Thermal Death Flashcards
What is the difference between pasteurization and sterilization?
Pasteurization only reduces #
Sterilization KILLS ALL.
What are some ways to extend shelf life?
- Reduce the increase of microorganisms
- Use pH, preservatives, drying, radiation.
Use of:
1. Bacteriostatic stops active growth
2. Bactericidical kills microbes
What are examples of bacteriostatic?
Freezing, osmotic pressure, desiccation and pH
What are some examples of bactericidal?
Heating, radiation, chemical. Sterilization
Bactericidal is meant for?
Spores and cells. Kill by baking, boil, frying or microwave. Exceeds 100C
What is the purpose of cooking? (at what temp)
< or = 100C to enhance flavor
What is the purpose of blanching?
<100C removes oxygen, destroys enzymes (not cooking b/c not held long enough at the temp, still kills enzymes)
Drying/ concentration
<100C Removes water, extends storage life.
Pasteurization
60-80C Kills target pathogens and spoilage microorganisms. Kills all vegatative cells, but spores are still pressent.
Sterilzation
> 100C Kills all microorganisms, including spores. (Use pressure to go over 100C).
What are the benefits of heath processing?
Cheap, quick, easy, may improve flavor (cooking), may inactivate undesirable enzymes ( blanching), enhances storage life of a product (drying), inactivation of pathogens and spoilage organisms (pasteurization).
Heat treatments: A few things about it.
Organisms specific sensitivity ( in a given environment
Rate of killing is log
Function of temp an time
For a time and temp there’s a constant % destroyed.
When performing heath processing caculations it’s good to know a few things like…
Concentration of microorganisms,
acceptable concentration of microorganisms that can survive
Thermal resistance of target organisms (most heat tolerant, establish temp requirements)
TIME AND TEMP relationship required for destruction.
1 log cycle is?
The time and temperature it takes to decrease the population by 90%. (from log 6 to log 5)
Thermal death is a ………….cycle.
log linear cycle
- given a specific time interval and temperature, the same % of population will be destroyed, regardless of population present.
What does a log cycle tell you if you have the time required to destroy one log cycle (90%), and you know the desired thermal reduction (# log cycles) it tells you…
The time it will take for you to get to the # of logs required.
If # of microorganisms increase, heating time will also have to increase..why?
To bring the time down to an acceptable level.
D value!!!!
DOES NOT MEAN SLOPE OR RATE
Expressed as time ( decimal reduction time)
Time to decrease Microbial population by 1 log (90%) at a given temp in a given system.