The main difference between Moist Heat Sterilization and Dry Heat Sterilization is that Moist Heat Sterilization is carried out through water (steam), whereas, Dry Heat Sterilization is carried out under dry conditions.
Moist Heat Sterilization vs. Dry Heat Sterilization
Heat is the best way to kill microbes as it destroys the enzymes present in them as well as their proteins. That is the reason; sterilization is the best process to kill microbes as this process uses heat in it either wet heat or dry heat. So, when this process is carried out at high pressure through water (steam), it is called moist heat sterilization. On the other hand, when the process of sterilization is carried out at high temperature with dry conditions, it is called dry heat sterilization. The temperature of the steam in moist heat sterilization is lower. Whereas, the temperature of the steam in dry heat sterilization is higher than moist heat sterilization. As their name suggests, both the processes have different principles of working to sterilize the types of equipment. The organism’s enzymes and the structural proteins are destroyed through moist heat sterilization. As a result, the death of the organisms occurs. Destructive oxidation method is used to kill the organisms in dry heat sterilization. This helps in destroying large contaminating bio-molecules like proteins. The moist heat sterilization method is more effective than the dry heat sterilization. For example, endospores of Bacillus anthracis are killed in 2-15 minutes through moist heat at the temperature of 100°C, but they are killed by dry heat sterilization process in 1-2 hours at the temperature of 15.
What is Moist Heat Sterilization?
In moist heat sterilization, water (steam) is used at a high-pressure level. This method is used for heat-sensitive materials and also for materials by which steam is permeable. Moist heat sterilization can also be used to sterilize the culture media. In the process of moist heat sterilization, the most resistant of the spores require 121°C temperature for around 30 minutes. It is a more effective method as compared to dry heat sterilization. This statement can be supported by the fact that by this method, sterilization can be achieved in a shorter duration at lower temperatures. This method is easy to control, non-toxic and is of low cost. There are chances of getting an instrument damaged because the instruments remain wet after the completion of the process and may lead to rust.
What is Dry Heat Sterilization?
Dry heat is used in this method for sterilizing different materials. It is an old technique to sterilize the instruments. It requires more time than moist heat sterilization. Heat can be supplied in the form of direct flame or hot air. In his process, microorganisms are killed by the oxidation of the chemical bonds and their proteins of microorganisms. The temperature required in this process is 160 to 170-degree Celsius while the time needed is 1 to 2 hours. Dry heat sterilization is harmless to the environment, and there are no chances of rusting of instruments in this type of sterilization because the instruments are not exposed to moisture.
- The process of sterilization which is carried out at high pressure through water (steam) is called moist heat sterilization, whereas, when the process of sterilization is carried out at high temperature with dry conditions, it is called dry heat sterilization.
- As the name shows, moist heat sterilization requires water and steam; on the other hand, in dry heat sterilization, there is no need for steam and water.
- Coagulating protein of the microbes helps very effectively to complete the moist heat sterilization, conversely, chemical bonds present in microbes and oxidation of the protein help in completing the dry heat sterilization.
- Moist heat sterilization is done under pressure, on the flip side, dry heat sterilization is done on direct flame.
- Autoclaving and Boiling are the further types of moist heat sterilization, while, hot air oven, incineration, microwave, and Bunsen burner (flame) are the further types which are used to carry out dry heat sterilization.
- Less time is required to complete the moist heat sterilization, whereas, dry heat sterilization requires more time to accomplish as compared to the moist heat sterilization.
- Moist heat sterilization causes rusting of instruments because they are exposed to moisture. Moreover, it cannot be performed for heat-sensitive instruments because they may be damaged if they are sterilized again and again whereas, whereas dry heat sterilization is harmless to the environment and there are no chances of rusting of instruments in this type of sterilization because the instruments are not exposed to moisture.
From the above discussion, it is summarized that moist heat sterilization is the process of sterilization that is carried out through water or steam, etc. and requires less time to complete whereas, dry Heat Sterilization is carried out under dry conditions and requires more time.