Sous vide, or low temperature cooking, is the process of cooking food at a very tightly controlled temperature, normally the temperature the food will be served at. This is a departure from traditional cooking methods that use high heat to cook the food, which must be removed at the exact moment it reaches the desired temperature.
Sous vide was first used as an upscale culinary technique in kitchens in France in the 1970s and traditionally is the process of cooking vacuum sealed (cryovac **) food in a low temperature water bath. This process helps to achieve texture and doneness not found in other cooking techniques, as well as introducing many conveniences for a professional kitchen. Sous Vide has slowly been spreading around the world in professional kitchens everywhere and is finally making the jump to home kitchens.
As sous vide has become more popular and moved to the home kitchen the term now encompasses both traditional “under vacuum” sous vide and also low temperature cooking. Some preparations rely on the vacuum pressure (cryovac) to change the texture of the food but in most cases the benefits of sous vide are realised in the controlled, low temperature cooking process.
The basic concept of sous vide cooking is that food should be cooked at the temperature it will be served at. For instance, if you are cooking a steak to medium rare, you want to serve it at 55°C
With traditional cooking methods you would normally cook it on a hot grill or oven at around 200-260°C and remove it at the right moment when the middle has reached 55°C. This results in a bulls eye effect of burnt meat on the outside turning to medium rare in the middle. This steak cooked sous vide would be cooked at 55°C for up to several hours. This will result in the entire piece of meat being a perfectly cooked medium rare. The steak would then usually be quickly seared at high heat to add the flavourful, browned crust to it.
There are two basic components to sous vide cooking at home: temperature and time. Each one of these can affect the end quality, texture, and taste of sous vide dishes. Learning to understand how they affect the food is one of the most important things as you begin sous vide cooking.
** Cryovac is the brand name of one of the first Companies to make food vacuum machines and food vacuum bags for the industry.
Benefits of Sous Vide
Just like any method of cooking there are many reasons to use the sous vide technique, depending on what you are trying to accomplish.
Because food cooked in the sous vide style is sealed it does not lose moisture or flavour to the cooking medium. The sous vide pouch holds in all the liquid released by the food. This is especially apparent when compared to traditional techniques such as roasting and braising where the meat has a tendency to dry out.
Also, as previously noted, the low heat used in sous vide prevents the collagen from constricting and forcing out more moisture. Controlling the collagen combined with the vacuum sealing results in very moist foods.
The sous vide technique allows you to cook tough cuts of meat at an incredibly low temperature, allowing you to tenderise them while remaining perfectly medium-rare. This is very effective for shanks, roasts and other pieces of meat that are typically braised or roasted, but often dry out or get overcooked in the process.
Using sous vide to cook food also exposes new textures. This is caused by two things. First, the vacuum sealing (cryovac) process can make lighter foods denser, like watermelon. Second, the lack of high heat used in cooking can result in silky and smoothly textured food that is impossible to replicate with traditional cooking techniques.
All sous vide cooking is done at temperatures below the boiling point of water and normally not above 85°C. You usually cook the food at the temperature you want it served at, so most settings are between 48° and 85°C, depending on the food being prepared.
While the range of temperature used in sous vide is much less variable than for traditional cooking, the precise control of the temperature is of great importance. When you set your oven at 200°C it actually fluctuates about 10-20°C degrees, sending it between 190°C and 220°C, which is fine when cooking at high temperatures. When cooking sous vide, the temperature of the water determines the doneness of your food, so a 20°C fluctuation would result in over cooked food. Most sous vide machines fluctuate less than 1°C and the best commercial machines are less than 0.1°C.
This precision is why many sous vide machines are very expensive. However, there are many more home machines with a low level of inaccuracy available in the last few years.
Cooking tenderises food by breaking down its internal structure. This process happens faster at higher temperatures. Because sous vide is done at such low temperatures the cooking time needs to be increased to achieve the same tenderisation as traditional techniques.
Also, your window of time to perfectly cooked food is much longer than with traditional cooking methods because you are cooking the food at the temperature you want it to end up at, rather than a higher temperature. This also allows you to leave food in the water bath even after it is done since keeping it at this temperature does not dry out the food, up to several hours longer for tougher cuts of meat. However, be careful not to take this concept too far as food can still become overcooked by sous vide, many times without showing it externally.
Temperature and Time Together
The power of sous vide cooking comes from precisely controlling both temperature and time. This is important because of the way meat reacts to different temperatures.
At 50°C meat slowly begins to tenderise as the protein myosin begins to coagulate and the connective tissue in the meat begins to break down. As the temperature increases so does the speed of tenderisation.
However, meat also begins to lose its moisture above 60°C as the heat causes the collagen in the cells to shrink and wring out the moisture. This happens very quickly over 65C and meat becomes completely dried out above 70°C.
Many tough cuts of meat are braised or roasted for a long period of time so the meat can fully tenderise, but because of the high temperatures they can easily become dried out. Using sous vide allows you to hold the meat below the 60C barrier long enough for the slower tenderisation process to be effective. This results in very tender meat that is still moist and not overcooked.