Difference Between Sterilization and Pasteurization


Sterilization and pasteurization are two common techniques used in food preservation, medical equipment sterilization, and other industrial processes. Although both methods are used to kill microorganisms, they differ in the degree of sterilization achieved and the purpose of their application. In this essay, we will discuss the differences between sterilization and pasteurization.

What is Sterilization?

Sterilization is the process of killing or eliminating all forms of life, including bacteria, viruses, fungi, and spores. Sterilization is essential in various industries, including food and medical industries, to prevent contamination and ensure the safety of products. Sterilization can be achieved using several techniques, including heat, radiation, chemicals, and filtration.

Heat sterilization is one of the most common methods used to achieve sterilization. Autoclaving, which is the use of steam under high pressure, is a popular heat sterilization method used in the medical industry. The heat generated during autoclaving kills all microorganisms, including spores.

Another method is dry heat sterilization, which involves heating objects at high temperatures for prolonged periods. Chemical sterilization is another technique used to achieve sterilization. It involves the use of chemicals such as ethylene oxide and hydrogen peroxide to kill microorganisms.

Cold physical sterilization is done with bacterial filters or with radiation. The radiation used for sterilization can be −

  • Non-ionizing ultraviolet radiation

  • Ultrasound

  • Ionizing rays

Practical application for sterilization have gamma rays from natural radioactive substances and high-speed electrons from high-voltage apparatus. They have a strong penetrating ability and the sterilized materials have a long shelf life.

Chemical sterilization is −

  • Gas sterilization using chemical agents

  • Cold chemical sterilization

Chemical sterilization can be done with −

  • Halogen-containing preparations (containing chlorine or iodine)

  • Phenol derivatives

  • Aldehydes

  • Alcohols

  • Oxidants

  • Surfactants

  • Guanidine compounds

  • Acids and bases

  • Combined preparations, etc.

The chemical compounds used for sterilization have different mechanisms of action, advantages, and disadvantages. For example, chlorine-containing compounds release chlorine, which leads to the formation of toxic chloramines in the bacterial cytoplasm. They have a wide spectrum of action and a strong bactericidal effect, but a lower virucidal, tuberculocidal, fungicidal and sporicidal effect. They emit a severe irritating odor and irritate the skin and mucous membranes in contacts.

Aldehydes alkylate cellular proteins and nucleic acids of the microorganisms. They have bactericidal, sporicidal, fungicidal, and virucidal action. Aldehydes are toxic and irritating to the skin, mucous membranes, respiratory tract, eyes, and have a carcinogenic effect (formaldehyde). They have a strong irritating smell and high allergenic potential.

What is Pasteurization?

Pasteurization, on the other hand, is a technique used to reduce the number of microorganisms in a substance, mainly liquids such as milk, beer, and juice. The purpose of pasteurization is to reduce the number of pathogenic bacteria present in the substance, thereby making it safe for consumption. Pasteurization does not eliminate all microorganisms but significantly reduces their number, making the substance safe for human consumption.

There are several methods of pasteurization, including high-temperature short-time (HTST) pasteurization, ultra-high temperature (UHT) pasteurization, and low-temperature long-time (LTLT) pasteurization.

  • HTST pasteurization involves heating the substance at high temperatures for a short period, typically around 72°C for 15 seconds. This method kills most of the bacteria present in the substance.

  • UHT pasteurization involves heating the substance at very high temperatures, usually around 135°C, for a few seconds to kill all bacteria present.

  • LTLT pasteurization involves heating the substance at a lower temperature, usually around 63°C, for a more extended period, usually 30 minutes.

Pasteurization at higher temperatures aims at killing the vegetative pathogenic and spoilage bacteria, denaturing serum proteins, and avoiding syneresis. It is used in the production of cheese, yogurt etc.

By repeated pasteurization (tyndallization) it is possible to obtain a completely sterile product. This process is used for the treatment of culture mediums, medicines, etc. that include thermolabile ingredients such as sugars and proteins. Tyndallization is carried out for 30 minutes at a temperature of 100° C for a period of several days. The first heating aims to kill the vegetative forms. After the cooling, until the heating on the next day, the surviving spores grow, which allows the heat to destroy their vegetative forms.

Differences: Sterilization and Pasteurization

In terms of effectiveness, sterilization is more effective than pasteurization in eliminating microorganisms. Sterilization kills all microorganisms, including spores, which pasteurization cannot eliminate. However, pasteurization is sufficient for most food and beverage products as it reduces the number of pathogenic bacteria present in the substance to safe levels. Sterilization is more appropriate for medical equipment and laboratory settings, where the risk of contamination is much higher.

Another significant difference between sterilization and pasteurization is the effect on the quality of the product. Sterilization can cause damage to the product, particularly if the method used involves high temperatures or radiation. This can result in changes in the taste, texture, and nutritional content of the product. Pasteurization, on the other hand, does not significantly affect the quality of the product. The product's taste, texture, and nutritional content remain relatively unchanged, making it more suitable for food and beverage products.

The following table highlights the major differences between Sterilization and Pasteurization −

Characteristics

Sterilization

Pasteurization

Definition

Sterilization is a destruction of all microorganisms and their spores.

Pasteurization is a process that kills the pathogenic bacteria by heating to a certain temperature for a set period of time.

Result

The process kills pathogenic and saprophytic microorganisms, vegetative and spore forms, viruses.

Assimilation implies an essentially unilateral approximation of one culture in the direction of the other (Teske, Nelson 363).

Types

Sterilization can be physical (sterilization with heat, cold sterilization) or chemical (gas sterilization using chemical agents, cold chemical sterilization).

Depending on the temperature and the time the pasteurization can be Vat (batch) pasteurization (63°C for 30 minutes), HTST (72°C for 15 seconds), HHST (89-100°C for 1.0 -0.01 seconds).

Shelf-life

Shelf-life of the sterilized products is longer than the one of the pasteurized ones.

Shelf-life of the pasteurized products is shorter than the one of the sterilized ones.

Application

Sterilization is applied in the medical surgery, microbiology, dentistry, packaging industry, food industry, etc.

Pasteurization is applied for the treatment of culture mediums, medicines, etc. that include thermolabile ingredients such as sugars and proteins, as a food preservation method in the food industry, etc.

Conclusion

In conclusion, sterilization and pasteurization are two essential techniques used in various industries to ensure the safety of products.

Sterilization is the process of killing all forms of life, including bacteria, viruses, fungi, and spores. Pasteurization, on the other hand, is the process of reducing the number of microorganisms in a substance, mainly liquids, to safe levels. Sterilization is more effective in eliminating microorganisms.

Updated on: 26-Apr-2023

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