Microbiology

PASTEURIZATION and APPERTIZATION

Written by MicroDok

Pasteurization is simply defined as the process of heating food during its production in order to destroy pathogenic microorganisms or food spoilage organisms in them. Food products or foods such as milk, yoghurt, dairy products and other liquid products are heated in this manner to destroy microorganisms that cause disease and spoilage in them. Pasteurization is the reduction of microbial growth in heat-sensitive products such as milk in order to inhibit or kill pathogenic microorganisms present in them. This technique of reducing or killing food spoilage organisms in food was discovered and developed by Louis Pasteur in 18-19th century as a method of preserving wine during storage; and Pasteur showed that pasteurization (which is the mild heating of milk) could kill pathogenic microorganisms in broth. Pasteurization is an important technique in most industrial applications especially in food industries where it is applied to contain food spoilage in food or food products. It is usually carried out at a temperature range of between 60-80oC; and pasteurization does not last too long when applied in food production. Generally, temperatures below 100oC are used during pasteurization of milk and other liquid food products; and the heating is usually done at various time intervals and at different temperature range. Pasteurization of food products or food is usually carried out at varying temperatures such as high-temperature short time.

High temperature short time (HTST) is applied in both pasteurization and appertization techniques to destroy pathogenic and spoilage microorganisms present in food. HTST is defined as the heating of milk and other liquid food products at high temperatures and at varying time intervals that can range from seconds to minutes and hours in order to inhibit or kill pathogenic microorganisms and other spoilage microbes present in them. Apart from inhibiting or killing pathogenic microorganisms present in food, pasteurization technique also helps to extend the shelf-life of the food being processed. Pasteurization technique is effective for killing milk flora as well as other disease-causing microorganisms present in the food. In general, pasteurization is a mild heating of milk and other heat-sensitive products and it is carried out at temperatures below 100oC. Pasteurization technique is effective in the killing of some food-borne pathogens including those that cause salmonellosis (Salmonella species) and even tuberculosis (Mycobacterium species). Metabolic products such as enzymes produced by food flora in food products and which stimulate food spoilage can also be inactivated and rendered ineffective during the process of pasteurization.

APPERTIZATION

Appertization is simply defined as the heat-treatment of food at certain temperature levels that inhibit or kill pathogenic microorganisms present in the food. Unlike pasteurization which uses temperatures below 100oC to kill microbes in food, appertization (which was discovered by Nicolas Appert in the 18th century) is generally a food preservation technique that is used to heat food at temperatures of 40oC which is lower than that used in pasteurization. In appertization, foods or food products are exposed to varying low temperatures and time which makes the food microbiologically fit for consumption. Food products are heated at this temperature in containers or cans in order to bring the microbial load in the food to levels that are generally safe for human consumption. Appertized food or food products are not necessarily sterile but they have been so treated at temperature levels that significantly reduce or limit the possibility of microbial growth in the food product during storage. This process of appertization is used in food industries such as in canning to produce canned food products. The rationale behind appertization is based on the fact that viable organisms that survive during processing will not be able to grow under normal storage conditions; and these organisms will be below certain levels after a particular temperature (e.g. 40oC) is applied to the food and at a specific time period during its processing. However, appertization can still be carried out at high temperatures (e.g. above 100oC) for some food products. High-temperature short time (HTST) is applied in both pasteurization and appertization techniques to destroy pathogenic and spoilage microorganisms present in foods including the spores of some food-borne pathogens such as Clostridium species. HTST is defined as the heating of milk and other liquid food products at high temperatures and at varying time intervals that can range from seconds to minutes and hours in order to inhibit or kill pathogenic microorganisms and other spoilage microbes present in them.

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