Sterilization definition, reasons, methods

Sterilization is a process to kill or inactivate all viable organisms. Chemical, thermal and irradiation are some sterilization methods. Sterilization is used in food industry.

Where sterilization process is done?

In a culture medium
in a gas
in the fermentation equipment

Sterilization process

It is not possible in practice to inactivate or kill all viable, harmful organisms. In industrial sterilization, it is done to reduce risk of contamination to an acceptable limit.

Sterilization in industry

Following parameters should be considered in sterilization in industrial scales.

Safety - Higher temperatures are used. Therefore safety of people and instruments should be considered.
Cost - We have to supply heat (energy) for sterilization. Supplying heat means we have to spend money. In industrial applications, cost should be minimized.
Effect on product - If temperature exceeds the limit, product can be deteriorated. Specially in food industry.

Reasons for sterilization

Many fermentation process should be done without foreign microorganisms. If foreign microorganisms exist with product microorganisms, all microorganism have to compete for nutrients. Also foreign microorganisms can produce harmful, toxic, unwanted products. Which will contaminate with required product.

Sterilization methods

Thermal
Chemical
Irradiation
Sonication
High speed centrifugation
Filtration

Thermal sterilization

Dry air or steam can be applied as the heating agent. Moist steam cab be used. If moist air is used, conditions of 121⁰C and and 2 bar should be provided. Moist air is more effective than dry air/steam.