Chapter 5 Microbial growth control Physical methods Chemical agents Food Preservation
Chapter 5 Microbial growth control Physical methods Chemical agents Food Preservation
Control of microorganisms 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 microorganisms 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
Control of microorganisms 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 microorganisms 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. Population composition. 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 microorganisms 3. Biofilm protection
Conditions influencing the effectiveness of antimicrobial agent activity • 1. Population size. • 2. Population composition. 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 microorganisms. 3. Biofilm protection
Microbial Growth Control Physical ways Heat sterilization (including autoclave and pasteurization) Radiation(microwaves, UV, X-rays, y-rays and electrons) Filtration(depth filter, membrane filter and nucleation track (nucleopore)filter
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 all organisms 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 microorganisms or spores in a sample at a specified temperature. D121
Heat(terms) • TDP: the lowest temperature at which a microbial suspension is killed in 10 minutes. • TDT: the shortest time needed to kill all organisms 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 microorganisms or spores in a sample at a specified temperature. D121