally had a lower
pH than the control. The reduction in calcium content resulted in an increase in protein hydration and a
decrease in hardness of the unheated cheese, and an increase in flowability of the melted cheese. Other
researchers (Fife et al., 1996; Merrill et al., 1994) have used milk preacidification in the manufacture of low
and reduced fat Mozzarella cheese. In these studies, modifications in manufacturing procedures included one
level of milk preacidification (pH 6.0) with lactic acid. An improvement in the functionality (melting and
stretching characteristics) of reduced fat Mozzarella cheese was observed with this manufacturing procedure
(Merrill et al., 1994).
Jensen et al., (1987) used glucono-delta-lactone (GDL) as an acidulant for low- moisture part skim milk
Mozzarella cheese produced from ultrafiltrated milk. El-Sayed et al., (1998) studied the effect of GDL on the
growth and biochemical activities of certain lactic acid bacteria and pathogenic bacteria in cow's and
buffaloe's milk. Results showed that the addition of 0.5% GDL increased the total acidity, V.F.A, free amino
groups and acetaldehyde production by both strains of lactic acid bacteria Strep. thermophilus and L.
bulgaricus and they were higher in cow's milk than buffaloe's milk. On the other hand 0.5% GDL decreased
the counts of Listeria monocytogenes, E. coli CNRZ 7 and Staphylococcus aureus CNRZ 4 in cow's milk
than buffaloe's milk.
On the other hand, milk type plays an important role in chemical composition as well as functional
properties of Mozzarella cheese. Abd El-Hamid et al., (2006) indicated that cow’s Mozzarella cheese had
significantly higher moisture and water slouble nitrogen (WSN) contents compared to buffaloe's Mozzarella
cheese. On the contrary, buffalo’s Mozzarella cheese showed the highest total calcium content, while cow's
Mozzarella cheese had the lowest. Also, cow's milk Mozzarella cheese had higher and significant meltability
and penetration (lower firmness) values compared to buffaloe's milk cheese. Mozzarella cheese from cow's
milk had the ability to climb the rod when fresh, which is good indication to cheese elasticity, obviously,
cheese from buffaloe's milk did not show any ability to stretch when fresh. Mozzarella cheese from cow's
milk showed the lowest value of free oil, while that of buffaloe's milk had the highest. The objective of this
study was to determine the effect of using GDL as acidulant on the chemical composition and rheological
properties of Mozzarella cheese made from buffaloe's, cow's or goat's milk.
Materials and Methods
Materials:
Fresh buffalo’s milk was obtained from El-Gemmeza Animal Production Research Station, whereas
fresh cow’s and goat’s milks were obtained from El-Serw Animal Production Research Station, Animal
Production Research Institute, Agriculture Research Center. The chemical composition of used milks is
recorded in Table (1).
Yoghurt starter culture (Yo-Fex,YC-350,DVS) consists of Streptococcus saliverus ssp. thermophilus
and L. delbrueckii ssp. bulgaricus were obtained from Chr. Hansenۥs Lab A/S Copenhagen, Denmark.
Liquid calf rennet was obtained from local market and was added to milk at a ratio of 30 mL 100 kg-
1milk. Dry coarse commercial food grade salt was obtained from El-Nasr Company of Alexandria. All
chemicals were of laboratory grade.
Glucono delta lacton (GDL) has lysactone name as a commercial product was produced by Roquette
Freres Company, Lille- France. It was added to the milk as a powder at a rate of 0.37 and 0.75% (w/w).
Table 1. Chemical composition of milks used in Mozzarella cheese manufacture
Type of milk
Acidity %
pH
TS %
Fat %
TP %
Buffaloe's milk
Cow's milk
Goat's milk
0.17
0.19
0.18
6.60
6.49
6.53
15.44
12.11
13.09
6.1
3.8
4.2
3.52
3.13
3.42
Methods:
Mozzarella cheese manufacture:
Fresh buffalo’s, cow’s and goat’s milk were used for manufacture of 9 treatments of Mozzarella cheese
as shown in Table (2).
Table 2. Code letters of the different Mozzarella cheese treatments
Treatments
Type of milk
Type of acidificatin
Buffaloe's milk
Cow's milk
Goat's milk
yoghurt starter %
GDL
%
A(control)
√
-
-
0.5
-
B
√
-
-
-
0.75
C
√
-
-
0.25
0.37
D
-
√
-
0.5
-
E
-
√
-
-
0.75
F
-
√
-
0.25
0.37
G
-
-
√
0.5
-
H
-
-
√
-
0.75
I
-
-
√
0.25
0.37
B: Buffaloe's milk C: Cow's milk G: Goat's milk
The nine batches of milk were made into Mozzarella cheese as described by Kosikowski (1982). The
resultant cheese were freeze storaged at -18°C and analyzed when fresh and after 15,30,45 and 60 days of
storage period.
