Page 28 - MNU-PM502- Pharmaeutical Microbiology Theoritical Book

Pharm D- Clinical Pharmacy Program Third Level Pharmaceutical Microbiology& Antimicrobials (PM 502)

• They do not require water and there is not much pressure build up within
the oven, unlike an autoclave, making them safer to work with.

• They are much smaller than autoclaves but still as efficacious.

• Disadvantages of hot air oven

• Many objects cannot withstand the very high temperatures required for dry
heat sterilization (ex: plastics and rubber would melt)

• It is relatively slow and takes longer time than steam sterilization.

B- Moist heat

Mechanism of destruction of microorganisms: Kills by protein coagulation
(denaturation)

1- At temperature below 100˚C

Pasteurization

a brief heat treatment to reduce the number of spoilage organisms so they are
unlikely to cause disease

• Used in milk industry, wineries

• These processes will destroy the non-spore forming pathogens such as Salmonella,
Mycobacterium, Brucella abortus that may be found in milk

• Heating and cooling times and temperatures vary according to the type of
pasteurization process being used

• 3 type of pasteurization process

Holder method Flash method
low-temperature long high-temperature short Ultrahigh temperature
time (LTLT) time (HTST) (UHT)

• 62°C for 30 minutes • 72°C for 15 seconds • 140°C for 1-2 second

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