Pasteur patented his wine-preservation method using heat in 1865.
The method grew out of Pasteur’s investigation into why wine sometimes became sour or otherwise spoiled. He argued that living microorganisms were responsible for these changes, challenging the older idea that fermentation and spoilage were merely chemical breakdown. By heating wine gently for a controlled period, he could destroy many harmful microbes without boiling the liquid or ruining its character.
Pasteur’s patent came in 1865, after experiments connected with the wine industry. The process later became known as pasteurization. It was first associated with wine and beer, not milk; applying comparable heat treatment to milk became widespread later and involved other researchers and public-health concerns.
The date is sometimes confused with 1864, when Pasteur conducted important wine-heating experiments in Arbois, or with 1866, when he published Études sur le Vin. Those are related milestones, but the patent itself belongs to 1865.