Methods of analysis:
Milk and whey samples were analyzed for titratable acidity (TA), total solids (TS), fat and total protein
contents according to Ling (1963). The pH values were estimated using a pH meter type CG 710.
Actual cheese yield was determined by dividing the weight of cheese by the weight of milk used to
make cheese, multiplied by 100. Moisture and salt adjusted cheese yield was calculated by Metzger et al.,
(2000) formula:
Adjusted yield = (actual yield × (100 − actual moisture+ actual salt)) / (100 − (55 + 1.5))
Cheese was analyzed for total solids (TS), titratable acidity (TA), pH, fat, total nitrogen (TN), water
soluble nitrogen (WSN) and ash contents according to Ling (1963). Salt contents of Mozzarella cheese were
estimated using Volhard method according to Richardson (1985). Calcium was determined using calcin as
indicator by the method described by Graham et al., (1962) and as modified by Abdel-Kader (1993). Total
volatile fatty acids (TVFA) was determined as described by Kosikowski (1978), and expressed as ml of 0.1N
NaOH, 100 g-1 cheese. Meltability and oiling off were determined as described by Kindsted and Rippe
(1990). The cheese samples were scored for flavor (50 points), body and texture (40 points) and appearance
and color (10 points) by ten panelists in El-Serw Animal Production Research Station.
The obtained results were statistically analyzed using a software package (SAS, 1991) based on analysis
of variance. When F-test was significant, least significant difference (LSD) was calculated according to
Duncan (1955) for the comparison between means. The data presented, in the Tables, are the mean (±
standard deviation) of 3 experiments.
RESULTS AND DISCUSSION
Chemical composition of cheese whey:
Mean composition values of cheese whey for different treatments are shown in Table (3). The acidity,
TS, fat and TN percetages of whey increased by adding GDL to cheese milk. Preacidification of goat's milk
with GDL (Treatmnet H) caused larger increase in acidity, TS, fat and TN contents in whey than
preacidification of buffaloe's and cow's milk (Treatments B and E). Increasing rates of acidity, TS, fat and
TN of whey of goat's milk were 33.3, 18.4, 50.0 and 10.0% respectively and were 16.7, 10.12, 40.0 and 5.0%
and 21.6, 12.5, 42.8 and 5.26% for whey of buffaloe's and cow's milk respectively.
Using of goat's milk in Mozzarella cheese manufacture (Treatments G) increased whey fat content more
than using buffaloe's or cow's milk (Treatments A and C). This may be due to the mean size of the fat
globules was larger in buffaloe's and cow's milk than that in goat's milk which allow to higher numbers of
fat globules to escape in whey. Obtained results of the acidity, pH, TS, fat and TN contents of Mozzarella
cheese whey were within the range obtained by Abdel-Kader and Ismail(2006) who used mixtures of
buffaloe's and cow's milk (1:1), buffaloe's and goat's milk (1:1) or cow's and goat's milk (1:1) milks in
Mozzarella cheese making.
Table 3. Chemical composition of cheese whey
Treatments
Acidity %
pH
TS %
Fat %
TN %
A
B
C
D
E
F
G
H
I
0.36
0.42
0.40
0.37
0.45
0.39
0.30
0.40
0.31
4.72
4.50
4.68
4.67
4.48
4.63
4.77
4.67
4.73
6.82
7.51
7.32
6.88
7.74
7.22
6.91
8.18
7.68
0.5
0.7
0.6
0.7
1.0
0.9
1.0
1.5
1.1
0.20
0.21
0.20
0.19
0.20
0.21
0.20
0.22
0.20
Yield and chemical composition of Mozzarella cheese:
The potential benefits of improved functionality of Mozzarella cheese that may be produced by
preacidification of milk could be less attractive if they are accompanied by large decreases in cheese yield.
Actual cheese yield and adjusted cheese yield values are shown in Table (4). Adding of GDL alone to
cheese milk decreased both actual and moisture and salt adjusted cheese yields (Treatments B, E and H)
more than using GDL with yoghurt starter as acidulant (Treatments C, F and I). The progressive reduction in
moisture and salt adjusted cheese yield with increasing preacidification was caused by a substantial reduction
in calcium recovery in the cheese and a tendency for decreased protein recovery in the cheese. This would
decrease moisture and salt adjusted yield (Metzger et al., 2000). On the other hand, the yield of goat's milk
cheese was more affedcted by addition of GDL than that of buffaloe's and cow's milk cheese.
