What Is Sous Vide? Cooking by Controlling Temperature Instead of Time

Food sealed in a bag is submerged in water held at a precisely controlled temperature, and it eventually reaches that temperature throughout and then stops changing. Because the bath is at the target rather than above it, there is no gradient driving the outside past doneness while the centre catches up, which produces uniform colour and texture from edge to edge. The name means under vacuum and refers to the bag rather than to anything essential about the cooking, since the vacuum's job is to keep water in contact with the food and to prevent the bag floating. Time still matters, for two separate reasons that are frequently conflated: reaching the target temperature takes a period determined by thickness rather than weight, and holding beyond that continues to break down connective tissue, which is what converts a tough cut into a tender one over many hours without raising its temperature at all.

The technique makes visible the fact that cooking is a series of separate changes occurring at different temperatures:

• •Myosin, one of the main muscle proteins, begins denaturing around fifty degrees, which firms the texture
• •Actin denatures around sixty-six degrees and squeezes out moisture, which is why meat cooked beyond that point is noticeably drier
• •Collagen, the connective tissue that makes tough cuts tough, converts to gelatin slowly at temperatures above about fifty-five degrees, with the rate increasing sharply as temperature rises
• •Holding a tough cut at a relatively low temperature for a very long time therefore converts collagen without ever denaturing actin, which is the combination no conventional method can achieve
• •Eggs illustrate the point most clearly, since yolk and white set at different temperatures, so a bath at a chosen intermediate temperature produces textures impossible by boiling
• •Vegetables behave differently, requiring higher temperatures because the pectin holding plant cells together breaks down above about eighty-five degrees, so they cannot be cooked alongside meat in the same bath

The method does one thing well and cannot do several others. It cannot brown anything, because the Maillard reaction that produces browning and most roasted flavour requires temperatures well above boiling, which is why sous vide is almost always followed by a brief sear in a very hot pan or with a torch. It is slow, with a thick piece of meat taking hours to reach temperature. It requires equipment, though an immersion circulator is now inexpensive. Texture can be unfamiliar, since meat held at a low temperature has a different mouthfeel from the same doneness reached quickly, which some people dislike. And the sealed low-oxygen environment creates a specific food safety requirement, since temperatures in the range used are within or near the range where bacteria grow, so safety depends on time at temperature rather than on reaching a lethal temperature instantly, and published tables specify how long a given thickness must be held at a given temperature to achieve the same reduction in pathogens that a higher temperature achieves immediately.

The technique developed in two strands. Scientific work on low temperature cooking of meat was done in the 1960s and 1970s, and the method was adopted industrially for cooking and holding food in institutional catering. The version that entered restaurant kitchens is credited to Georges Pralus, working for a French restaurant in the 1970s and using it initially to reduce shrinkage and fat loss in foie gras, and to Bruno Goussault, who developed the temperature and time parameters systematically and taught the method to a generation of chefs. It spread through high-end restaurants because it solved a production problem as much as a quality one: food can be cooked in advance, held precisely and finished to order, which makes consistent results possible across a busy service. Domestic adoption followed once circulators became cheap, and the same equipment is now used for fermentation, yoghurt, infusions and confit. The criticism that it produces uniformity at the expense of character is a genuine aesthetic position rather than a technical objection.

Sous vide holds food in a water bath at exactly the temperature it should reach, so nothing overshoots and the texture is uniform throughout. Time then controls something separate, since holding a tough cut for many hours converts collagen to gelatin without pushing past the temperature at which actin denatures and squeezes out moisture. It cannot brown anything, so a hot sear is needed afterwards, and safety depends on holding for a specified period rather than on reaching a lethal temperature.