文档介绍：Chapter 5 Microbial growth control
Physical methods
Chemical agents
Food Preservation
Control of anisms by physical and chemical agents frequently used terms
Sterilization: the process by which all living cells, viable spores, virus, and viroids are either destroyed or removed from an object or habitat.
Disinfection: the killing, inhibition, or removal of anisms that may cause disease.
Sanitization: the microbial population is reduced to levels that are considered safe by public health standards.
Antisepsis: the prevention of infection or sepsis
-cide: kill; -static: stop
germicide: kill pathogens but not necessarily endospores. Bactericide; fungicide; algicide; viricide; bacteriostatic; fungistatic
Conditions influencing the effectiveness of antimicrobial agent activity
1. Population size.
2. position. Spore, young/mature
3. Concentration or intensity of an antimicrobial agent.
4. Duration of exposure.
5. Temperature. higher
6. local environment.
eg. 1. Heat kill more readily at an acid pH.
2. Organic matter protect anisms.
3. Biofilm protection.
Microbial Growth Control
Physical ways
Heat sterilization (including autoclave and pasteurization)
Radiation (microwaves, UV, X-rays, g-rays and electrons)
Filtration (depth filter, membrane filter and nucleation track (nucleopore) filter)
Heat(terms)
TDP: the lowest temperature at which a microbial suspension is killed in 10 minutes.
TDT: the shortest time needed to kill anisms in a microbial suspension at a specific temperature and under defined conditions.
Decimal reduction time (D) or D value: the time required to kill 90% of the anisms or spores in a sample at a specified temperature. D121
Moist heat sterilization
Autoclave: a device somewhat like a fancy pressure cooker.
The air initially present is forced out the chamber is filled with saturated stream
121oC or 15 pounds 15-30min
1. All air must be flushed out of the chamber, or it will not reach 121oC even though it may reach pressure of 15 pounds