Moist-heat sterilization inactivation

Moist-heat sterilization is achieved when water vapor (or, more generically, moist heat, i.e., a suitable combination of temperature and humidity) at a definite temperature is introduced or generated (even indirectly) at the level of the micro-organisms to be inactivated and is maintained in such conditions for a definite time. As explained in detail hereafter, moist-heat sterilization proceeds as an inverse logarithmic progression. Therefore, only a treatment of infinite duration provides absolute certainty that all micro-organisms have been inactivated. 

Moist-heat sterilization is achieved when a suitable combination of temperature and humidity can be introduced (or indirectly generated) at the level of the micro-organisms to be inactivated. The classic way to achieve this is by means of pressurized saturated steam at the temperature of 121°C (250°F). However, other sterilizing media (e.g., superheated water or a steam-air mixture) are also frequently used to obviate certain problems that pure steam may pose. Sometimes the load is rotated inside the chamber of the sterilizer to achieve particular results. 

As with sterilization by saturated steam, thermal damage to biological systems as a result of dry heat sterilization processes is a function of absorbtion of heat energy. Inactivation of microorganisms is by oxidation. The kinetics of oxidation and population death approximate to first-order reactions, but they are significantly different from the processes of coagulation of cellular proteins found with moist heat sterilization in that they require far higher temperatures and proceed more slowly. 

Moist heat (<100°C) Cold/freezing Ionizing radiation Disinfection Preservation Sterilization Inactivation of bacterial cells (56°C) in vaccine production See text... 

---