As it is expected and because milk used in cheese manufacture did not standardized, the yield values of
buffaloe's milk cheese were higher than that of cow's or goat's milk cheese. Actual yield values of treatments
A, D and G were 14.81, 10.15 and 9.86% respectively.
Cheese acidity and pH were affected by treatment and the interaction of treatment x age (Table 4). The
acidity percentages of GDL cheese treatments were higher than that of control cheese. Of cours, this
attributed to the acidic properties of GDL. The observed differences in cheese acidity and pH between the
control and preacidified treatments may be related to a difference in cheese buffering capacities as a result of
different calcium levels (Metzger et al., 2001). The acidty of buffaloe's milk cheese was lower than that of
cow's or goat's milk cheese. This could be explained by the fact that buffalo’s milk cheese possesses a higher
buffering capacity than those of cow's milk (Abdel-Kader 1993). However, Mozzarella cheese stored at -
18°C, the titratable acidity of all cheese treatments increased significantly (P< 0.001), while the pH values of
all samples decreased significantly (P< 0.001) during stroage.
In contrast to the above, the results of Guinee et al.,(2002) indicate that the pH of the Mozzarella
cheese increased gradually during storage at 4°C for 70 d.There was a significant effect of the interaction
between make procedure and storage time on pH, with the rate of increase during storage being highest for
the cheese made using a combination of lactic acid and GDL and lowest for cheese made using lactic acid
alon. The increase in pH during storage was noted by Metzger et al., (2001) for low fat, and by Guo et al.,
(1997) for full fat in Mozzarella cheeses made using a starter culture. The increase in pH may be associated
with the gradual increase in para-casein hydration and the increased availability of various protein residues
(e.g., ε- and α-carboxyl groups of aspartic and glutamatic acids), which combine with H+ during storage and
thereby reduce the hydrogen ion activity of the moisture phase of the cheese. In turn, the increase in para-
casein hydration may be affected by changes in the equilibrium concentrations of soluble and colloidal
calcium phosphate (Guo et al., 1997), migration of salt in moisture in contact with the protein phase (e.g., ice
structure water, imbibed water; Geurts et al., 1974a, b), and proteolysis.
The composition of the cheese is shown in Table (4). The addition of GDL to cheese milk decreased
markedly the total solids, ash and salt contents of the resultant cheese. Using GDL with yoghurt starter had
little effect on composition of Mozzarella cheese comparing with using GDL alone. Similar results were
found by Jensen et al., (1987) who used GDL or acetic acid for Mozzarella cheese making from ultrafiltered
milk. They found that the preacidification to pH 5.8 increased fat losses and cheese moisture.
The higher moisture content of direct acidification (DA) Mozzarella cheese may be due to its relatively
low Ca-to-casein ratio, which would be conducive to a greater degree of casein hydration. This result
concurs with those of Shehata et al., (1967) and Keller et al., (1974), each of which showed a linear increase
in the moisture content of DA Mozzarella as the Ca level in the cheese decreased. In contrast to the results of
the current study and those of Shehata et al., (1967) and Keller et al. (1974), Metzger et al., (2000) reported
that the moisture content of reduced- fat Mozzarella was not significantly affected by varying the Ca level in
the range 17.5 to 30.2 mg/g of protein. The discrepancy between the results of Metzger et al., (2000) and
those of the other studies may be related to differences in the pH of the curd at stretching, which, in
conjunction with Ca content, probably have a major effect on the hydration of the para-casein. Model studies
on rennet-treated skim milk have shown that the hydration of casein micelles increases markedly as the pH is
reduced from 6.0 to 5.4 but decreases markedly as the pH is reduced further toward the isoelectric pH
(Creamer, 1985). The decrease in hydration at pH values <5.4 is probably a consequence of increased
hydrophobic interactions, which are effected by a decrease in the net micellar charge due to increased
concentrations of H+ and Ca2+ (van Hooydonk et al., 1986; Guinee et al., 2000). In the study of Metzger et
al., (2000), the control (high Ca, 30.2 mg/g of protein) cheese was salted at pH 5.5, while the cheeses made
using a combination of acid and starter culture (low Ca, 25.7 to 17.8 mg/g of protein) were salted at pH 5.3.
