Textbook Question
Foods packed in plastic for microwaving are
a. Dehydrated.
b. Freeze-dried.
c. Packaged aseptically.
d. Commercially sterilized.
e. Autoclaved.
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11. Controlling Microbial Growth
Physical Methods to Control Microbial Growth
2:49 minutesProblem 14
Textbook Question
A sample of E. coli has been subjected to heat for a specified time, and 90% of the cells have been destroyed. Which of the following terms best describes this event?
a. Thermal death point
b. Thermal death time
c. Decimal reduction time
d. None of the above
Verified step by step guidance1
Step 1: Understand the definitions of the terms given in the options. Thermal death point (TDP) is the lowest temperature at which all microorganisms in a liquid culture are killed in 10 minutes.
Step 2: Thermal death time (TDT) refers to the minimum time required to kill all microorganisms at a specific temperature.
Step 3: Decimal reduction time (D-value) is the time required at a certain temperature to reduce the microbial population by 90%, meaning to kill 90% of the cells.
Step 4: Since the problem states that 90% of the E. coli cells have been destroyed after heat treatment, this corresponds to the definition of decimal reduction time.
Step 5: Therefore, the term that best describes the event where 90% of cells are destroyed by heat is the decimal reduction time.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Thermal Death Point (TDP)
Thermal death point is the lowest temperature at which all microorganisms in a liquid culture are killed in 10 minutes. It indicates a specific temperature threshold for complete microbial destruction within a fixed time.
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Thermal Death Time (TDT)
Thermal death time is the minimum time required to kill all microorganisms in a sample at a specific temperature. It measures how long heat must be applied to achieve total sterilization at that temperature.
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Decimal Reduction Time (D-value)
Decimal reduction time is the time needed at a certain temperature to reduce the microbial population by 90%, or one log cycle. It quantifies the rate of microbial death under heat treatment, matching the scenario described.
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