Why did margarine become important during World War II?

Margarine became particularly important during World War II because it served as a vital substitute for butter, which was subject to rationing during the conflict.1

The production of margarine relied on the industrial process of hydrogenation, which converts liquid vegetable oils into a semisolid fat. This process was essential for creating a stable, spreadable product that could effectively replace butter when traditional dairy supplies were limited. Beyond margarine, the war period generally spurred significant innovation in processed foods, as manufacturers sought to improve the shelf life and transportability of goods to support wartime needs.12