Chemical Methods of Sterilization
Several chemical agents are used as antiseptics as well as dis-infectants. All these chemical agents (e.g., alcohols, aldehydes, etc.) are described later in detail under disinfection.
Although it is true that cold temperatures kill some microbes, gradual cool-ing, long-term refrigeration, or deep-freezing does not adversely affect most of the microorganisms. In fact, freezing tempera-tures, ranging from 270 to 2135°C, provide an environment that can preserve cultures of bacteria, viruses, and fungi for lon-ger periods. Some psychrophiles grow very slowly even at freez-ing temperatures and can continue to secrete toxic products.
S. aureus, Clostridium species (spore formers), Streptococcus species,and several types of yeasts, molds, and viruses are the pathogens that can survive for several months in the refrigerated food items.
As a general rule, chilling, freezing, and desiccation are not considered as methods of disinfection or sterilization because their antimicrobial effects are erratic and uncertain, and one cannot be sure that pathogens subjected to these procedures have been killed.