#8: Sterilization Please refer to Figure 10.12 (b) in the text, which indicates
ID: 263003 • Letter: #
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#8: Sterilization Please refer to Figure 10.12 (b) in the text, which indicates the death rate for E.coli at different temperatures. Using the line for a temperature of 56 °C given in this figure, determine the decimal reduction time D (in minutes) and the first order death rate k (in inerse minutes) for E. coli at that temperature. Then use that ke value and the sterilization chart in Figure 10.14 to determine the time duration necessary for sterilizing a vessel with 104 probability of failure and an estimated initial contamination with ten thousand E. coli cells.Explanation / Answer
Decimal Reduction Time or D value is the time when 90% of the organismas are killed, means reduction by one log or one decimal.
From the graph give, D value at 560 C [D56 ] = 6 mins.
First order death rate, k = 2.303 / D = 2.303 /6 = 0.38 mins -1
From Sterilization chart given, duration of sterilization = 18.5 mins.
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