Choosing an Autoclave by Load Type Liquid

Fluid or liquid loads typically comprise solutions or chemicals used in the laboratory environment, e.g. a growth medium, but could be any non-solid that requires sterilization. A growth medium or culture medium is a solid, liquid or semi-solid designed to support the growth of micro-organisms or cells under test conditions. Different types of media are used for growing different types of cells. An autoclave is used to sterilize media before use. Although many types of media require sterilization at 121°C for 15 minutes, different sterilizing temperatures and times may be necessary for certain types of media, and therefore any autoclave used for the sterilization of media must be capable of sterilizing at a variety of temperatures.

A fast heat up and cool down is beneficial to maintain the quality of the finished product and prevents ‘over cooking’ which leads to a deterioration in the quality of the growth medium. Should the autoclave be opened at a temperature higher than 80°C, the sudden change in pressure can not only cause the media (or other fluids) to boil over; there is also a significant danger that bottles could break or explode!

Boil-over of fluids is usually caused when the chamber pressure during the cooling stages falls quicker than the temperature in the load. All Astell autoclaves can be used to sterilize fluids, but to do so quickly necessitates some cooling options. If fast cooling is required you need to replace the steam with air ballast during cooling to reduce the possibility of boil over. A water jacket (with an internal fan, when required) is an extremely efficient means of cooling and will require the addition of air ballast to prevent the boil-over of bottled media etc.

Non-rigid containers will benefit from ramped cooling where the chamber pressure is lowered in a number of steps to coincide with the load temperature to prevent non-rigid containers deforming or bursting during the cooling stage.