Sterilization is a process that effectively kills or eliminates transmissible agents or microorganisms such as fungi, bacteria, viruses and prions from a surface, equipment, foods, medications, or biological culture medium. In the laboratories, the sterility is acquired by exposure of the object that is needed to be sterilized, to chemical or physical agent for a specified time. Some of the wide ranges of agents used as steriliants are:

• elevated temperature,
• ionizing radiation,
• Chemical liquids or gases etc.

The success of the process of sterilization depends upon the choice of the method adopted for sterilization like in case of heat it can either be moist heat sterilization or dry heat sterilization.

Dry heat destroys bacterial endotoxins/pyrogens which are difficult to eliminate by other means and this property makes it applicable for sterilizing glass bottles which are to be filled aseptically and it can only be used for thermo stable, moisture sensitive or moisture impermeable pharmaceutical and medicinal.

These include products like; Dry powdered drugs, Suspensions of drug in non aqueous solvents, Oils, fats waxes, soft hard paraffin silicone, Oily injections, implants, ophthalmic ointments and ointment bases etc.

Reasons why dry heat sterilization is important;

• the need to sterilize small objects, particularly syringes, and
• the apparatus required is comparatively inexpensive when compared with the autoclave.

Batch sterilizer; is one of the appropriate technique for the dry sterilization as it enables proper mixing cum perfect sterilization of the product and the Vacuum inside the chamber ensures that the microbiological and organoleptic properties of the product are preserved that is it does not destroys the microbiological properties of the products that can be proteins denaturation.

Batch sterilizer is consists of a conical shaped vessel fully closed jacketed in which material need to be sterilized is loaded. The vessel is then subjected to vacuum and the material is subjected to steam sterilization. At the same time the material is tumbling inside the vessel. This methos provides the proper mixing cum perfect sterilization of the required product.

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Sterilization is the process of complete removal/destruction of the entire viable microorganism or Sterilization can be defined as any process that effectively kills or eliminates transmissible agents (such as fungi, bacteria, viruses and prions) from a surface, equipment, foods, medications, or biological culture medium.

Various methods used for sterilization are Heat (Dry and Moist), Radiation, chemical compounds and gases etc.

• Moist heat sterilization is the most efficient Biocidal Agent. In the pharmaceutical industry it is used for Surgical dressings, Sheets, Surgical and diagnostic equipment, Containers, Closures, Aqueous injections, Ophthalmic preparations and Irrigation fluids etc.
• Dry heat sterilization can only be used for thermo stable, moisture sensitive or moisture impermeable pharmaceutical and medicinal. These include products like; Dry powdered drugs, Suspensions of drug in non aqueous solvents, Oils, fats waxes, soft hard paraffin silicone, Oily injections, implants, ophthalmic ointments and ointment bases etc.

• Gaseous sterilization is used for sterilizing thermo labile substances like; hormones, proteins, various heat sensitive drugs etc.

• U.V light is perhaps the most lethal component in ordinary sunlight used in sanitation of garments or utensils.

• Gamma-rays from Cobalt 60 are used to sterilize antibiotic, hormones, sutures, plastics and catheters etc.

Dry Heat Sterilizers

Hot air oven is one of the dry heat sterilizers. These sterilizers use dry heat for killing microorganism and are better than the steam sterilizers in the sense that the process does not corrode the machines. This is also used to sterilize liquids with low moisture content and also for treatment of medical powders. The process completely destructs all microorganisms and does not cause any environmental pollution or inconvenience to humans. Usually made up of stainless steel, the shape and position of heating elements in the chamber ensure uniform temperature distribution. The entire process includes drying, heating, sterilizing and cooling phase.

The benefit of dry heat includes good penetrability and non-corrosive nature which makes it applicable for sterilizing glass wares and metal surgical instruments. It is also used for sterilizing non-aqueous thermostable liquids and thermostable powders. Dry heat destroys bacterial endotoxins (or pyrogens) which are difficult to eliminate by other means and this property makes it applicable for sterilizing glass bottles which are to be filled aseptically.

Dry heat kills the organisms by destructive oxidation of essential cell constituents. Killing of most resistant spores by dry heat requires a temperature of about 160 degree C for 60 minutes.

Maintenance of Dry Heat Ovens

Maintenance of dry heat oven is an integral part of every dry heat sterilization procedure it can be achieved by

• Keeping the oven clean at all times
• Temperature gauge should be check on regular basis. This can be done by putting a thermometer in the oven and comparing the temperature reading with the one on the gauge.

Application of Dry Heat Sterilizers

• Sterilizing laboratory instruments
• Sterilizing ampoules
• Sterilizing injection bottles
• Sterilizing pharmaceutical vessels
• Sterilizing medical instruments

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