Review Sheet Week 5
Exercise 12.1 and 12.2
1. How are microorganisms destroyed by moist heat? By dry heat?
coagulates microbial proteins inactivating them. Dry heat does not due much as
far as breaking down the proteins; however, if the heat is increased to 160-170
degrees Celsius for extended period of time (1-2 hours)
2. Are some microorganisms more resistant to heat than others? Why?
microorganisms are more resistant to heat than others because each bacteria has
different time where they can damage the bacterial protein causing death.
Resistance to heat varies with type of proteins and the damaging reaction, no two
bacteria’s are made up of the same enzymes and proteins; all of this information
relates to where the bacteria is primarily found and what structures they have to
be able to survive their environments.
3. Is moist heat more effective than dry heat? Why?
Moist heat is more effective than
dry heat because moist heat coagulates microbial protein structures at a faster
rate and inactivates the proteins permanently. Some protein structures may be
stable with dry heat, with said, dry heat has to be applied at higher temperatures
for longer period of time than moist heat in order for microorganism to be
4. Why does dry heat require higher temperatures for longer time periods to
sterilize than does moist heat?
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