To pasteurize something means to heat it up to a specific temperature for a set amount of time to kill harmful bacteria and germs, then cool it back down. The process is named after Louis Pasteur, a French scientist who developed it in the 1860s.

When milk gets pasteurized at a dairy, workers heat it to about 161°F for 15 seconds. This kills dangerous bacteria like salmonella without cooking the milk or changing its taste much. Before pasteurization was invented, people often got sick from drinking milk because it could carry diseases. Pasteur's discovery made milk and other beverages much safer.

Most of the milk, juice, and other drinks you buy at the store have been pasteurized. You'll sometimes see unpasteurized products at farmers' markets or specialty stores, but these need to be handled more carefully and consumed quickly because they can spoil faster or make people sick if harmful bacteria are present.