How to pasteurize liquids in-line ?

Pasteurization is one of the main food preservation methods. Discover the most common continuous heating methods to pasteurize liquid and pasty products.

The pasteurization process

The process of pasteurization was named after Louis Pasteur who discovered that spoilage organisms could be inactivated in wine by applying heat at temperatures below its boiling point. Pasteurization is a preservation process that aims to limit spoilage of a food product by greatly, but not totally, reducing the presence of micro-organisms in it.


This process consists in subjecting the food to heat, high pressure, or electric impulsion for a determined period of time. By subjecting the food to one of these treatments, the growth of bacteria, yeasts, pathogenic microorganisms and enzymatic activity is slowed down and the product can thus be stored in a cold place for a longer period.

Liquids pasteurization

Pasteurization of liquids is used on many products to preserve it. It is a technique generally used on drinks : milk, dairy products, fruit juice, etc. It is also used on pasty products such as jam.


Conventionally, pasteurization is carried out with a heat exchanger whose principle is the energy transfer through a wall (surface).

How does it work ?

A pasteurizer is made up of four sections:  recovery or preheating, heating to the pasteurization temperature , temperature holding during the requested time, and finally the optional cooling step before packaging.


Most of pasteurizers works with heat exchangers, who consist in transferring thermal energy from one liquid, often water, to another. The heat energy mostly comes from steam or hot water generated by a gas boiler or an electric source. The main technologies are presented here :

The pasteurization by microwave

SAIREM has developed a fast and efficient solution with a reduced footprint: an in-line microwave heater. This equipment works with both liquids, pasty, or grain products. It is currently used to heat the product to the temperature you need within a few seconds, or to start a pasteurizing process.


Depending on product’s, power, and requested temperature raise, it can process up to 12 tons of product per hour.

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Our free microwave and radio-frequency guide for food applications will help you to better understand these technologies, and find the solution the most adapted to your needs.

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