Ozone is formed photochemically in the stratosphere, in high-voltage electrical arcs, in photochemical smog and by ultraviolet (UV) sterilisation lamps and gamma radiation plants (Mustafa 1990). The characteristic fresh, clean smell of air following a thunderstorm represents freshly generated ozone in our atmosphere. The passage of new regulations (please see Chapter 2) and broad spectrum application may make ozone a greener alternative to traditional approaches for various food applications. Generally Recognised as Safe (GRAS) status and US Food and Drug Administration (FDA) approval of ozone as an antimicrobial agent for direct food contact (FDA 2001) have allowed ozone to be used in food processing. Because of residual compounds and reaction byproducts, chemical sanitising agents have come under scrutiny. For example, chlorination byproducts such as trihalomethanes and chloramine compounds are potentially carcinogenic (Pascual et al. 2007). Ozone reaction products from oxidation of organic compounds, such as aldehydes, ketones or carboxylic acids, have not been reported to have adverse health consequences (Pascual et al. 2007). Ozone is also considered as an alternative to chlorine to prevent the formation of halogenated organic compounds. However, the efficacy of ozone on food and food products within the food industry depends on its physicochemical properties. This chapter discusses the physical, chemical and antimicrobial properties of ozone as they apply to the food industry.