The key difference between dry heat sterilization and steam sterilization is that dry heat sterilization does not have water vapor, whereas steam sterilization involves water vapor.
Sterilization is the process used to destroy all microorganisms in a sample or an environment to prevent the spread of infections. Dry air sterilization and steam sterilization are two such techniques of sterilization.
CONTENTS
1. Overview and Key Difference
2. What is Dry Heat Sterilization
3. What is Steam Sterilization
4. Dry Heat Sterilization vs Steam Sterilization in Tabular Form
5. Summary – Dry Heat Sterilization vs Steam Sterilization
What is Dry Heat Sterilization?
Dry heat sterilization is the use of hot air that usually does not have water vapor for sterilization. However, sometimes this hot air contains a trace amount of water vapor. We can use this sterilization technique for objects. The moisture plays a minimal or no role in this sterilization process.
Conduction is the method used in accomplishing the transfer of heat from a heat source to the object to be sterilized. Heat is usually absorbed by the exterior surface of the object and then is passed to the interior structure and the next level. Finally, the entire object reaches a sufficient temperature required for dry heat sterilization to occur. Generally, this temperature is 160 degrees Celsius for 2 hours or 170 degrees Celsius for 6 – 12 minutes. However, the object has to be dry before the sterilization process; otherwise, water can interfere with the process. Moreover, the dry heat can kill microorganisms through the denaturation of proteins.
Figure 01: A Dry Sterilizer
The two major types of hot air convection sterilizers are gravity convection and mechanical convection. Among them, mechanical convection is common and done using an oven consisting of a blower that can actively force heated air through all the areas of the chamber. This creates a flow in the presence of the blower and ensures achieving a uniform temperature and an equal transfer of heat. Therefore, it is the most efficient method of these two methods.
Typically, the dry heat can lyse proteins in microorganisms, causing oxidative free radical damage to occur and making the cells dry. This can even burn microorganisms into ashes in a similar way to incineration.
What is Steam Sterilization?
Steam sterilization or moisture sterilization is a sterilizing technique involving water vapor. It describes sterilization using hot water vapor as the sterilizing agent. There are different steam sterilization methods that can destroy microorganisms via the denaturation of macromolecules.
This type of sterilization technique uses hot air heavily laden with water vapor. This plays a major role in the sterilization process. Typically, boiling an object or sample for about 30 minutes can kill vegetative cells of microorganisms but not spores. These spores can then germinate in a short time to resume growth. But stem sterilization can kill these spores as well.
Moist hot air can destroy microorganisms via denaturing macromolecules such as proteins. Lysis of cells to destroy them can also play a role. Since sterilization does not refer to the destruction of infectious matter, this method cannot deal with prions. Therefore, prions can survive steam sterilization.
There are two major methods used in this process: tyndallization and the high-pressure method. Tyndallization is an effective method that uses three successive steam treatments over the course of three days. This method can kill vegetative cells, allowing the germination of surviving spores, and also killing the resulting vegetative cells before giving them enough time to form more spores. The high-pressure method, on the other hand, involves the achievement of sterilization after 15 – 30 minutes under a pressure of 106 kPa (1atm) once all the surfaces have reached a temperature of 121 degrees Celsius.
What is the Difference Between Dry Heat Sterilization and Steam Sterilization?
Dry heat sterilization and steam sterilization are two important methods of carrying out the destruction of microorganisms on an object. The key difference between dry heat sterilization and steam sterilization is that dry heat sterilization does not involve water vapor, whereas steam sterilization involves water vapor. Moreover, steam sterilization is more efficient than dry heat sterilization due to the former’s higher penetration ability.
The below infographic presents the differences between dry heat sterilization and steam sterilization in tabular form for side-by-side comparison.
Summary – Dry Heat Sterilization vs Steam Sterilization
Dry heat sterilization is the use of hot air that usually does not contain water vapor for sterilization. Steam sterilization or moisture sterilization is a sterilizing technique involving water vapor. Therefore, the key difference between dry heat sterilization and steam sterilization is that dry heat sterilization does not involve water vapor, whereas steam sterilization involves water vapor.
Reference:
1. “Heat Sterilisation.” An Overview | ScienceDirect Topics.
Image Courtesy:
1. “Dry sterilizer, Autoclave” By Делфина – Own work (CC BY-SA 4.0) via Commons Wikimedia