Bacteria or spores in food
Tyndallisation was a progressive sterilisation process developed in the late 19th century by Irish physicist John Tyndall; it essentially consists of heating the substance to boiling point (or just a little below) for 15 minutes, three days in succession. It was used for food because it is gentler and less damaging on foods - usual sterilisation takes the substance to well over boiling point (121 °C).
