Exam FOUR-Part 1 - PowerPoint Lecture MICROBIAL...

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PowerPoint ® Lecture Slide Presentation 1 CONTROLLING MICROBIAL GROWTH BY PHYSICAL AND CHEMICAL MEANS
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2 Sterilization Aseptic Disinfection/disinfectants Antisepsis/antiseptic Terminology of Microbial Control Pasteurization Chemotherapeutics Suffix –stasis/-static Suffix – cide/-cidal
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3
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4 Exposure to extremes of heat Exposure to extremes of cold Desiccation Filtration Osmotic pressure Radiation Physical Methods of Microbial Control
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5 Effects of high temperatures Denature proteins Interference w/ integrity of cell membrane, cell wall Disruption of structure and function of nucleic acids Thermal death point –TDP- lowest temperature that kills all cells in broth in 10 minutes Thermal death time –TDT- time to sterilize volume of liquid at set temperature Heat-Related Methods
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6 Used to disinfect, sanitize, and sterilize Kills by denaturing proteins and destroying cell membranes More effective than dry heat; penetrate better Different forms of moist heat: Boiling Autoclaving Pasteurization Ultrahigh-Temperature Sterilization Moist Heat
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Steam under Pressure Boiling temp increases as pressure increases Autoclave conditions – 121ºC, 15 psi, 15 minutes Kills ALL life forms 7 Kills vegetative cells of bacteria and fungi, protozoan trophozoites, and most viruses in 10 min Temperature cannot exceed 100ºC Boiling time is critical Endospores, protozoan cysts, and some viruses can survive boiling Boiling Autoclaving
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8 Kills harmful germs Not sterilization; heat-tolerant and heat-loving microbes survive These do not cause spoilage prior to consumption These are generally not pathogenic Pasteurization Milk Batch method – 30 minutes at 63ºC Flash pasteurization 72ºC for 15 seconds Ultrahigh-temperature pasteurization 134ºC for 1 second
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9 Used for materials that cannot be sterilized with or are damaged by moist heat Denatures proteins and oxidizes metabolic and structural chemicals Requires higher temperatures for longer time than moist heat Incineration – ultimate means of sterilization Dry Heat
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10 Decrease microbial metabolism and growth Psychrophilic microbes can multiply in refrigerated foods Slow freezing more effective than quick freezing Refrigeration and Freezing Desiccation and Lyophilization Drying inhibits growth due to removal of water; only microbiostatic Lyophilization used for long term preservation of microbial cultures Prevents formation of damaging ice crystals
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11 Filtration Osmotic Pressure High concentrations of salt/sugar in foods to inhibit growth Water in cell is drawn out by osmosis; cell desiccates Fungi have greater ability than bacteria to survive hypertonic environments
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12 Radiation: Shorter wavelength equals more energy and greater penetration Two types of radiation: Inonizing-X-ray, Gamma ray-Break DNA-used for meats-fresh
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This note was uploaded on 11/27/2011 for the course MCB 2000 taught by Professor Staff during the Fall '08 term at University of Florida.

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Exam FOUR-Part 1 - PowerPoint Lecture MICROBIAL...

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