Livestock Research for Rural Development 22 (5) 2010 Notes to Authors LRRD Newsletter

Citation of this paper

Influence of cold storage and mixing on properties of buffalo’s and cow’s milk

E M A Ammar, M M Ismail*, A A El-Shazly and M Z Eid*

Dairy Department, Faculty of Agriculture, Mansoura University, Egypt
* Dairy Technology Department, Animal Production Research Institute, Agriculture Research Center, Egypt
abo-omar98@hotmail.com

Abstract

The effect of cold storage (4-5C) for 48 hours and blinding different milkings to cold stored milk on some chemical composition, rheological properties and microbial quality of the buffalo’s and cow’s  milk were studied. The results obtained indicate that no clear effects of  cold storage of buffalo's and cow's milk on them TS, fat and total protein contents whereas the acidity values slightly increased. Cold storage of both kinds of milk increased the rennet coagulation time (RCT), curd tension and curd syneresis values. Also, preservation of  buffalo's and cow's milk at 4-5C increased total viable bacterial (TVBC), lactic acid, psychrophilic bacteria, proteolytic, lipolytic, colifom bacteria, sporeformers, and moulds and yeast counts.

 

Adding evening and morning milk to cold stored buffalo's and cow's milk decreased the acidity and curd syneresis values and increased the pH, TS, fat, total protein, RCT and the curd tension  values. Mixing evening and morning milk with cold stored milk lowered the above mentioned microbial groups.

Key words: different milkings, milk refrigeration, rheological properties of milk


Introduction

Milk is highly nutritious food which is suitable for both children and adults as an excellent source of energy, protein, vitamins and minerals. However, due to its rich nutritional composition, it is also ideal for microbial growth. Fresh raw milk is easily deteriorated to become unsuitable for processing and human consumption.

      

The distance between the farm, the dairy and the consumer became greater, as did the time lapse between milking and the drinking of milk. Milk storage on the farm, and the time taken to bridge the gap between producer and consumer gave bacteria the chance to acclimatize and grow in this nutritious liquid. It became a problem to keep milk quality at the same level as just after milking.

      

Scientific research has revealed that lactoperoxidaes, a naturally existing enzyme in raw milk, catalyses the chemical reaction of thiocyanate, which is also naturally found in milk, in the presence of  hydrogen peroxide. The resulting compound has a bacteriostatic effect on most bacteria and even a bactericidal effect on some bacteria e.g. E.coli. However, the LP-s loses its effect in raw milk within 2 hours after being drawn from the udder. Growth of microorganisms then begins. A safe and effective system of raw milk preservation is therefore required by the dairy sector. Preservation should not adversely affect the nutritional characteristics of raw milk. Refrigeration is currently recognized as the preferred milk preservation method. At low temperature chemical processes and microbiological growth will slow down, delaying the reduction in the quality of stored milk.

      

The rate at which milk is cooled has a major influence on the bacterial content of raw milk. After having followed the right milking and hygienic procedures, milk should be cooled to 4C or below as soon as possible after it leaves the udder. It should be cooled to this temperature within 3 hours of the start of milking. However, any reduction in cooling time will increase milk quality and reduce energy costs. It is also very important for the milk to be stored at below 4C between milkings. Bacteria counts rise rapidly once milk temperatures rise above 4C. Refrigeration is the single most important factor in maintaining quality after the milk leaves the udder.

      

On the other side, many of cheese makers in Egypt believe that the addition of fresh milk to cold milk stored in cooling tank had bad impact on the properties of the resultant cheese. So, the aim of this investigation was to study the effect of cold storage and mixing different lactating milk with equal amounts on the chemical composition, rheological properties and microbial quality of the buffalo’s and cow’s  milk.

 

Material and methods 

Materials

 

Fresh cow’s milk which used in this study were obtained from El-Serw Animal Production Research Station, whereas fresh buffalo’s milk was obtained from Mahlt Moussa Animal Production Research Station, Ministry of Agriculture. All chemicals used were analytical grade.

 

Methods

 

Milk 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. The curd tension was determined using the method of Chandrasekhara et al (1957).The rennet coagulation time (RCT) was determined according to Davies and White (1958) whereas the curd syneresis was measured as given by Mehanna and Mehanna (1989). Milk samples were analyzed for total viable bacterial count (TVBC), lactic acid (LAB), proteolytic, lipolytic, colifom, sporeformers, psychrophilic bacteria, moulds and yeast counts according to the methods described by the American Public Health Association (1992). The obtained results were statiscally analyzed using software package (SAS 1991) based on analysis of variance. When F-test was significant, least difference (LSD) was calculated according to Duncan (1955) for the comparison between means.