The pH at plasticization was probably somewhat lower as the pH usually decreases somewhat (typically 0.05
to 0.1/U over 20 min) during mellowing, since salt diffusion to the center of curd chips is not instantaneous,
and hence, the growth of the starter culture is not immediately inhibited. Therefore, the pH of all cheeses at 1
day were similar at 5.23, and at 15 day ranged from 5.15 to 5.2 in the low-Ca cheeses to 5.3 in the CL
cheese (Metzger et al., 2001).
Preacidification of goat's milk with GDL decreased TS, ash and salt contents of Mozzarella cheese
more than preacidification of buffaloe's and cow's milk. On the other side, the TS content of cheese as well
as the ash and salt values were varied due to the type of milk used in making Mozzarella cheese. Results
found in Table (4) showed that high TS and low ash and salt contents in buffaloe's milk cheese as compared
with cow's or goat's milk cheese. Generally, TS, ash and salt contents of cheese significantly (P< 0.001)
increased as storage period progressed. These results are in agreement with El-Batawy et al., (2004).
Table 4. Yield, acidity, pH and chemical composition of Mozzarella cheese
Treatments
Storage period
(days)
Actual Yield
%
*Adjusted
Yield %
Acidity
%
pH
TS
%
Ash
%
Salt
%
Calcium
%
A
0
15
30
45
60
14.81
-
-
-
-
18.72
-
-
-
-
0.51
0.54
057
0.59
0.62
5.69
5.65
5.60
5.54
5.52
56.69
57.18
57.83
58.37
58.71
3.17
3.39
3.54
3.70
3.84
1.70
1.81
1.89
1.98
2.07
1.097
1.116
1.131
1.140
1.149
B
0
15
30
45
60
14.16
-
-
-
-
16.84
-
-
-
-
0.57
0.61
0.65
0.68
0.72
5.58
5.54
5.52
5.48
5.43
53.56
54.19
54.96
55.84
56.71
3.09
3.31
3.46
3.58
3.62
1.59
1.73
1.82
1.91
2.00
0.817
0.835
0.844
0.852
0.860
C
0
15
30
45
60
14.39
-
-
-
-
17.94
-
-
-
-
0.54
0.57
0.59
0.63
0.66
5.67
5.61
5.57
5.53
5.49
55.91
56.64
57.11
57.72
58.22
3.12
3.35
3.55
3.68
3.80
1.68
1.80
1.91
1.98
2.05
1.085
1.104
1.112
1.122
1.130
D
0
15
30
45
60
10.15
-
-
-
11.25
-
-
-
-
0.66
0.70
0.73
0.76
0.78
5.45
5.39
5.35
5.31
5.28
50.13
50.91
51.65
52.03
52.69
3.65
3.83
3.96
4.13
4.27
1.91
2.05
2.16
2.28
2.37
0.598
0.621
0.630
0.641
0.653
E
0
15
30
45
60
9.93
-
-
-
-
10.13
-
-
-
-
0.71
0.74
0.78
0.83
0.86
5.39
5.35
5.30
5.22
5.17
46.13
46.86
47.53
48.41
49.01
3.52
3.78
3.92
4.03
4.17
1.77
1.86
1.94
2.04
2.15
0.401
0.424
0.437
0.449
0.461
F
0
15
30
45
60
10.11
-
-
-
-
10.93
-
-
-
-
0.69
0.71
0.75
0.79
0.81
5.43
5.38
5.33
5.24
5.21
48.88
49.5
50.31
51.16
51.88
3.59
3.82
3.95
4.15
4.24
1.87
2.03
2.11
2.20
2.29
0.591
0.615
0.626
0.634
0.645
G
0
15
30
45
60
9.86
-
-
-
-
11.39
-
-
-
-
0.64
0.66
0.68
0.71
0.73
5.55
5.52
5.48
5.43
5.39
52.21
52.84
53.41
54.05
54.59
3.77
3.98
4.15
4.30
4.41
1.97
2.15
2.24
2.35
2.43
0.692
0.717
0.728
0.737
0.749
H
0
15
30
45
60
9.41
-
-
-
-
9.96
-
-
-
-
0.67
0.70
0.75
0.79
0.83
5.50
5.43
5.38
5.30
5.24
47.95
48.62
49.19
49.69
50.39
3.70
3.93
4.09
4.21
4.33
1.89
2.05
2.16
2.27
2.36
0.563
0.587
0.596
0.607
0.619
I
0
15
30
45
60
9.66
-
-
-
-
10.95
-
-
-
-
0.66
0.68
0.72
0.75
0.79
5.47
5.44
5.40
5.37
5.31
51.24
52.09
52.86
53.48
54.06
3.74
3.97
4.11
4.26
4.38
1.92
2.13
2.22
2.31
2.40
0.679
0.698
0.711
0.721
0.730
*Moisture and salt adjusted cheese yield
The total calcium content of cheese was affected by preacidification treatment, age and the interaction
of treatment x age (Table 4). The preacidified treatments had less calcium content than the control at all
times, and this was correlated with lower cheese pH. Preacidification with GDL caused a larger decrease in
calcium than preacidification with yoghurt starter and GDL. Generally, the observed decrease in cheese
calcium content and increase in whey calcium content with preacidification was expected. The addition of
acid to milk causes an increase in nonmicellar calcium. During cheese manufacture, the micellar calcium in
milk is retained in the cheese, while the nonmicellar calcium is lost in the whey. Therefore, as a result of
preacidification, the high level of nonmicellar calcium caused the observed decrease in cheese calcium
content and increase in whey calcium content. Increased calcium content, decreased pH, and increased
acidity of the whey resulting from preacidification may have impacts on whey processing and whey product
functionality (van Hooydonk et al., 1986 and Dalgleish and Law 1988). Also, calcium content was higher in
buffaloe's milk cheese than that cow's or goat's milk cheese. During freezed storage the calcium content of
cheese increased in all treatments.
