About processes happening in an autoclave

From earlier articles we know, we know that all autoclaves do the same serious work – heat the products loaded into them in tight packing to temperature of sterilization and provide maintenance of this temperature during time of the guaranteed destruction of bacteria in a tight container.

At the solution of a problem of sterilization it is important that in everyone hermetically packed can, retort package, steralcon, etc., during a running cycle of autoclaving sterilization temperature is reached and remained during sufficient time. Otherwise after a while bacteria will triumph, and jars will be blown up (bloat).

Temperature condition of a product in each jar placed in the autoclave depends on several factors:
- from a way of a heat transfer in the autoclave
- from the power of the heat flux created in the autoclave
- from properties of the container (geometry, heat conductivity)
- from properties of the product (viscosity, heat conductivity, thermal capacity, etc.) loaded into it
- from a way of loading of products in the autoclave

The most widespread ways of a heat transfer in the autoclave are:
washing of products water flow (like a rain) – jet irrigation;
washing of products a steam-and-water cloud – nozzle irrigation.

Usually at sterilization of products in a rigid container (a tin can, a glass jar, a bottle, etc.) use jet irrigation of the products loaded into a special container layer-by-layer. For formation of layers, distributions of loadings and improvement of conditions of washing of products the interlaminar heat-resistant punched laying is used.

For sterilization of products in soft packing it is necessary special retorts packings which maintains temperature to 135ºС. The form of retorts packings can be different – in the form of standing packages (doypack), in the form of lying packages (four-sutural) and other packages. For sterilization of products in soft retorts packings both jet and nozzle irrigation can be used. The main feature is that packages are kept within the low punched corrosion-proof baskets which are put one on another in "pile". Height of a basket has to be such that the bottom of the top basket do not adjoin a package in the lower basket.

On photos some types of tight packing before its loading to the autoclave are presented.

At a stage of working off of technology of autoclaving for a concrete product in a concrete type of a container, there is experimentally chosen the schedule of temperature change of the environment in the autoclavechosen at which it will be guaranteed provided:
- temperature in any place in any packing (jar)will reach value of temperature of sterilization;
- temperature in any place in any packing (jar) will be not less sterilization temperatures during the time sufficient for destruction of bacteria;
- integrated thermal impact on a product will provide its readiness for the use.

It is clear, that the same product packed into different types of packing has own lag effect at warming up and, respectively, it has to be considered by the technologist when forming temperature condition of sterilization of a product in concrete packing.

Of course, the technologist can set temperature condition so that in each jar temperature will be reached, with guarantee there are more than temperature sterilizations and time it is possible to set with a stock. It would guarantee destruction of all bacteria "with a stock", but in this case occurs «overcooking» of products, loss of tastes and change of structure of a product, excess time, energy and money is spent. Therefore temperature condition of processing of a product in the autoclave has to be set so that to all harmful bacteria in a product disaster came,and the product is welded (to readiness for the use), but not overcooked.

It is clear, that theoretically optimum mode for any specific case cannot be calculated therefore at a stage of working off of the mode of autoclaving of a product in this type of packaging the technologist makes experimentally selection of the mode of autoclaving. As criterion serves, finally, the lack of harmful bacteria in a product after autoclaving that is confirmed by laboratory researches and results of long-term storage of lots of products and tastes.

At experimental selection of the mode of autoclaving for the guaranteed destruction of bacteria often the mode is set with a large supply that guarantees quality of sterilization, but has an adverse effect on quality of a product, demands additional time expenditure and additional energy consumption.

Due to the above, at working off of the modes of autoclaving it is important to give to the technologist tools which would allow to carry out measurement (registration) of temperature conditions during autoclaving directly in jars (product temperature). For obvious reasons realization of such measurements is accompanied by a number of technical difficulties (high temperature, pressure, the tight case of the autoclave, hermetically packed jar, etc.)

In the autoclaves of AH-1200 series made by our enterprise the possibility of direct measurement of sterilizing effect in two jars in the course of autoclaving is realized (as an option).

Further we will be telling about a concept of the sterilizing effect, ways of its measurement and calculation.

Read in more detail about
main advantages and distinctive features of the AH-1200 autoclaves.