20 Questions
What is the purpose of a replaceable HEPA filter?
To separate particles of different sizes
At what temperature does freezing typically stop microbial growth?
-10°C
What is the effect of high pressure on proteins?
It denatures them
What is the purpose of desiccation in food preservation?
To remove water from food
What is the effect of osmotic pressure on microbial cells?
It causes plasmolysis
What is the purpose of low-temperature storage?
To slow down microbial growth
What type of microorganisms can grow at low temperatures?
Psychrophiles
What is the purpose of lyophilization in food preservation?
To remove water from food
What is the temperature required to destroy vegetative microorganisms, bacterial endospores, and viruses during autoclaving?
121.5oC
What is the primary mechanism by which autoclaving achieves sterilization?
Increased pressure forces steam into materials
What is the purpose of using pressure-sensitive tape or spore strips during autoclaving?
To ensure proper sterilization of materials
What is the minimum time required for autoclaving at 15 psi and 121.5oC to achieve sterilization?
20 minutes
What type of processing is autoclaving an example of?
High Pressure Processing
What is the result of increasing pressure during autoclaving?
An increase in temperature
What is the purpose of soaking filter paper disks in a chemical and placing them on a culture?
To observe the zone of inhibition
What is the mechanism of action of phenol and phenolics?
They disrupt plasma membranes, causing leakage
What is the characteristic of bisphenols?
They contain two phenol groups connected by a bridge
What is the mechanism of action of chlorhexidine?
It disrupts plasma membranes, causing leakage
What is the mechanism of action of iodine?
It impairs protein synthesis and alters membranes
What is the term for a solution of iodine in aqueous alcohol?
Tincture
Study Notes
Autoclaving
- Increased pressure raises the temperature above 100°C and forces steam into materials being sterilized
- Autoclaving at 15 psi at 121.5°C for 20 minutes destroys vegetative microorganisms, bacterial endospores, and viruses
- Pressure-sensitive tape or spore strips can be used as a quality control measure to ensure proper autoclaving
Chemical Methods to Inhibit Microbial Growth
- Phenol and phenolics injure lipids of plasma membranes, causing leakage
- Bisphenols contain two phenol groups connected by a bridge and disrupt plasma membranes
- Examples of bisphenols include hexachlorophene and triclosan
- Biguanides, such as chlorhexidine, are used in surgical hand scrubs and disrupt plasma membranes
- Halogens, such as iodine, impair protein synthesis and alter membranes
Physical Methods to Inhibit Microbial Growth
- Low temperature inhibits microbial growth by slowing down microbial metabolism
- Examples of low temperature include refrigeration (5°C) and freezing (-10°C)
- High pressure can denature proteins
- Cold storage at low temperatures can inhibit growth, but psychrophiles can still grow
- Dessication removes water from cells, inhibiting growth and metabolism
- Osmotic pressure uses high concentrations of salts and sugars to create a hypertonic environment, causing plasmolysis
- Drying methods include desiccation, lyophilization (freeze-drying), and adding salt or sugar to food
This quiz covers the process of autoclaving, a method of sterilization that uses high pressure and temperature to kill microorganisms. It explains how increased pressure raises the temperature above boiling point, forcing steam into materials to be sterilized.
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