Sous vide is both a method for storing fresh food, and for cooking it.
As a storage method, it can be for short-term or long-term storage. It involves putting fresh food in bags, using a device to pump the air in the bag out leaving a vacuum behind, then sealing the bag. The vacuum removes oxygen which would otherwise shorten the storage life of the food. The seal also prevents something else cross-contaminating the food.
Sous Vide provides a storage method for food that doesn’t change the food, the way freezing and canning do. And for food items that would discolour through browning from exposure to air, you don’t have to add an acid to prevent browning.
The food that goes into the pouch needs to be completely hygienic, as any germs in the food can breed undisturbed in the protected environment. Large food chains pack their Sous Vide food by people wearing sterile gloves and masks, in an impeccably sterile area, working at temperatures below 50 F (10 C.)
The food packed Sous Vide can be cooked immediately, stored chilled for immediate-future use, or frozen for longer-future use.
As a cooking method, the food that has been packed into the vacuum-sealed bag is also cooked right in it. This is not the same as the “boil-in-the-bag” approach, in which the food is cooked first before being packed in the bag.
The bag is usually cooked at a simmer in water between 180 to 200 F (82 to 93 C), making it basically another way of braising food. You won’t get any roasted or grilled flavours, or any carmelization, or Maillot effect, but all the flavours of the food will be intense because they cannot escape the bag. Consequently, a light hand is needed with seasonings.
Vegetables retain their colours very well when cooked Sous Vide, particularly carrots and artichoke hearts. Meat cooked by this method is often at the end removed from the bag and seared for flavour and appearance.
Sous Vide packaging and cooking is currently being used commercially used by chains such as Hilton International, British Airways, Bass, and SNCF (the French railroad company.) For them, Sous Vide gives better profit margins by allowing centralized portion control and by decreasing weight loss of food when cooked. It also makes it easier to prepare food without the need for added oil or butter, providing the lower-fat food asked for by their customers.
To cook Sous Vide at home, use heavy duty freezer bags double-bagged. Put the raw food item in, press the air out, and seal the bags. The more air you get out, the easier it will be to keep the bags submerged in water. Bring and hold a pot of water at around 150 F (65 C) and cook the food in it. Some writers on the topic advocate cooking meat at 131 F (55 C.)
You can also buy home-use vacu-pack machines, and the appropriate food-safe plastic bags to use with them.
The Sous Vide method was developed by Georges Pralus in 1974 at the Troigrois restaurant in Roanne, France. Pralus had been challenged to find a method of reducing the nearly 50% weight loss encountered when cooking foie gras.
He hit upon sealing it in plastic first. He asked the Cryovac Division of WR Grace company to see if they could come up with a plastic bag that would be waterproof, heat-resistant, and airtight. They developed multi-layered pouches for him.
Pronounced “soo — veed.” Sous Vide means “under vacuum.”
Rayner, Jay. Sous vide: the art of cooking in a vacuum. Manchester, England: The Guardian. 3 April 2011.