 

Results and discussion 

Effect of cold storage and mixing various lactating milks on chemical composition of milk

 

Chemical composition of buffalo's or cow's milk as affected by refrigerated storage and blending different lactation milks was tabulated  in Table 1.  

Table 1.  Effect of cold storage and mixing various lactating milk on the chemical composition of buffalo's and cow's milk

Treatments

Acidity, %

pH values

Total solids, %

Fat, %

Protein, %

Buffalo

Cow

B

C

B

C

B

C

B

C

A

0.16

0.15

6.38

6.40

16.7

11.6

3.3

7.4

4.84

3.14

B

0.17

0.16

6.36

6.37

16.7

11.7

3.3

7.5

4.81

3.17

C

0.15

0.14

6.43

6.42

16.8

11.9

4.0

7.7

4.94

3.27

D

0.16

0.15

6.39

6.39

16.7

11.7

3.7

7.6

4.85

3.18

E

0.17

0.16

6.35

6.38

16.7

11.7

3.7

7.6

4.86

3.16

F

0.17

0.15

6.36

6.38

16.6

11.7

3.8

7.2

4.77

3.17

G

0.18

0.16

6.33

6.35

16.6

11.7

3.7

7.6

4.82

3.14

H

0.18

0.16

6.32

6.36

16.8

11.8

3.8

7.7

4.85

3.14

I

0.19

0.17

6.30

6.31

16.8

11.8

3.8

7.5

4.83

3.11

J

0.18

0.16

6.32

6.35

16.8

11.7

3.6

7.7

4.85

3.15

A: Fresh morning milk.

B : Cold milk at 4 -5C for 10 hours.

C : Fresh evening milk.

D : Mixing milk of treatments B and C.

E : Milk of treatment D after storage at 4 -5C for 24 hours.

F : Mixed milk of  treatments A and E.

G : Milk of treatment F after cold storage 4 -5C for evening next day.

H : Mixed milk of  treatments C and G.

I : Milk of treatment H after cold storage 4 -5C for 48 hours.

J : Mixed milk of  treatments A and I.

Generally, it is observed that buffalo's milk had higher total solid (TS), fat and total protein contents than those of cow's milk. Acidity and pH values were similar in both types of milk.

      

However, buffalo's and cow's milk were preserved at 4-5C, but the acidity ratios slightly increased and pH values deceased after 10 hours of cold storage (Treatment B). On the other hand, evening milk had lower acidity and higher pH values than those of morning milk so when fresh evening milk (Treatment C) was added to cold stored milk (Treatment B), the acidity value lowered again (Treatment D) but it raised after storage of milk for morning second day (Treatment E). This may be due to the growth of lactic acid bacteria. As a general, the changes in acidity and pH values of buffalo's or cow's milk between increasing and decreasing were observed during storage of milk for 48 hours at 4-5C and adding fresh morning and evening milks to stored milk.

      

Ibrahim and Hanafy (1990) reported that cooling of milk at low temperature (8-12C) for 15-18 hrs., increased the acidity of stored milk by about 0.01-0.02% an made the milk suitable for cheese making compared with fresh milk. El-Wahsh (1998) showed that significant increase in acidity % of raw, pasteurized and boiled cow's and buffaloe's milk samples and consequently significant decrease in their pH values through the cold storage was observed. Abdel-Kader (1999) stated that cooling the cow's milk resulted in crease of acidity and decrease of pH, this is may be due to the activity of psychrotrophic bacteria during 48 hours.

      

It could be concluded from Table 1 that the rates of increasing of acidity values during cold storage of buffaloe's milk were higher than that of cow's milk. The acidity increasing rates after 48 hours of refrigerated storage were 18.75 and 6.67% for buffaloe's and cow's milk respectively. Similar results were found by Ismail (1997)  who represented that lower rate of development of acidity was observed in cow's than those of buffaloe's milk samples. After 8 hours of incubation at 30C the rate of buffaloe's acidity development was 31.7% , while respective value for cow's milk was 15.5%.

      

No clear effects of  cold storage of buffaloe's and cow's milk on TS, fat and total protein contents were observed. Similar results were found by Ghaleb and Rashed (1983). Mixing evening milk to the morning one increased TS, fat and total protein values of the resultant milk. This may be explained by the higher TS, fat and total protein contents of evening milk as compared with that of morning milk.

