Chapter 9 Lecture 3

Physical methods of Microbial control

exposure to extreme heat or cold

desiccation

filtration

osmotic pressure

radiation

heat related methods

denature proteins

interfere with integrity of cytoplasmic membrane and cell wall

disrupt structure and function of nucleic acids

heat can be used for sterilization

microorganisms vary in their susceptability

Moist Heat

commonly used to disinfect, sanitize, sterilize, pasteurize, cells by denaturing proteins and destroying the cytoplasmic membrane

more effective than dry heat

methods of microbial control using moist heat

boiling

autoclaving

pasteurization

ultra high temp sterilization

boiling

kills vegetative cells of bacteria and fungi, protozoan trophozoites, and most viruses within 10 minutes at sea level

different elevations require different boiling temps

autoclaving

higher temp than boiling

kills all microbes

Pasteurization

moist heat

milk, ice cream, yogurt, fruit juice

Dry heat

hot air denatures proteins and promotes corrosion