The fat content of the cheese made using yoghurt starter (control) was significantly higher than that of
the DA cheeses (Table 5). Moreover, the Fat/DM level of the GDL cheeses was lower than that of the control
cheeses, suggesting higher losses of fat to the cheese whey and/or the stretch water during the manufacture
of the former cheeses.Data of TN contents of cheese are summarized in Table (5). As total solids of cheese
decreased, TN contents decreased when GDL was added to cheese milk. Addition of 0.75% GDL increased
the decrease rate of fat, Fat/DM and TN whereas slight decrease was found when 0.25% yoghurt starter and
0.37% GDL were added. Similar results were found by Feeney et al., (2002) who acidified cheese milk with
lactic acid and added mixture of GDL as a powder with salt to the curd. The fat, Fat/DM, TN and TN/DM
contents in Treatment A (cheese made from buffalo’s milk) was significantly higher than that of the other
cheeses. The concentrations of fat and TN increased significantly in all cheese during storage at -18°C for 60
days. These results are in agreement with El-Zoghby (1994).
The changes in WSN, WSN/TN and TVFA contents of cheese between different treatments and within
storage are shown in Table (5). Treatments had a large impact on both WSN and TVFA. Age (i.e., storage
time) also had an effect on WSN and TVFA. The preacidified treatments had higher water soluble N,
WSN/TN and TVFA than the control. This is in accordance with the results of Abdel-Kader (1993). As
storage time increased, both WSN and TVFA significantly (P< 0.001) increased in all cheese treatments. The
rate of increase in proteolysis during storage occurred faster in cheese made using GDL with yoghurt starter.
Sheehan and Guinee (2004) produced cheeses at pH 5.9 (by direct acidification) and pH 5.5 (directs
acidification and culture addition) and observed greater stretchability and flowability of the pH 5.5 cheese
even though both had similar calcium levels. However, because of adding culture, the pH 5.5 cheese had
higher protein breakdown during 70 days of aging.
Results in Table (5) show that manufacture of Mozzarella cheese from buffaloe's milk led to slow the
protein decomposition of resultant cheese .Also, the TVFA content of Mozzarella cheese made from cow's or
goat's milk was higher than that made from buffaloe's milk .
Meltability and oiling off of Mozzarella cheese:
In a statistical analysis of all of the data for days 0,15,30, 45, and 60 combined, the cheese meltability
and oiling off were affected (P < 0.001) by preacidification treatment and day of storage.
