Sous vide is French for "under vacuum". In the US the term "Cryovacked" is often used instead of Sous vide. It is a technique where the ingredients are put in a vacuum-sealed plastic pouch, usually for a long time and cooked at a low temperature (usually around 60°C = 140°F). In some cases food is cooked for 24 hours or more. Although many excellent dishes can be prepared in under 30 minutes. The technique is currently being used by many of our top chefs including: Thomas Keller, Paul Bocuse, Joël Robuchon, Charlie Trotter, Wylie Dufresne Heston Blumenthal. Recently we have begun to see Sous vide cooking being adapted into the home kitchen
The rule of thumb among food service professionals is that foods should stay in the so-called "danger zone" (temperature range of 40F to 140F degrees) as briefly as possible since bacteria thrive in that range. However much of sous vide cooking occurs at lower temperatures and even cooking at 140F can be dangerous if one is not familiar with the various D-values for microbes.
D-value refers to decimal reduction time - The time required at a certain temperature to kill 90% (or 1 log10) of the organisms being studied. Thermal inactivation of Salmonella requires a value of 7-D ( 7 log10) and a 12-D reduction is required of C. botulinum in canning.
D-values can be depend on pH and salt concentrations as well as fat content in food.
Most professional cooking relies on a cook's ability to judge doneness based on sight and feel. With sous vide, it is all about precise times and temperatures. In sous vide cooking once the proper temperature and time is determined restaurants are able to reproduce taste and texture fairly easy.
The 'art' of sous vide cooking is in determining the perfect 'core' temperature you need to reach to achieve the desired taste and texture. Professional sous vide chefs use a thin hypodermic needle thermometer, inserted through a piece of spongy self-sealing tape, to test the internal temperature of the vacuum-packed foods without breaking the package's vacuum seal. Meats are usually seared before serving, which not only crisps the food, but kills any surface bacteria.
Maintaining a slow cooker or pan of simmering water at just the right temperature is a very time-consuming, hands-on process. Also, because they don't circulate the cooking liquid, these devices can develop hot and cool zones that adversely affect the cooking process.Restaurants require professional equipment for sous vide cooking that will maintain temperature without constant adjustments. Cuisinetechnology by Polyscience is a leader in the field with a long list of top chefs as clients (Thomas Keller, Paul Bocuse, Joël Robuchon, Charlie Trotter, Wylie Dufresne Heston Blumenthal).