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Sterilization of canned in glass containers

Sterilization of canned in glass containersHere we will explain what sterilization of canned food in glass containers is. When sterilizing canned food in a glass container, the process is carried out in such a way that the pressure arising in the container is balanced by the pressure from the outside so that the lid does not swell up and there is no threat of disrupting it from the mouth of the can. This method of sterilization is called back pressure sterilization, meaning that part of the total pressure in the autoclave must be created in a “hot” way, using steam to provide the required sterilization temperature, and part by the “cold” way, i.e. wherein the pressure in the autoclave is increased without increasing the temperature, by using, for example, compressed air or pressurized water.


The sterilization technique with air back pressure is as follows. Before loading the grids with cans, the water in the autoclave is heated to a temperature that exceeds the product temperature by 10–15 C. Then the grids with cans are loaded into the autoclave in such a way that they are completely covered with water.Next, the autoclave is closed, a mixture of steam and air or only compressed air is fed into it through a bubbler so as to quickly create the necessary backpressure. When the desired value has been reached, the air supply is stopped and steam is allowed into the autoclave (or continue to flow) until the sterilization temperature is reached. Then cover the steam valve and proceed to the actual sterilization.


The pressure in the autoclave must be kept constant during the entire heating and sterilization period. The value of this pressure is indicated in the sterilization formula, which in this case is


The last stage of the process - cooling is as follows. Turn on the pump and begin to supply water to the top of the autoclave. Then immediately open the lower valve on the drain pipe and start releasing hot water. At the same time, cold water goes down, mixing with hot water, which is discharged from below, as a result of which the temperature of the water in the autoclave gradually decreases.


In addition to schemes with manual adjustment of temperature and pressure, many canneries also have autoclave equipment for automatic control of the sterilization process.For this purpose, pneumatic and electric program thermostats are used using a time relay, sound and light alarm, with automatic recording of temperature and pressure over time. The resulting thermogram is the most important document for the subsequent monitoring of the sterilization station. In recent years, new, more advanced designs of autoclaves of domestic and imported origin have appeared at a number of factories. It should be noted devices with gridless loading of cans, which provide for the supply of cans in bulk, directly to hot water. This method of loading allows several times to reduce labor costs, speed up the processes of loading and unloading, reduce steam consumption and the necessary production area.


The company "Lübeck" delivers to the fish canneries of our country a four-basket horizontal sterilizing apparatus of periodic action with programmed process control.


Rotamat autoclaves “Mittelhauser und Walter” by Rotamat are in many respects similar to Lübeck’s autoclaves, but they allow sterilization using the rotation of cans “from bottom to lid” with rotation frequency of 4–8 rpm.As noted above, the rotation can significantly reduce the duration of the sterilization process.


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