Table (6) presents the changes in meltability of Mozzarella cheeses over 60 d of storage at -18°C. The
control cheeses made without adding GDL to cheese milk (Treatments A, D and G) displayed the lowest
meltability. Cheeses containing GDL and yoghurt starter (Treatments C,F and I) were expected to show
greater meltability resulting from the combined effects of preacidification that reduced the calcium–casein
interactions and stimulated primary proteolysis by starter. This occurred in cow's milk cheese, meltability
increased by 83.51, 83.37 and 87.19% at the end of stroage for control (yoghurt starter), GDL and GDL and
yoghurt starter treatments respectivly.These results establish the impact of calcium reduction on meltability
of cheese. Reducing the calcium causes increased interaction of proteins with surrounding serum, causing
more hydration of proteins and better melting of the cheese. As indicated from studies of Joshi et al., (2004)
on the microstructure of the cheeses containing different levels of calcium, more free serum is observed
around high calcium cheese, and is absorbed in the protein matrix with reduction in calcium content of
cheese. As moisture is absorbed from fat serum channels into the protein matrix, the proteins become more
hydrated. This allows the proteins to flow more easily when heated and results in improved meltability. The
microstructure of reduced calcium cheeses also showed that such cheeses had more fat particles entrapped in
the protein matrix compared with the control cheese, which might have contributed in better melting. Casein
in the reduced calcium curd better emulsifies fat so that less fat oozes out when the cheese is heated,
resulting into better melting (McMahon et al., 1993). During storage, an increase in melt area of the cheeses
was observed (Table 6). However, improvement in meltability of high calcium cheeses (control) was more
noticeable upon storage compared with that of the low calcium cheeses (GDL cheese). Changes in cheese
structure due to protein breakdown play an important role in contributing to increase melting of cheese
during storage. Proteolysis of casein allows fat globules, which are initially dispersed in the protein matrix,
to coalesce when cheese is heated, increasing its meltability (Kiely et al., 1992; Tunick et al., 1997). An
increase in the meltability of cheese during storage can be explained in terms of changes in water and protein
status within the cheese.
Table 5. Fat, TN and some ripening indices of Mozzarella cheese
Treatments
Storage period
(days)
Fat
%
Fat/DM
%
TN
%
TN/DM
%
WSN
%
WSN/TN
%
TVFA*
A
0
15
30
45
60
34.6
35.2
35.2
36.1
36.4
61.03
61.56
61.39
61.85
62.00
4.64
4.80
4.89
4.92
4.96
8.18
8.39
8.45
8.43
8.45
0.154
0.178
0.193
0.219
0.235
3.32
3.71
3.95
4.45
4.74
3.6
4.8
5.6
6.2
6.8
B
0
15
30
45
60
32.1
32.6
33.1
33.4
33.9
59.93
60.16
60.22
59.81
59.78
4.29
4.39
4.44
4.47
4.51
8.01
8.10
8.08
8.01
7.95
0.178
0.204
0.226
0.241
0.275
4.15
4.65
5.09
5.39
6.10
5.2
6.4
7.0
8.0
8.8
C
0
15
30
45
60
33.8
34.3
34.9
35.4
35.9
60.45
60.56
61.11
61.33
61.66
4.52
4.61
4.65
4.67
4.70
8.08
8.14
8.14
8.09
8.07
0.161
0.193
0.214
0.230
0.252
3.56
4.19
4.60
4.92
5.36
4.4
5.8
6.2
7.0
7.6
D
0
15
30
45
60
23.7
24.4
24.9
25.2
25.8
47.28
47.93
48.21
48.43
48.96
3.51
3.70
3.80
3.84
3.89
7.00
7.28
7.35
7.38
7.38
0.260
0.284
0.315
0.352
0.400
7.41
7.67
8.29
9.17
10.28
6.4
7.8
8.4
9.0
9.8
E
0
15
30
45
60
20.9
21.6
22.1
22.5
23.1
45.31
46.09
46.50
46.48
47.13
3.26
3.39
3.43
3.47
3.50
7.07
7.23
7.22
7.17
7.14
0.281
0.307
0.342
0.389
0.431
8.26
9.06
9.97
11.21
12.31
7.8
9.0
9.8
10.2
11.0
F
0
15
30
45
60
21.9
22.6
23.3
23.9
24.6
44.80
45.61
46.31
46.72
47.42
3.38
3.49
3.54
3.58
3.61
6.91
7.04
7.04
7.00
6.96
0.271
0.293
0.332
0.364
0.412
8.02
8.39
9.38
10.17
11.41
6.8
7.8
8.6
9.2
10.0
G
0
15
30
45
60
26.1
26.9
27.4
27.8
28.3
49.99
50.91
51.30
51.43
51.84
3.75
3.87
3.93
3.95
3.99
7.18
7.32
7.36
7.31
7.31
0.239
0.251
0.290
0.334
0.371
6.37
6.48
7.38
8.45
9.30
7.0
8.6
9.4
10.0
10.8
H
0
15
30
45
60
24.2
24.92
25.4
26.0
26.5
50.47
51.21
51.64
52.32
52.59
3.32
3.43
3.50
3.55
3.59
6.92
7.05
7.11
7.14
7.12
0.266
0.298
0.327
0.365
0.413
8.01
8.69
9.34
10.28
11.50
9.4
10.8
11.4
12.0
12.8
I
0
15
30
45
60
25.3
26.1
26.5
27.0
27.4
49.37
50.10
50.13
50.49
50.68
3.59
3.71
3.75
3.79
3.82
7.01
7.12
7.05
7.05
7.07
0.244
0.276
0.312
0.345
0.391
6.80
7.44
8.32
9.10
10.23
8.2
9.8
10.4
11.0
11.4
* expressed as ml 0.1N NaOH 100g-1 cheese.
