Textbook Question
Which of the following cannot be used to sterilize a heat-labile solution stored in a plastic container?
a. Gamma radiation
b. Ethylene oxide
c. Supercritical fluids
d. Autoclaving
e. Short-wavelength radiation
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11. Controlling Microbial Growth
Physical Methods to Control Microbial Growth
1:56 minutesProblem 3
Textbook Question
Why is a can of blackberries preserved by commercial sterilization typically heated to 100°C instead of at least 116°C?
Verified step by step guidance1
Understand the concept of commercial sterilization, which aims to eliminate pathogenic and spoilage microorganisms to ensure food safety and shelf stability without necessarily achieving complete sterility.
Recognize that blackberries are acidic fruits, and the acidity (low pH) inhibits the growth of many harmful bacteria, including Clostridium botulinum, which requires higher temperatures to be destroyed.
Recall that the thermal death time of microorganisms depends on both temperature and pH; acidic foods require less severe heat treatment because acid-sensitive pathogens are already inhibited.
Note that heating to 100°C (boiling point of water) is sufficient to inactivate most spoilage organisms and pathogens in acidic foods like blackberries, making higher temperatures unnecessary.
Understand that heating above 100°C (such as 116°C) would require pressurized conditions and could negatively affect the texture, flavor, and nutritional quality of the blackberries, so commercial sterilization balances safety and quality by using 100°C.
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Video duration:
1mKey Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Commercial Sterilization
Commercial sterilization is a heat treatment process designed to eliminate pathogenic and spoilage microorganisms to ensure food safety and shelf stability. It aims to destroy Clostridium botulinum spores, which are highly heat-resistant, but does not necessarily achieve complete sterility. This process balances microbial safety with preserving food quality.
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Thermal Death Point and Temperature Selection
The thermal death point is the lowest temperature at which all microorganisms in a sample are killed within a specific time. Heating to 100°C is often sufficient for acidic foods like blackberries because their low pH inhibits Clostridium botulinum growth, allowing lower temperatures to ensure safety without overprocessing.
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Effect of pH on Microbial Heat Resistance
Acidic environments (pH below 4.6) reduce the heat resistance of many microorganisms, including spores. Blackberries are naturally acidic, so commercial sterilization at 100°C is effective because the acidity prevents growth of heat-resistant pathogens, eliminating the need for higher temperatures like 116°C used for low-acid foods.
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