Physical Control of Microbial Growth Quiz Notes

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Mini Quiz (page 786)

Why is heat an effective sterilizing agent?

High temperatures for the appropriate amount of time are capable of denaturing essential protein structures within bacteria. Denaturation casues macromolecules to loose their structure and function.

Why is moist heat more effective than dry heat for sterilization?

Moist heat is more effective than dry heat because it has better penetration power and at a given temperature produces a faster reduction in the number of living organisms.

What steps are necessary to ensure the sterility of material contaminated with bacterial endospores?

The sterility of bacterial endospores requires higher temperatures for longer application times (10-15 instead of 5-6) at higher pH’s.

Distinguish between the sterilization of microbiological media and the pasteurisation of dairy products.

  • Sterilization kills the entire bacterial load whilst pasteurisation only kills the majority.
  • Pasteurisation involves the rapid heating and cooling of milk whereas sterilisation is only rapid heating
  • Autoclave sterilization is carried out under pressure (15 pounds per square inch) whereas pasteurisation is carried out in large vats
  • Pasteurisation can be carried out as a continuous flow

Mini Quiz (page 788)

Define the decimal reduction

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