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Questions and Answers
What is the primary purpose of thermization in milk processing?
What does UHT stand for in food processing, and what does it primarily target?
How does moist heat differ from dry heat in terms of effectiveness?
Which of the following is a common misconception regarding HEPA filters?
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What is the role of alcohol in the context of spore formation?
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What temperature and pressure are typically achieved in an autoclave to kill bacteria?
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Which enzyme does triclosan specifically target?
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What is the primary method of action for high energy radiation in sterilization?
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Study Notes
Differential Staining
- May counterstain nearly all bacteria, including endospores.
Physical and Chemical Methods
- Steam with formaldehyde can be used against vegetative cells.
Historical Methods
- The Great Plague of London (1665) saw doctors wearing "plague doctor" masks with beaks.
- The beaks contained sweet or strong odors, as the plague was believed to be caused by bad air.
Moist Heat
- More effective than dry heat as it can penetrate better.
- Targets macromolecules.
Dry Heat
- Usually direct heat.
Thermal Death Time
- The duration required to kill a specific bacteria at a particular temperature.
Pasteurization
- Thermization: Heating milk to 57-68°C for 15 minutes.
- Low-Temperature Long Time (LTLT): Kills spoilage microorganisms, preserving the quality of the sample.
- High-Temperature Short Time (HTST): Targets pathogenic bacterial spores.
- Ultra High Temperature (UHT): Kills Coxiella burnetii, the causative agent of Q fever.
- Hydrogen peroxide (30% concentration) is used to sterilize food cartons at 70°C for 6 seconds.
Autoclaves
- Used for both sterilization and decontamination.
- Achieves high temperatures (121°C) under 15 psi pressure, which kills bacteria.
Filtration
- Particularly useful for sterilizing glass plates.
- Membrane filters are not the same as HEPA filters, despite the similar principle.
HEPA Filters
- Filter particles between 0.5 and 2 µm in size.
- Particles are removed by collision with gas molecules and the glass fibers.
Desiccation
- Primarily targets the removal of moisture to inhibit microbial growth.
- Food could be preserved for an extended period with proper packaging.
- Removes around 98% of water from food.
Freeze-Drying (Lyophilization)
- Uses the principle of sublimation to remove moisture, preserving food nutrients and properties.
Osmotic Pressure
- High solute concentration draws out moisture, inhibiting microbial growth.
Ionizing Radiation
- Damages DNA, leading to microbial death.
- High penetration power allows for sterilization of internal tissues.
- Suitable for diverse materials.
- Can be risky for those exposed: high risk of mutation.
- More expensive than other methods.
UV Radiation
- Readily absorbed by DNA at 260 nm.
Chemical Agents: Triclosan
- An antibacterial and antifungal agent.
- Polychlorophenoxy phenol.
- Fat-soluble.
- Targets and poisons certain enzymes, such as Enoyl-acyl carrier protein reductase (ENR).
Alcohol
- Can affect the permeabilization of spores.
- 70% alcohol can impact spore formation.
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Description
Explore various methods used for bacterial control, including differential staining and thermal death time. Learn about the historical context of disease prevention and pasteurization techniques that ensure food safety. This quiz covers key concepts in microbiology and sanitation.
