High pressure is called pascalization. It is used to kill many pathogens by exposing food to high pressures. It will not always kill the endospores. Hyperbaric oxygen is used in a medical setting to fight the growth of anaerobic organisms using both oxygen and high pressure. Drying or desiccation will preserve many types of foods but the organisms will often grow back if the environmental conditions involve higher temperatures and higher water content. Lyophilization is used in the laboratory, which involves freeze-drying the organism. These can later be stored in dry conditions, even at room temperature. Some foods are dried with salt or sugar to decrease the ability of organisms to grow. Ionizing radiation can kill organisms. It can pass through cells and damage cellular components. There will be mutations to the food products that have been irradiated. Many processed foods in plastic and paper can be treated with ionizing radiation and certain laboratory equipment can be sterilized this way. UV light or nonionizing radiation can kill organisms. UV light-related purifiers will clean water for campers. It does not penetrate solid objects, however, so it has limited capabilities. Other techniques for reducing the organisms in a substance includes sonication, which involves high-frequency ultrasound waves. HEPA filters are used to sterilize the air in certain clinical settings. They are also found in airplanes, automobiles, air purifiers, and air conditioning systems. Membrane filters are used to filter antibiotic and vitamin solutions as well as culture media in order to sterilize the liquid without the damaging effects of heat.
ANTISEPTICS Antiseptics involve chemical control of microorganisms. The earliest antiseptic used was phenol. This is what Listerine is made from. It is too irritating to be used on skin surfaces in surgery. There are related compounds called phenolics. These include products called Lysol and Phisohex. Triclosan is used in antibacterial hand soaps and toothpaste. Triclosan is bactericidal. Other antiseptics contain heavy metals but these are also damaging to humans by denaturing proteins. These include mercury, which was used once to treat syphilis. 168
