Difference Between Pasteurization and Sterilization

Main Difference – Pasteurization vs Sterilization

Foods consist of different major nutrients such as carbohydrate, protein, fat, minerals and vitamins. As a result of rich nutrient content in fresh foods, they are highly susceptible to microbial spoilage. Thus, food is often pasteurized or sterilized in order to destroy their pathogenic microbial load. Pasteurized and sterilized food can be stored for a longer period of time under refrigerated conditions or normal atmospheric conditions, respectively. Sterilization is a temperature based preservation technique referring to any process that removes or destroys all forms of life and other biological agents mainly in food items. In contrast, pasteurization is a temperature based preservation technique referring to any process that removes or destroys all forms of pathogenic microorganisms mainly in food items. Although this is the main difference between Pasteurization and Sterilization, the nutritional and organoleptic properties of these products may also differ between them. Thus, it is important to identify the difference between Pasteurization and Sterilization in order to select healthier options. In this article, let’s look at the difference between Pasteurization and Sterilization in terms of changes of nutrients and sensory parameters.

What is Sterilization

Sterilization can be defined as any process that eliminates or destroy all forms of microorganisms and other biological agents (such as spores) present in a specified region, such as a food item, surface, a volume of fluid, packaging material, medication, instruments or in a biological culture media. Sterilization can be accomplished with one or combination of these food technologies such as heat, chemicals, irradiation, high pressure, and filtration. Sterilization is different from disinfection, sanitization, and pasteurization process in that sterilization eradicates, disables, or removes all forms of life and other biological agents.

What is Pasteurization

Pasteurization is a heating process that destroys harmful pathogenic bacteria by heating to a specific temperature for a set period of time. For example, pasteurized milk is a form of milk that is heated to a high temperature so that any harmful pathogenic micro-organisms which may be present in the raw milk are destroyed. The pasteurized milk is then packaged into sterile containers under aseptic conditions such as Tetra packaged milk or glass-bottled milk. This process was invented by French scientist Louis Pasteur during the nineteenth century. The target of heat treated food is to produce food which is safe for human consumption and to improve its shelf life. Thus, heat-treated foods/ pasteurized foods have a longer shelf life (Eg. UHT pasteurized milk can store for about 6 months). Pasteurization is a popular method of heat treatments used to produce long-life milk and fruit juice. But pasteurized products should be stored under refrigerated conditions because this heat treatment in not sufficient to destroy the spores of pathogenic microorganisms. However, the heat treatment results in an alteration of organoleptic properties ( ex: taste and color) and a slight decrease in the nutritional quality of the food. 

Difference Between Pasteurization and Sterilization

The difference between pasteurization and sterilization can be identified under following major categories:

Definition

Sterilization: Sterilization is any process that eliminates all forms of life and other biological agents present in a surface, food, packaging material, a volume of fluid, medication, instruments or in a biological culture media.

Pasteurization: Pasteurization is a process that kills pathogenic bacteria in liquid food.

Shelf-life

Sterilization: Shelf-life is longer than pasteurized products or has extended shelf-life.

Pasteurization: Pasteurized products have a shorter shelf life compared to sterilized product

Processing steps (Example is milk)

Sterilized milk: Various processing steps are involved during milk sterilization are shown in figure 1.Main Difference - Pasteurization vs Sterilization

Figure 1: Sterilized milk production

Source: BAT for Food, Drink and Milk Industries, June 2005

Pasteurized milk: Various processing steps are involved during milk pasteurization are shown in figure 2.

Difference Between Pasteurization and Sterilization

Figure 2: Pasteurization process of milk

History

Sterilization:  Food sterilization was discovered by Nicolas Appert. He discovered canning of foods which has helped to reduce foodborne illness.

Pasteurization: Pasteurization was developed by French scientist Louis Pasteur during the nineteenth century.

Destruction of Microorganisms

Sterilization: Sterilization eliminates all forms of microorganisms (Spoilage and pathogenic microbes) and their spores.

Pasteurization: Pasteurization only eliminates pathogenic microorganisms. So pasteurized products should be stored under refrigerated conditions. If the product is exposed to the microbial growth desirable environment conditions pasteurized food may be contaminated.

Forms of sterilization/pasteurization and classification based on heat treatment

Sterilization: Sterilization can be accomplished with one or combination of heat, chemicals, irradiation, high pressure, and filtration. Autoclave is a widely used method for heat sterilization and it generally uses the following time-temperature combination 121 °C at 100 kPa for about 3 to 15 minutes, to sterilize a product.

Pasteurization: Pasteurization can be accomplished with heat. Milk, for example, can be pasteurized to three different stages. They are ultra-high temp (UHT), high-temperature-short-time (HTST) and low-temp long time (LTLT).

Application

Sterilization:Sterilization is mainly applied in the food industry, medical surgery, Packaging industry, microbiology, etc.

Pasteurization: Pasteurization is mainly applied in food industry (food preservation method)Difference Between Pasteurization and Sterilization - infographic

In conclusion, people believe that raw, fresh food is a safe healthier alternative because pasteurized or sterilized food usually undergoes various heat treatments which result in the destruction of some organoleptic and nutritional quality parameters of food. Also, long-term consumption of fresh raw milk is responsible for causing numerous foodborne illnesses but pasteurized, or sterilized milk are not (or rarely) responsible for causing numerous foodborne illnesses. Although, from a nutritional standpoint, raw and fresh food is best, pasteurized or sterilized food is safe for human consumption.

References:

Brown, Amy Christian (2007). Understanding Food: Principles and Preparation (3 ed.). Cengage Learning. p. 546. ISBN 978-0-495-10745-3.

Feskanich, D., Willett, W. C., Stampfer, M. J. and Colditz, G. A. (1997). Milk, dietary calcium, and bone fractures in women: a 12-year prospective study. American Journal of Public Health, 87(6): 992–997.

Montville, T. J., and K. R. Matthews: food microbiology an introduction, page 30. American Society for Microbiology Press, 2005.

Wilson, G. S. (1943). The Pasteurization of Milk. British Medical Journal, 1(4286): 261–2.

About the Author: Geesha

Geesha has a BSc (Hons) degree in Food Science and Technology and Master's degree in Food and Nutrition. She is currently reading for her PhD in Food science and technology. Sharing what she learned is a passion of hers and enjoys writing.


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