Physical Means of Controlling Microbial Growth Flashcards
- Removes particles less than 3um and greater than 10um in size with 99.9% efficiency, but does not ensure sterilization
- Used in clean rooms: quarantine, biological safety labs
High-efficiency particulate air (HEPA) filter (disinfection)
Practice of using chemical agents used on body surfaces to safely reduce microbial numbers
Antisepsis
Methods of heat sterilization
- Dry heat
- Moist heat
Thermal death time determines
Heat sensitivity of microorganism
Food-related factors that may affect heat sensitivity of endospores
- Low acidic pH kills microorganisms faster
- High sugar, protein, or fat content decreases heat penetration
- Effect of salt conc. is species specific
Endospores must be exposed for a (blank) period of time and (blank) temp. when using dry heat
longer, higher
True or false. UV light is limited to disinfecting exposed surfaces only.
True.
Which kills in autoclaving, temperature or pressure?
Temperature
True or false. Sanitization is less effective than disinfection. Because of this, it is not safe for food contact surfaces.
False. It is safe and does not involve toxic levels of anti-microbial agents.
- X-rays and gamma rays
- Produces high reactive molecules that can destroy DNA, lipids, and proteins
Ionizing radiation (sterilization)
Most accessible and widespread method of controlling microbial growth
Heat sterilization
- Prevents spoilage and preserves food by decreasing microbial growth rate
- Does not kill microorganism
Refrigeration and freezing
Factors that affect efficacy of disinfection
- Nature and no. of cells
- Type and conc. of disinfectant
- Type and condition of surface to be disinfected
- Duration of exposure
Serves to reduce the no. of microorganisms to a safe hygienic level
Sanitization
- Subjects milk in 74°C -> 140°C -> 74°C in less than 5 mins.
- Allows milk to be stored in room temp. for 1-3 months
Ultra-high temperature (UHT) (sterilization)
Simplest method of decontamination, temperature at 100°C kills most pathogenic organisms
Boiling (disinfection)
- Non-ionizing radiation
- Uses wavelengths that cause mutations in microbial DNA that result to death
- May be ineffective bc of light activated repair mechanisms
UV Radiation
Use of conduction, usually at 170°C for 1 hr, 160°C for 2hrs
Hot air convection oven (sterilization)
- Made of high tensile-strength polymers with numerous microscopic pores
- Used with a syringe and sterile collecting vessel; acts like a sieve to trap particles
Liquid filtration via membrane filters (sterilization)
Completely eliminates all viable microorganisms, including endospores
Sterilization
Use of open flame
Flame-sterilization (sterilization)
True or false. Relationship of (D) with time is exponential.
True.
- Used for milk and heat-sensitive liquids
- Does not kill all, only reduces microbial load
- Increases shelf life of perishable liquids
Pasteurization (disinfection)
- Water from frozen materials are drawn out in a vacuum
- High-quality products viable for years
Freeze-drying (lyophilization)
