CAM102 Lecture Notes - Lecture 24: D-Value (Microbiology), Pasteurization, Ultra-High-Temperature Processing
Lecture 1
Learning Concepts
• When did antimicrobial control start?
• What types of techniques are involved in microbial control?
• How do antibiotics work?
• What classes of antibiotics are there?
Terminologies
Sterilisation
The removal of all microbial life
Decontamination
Treatment that renders an object or surface safe to handle
Disinfection
The removal of pathogens from an inanimate object or surface
Antisepsis
The removal of pathogens from living tissue
Sanitation
The reduction of the number of microbes in water or on an object
Physical Methods of Microbial Control
Used for:
• Sterilisation
• Decontamination
• Disinfection
• Sanitation
Involves:
• Heat
• Radiation
• Filtration
Heat
Dry Heat
• Flaming (eg methane flame ~2000℃)
• Oven heating (170℃, 2hr)
Moist Heat
• Boiling (100℃)
• Pasteurisation (eg for milk 72℃, 30 sec)
• Ultra High Temperature UHT (140℃, 1 sec)
• Steam autoclaving (121℃, 15 mins, 134℃, 15 mins)
Thermal Death Point (TDP)
Lowest temp at which all cells in a culture are killed in 10 min
Thermal Death Time (TDT)
Time to kill all cells in a culture
Decimal Reduction Time (DRT)
Time to kill 90% of a population at a given temp
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The effect of temperature on the viability of a mesophilic bacterium was measured and expressed in
terms of the decimal reduction time (D), the time taken to kill 90%of a population due to a given
treatment. D was obtained for the bacterium at three different temperatures
D = 42 min at 50℃
D = 12 min at 60℃
D = 3 min at 70℃
Steam Autoclaving
Radiation
Ionising Radiation
• X-Rays
• Gamma Rays
Non-Ionising Radiation
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• Ultra-Violet Light (UV)
Filtration
Entails the removal of organisms based on size exclusions
Liquid filtration
Cellulose or plastic polymers
Air filtration
High Efficiency Particulate Air (HEPA) filters (pore size 0.3µm) which are used in lamina flow hoods
Chemical Methods of Microbial Control
Used for:
• Sterilisation
• Decontamination
• Disinfection
• Sanitation
• Antisepsis
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find more resources at oneclass.com
Document Summary
Treatment that renders an object or surface safe to handle. The removal of pathogens from an inanimate object or surface. The reduction of the number of microbes in water or on an object. Moist heat: boiling (100 , pasteurisation (eg for milk 72 , 30 sec, ultra high temperature uht (140 , 1 sec) Lowest temp at which all cells in a culture are killed in 10 min. Time to kill all cells in a culture. Time to kill 90% of a population at a given temp. Steam autoclaving (121 , 15 mins, 134 , 15 mins) The effect of temperature on the viability of a mesophilic bacterium was measured and expressed in terms of the decimal reduction time (d), the time taken to kill 90%of a population due to a given treatment. D was obtained for the bacterium at three different temperatures. Entails the removal of organisms based on size exclusions.