 

Effect of cold storage and mixing various lactating milks on some rheological properties of milk

 

Effect of refrigerated storage and blending different milking milks on rennet coagulation time (RCT), curd tension and curd syneresis values of buffalo's and cow's milk were illustrated in Table 2.

Table 2.  Effect of cold storage on some rheological properties of buffalo's and cow's milk.

Treatments

RCT, sec.

Curd Tension, gm

Curd syneresis, gm/15 gm of curd*

Time, minutes

10

30

60

120

Buffalo

Cow

B

C

B

C

B

C

B

C

B

C

A

94

160

46.33

27.49

3.54

5.46

5.21

7.51

6.42

8.83

7.51

9.47

B

88

149

47.65

28.56

3.60

5.93

5.41

7.73

6.53

8.91

7.58

9.69

C

90

143

47.11

30.92

2.68

4.35

4.31

6.95

5.46

8.25

6.46

8.97

D

92

150

47.59

29.97

3.32

4.74

4.73

7.18

5.91

8.69

6.75

9.61

E

83

142

43.55

27.05

4.11

5.62

5.74

7.21

6.85

8.77

7.72

9.52

F

91

148

45.14

28.01

3.72

5.62

5.35

7.38

6.57

8.31

7.54

9.41

G

85

140

42.04

26.53

3.74

5.65

5.77

8.55

6.64

8.97

7.64

9.86

H

85

143

45.14

27.70

3.54

5.13

5.31

7.75

6.43

8.61

7.43

9.42

I

79

140

44.09

26.31

3.93

5.28

5.69

9.14

6.81

10.32

7.91

11.07

J

84

150

44.84

26.63

3.36

6.11

5.16

8.68

6.65

9.89

7.73

10.64

*Whey excluded (grams) from 15 gm of curd kept at room temperature after 10, 30, 60 and 120min.

A: Fresh morning milk.

B : Cold milk at 4 -5C for 10 hours.

C : Fresh evening milk.

D : Mixing milk of treatments B and C.

E : Milk of treatment D after storage at 4 -5C for 24 hours.

F : Mixed milk of  treatments A and E.

G : Milk of treatment F after cold storage 4 -5C for evening next day.

H : Mixed milk of  treatments C and G.

I : Milk of treatment H after cold storage 4 -5C for 48 hours.

J : Mixed milk of  treatments A and I.

Buffalo's milk had lower RCT and curd syneresis and higher curd tension values than those of cow's milk. El-Shazly et al (1998) showed that RCT of cow's milk was longer than that of buffaloe's being 185 and 90 sec., respectively.

       

El-Senaity et al (2000) found that the type of milk clearly affected the RCT and curd syneresis. Ewe milk gave the longest RCT, followed by cow milk and buffaloe milk, while goat milk showed the shortest RCT. Ewe and buffaloe milk gave a little amounts of whey (syneresis values) while cow and goat milk gave much amounts of whey. This might be attributed to the higher total solids content of ewe and buffaloe milk, which gave a compact curd less whey drainage.

      

Cooling of buffalo's or cow's milk at 4-5C for 10 hours slightly decreased the RCT. With prolongation of cold storage, more reduction in RCT values of cow's milk was noticed. This effect could be referred to the increasing acidity of milk within cold storage. It is known that development of dissolves colloidal calcium, consequently increased Ca++ which produce firm curd and reduced the RCT (Abdel-Kader 1999).Also, similar trend was found by Farag et al (1993) and Ismail (2005) who reported that increasing acidity value of buffaloe's milk as result of adding sour buttermilk decreased the RCT values.

      

On contrast, the decrease in RCT disagree with those reported by Youssef et al (1975) and Ibrahim et al (1988), That cold storage caused a noticeable increase in RCT and this increase might be due to the dissociation of casein into the soluble casein, particularly β-casein (Fox 1969, Rose 1968 and Ali et al 1980).

      

On the other side, RCT values of evening buffalo's and cow's milk were lower than those of morning milk. Blending of fresh raw milk from various milking with cold stored milk increased its RCT values.

     

With regard to curd tension, cold preservation of fresh buffalo's or cow's milk for 10 hours slightly raised the curd tension meanwhile, adding fresh morning and evening milk to stored milk and re-storage under 4-5C decreased the curd tension of the resultant milk. El-Wahsh (1998) showed that results obtained from cold-storage raw buffaloe's milk revealed significant increase in curd tension of milk.

