If you want to keep food fresh and safe, air is the enemy. Vacuum sealers get the air out. Industrial sealers were invaluable during World War II, helping to preserve food for shipment to U.S. forces overseas. After the war, the machines were adapted for use in commercial food production facilities, supermarkets, and restaurant kitchens. One common use of vacuum sealing today is in sous-vide (literally "under vacuum") cooking. This technique was first conceived by physicist Sir Benjamin Thompson in 1799, but the idea languished until the mid-20th century, when scientists developed it for commercial food production. French chef George Pralus, working with chefs Pierre and Michel Troisgro at their three-star restaurant in Roanne, introduced it to the world of haute cuisine. It has since become vital to the kitchens of star chefs like Ferran Adrià, Heston Blumenthal, and Thomas Keller.