Tyndallization is an old process for sterilizing food. It is still occasionally used.A simple, effective, modern sterilizing method is to heat the substance being sterilized to 121°C for 15 minutes in a pressured system. If a pressured system is unavailable and sterilization proceeds instead using unpressurized heating up to 100°C, the heat will kill the bacterial cells but the bacterial spores may survive. In this case the Tyndallization process can be used to destroy the spores. The process is named after its inventor, the 19th century scientist John Tyndall.Tyndallization essentially consists of heating the substance for 15 minutes for three days in a row (usually by boiling it). On the second day most of the spores that survived the first day will have germinated into bacterial cells. These cells will be killed by the second day's heating. The third day kills bacterial cells from late-germinating spores. During the waiting periods over the three days, the substance being sterilized is kept at a warm room temperature; i.e., a temperature that is conducive to germination of the spores. Germination also requires a moist environment. When the environment is conducive to the formation of cells from spores, the formation of spores from cells does not occur (see bacterial spores). The Tyndallization process is generally effective, but its reliability is not considered 100% certified. It is not often used today, but it has applications in sterilizing some things that cannot withstand pressurized heating, such as plant seeds. It is not necessary to bring the temperature all the way up to 100°C to kill bacterial cells.