Quantitative Measure Of Sterilization

The rates of reactions in foods, such as the destruction of microorganisms or nutrients, are generally first-order reactions described by

where c is the concentration of any component at time t and kT is the rate constant at temperature T. The temperature dependency of the rate constant is given by the well-known Arrhenius law kT = k<fi-E°/RT

where k0 is a constant called frequency factor, Ea is the activation energy, and R is the gas constant. The temperature T normally varies in a heating process. To obtain the final concentration in changing temperature, equation 1 is integrated between initial concentration C; and final concentration c at time t to get

°IRTdt

In the food literature, equation 3 is used in a different form. Instead of referring to a final concentration, an equivalent heating time of F0 is used that gives the same final concentration when temperature T is constant at a reference value. For a reference temperature of TR, if the rate constant is kTn,

-EJRTg

When the process temperature T stays close to TR, equation 4 can be simplified by noting TTR T%. A new parameter Z is defined in terms of the activation energy Ea to describe the temperature dependence of reaction as

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