Tyndallization

Tyndallization is a nineteenth century process for sterilizing food and other substances, named for its inventor John Tyndall, used to kill heat resistant bacterial endospores that a single round of boiling cannot destroy. The technique involves heating the material to boiling point and holding it there for about fifteen minutes on three consecutive days; between each heating, any spores that have germinated into active bacterial cells are killed in the following round. The method is now considered outdated for most purposes, since some spores can still survive and later multiply, but it remains occasionally useful for sterilizing material too sensitive for high pressure heating, such as plant seeds.