On the other hand, meltability of cheese made from cow's or goat's milk was higher than that made from
buffalo’s milk either in GDL or traditional cheese.
Data presented in Table (6) showed that direct acidification significantly decreased (P< 0.001) the oiling
off values of the cheese. This may be explained by added acids formed certain emulsifying system led to the
retention and binding tightly the fat in the curd (El-Zoghby 1994).
From the obtained results we found that the type of milk affected the values of oiling off, and in general
buffalo's cheese showed the highest oiling off in all treatments.This may be related to the size of fat globules
of the milk. The bigger size of fat glouble in buffaloe's milk led to more oiling off in the cheese product
(Bikash et al., 1996). Also, Kindstedt (1993) mentioned that fat leakage was increased with increasing
cheese fat on DM basis. The amount of free oil increases at higher cheese fat levels (Tunick, 1994),
Organoleptic evaluation of Mozzarella cheese:
Test panel evaluation values were recorded in Table (7). Mozzarella cheese made using 0.25% yoghurt
starter and 0.37% GDL gained the highest score when it was fresh and also at the end of storage period.
Also, buffaloe's milk cheese had higher score than that of other treatments. The sensory evaluation of all
cheese treatments gradually improved during storage period reaching the highest score after 60 days of
storage.
So, from the previous study acceptable Mozzarella cheese can be made using 0.25% yoghurt starter and
0.37% GDL regardeless of the type of the milk.
Table 6. Meltability and oiling off Mozzarella cheese
Properties
Storage
period
(days)
Treatments
A
B
C
D
E
F
G
H
I
Meltability
(%)
0
15
30
45
60
10.96
15.11
21.72
25.93
31.03
13.41
19.26
25.12
30.41
35.49
11.71
16.94
22.34
26.68
33.41
24.08
30.65
35.75
39.87
44.19
26.82
32.91
38.73
45.01
49.28
24.91
31.42
37.10
41.18
46.63
12.81
16.73
22.56
27.91
32.40
13.72
18.35
23.96
28.22
33.86
13.16
17.21
22.95
27.81
33.42
Oiling off
(%)*
0
15
30
45
60
70.23
78.31
82.45
90.59
95.81
61.35
66.86
73.43
79.82
85.63
67.39
71.43
76.74
83.95
89.63
47.25
53.84
59.56
65.84
71.86
40.84
44.00
49.68
55.26
62.64
45.48
50.23
54.93
60.26
66.11
50.71
55.92
61.68
68.74
75.10
39.56
45.38
49.52
54.30
60.42
46.20
50.99
56.54
60.98
67.82
* areia of fat diffusions.
Table 7. Organoleptic properties of Mozzarella cheese
Properties
Storage
period
(days)
Treatments
A
B
C
D
E
F
G
H
I
Appearance
& Color
(10)
0
15
30
45
60
9
8
8
7
7
9
8
8
7
7
8
8
8
7
7
7
7
6
6
5
7
6
6
6
5
7
7
7
6
6
8
8
7
7
6
7
7
7
6
6
8
7
7
6
6
Body &
Texture
(40)
0
15
30
45
60
30
32
32
33
35
29
30
31
32
34
31
32
33
33
36
29
30
32
32
33
27
27
28
29
34
29
30
31
32
34
27
29
29
29
31
27
28
29
30
30
27
30
30
31
32
Flavour
(50)
0
15
30
45
60
33
35
36
37
39
31
32
32
33
35
35
37
38
39
41
32
34
36
36
38
30
32
33
33
35
33
35
37
38
39
24
25
27
28
29
22
23
24
24
25
25
27
28
30
31
Total
(100)
0
15
30
45
60
72
75
76
77
81
69
70
71
72
76
74
77
79
79
84
67
71
74
75
76
64
65