      

Curd tension values of evening milk were always higher than those of morning milk. This may by attributed to the high TS, fat and protein contents in evening milk comparing with morning milk. Because the curd tension values of fresh milk were more than that of stored and mixed milks, so adding the former milk to the later increased its curd tension values.

      

From Table 2, it could be observed that cooled storage of buffalo's or cows' milk markedly increased the curd syneresis values compared with fresh milk. The obtained results agreed with those of Salama et al (1982) who stated that pasteurization and cold storage increased the rennet coagulation time of milks, whereas the rate of whey drainage of curd decreased on pasteurization and increased upon storage. Kehagias (1983) showed that curd syneresis of ewes' and cows' bulk milk stored  for 0,1 or 2 days at 4-5C increased with storage time increase.

      

Significant decrease in curd syneresis values of evening buffalo's and cow's milk was found comparing with that of morning one. Adding fresh milk from various lactations to buffaloe's or cow's milk preserved at 4-5C reduced the curd syneresis. This may by due to increase the TS content of stored milk by adding evening milk which had reveres effect on curd syneresis. General speaking, the amount of whey drained from 15gm of curd increased as syneresis time increased and in all treatments. Statistical analysis of variance (Tables 3 and 4) showed that the differences in RCT, curd tension and curd syneresis values between treatments were highly significant (P<0.001).

Table 3.  Statistical analysis of buffalo's milk treatments

Effect of buffaloe's milk treatments

Analysis

LSD

J

I

H

G

F

E

D

C

B

A

0.3*

0.19a

0.19a

0.18ab

0.18ab

0.17ab

0.17ab

0.16ab

0.15b

0.17ab

0.16ab

Acidity

0.03***

6.30f

6.30f

6.32ef

6.33def

6.36bcd

6.35cde

6.39a

6.43a

6.36bcd

6.38bc

pH

0.03***

16.8c

16.9b

16.8c

16.6g

16.6h

16.7ef

16.7d

16.8bc

16.7de

16.7fg

TS

0.30***

7.50bc

7.60ab

7.70ab

7.60ab

7.50bc

7.60ab

7.60ab

7.70ab

7.50bc

7.40bcd

Fat

0.03***

4.83cde

4.87b

4.85bcd

4.82de

4.84bcde

4.86bc

4.94bcd

4.94a

4.81e

4.84bcde

TP

3.05***

84.0f

79.0g

85.0ef

85.0ef

91.0bcd

83.0f

92.0bc

90.0cd

88.0de

94.0 ab

RCT

2.16***

44.8i

44.1j

45.1h

42.0l

45.1h

43.6k

47.6b

47.1d

47.7a

46.3g

Curd tension

0.03***

3.36g

3.93b

3.54f

3.74d

3.72d

4.11a

3.32h

2.68l

3.60e

3.54f

Curd syneresis10min

0.03***

5.16h

5.69b

5.31f

5.77a

5.35e

5.74a

4.73i

4.31j

5.41d

5.21g

Curd syneresis30min

0.03***

6.65c

6.81b

6.43g

6.57c

6.57d

6.85a

5.91i

5.46j

6.53e

6.42g

Curd syneresis60min

0.03***

7.73b

7.91a

7.43f

7.64c

7.54e

7.72b

6.75h

6.46i

7.58d

7.51e

Curd syneresis120min

3.05***

195a

194a

122c

1310b

1050e

110d

90.0f

83.0g

102f

91.0f

Total bacterial count

3.05***

70.0a

69.0a

51.0d

56.0c

42.0e

40.0e

32.0f g

19.0k

34.0f

25.0i j

Lactic acid bacteria

3.05***

100.0a

98.0a

63.0c

97.0b

54.0d

53.0d

40.0f

24.0i

75.0e

37.0fg

Psychrophilic bacteria

3.05***

22.0b

24.0a

15.0c

15.0c

10.0de

11.0d

7.00ef

3.0g

10.0de

7.00ef

Proteolytic bacteria

3.05***

95.0b

98.0a

80.0d

85.0c

73.0e

77.0d

67.0f

49.0j

72.0e

61.0g

Lipolytic bacteria

3.05***

75.0b

79.0a

59.0c

62.0c

53.0d

51.0d e

42.0f

30.0g h

49.0e

42.0i

Coliforms bacteria

3.05***

22.0ab

25.0a

17.0bc

20.0bc

12.0de

13.0d

9.0ef g

5.00h

11.0d e f

6.0g h

Spore forming bacteria

3.05***

95.0a

98.0a

84.0b

82.0b

72.0d

75.0cd

68.0e

61.0g

78.0c

72.0d

Moulds and yeasts

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 .
 A: Fresh morning milk.

