Moist Heat Sterilization
Mechanism of Action
- Denaturation and coagulation of proteins
Temperature below 100oC:
- For pasteurization of milk
- Holder method
- 65oC for 30 min
- Flash Process
- 72oC for 15 sec
- Pasteurization kills nearly 90% of the bacteria in milk
- Including the more heat resistant – Tubercle bacilli
- It does not kill bacterial spores.
- It does not kill the thermoduric bacteria.
- Also used for :
- Vaccines of nonsporing bacteria
- Serum or body fluids containing coagulable proteins.
Methylene blue Reduction test:
- Indirect test
- Detection of microorganism in milk.
- Prior to the process of pasterurization
Pasteurization of milk is determined by:
- Phosphatase test
- Alkaline Phosphatase (ALP) is an enzyme naturally present in all raw milk
- Used as an indicator of proper milk pasteurization.
- Complete pasteurization will inactivate the enzyme .
- Coliform count
- Standard plate count
Temperature at 100oC (Boiling):
- Rolling boil
- boiling for 5-10 minutes
- Kill bacteria, but not spores or viruses
Steam at Atmospheric Pressure 1000C:
- Koch or Arnold steamer is usually used the container
- Culture media are simultaneously sterilized.
- A single exposure of 20 min usually ensures sterilization
- Tyndallization
- An exposure of 100oC for 20 minutes
- For three successive days
Steam under pressure /Autoclave/steam sterilizer (>100oC)
- Most effective sterilizing agent for
- dressing
- instruments
- laboratory wares
- media and pharmaceutical products
- aqueous solutions.
- Not for sharp instruments
- Done at:
- Temperature of 121oC
- keeping chamber pressure of 15lb per square inch
- For 15 min.
- 126oC
- 20lbs psi
- for 10 min
- on 133oC
- 30 lbs psi
- for 3 min.
- Biological indicators
- Spores of Bacillus stereothermophilus (Geobacillus stearothermophilus) are used.
- Spores of Bacillus subtilis and Bacillus pumilis are also used.
Exam Question
Temperature below 100oC:
- For pasteurization of milk
- Holder method
- 65oC for 30 min
- Flash Process
- 72oC for 15 sec
- Pasteurization kills nearly 90% of the bacteria in milk
- Including the more heat resistant – Tubercle bacilli
- It does not kill bacterial spores.
- It does not kill the thermoduric bacteria.
- Pasteurization of milk is determined by:
- Phosphatase test
- Alkaline Phosphatase (ALP) is an enzyme naturally present in all raw milk
- Used as an indicator of proper milk pasteurization.
- Complete pasteurization will inactivate the enzyme .
- Coliform count
- Standard plate count
Steam under pressure /Autoclave/steam sterilizer (>100oC)
- Most effective sterilizing agent for
- dressing
- instruments
- laboratory wares
- media and pharmaceutical products
- aqueous solutions.
- Not for sharp instruments
- Done at:
- Temperature of 121oC
- keeping chamber pressure of 15lb per square inch
- For 15 min.
- 126oC
- 20lbs psi
- for 10 min
- on 133oC
- 30 lbs psi
- for 3 min.
- Biological indicators
- Spores of Bacillus stereothermophilus (Geobacillus stearothermophilus) are used.
- Spores of Bacillus subtilis and Bacillus pumilis are also used.
Don’t Forget to Solve all the previous Year Question asked on Moist Heat Sterilization
