Before the mid-19th century, drinking milk was a risky endeavor due to foodborne illnesses like tuberculosis and typhoid fever. Louis Pasteur, a French scientist, developed the process now known as pasteurization. Originally designed to prevent wine and beer from souring, the process involves heating the liquid to a specific temperature for a set period to kill harmful pathogens without curdling the milk. The most common method today, High-Temperature Short-Time (HTST) pasteurization, heats milk to 161°F (71.7°C) for 15 seconds. This breakthrough transformed milk from a dangerous local product into a safe, mass-distributed staple. Pasteurization significantly reduced infant mortality rates in cities during the late 19th and early 20th centuries.