B : Cold milk at 4 -5C for 10 hours.

C : Fresh evening milk.

D : Mixing milk of treatments B and C.

E : Milk of treatment D after storage at 4 -5C for 24 hours.

F : Mixed milk of  treatments A and E.

G : Milk of treatment F after cold storage 4 -5C for evening next day.

H : Mixed milk of  treatments C and G.

I : Milk of treatment H after cold storage 4 -5C for 48 hours.

J : Mixed milk of  treatments A and I.

Table 4.  Statistical analysis of cow's milk treatments

Effect of cow's milk treatments

Analysis

LSD

J

I

H

G

F

E

D

C

B

A

0.031

0.16a

0.17a

0.16a

0.16a

0.15a

0.16a

0.15a

0.14a

0.16a

0.15a

Acidity

0.090*

6.35ab

6.31b

6.36ab

6.35ab

6.38ab

6.38ab

6.39ab

6.42a

6.37ab

6.40a

pH

0.031***

11.7d

11.8b

11.8b

11.7d

11.7cd

11.7bc

11.7cd

11.9a

11.7e

11.6e

TS

0.900

3.60a

3.80a

3.80a

3.70a

3.80a

3.70a

3.70a

4.00a

3.30a

3.30a

Fat

0.031***

3.15cd

3.11ef

3.140de

3.140de

3.170bcd

3.16cd

3.18bc

3.27a

3.17bcd

3.14de

TP

3.055***

150d

140e

143e

140e

148d

142e

150d

143e

149d

160b

RCT

0.031***

26.6k

26.3m

27.7f

26.5l

28.0e

27.1h

30.0b

30.9a

28.6d

27.5g

Curd tension

0.031***

6.11b

6.28a

5.13h

5.65d

5.62d

5.62d

4.74i

4.35j

5.93c

5.46e

Curd syneresis10min

0.031***

8.86b

9.14a

7.75d

8.55c

7.38g

7.21j

7.18j

6.95k

7.73d

7.51f

Curd syneresis30min

0.031***

9.89b

10.32a

8.61h

8.97c

8.31j

8.77f

8.69g

8.25k

8.91d

8.83d

Curd syneresis60min

0.031***

10.64b

11.07h

9.42h

9.86c

9.41i

9.52f

9.61e

8.97i

9.69d

9.47g

Curd syneresis120min

3.055***

172b

176a

109d

115c

89.0e

91.0e

79.0g

61.0i

83.0f

68.0h

Total bacterial count

3.055***

70.0b

74.0a

48.0c

50.0c

38.0d

37.0d

21.0fgh

18.0h

23.0fg

20.0h

Lactic acid bacteria

3.055***

140a

142a

88.0c

92.0b

61.0e

68.0d

40.0f

9.0h

43.0f

32.0g

Psychrophilic bacteria

3.055***

14.0a

15.0a

8.0bc

9.0b

6.0bcd

6.0bcd

4.0de

2.0e

5.0cde

4.0de

Proteolytic bacteria

3.055***

86.0a

89.0a

63.0c

67.0b

50.0e

55.0d

41.0g

37.0i

46.0f

49.0i

Lipolytic bacteria

3.055***

72.0a

74.0a

55.0c

61.0b

45.0d

46.0d

31.0g

22.0h

35.0f

29.0g

Coliforms bacteria

2.935***

13.0a

15.0a

9.0b

9.0b

4.0cd

5.0c

2.0de

0.0e

3.0cd

2.0de

Spore forming bacteria

3.055***

94.0b

98.0a

82.0d

86.0c

74.0e

72.0e

57.0f

39.0i

56.0f

48.0g

Moulds and yeasts

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 .

A: Fresh morning milk.

B : Cold milk at 4 -5C for 10 hours.

C : Fresh evening milk.

D : Mixing milk of treatments B and C.

E : Milk of treatment D after storage at 4 -5C for 24 hours.

F : Mixed milk of  treatments A and E.

G : Milk of treatment F after cold storage 4 -5C for evening next day.

H : Mixed milk of  treatments C and G.

I : Milk of treatment H after cold storage 4 -5C for 48 hours.

J : Mixed milk of  treatments A and I.

A: Fresh morning milk.

B : Cold milk at 4 -5C for 10 hours.