67
68
71
69
72
76
76
79
59
62
63
64
66
56
58
59
60
61
61
64
65
67
69
Table 8. Statistical analysis of Mozzarella cheese treatments
Analysis
Effect of cheese treatments
A
B
C
D
E
F
G
H
I
LSD
Whey Acidity
0.34de
0.42ab
0.40bc
0.37dc
0.45a
0.39bc
0.30f
0.40bc
0.31ef
0.039***
Whey pH
4.72ab
4.50d
4.68bc
4.67bc
4.48d
4.63c
4.77a
4.67bc
4.73ab
0.079***
Whey TS
6.82f
7.51cd
7.32de
6.88f
7.74b
7.22e
6.91f
8.18a
7.68bc
0.204***
Whey Fat
0.50e
0.75cd
0.60de
0.75cd
1.05b
0.85c
1.05b
1.50a
1.10b
0.192***
Whey TN
0.20a
0.21a
0.20a
0.19a
0.20a
0.21a
0.20a
0.22a
0.20a
0.037
Yield
14.81a
14.10c
14.39b
10.15d
9.93e
10.11d
9.86e
9.41g
9.66f
0.096***
Cheese acidity
0.569f
0.650e
0.598f
0.727bc
0.785a
0.753b
0.684d
0.753b
0.721c
0.029***
Cheese pH
5.61a
5.51ab
5.57a
5.36c
5.29c
5.32c
5.47b
5.37c
5.30c
0.099***
Cheese TS
57.76a
55.05b
57.12a
52.48c
47.59e
50.36d
53.42c
49.19d
52.75c
1.351***
Cheese Ash
3.53e
3.41f
3.50e
3.97c
3.88d
3.95c
4.12a
4.05b
4.09ab
0.055***
Cheese Salt
1.89e
1.81f
1.88e
2.15bc
1.95d
2.10c
2.29a
2.15bc
2.20ab
0.061***
Cheese Ca
1.13b
0.84bc
1.71a
0.63bc
0.43c
0.62bc
0.73bc
0.59bc
0.71bc
0.0571***
Cheese Fat
35.54a
33.02c
34.85b
24.79g
22.04i
23.26h
27.30d
25.41f
26.47e
0.350***
Cheese TN
4.84a
4.42c
4.63b
3.72e
3.41g
3.52f
3.90d
3.47fg
3.73e
0.104***
Cheese WSN
0.198f
0.225e
0.210ef
0.321bc
0.350a
0.334ab
0.294d
0.335ab
0.313c
0.018***
Cheese TVFA
5.33h
7.09f
6.21g
8.29e
9.57c
8.39e
9.18d
11.29a
10.16b
0.292***
Meltability
21.23f
24.74d
22.16ef
34.19c
38.55a
36.24b
22.62e
24.74d
22.91e
0.081***
Oiling off
83.48a
73.41c
77.83b
59.67e
50.49g
55.40f
62.43d
49.84g
56.51f
1.319***
Appeance& color
7.90a
7.90a
7.60ab
6.10d
6.10d
6.60cd
7.20abc
6.60cd
7.00bc
0.86***
Body& Texture
32.50de
31.20e
33.00de
36.20a
33.40cd
36.10ab
34.00bcd
33.80cd
35.40ab
2.131***
Flavor
36.00b
32.60c
38.00b
40.40a
37.60b
41.40a
31.60c
28.60d
33.20c
2.356***
Effect of storage time (days)
0
15
30
45
60
LSD
Cheese Acidity
0.628e
0.659d
0.693c
0.727b
0.759a
0.022***
Cheese pH
5.47a
5.50a
5.44ab
5.38bc
5.34c
0.074***
Cheese TS
51.42c
52.10bc
52.76b
53.97a
54.03a
1.007***
Cheese Ash
3.484e
3.708d
3.859c
4.005b
4.117a
0.041***
Cheese Salt
1.811e
1.957d
2.049c
2.147b
2.236a
0.045*
Cheese Ca
1.059a
0.747a
0.758a
0.767a
0.778a
0.425
Cheese Fat
26.94e
27.6d
28.12c
28.59b
29.09a
0.261***
Cheese TN
3.805c
3.917b
3.992ab
4.027a
4.063a
0.077***
Cheese WSN
0.225e
0.255d
0.284c
0.315b
0.353a
0.014***
Cheese TVFA
6.49e
7.81d
8.45c
9.20b
9.90a
0.217***
Meltability
16.81e
22.16d
27.93c
32.80b
38.13a
0.805***
Oiling off
52.11e
57.44d
62.72c
68.86b
75.00a
0.983***
Appeance& color
7.78a
7.50a
7.17a
6.44b
6.11b
0.641***
Body& Texture
31.89c
33.11bc
33.94b
34.67ab
36.17a
1.589***
Flavor
32.78d
34.44cd
35.67bc
36.55ab
38.00a
1.756***
Significant different at p ( *0.05, **0.01, ***0.001). For each effect the different letters in the means the multiple comparison are different from each.
Letters a is the highest means followed by b, c …..etc.
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