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Example-sterilization - C vit = C vit,0 e-Kd,v t where C...

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1. A 10-L medium containing a vitamin is to be sterilized. Assume that the number of spores initially present is 10 5 /L. The values of the activation energy E 0d for spores destruction and the pre-Arrhenius constant α are E 0d = 65 kcal/g-mol α =10 36 min -1 The dependence of the specific death rate k d on temperature is given by the Arrhenius equation: k d = αe -Eod/RT where R is 1.987 cal/g-mol- o K. a) If the medium is sterilized at 121 o C, how long will it take to achieve the probability of an unsuccessful fermentation be 10 -3 ? (Assumes that the heating-up and cooling-down periods do not make measurable contributions to sterilization. ) b).If the initial concentration of the vitamin C vit,0 is 30 mg/L. The inactivation of the vitamin is first order, i.e.
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Unformatted text preview: C vit = C vit,0 e-Kd,v, t where C vit is the vitamin concentration at time t (mg/L). K d,v is the inactivation rate constant of vitamin and follows the Arrhenius equation. The corresponding values of E 0d and α are E 0d = 10 kcal/g-mol α =10 4 min-1 The temperature history of the heating, holding and cooling of the medium is as follows: Duration (min) Temperature Δt1=30 T= 80 C Δt2 (from question a) ) T= 121 C Δt3 = 20 T= 50 C Determine the amount of active vitamin in the sterilized medium. c) Compare the Kd of spores at the above three temperatures, and discuss whether it is reasonable to neglect the contributions of heating and cooling periods to sterilization....
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