C : Fresh evening milk.

D : Mixing milk of treatments B and C.

E : Milk of treatment D after storage at 4 -5C for 24 hours.

F : Mixed milk of  treatments A and E.

G : Milk of treatment F after cold storage 4 -5C for evening next day.

H : Mixed milk of  treatments C and G.

I : Milk of treatment H after cold storage 4 -5C for 48 hours.

J : Mixed milk of  treatments A and I.

Effect of cold storage and mixing various lactating milks on some microbial groups of milk

 

Effect of cold storage and mixing various lactations milks on total viable bacterial (TVBC), lactic acid, psychrophilic bacteria, proteolytic, lipolytic, colifom bacteria, sporeformers, and moulds and yeast counts of buffalo's and cow's milk were recorded in Table 5.

Table 5. Effect of cold storage on some microbial groups of buffalo's and cow's milk.

Treatments

TVBC,

x106

Lactic acid

Bacteria, x103

Psychrophilic

Bacteria, x103

Proteolytic

Bacteria, x103

Lipolytic

Bacteria, x103

Coliform

Bacteria, x103

Spore forms

bacteria, x103

Moulds and

Yeasts, x103

Buffalo

Cow

B

C

B

C

B

C

B

C

B

C

B

C

B

C

A

91

68

25

20

37

22

7

4

61

49

42

29

6

2

72

48

B

104

83

34

23

50

43

10

5

72

46

49

35

11

3

78

56

C

83

61

19

18

24

9

3

2

49

37

30

22

5

-

61

39

D

90

79

32

21

40

40

7

4

67

41

42

31

9

2

68

57

E

110

91

40

37

53

68

11

6

77

55

51

46

13

5

75

72

F

105

89

42

38

54

61

10

6

73

50

53

45

12

4

72

74

G

131

115

56

50

67

94

15

9

85

67

62

61

20

9

82

86

H

122

109

51

48

63

88

15

8

80

63

59

55

17

9

84

82

I

194

176

69

74

98

142

24

15

98

89

79

74

25

15

98

98

J

195

172

70

70

100

140

22

14

95

86

75

72

22

13

95

94

A: Fresh morning milk.

B : Cold milk at 4 -5C for 10 hours.

C : Fresh evening milk.

D : Mixing milk of treatments B and C.

E : Milk of treatment D after storage at 4 -5C for 24 hours.

F : Mixed milk of  treatments A and E.

G : Milk of treatment F after cold storage 4 -5C for evening next day.

H : Mixed milk of  treatments C and G.

I : Milk of treatment H after cold storage 4 -5C for 48 hours.

J : Mixed milk of  treatments A and I.

The numbers of these microbial groups were higher in buffalo's milk than those of  cow's milk. As it is expected, all the previous microbial groups numbers increased throw cold storage of  milk. Sanjuan et al (2003) found that significant growth (P < 0.001) was detected for mesophiles, Pseudomonas spp. and lactococci after 96 h storage at 6C; however, numbers of thermodurics, coliforms, lactobacilli and enterococci, did not increase (P > 0.05).

 

The counts of total viable bacterial (TVBC), lactic acid, psychrophilic bacteria, proteolytic, lipolytic, colifom bacteria, sporeformers, and moulds and yeast were higher in fresh morning milk than those of fresh evening milk. As a result of reducing microbial groups numbers in fresh milk compared with cold stored milk, mixing both types of milks decreased the counts of microorganisms of stored buffaloe's milk. However, adding fresh morning third day milk (Treatment L) to stored milk for 48 hours (Treatment K) did not lowered microbial groups number especially total viable bacterial (TVBC),  lactic acid and  psychrophilic bacteria counts. This may be attributed to two reasons: 1) increasing of microbial numbers during cold storage to raise to high counts after 48 hours 2) because continues adding of fresh milk to stored milk, the amount of later milk after 48 hours became higher than that of the former milk so the effect of reducing microbial counts of fresh milk was not pronounced.

      

The numbers of different microorganisms of various buffalo's and cow's milk samples followed the order : total viable bacterial > psychrophilic bacteria >lactic acid bacteria > moulds and yeasts > lipolytic bacteria > coliform bacteria > spore forms bacteria > proteolytic bacteria.

       

The data in Tables 3 and 4 referred to the differences in microbial groups numbers between treatments were highly significant (P<0.001).

 

Conclusion 

 

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Received 3 February 2010; Accepted 31 March 2010; Published 1 May 2010

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