1/17/2016 Dry Heat Filtration ·Dry heat uses higher Physical removal of microbes by temperatures than moist heat passing a gas or liquid through filter Mode of action:oxidation Used to sterilize heat sensitive liguids and air in hospital isolation Incineration-flame or units and industrial clean rooms electric heating coil High-efficiency particulate air -ignites and reduces (HEPA)filters remove almost all microbes and other microorganisms larger than about substances to ash 0.3μm Hot-air sterilization or dry Pore size for bacteria:0.2-0.4 jm ovens-150-1800C for 2-4 hrs Pore size for viruses:0.01 um Cold High Pressure .Microbiostatic-slows the growth of microbes High pressure applied to liquid solutions is Refrigeration 0-159C and freezing OC transferred instantly and evenly throughout the sample Used to preserve food,media,and cultures ·If pressure is high enough, molecular Ice crystals that form with freezing are structure of proteins and carbohydrates are damaging to microbes cellular structure. altered inactivating vegetative bacterial cells. Bacterial cell numbers are reduced. Fruit juices have been treated this way and Many eukaryotic parasites are killed after has the advantage that it preserves the flavor,color,and nutrient value of the several days at freezing temperatures. product. 81/17/2016 8 Dry Heat • Dry heat uses higher temperatures than moist heat • M d f ti Mode of action: id ti oxidation • Incineration – flame or electric heating coil - ignites and reduces microbes and other substances to ash • Hot-air sterilization or dry ovens – 150-1800C for 2-4 hrs Filtration • Physical removal of microbes by passing a gas or liquid through filter • Us d t st ili h t s siti Used to sterilize heat sensitive liquids and air in hospital isolation units and industrial clean rooms • High-efficiency particulate air (HEPA) filters remove almost all microorganisms larger than about 0.3 m • Pore size for bacteria: 0.2 – 0.4 m • Pore size for viruses: 0.01 m Cold • Microbiostatic – slows the growth of microbes • Refrigeration Refrigeration 0-150C and freezing < and freezing <00C • Used to preserve food, media, and cultures • Ice crystals that form with freezing are damaging to microbes cellular structure. • Bacterial cell numbers are reduced. • Many eukaryotic parasites are killed after several days at freezing temperatures. High Pressure • High pressure applied to liquid solutions is transferred instantly and evenly throughout the sample • If pressure is high enough, molecular structure of proteins and carbohydrates are altered inactivating vegetative bacterial cells. • Fruit juices have been treated treated this way and has the advantage that it preserves the flavor, color, and nutrient value of the product