Answers to each part are in BOLD The following data were obtained from a thermal
ID: 65656 • Letter: A
Question
Answers to each part are in BOLD
The following data were obtained from a thermal resistance experiment conducted on a spore suspension at 113oC. Determine the DT value of the microorganism (4 min).
Time (min)
Number of spore survivors
0
106
4
1.05 x 105
8
1.08 x 104
12
1.03 x 103
) For the same spore suspension, a set of DT was measured at different temperatures, as shown below. Determine the thermal resistance of the spore, z value in oC (11oC).
Temperature (°C)
D (minutes)
104
27.5
107
14.5
110
7.5
113
4.0
116
2.2
3-c) A sterilizer is used to obtain a 12-log reduction of the same spore in a juice product with an initial load of 5.7 x 108 spores per mL of product. How long would it take to achieve the 12 log reduction at the following temperature: a) 116 °C and b) 121oC; c) what is the final concentration of spores per liter? d) what is F0? (26.4 min; 9.3 min; 0.57/L; 9.3 min)
Time (min)
Number of spore survivors
0
106
4
1.05 x 105
8
1.08 x 104
12
1.03 x 103
Explanation / Answer
1. The solution is found by plotting a graph. On a semilog grapg, number of spore survivors and time in min is plotted. From the straight line the time for one log reduction in the population of spores is determined. which gives D value.
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