B: Physical Methods of Control Flashcards
How does moist heat work?
denatures proteins and nucleic acids. boiling water for 10 mins disinfects it
What is pasturization
brief moist heating of a liquid to kill pathogens and reduce number of food spoilage organism milk and juice
How does an autoclave use moist heat
uses moist heat and pressure to produce 121 C. used to sterilize liquids like media
How does dry heat heat work?
denaturation of proteins and nucleic acid but less effective. can sterilize or disinfect
give examples of dry heating (3)
loop in bacticinerator, food in oven, lab equipment in over
How does filtration work? (fluids)
fluids- a 0.2 um pore filter removes vegetative cells from heat sensitive fluids
How does filtration work? (air)
air -masks filter air to protect worker -HEPA filters (high efficiency particulate air) filter air eg. Biological Safety Cabinets use HEPA to protect workers from pathogens inside cabinets and protect sample from contamination
How does low temp work (freezing)
freezing stops cells from growing but doesn’t kill them.
-80 C freezers used to preserve bacterial samples in lab.
lyophilization method
How does low temp work (refrigeration)
4 C slows the growth of pathogens but not food spoilage psychotrophs
Water activity
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Radiation (ionization radiation)
gamma rays have high nrg. penetrates into objects. works by producing toxic oxygen products that damage cellular components
gamma rays used on what
foods like spices and meat, heat sensitive material like syringes
Radiation (non-ionizing radiation)
UV light at 260 nm has less nrg than gamma rays and does not penetrate well
How does non-ionizing radiation kill bactera
by linking adjacent thymine in DNA producing thymine dimers. these distort DNA and produce errors in replication
What other areas do non-ionizing radiation disinfect
used to disinfect surfaces and air. eg biological cabinets (when not in use) or disinfects water (water must be thin layer)
