To pasteurise is to heat a food, usually a liquid such as milk, juice, or beer, to a defined temperature for a set time to kill harmful bacteria and extend keeping quality. The process targets vegetative pathogens while minimising damage to flavour, colour, and nutrients, distinguishing it from sterilisation, which destroys all microorganisms including spores but alters the product more severely. Standard combinations include HTST (72 °C for 15 seconds) for milk and vat pasteurisation (63 °C for 30 minutes) for smaller batches, with time-temperature pairs validated to achieve the required pathogen kill. Pasteurising must be followed by rapid cooling and hygienic handling, since the surviving spoilage flora will multiply if temperature abused. The verb honours Louis Pasteur, though the practice of heating wine and beer to prevent spoilage predates his scientific explanation of it.