A Microorganism or commonly known as a microbe is an organism that is only visible through the microscope. Such microorganisms may be either unicellular, multicellular, or cell clusters.
There are infinite microorganisms in existence. They can be broadly divided into seven categories: fungi, algae, bacteria, protozoa, archaea, viruses, and animal parasites. Some are useful and beneficial for everyday life as they produce oxygen thereby maintaining human health, provide nutrients for plants as they help in decomposing organic material whereas some microorganisms may cause harm as they spread diseases.
There are several methods that are used to kill harmful microorganisms. Two common methods used are sterilization and pasteurization.
Sterilization vs Pasteurization
The main difference between sterilization and pasteurization is that sterilization is a method used to kill all microorganisms and their spores, whereas pasteurization is the method that is used to kill only the vegetative form of the bacteria where the spores survive.
Comparison Table Between Sterilization and Pasteurization
| Parameters of Comparison | Sterilization | Pasteurization |
|---|---|---|
| Definition | It is a method used to eliminate all microorganisms and their spores. | It is a method used to get rid of only the vegetative form of bacteria by heating it to a certain temperature |
| Types | Sterilization can be both physical or chemical. Physical sterilization means sterilization with heat or even cold sterilization. Chemical sterilization means gas sterilization using chemical agents or cold sterilization. | Pasteurization depends on temperature and can be vat pasteurization, HHST, HTST. |
| Effect | This method kills all microorganisms including vegetative and spores’ forms. | This method eliminates only the vegetative forms of bacteria. |
| Usage | Sterilization is used in microbiology, food industry, packaging industry, etc. | Pasteurization is used in medicines, culture mediums, etc. It is used in food preservation methods in the food industry. |
| Period of validity | The period of validity for sterilized products is longer than pasteurization products. | The period of validity of pasteurized products is shorter than that of sterilization products. |
What is Sterilization?
Sterilization is the method that is used for the destruction of all microorganisms and their spores. This method eliminates pathogenic and saprophytic microorganisms. It also destroys vegetative and spores forms of bacteria that are present in fresh foods.
The sterilization process may be of 2 types, namely physical sterilization or chemical sterilization.
Physical sterilization includes sterilization with heat or cold sterilization.
Further, sterilization with heat may be wet or dry. The dry heat sterilization uses hot air whereas the wet heat sterilization uses water vapor. When the temperature rises above a certain level the microorganisms die. The weakest forms are the vegetative forms of the bacteria. They are not much resistant to heat and hence die quickly. Next are the molds and viruses which are somewhat heat resistant and lastly the spores which are most resistant.
Cold sterilization is performed using radiation or bacterial filters. There are different types of radiation used for cold sterilization. They may be- ultrasound, ionizing rays, non-ionizing ultraviolet radiation.
Chemical sterilization on the other hand includes Cold chemical sterilization and Gas sterilization with chemical agents.
Chemical sterilization is possible with alcohol, surfactants, aldehydes, oxidants, phenol derivatives, acids and bases, preparations containing halogen, combined preparations, and so on.
What is Pasteurization?
Pasteurization is a method used to get rid of the vegetative form of bacteria only, by heating it to a certain temperature for a specific time period. Here, the spores live. It is necessary to store the products in a refrigerator after pasteurization to stop the growth of the saprophytic bacteria that survived.
For different purposes, different pasteurization processes are used. The type of the pasteurized product, its purpose, its volume, the availability of the equipment, and the microorganisms targeted are what the choice of pasteurization methods depend on.
Vat pasteurization, HHST, HTST are the different types of pasteurization methods depending on the time and temperature.
It can be said that the Vat pasteurization is primarily used in the food industry. It focuses on destroying the pathogenic microorganisms. It also aims at improving the products’ shelf life. It conserves almost all the physicochemical values of the food products. Vat pasteurization is also used in the manufacture of beer, milk, etc.
High-temperature pasteurization focuses on destroying the vegetative pathogen. It changes the serum proteins and is mainly used in the manufacture of yogurt, cheese, etc.
It is possible to acquire a wholly pure and clean product by repeated sterilization. It is used in the treatment and care of medicines, where it is implemented for 30 minutes for many days at 100-degree Celsius temperature.
Main Differences Between Sterilization and Pasteurization
- Sterilization is a method used to get rid of all microorganisms and their spores, whereas Pasteurization is the process that helps to kill only the vegetative form of bacteria but the spores live.
- The result of Sterilization is that it kills all microorganisms, vegetative as well as spores’ forms. The effect of Pasteurization is that it kills only the vegetative forms of bacteria.
- The shelf life of sterilization products is longer as compared to pasteurized products, which is shorter.
- There are two types of sterilization, physical or chemical. Physical sterilization is the sterilization with heat or even cold sterilization. Chemical sterilization is the gas sterilization using chemical agents or cold sterilization. Pasteurization is dependent on temperature and can be vat pasteurization, HHST, HTST.
- Microbiology, food industry, packaging industry, etc use sterilization. On the other hand, in medicines, culture mediums, etc pasteurization is used. Also, it is used in the food industry for food preservation methods.
Conclusion
Certain microorganisms may cause harm as they spread diseases. They must be killed so that they do not cause harm. There are many methods of eliminating such microorganisms, two of them include sterilization and pasteurization.
People often think sterilization and pasteurization are one and the same thing. This is not true. Sterilization is the process that kills all microorganisms and their spores whereas pasteurization kills only the vegetative form of bacteria and not the spores. The approach used by each method may also vary.
References
- https://sfamjournals.onlinelibrary.wiley.com/doi/abs/10.1111/j.1365-2672.1971.tb02309.x
- https://edisciplinas.usp.br/pluginfile.php/128445/mod_resource/content/1/C28.microwave.pdf