topic_15_for_students - Topic 15 Microbial control...

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Unformatted text preview: Topic 15 Microbial control Prevention of microbial growth Critical importance spanning health and industry Food industry Industrial processes (e.g. biofouling of oil pipelines) Health care (e.g. nosocomial infections) Drinking water distribution systems Strategies for microbial control include: Heat Radiation Filtration Chemicals T e m p e r a t u r e Temperature and viability decimal r eduction time ( D ) : time required for a 10-fold reduction in population density at given temperature ther mal death time (TDT) : time required to kill all cells at a given temperature; population size-dependent d a t a f o r a m e s o p h i l e igure 27.1 (a) = mesophile (b) = ther mophile Temperature and killing rate As temper atur e incr eases, the decimal r eduction time ( D ) decr eases. Figure 27.2 Steam under pressure 121°C 15 psi “Pressure cooker” Efficiency determined by Destruction of endospores Vegetative cells Autoclave Figure 27.3 Wikipedia Autoclave and steam flow Temperature kills, not pressure. Figure 27.3 Typical autoclave cycle Autoclave time Sterilization Exhaust Figure 27.3 Autoclave tape Pasteurization Reduces microbial load Destroys pathogens 90-99% kill of other microbes Increase shelf life Does NOT sterilize Louis Pasteur developed for wine preservation Flavour and bouquet maintained 5000 L/h http://www.fdb.it/ Common process: high-temp short time (HTST) 72°C for 15 seconds Other processes UHT: 135°C for < 1 second ESL: filtration, then lower-temp treatment Pasteurization R a d i a t i o n Ultraviolet (UV) radiation...
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This note was uploaded on 01/24/2011 for the course BIOL 140 taught by Professor Cruise during the Spring '10 term at Lahore University of Management Sciences.

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topic_15_for_students - Topic 15 Microbial control...

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