Effectiveness of the Thermal Treatments Used for Curd Stretching in the Inactivation of Shiga Toxin-Producing O157 and O26 Escherichia coli
Table 2
Characteristics of curd, temperature profiles recorded during the stretching phase, and changes in the counts () of O157 and O26 Escherichia coli.
E. coli serogroup
O26
O157
Microbial starters
Curd pH
5.1
5.0
5.2
5.0
5.1
5.1
5.2
5.0
5.3
Temperature profile
nc
nc
nc
1
2
3
1
2
3
Temperature range (°C)
Time in seconds
56.1–64
325
102
147
21
22
6
23
144
109
64.1–66
650
204
294
21
22
6
16
69
68
66.1–68
11
90
27
14
18
6
17
69
102
68.1–70
40
1
12
13
4
24
75
39
70.1–72
4
1
4
27
9
32
88
10
72.1–74
2
1
7
24
16
40
134
74.1–76
56
10
38
68
14
76.1–78
19
36
221
9
78.1–80
10
12
10
>80
16
Max temperature
65
71
64
75
73
77
79
80
72
Stretching time (min)
21.9
9.1
10.3
1.9
1.5
1.9
7.9
12.8
5.1
Count before stretching
4.23
4.12
4.05
4.39
4.43
4.53
4.85
4.46
4.45
Count after stretching
3.04
1.36
3.04
−0.04
0.88
0.44
<−0.53
<−0.53
0.63
, natural whey left over from the previous day’s cizza is added to lukewarm milk; , artificial starter culture of Streptococcus thermophilus is inoculated in lukewarm milk; nc, not considered for the modelling purpose.
