Difference Between Dry Heat and Moist Heat Sterilization

The key difference between dry heat and moist heat sterilization is that dry heat sterilization refers to the sterilization under high temperature in dry conditions, while moist heat sterilization refers to the sterilization under high temperature and pressure generated through water steam.

Sterilization is the process of killing, inactivating, or removing all microorganisms from a given product or a surface, either in the vegetative or spore state. In other words, it is the destruction of all forms of life including bacterial spores, viruses and prions. There are two main methods of sterilization: physical methods and chemical methods. Physical methods mainly involve heat, filtration techniques and radiation methods. The use of heat has several types; dry heat, moist heat, tyndallization, etc. However, this article mainly focuses on the difference between dry heat and moist heat sterilization.

CONTENTS

1. Overview and Key Difference
2. What is Dry Heat Sterilization
3. What is Moist Heat Sterilization
4. Similarities Between Dry Heat and Moist Heat Sterilization
5. Side by Side Comparison – Dry Heat vs Moist Heat Sterilization in Tabular Form
6. Summary

What is Dry Heat Sterilization?

Dry heat sterilization is one of the physical methods of sterilization. It uses high temperature under dry conditions in order to remove all forms of life from the given sample or a surface. Since it uses only high temperature, it takes more time to sterilize.

Moreover, there are several methods of dry heat sterilization. Hot air oven is the most popular equipment used in dry heat sterilization. Normally, in a hot air oven, the things are kept under 180 0C temperature for 2 hours time. Hot air oven is useful in sterilizing Glassware.

Sunlight, incineration and direct flaming are other dry heat sterilization methods commonly used in sterilization. Inoculating loops and needles can be sterilized by direct flaming. Dry heat kills microorganisms by protein denaturation, oxidative damage and toxic effect of elevated level of electrolytes.

What is Moist Heat Sterilization?

Moist heat sterilization is another physical method used in sterilization. As its name indicates, it utilizes water steam. Thus, moist heat sterilization takes place under wet conditions. Generally, moist heat sterilization occurs under high pressure and high temperature. Hence, it takes less time to sterilize, unlike dry heat sterilization.

Autoclave is the most popular example of moist heat sterilization. Autoclaving is an effective way of sterilizing culture media using for microorganism culturing. It operates under 121 oC for 15 minutes at a pressure of 15lbs/sq. In addition to autoclaving, boiling and pasteurization are two methods of moist heat sterilization.

What are the Similarities Between Dry Heat and Moist Heat Sterilization?

• Dry heat and moist heat sterilization are two physical methods of sterilization.
• In both methods, heat is the main mode of sterilization.
• Scientists use both methods in microbiological labs.

What is the Difference Between Dry Heat and Moist Heat Sterilization?

Dry heat sterilization occurs under dry conditions while moist heat sterilization occurs under wet conditions. Besides, dry heat sterilization utilizes high temperature to sterilize, while moist heat sterilization utilizes high temperature and high pressure generated by water steam. So, this is the key difference between dry heat and moist heat sterilization.

Moreover, another difference between dry heat and moist heat sterilization is that dry heat sterilization needs comparatively more time to sterilize while moist heat sterilization needs comparatively less time to sterilize. Besides, hot air oven is most widely in use for dry heat sterilization, while autoclave is most widely in use for moist heat sterilization.

Below infographic summarizes the difference between dry heat and moist heat sterilization.

Summary – Dry Heat vs Moist Heat Sterilization

Dry heat and moist heat sterilization are two physical methods of sterilization. Dry heat sterilization takes place at high temperature under dry air while moist heat sterilization takes place at high temperature and pressure generated by the steam of water. So, this is the key difference between dry heat and moist heat sterilization. Moreover, dry heat sterilization takes more time to sterilize while moist heat sterilization takes less time to sterilize. Furthermore, hot air oven is the most widely used method of dry heat sterilization while autoclave is the most widely used method of moist heat sterilization.

Reference:

1. “Dry-Heat Sterilization: Principle, Advantages and Disadvantages.” Microbeonline, 27 Apr. 2018, Available here.
2. “Moist Heat Sterilization.” Wikipedia, Wikimedia Foundation, 26 Jan. 2019, Available here.

Image Courtesy:

1. “Hot air oven” By Yatherm – Own work (CC BY-SA 4.0) via Commons Wikimedia
2. “Autoclave” By User:Utkarshsingh.1992 – Own work (CC BY-SA 3.0) via Commons Wikimedia