Basic Kinetic Approaches in Sterilization Kinetics

The death rate for a population of microbial cells is commonly found to obey a logarithmic law, and this is expressed by formal first-order kinetics 

A consequence of the first-order law is that t - 00 for = 0. However, the first-order concept cannot predict the behavior of a single cell it is only a statistical approach to the behavior of a large population. Integrating Equ. 5.265 with initial conditions N = Nq and t = Iq gives 

Alternative expressions for the kinetic constants are sometimes used in different technologies (see Equs. 5.8 and 5.9). Supplementary to the D value and Z value, an F value is known, representing the value of at 121°C. 

Another case of logarithmic behavior appears when air is sterilized (filtered) by fibrous media, and the log-penetration law is valid. This law relates filter effectiveness (N/Nq) to the filter thickness L and a factor Kp 

The filter constant Kp depends on fiber diameter, volume fraction of fibers in the filter, and a fiber effectiveness factor (Chen, 1955). 

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