How does sterilization by autoclave work?

The preservation of food has been a permanent concern of man since prehistoric times. With the discovery of pathogenic bacteria and micro-organisms, the need to sterilise products has become increasingly important, particularly in the food industry. As a result, heat treatment equipment, such as the autoclave, was developed. Find out how autoclave sterilisation works in industry.

The operating process of industrial autoclave sterilisation

The principle of the autoclave was invented by Denis Papin in 1679. However, it was Nicolas Appert who perfected his process for sterilising canned food.

Short material description of an industrial autoclave

Autoclaves are devices consisting of a sterilisation chamber with a lid. They are made of stainless steel and come in different sizes depending on the products to be sterilised. Autoclaves are equipped with temperature and pressure control instruments. An improved and industrial version of the electric steriliser, this sterilisation equipment is subject to pressure equipment regulations. It is therefore equipped with safety devices that are subject to periodic checks.

The process of sterilisation by industrial autoclave

Sterilisation by autoclave uses different types of sterilising agent:

• water: in the sprinkler, trickle or immersion process;
• Steam: in the air/steam process;
• Saturated steam.

Temperatures and pressures can vary according to the type of autoclave. For example, in a saturated steam process, the pressure is given by the temperature. It is also possible to dissociate temperature and pressure for better preservation of the packaging.

The different phases of an autoclave sterilisation

Sterilisation by autoclave follows a rigorous process. The autoclave packaging and the sterilisation cycle are carried out in 5 phases.
The sterilisation cycle is as follows.

• Phase 1 (in the case of steam autoclaves): purge phase which allows the air to be removed from the autoclave so that only steam is present in the chamber.
• Phase 2: heating of the autoclave for preheating. The energy requirement is high, as the entire chamber, and particularly the stainless steel, must be heated. The temperature rise is associated with an automatically controlled pressure rise.
• Phase 3: Sterilisation phase. This is the most important and critical phase of the heat treatment, the respect of the time/temperature pair is mandatory. The time is programmed according to the sterilising value of the product.
• Phase 4: cooling phase, which initially allows the temperature and pressure of the autoclave to drop. It then promotes the temperature reduction of the products.
• Phase 5: phase of emptying the autoclave of water and expelling any remaining air to return to atmospheric pressure.

The different types of autoclave for sterilisation

Here we detail the different types of industrial autoclaves and their use for sterilisation.

Sterilisation by steam air autoclave

A mix of air and steam is used for sterilisation in this type of autoclave. Thanks to this mixture, the packaging can be preserved. Cooling is achieved by means of top and side nozzles for spraying water onto the products. The temperature distribution is homogeneous inside the chamber thanks to the turbine placed at the bottom of the autoclave which allows the circulation of steam.

The water spraying autoclave for sterilisation

This type of autoclave allows water to be sprayed under pressure onto the products to be sterilised. Depending on the sterilisation cycle, this water is heated by steam and then cooled via an exchanger. This economical autoclave recycles the water during the cycle. The heat distribution in the heart of the machine is optimal.

Sterilisation of products by bi-process autoclaving

This type of autoclave combines the two processes: steam air and water spraying. The heat is thus homogeneous inside the tank and evenly distributed. The temperature rise and fall phases are therefore faster. It is perfectly suited to large capacity autoclaves.

The immersion autoclave to sterilise your products

The immersion autoclave works in the same way as the sterilisers used for our grandmothers’ tins. The products to be sterilised are covered with superheated water which rises in temperature and pressure according to the dedicated cycle.

Regulations on autoclaves and steam pressure vessels

Industrial autoclaves have to comply with many standards, such as the CE standard. Other regulations must be respected on a case by case basis (FDA, ASME or GAMP). Periodic checks are necessary on this type of equipment and must be carried out by certified organisations.

Do you need an autoclave for your workshop? Do not hesitate to consult our range of professional autoclaves. You will find the right autoclave for your needs. We are available by e-mail to answer all your questions about our autoclave range.