Sous vide and low temp cooking.

Sous vide – I mention it from time to time, but haven’t gotten into specifics.

Sous vide, or “under vacuum” – refers to a food preparation method that involves placing food in plastic bags, and removing as much air as possible. Contrary to popular misstatements, “sous vide” does not refer to the controlled temperature water bath cooking that often takes place after sealing. Sous vide refers only to the sealing under vacuum. Nonetheless, sous vide usually is used in conjunction with low temperature cooking because it avoids any temperature differentials due to the presence of free air or liquid in the cooking vessel.

What are the advantages of low temperature cooking sous vide?

* Low temperature cooking sous vide enables the cook to prepare proteins (among other foods) to a precise level of doneness, consistently throughout the product. Medium rare steak, for example, should be cooked to an interior temperature of 55C-57C (130F-135F). Depending on the thickness and evenness of the meat, however, the temperature of the cooking environment, and the means used to cook the meat (pan frying versus air circulation, for example), the meat may reach a far greater doneness at some points than at others. It may be well-cooked at the ends before reaching 55C at the center. Product cooked sous vide reaches the temperature of the water bath, and does not exceed that temperature. Accordingly, a steak cooked sous vide at 55C will reach 55C throughout, and can be held at that temperature for some time.

* Low temperature cooking sous vide allows long-duration cooking of flavorful but tough/high collagen cuts of meat. Because collagen breaks down over relatively long periods, tough cuts like brisket and short rib require longer cooking; at high temperatures, they may dry out. Cooked sous vide at a constant temperature, the collagen in these cuts breaks down without toughening and shortening the muscle fibers in the meat.

* Low temperature cooking sous vide allows controlled cooking of vegetables/fruits and allows preservation of brilliant color and firm texture.

Generally speaking, low temp sous vide cooking requires two basic elements: the means to seal the product and remove as much air as possible; and the means to cook the product in a water bath at a controlled temperature, which is even at all points in the bath. So can you do it at home without special equipment other than a thermometer? Not really, although in limited circumstances it is possible. For example, if doneness over a certain safe temperature is essential but precision to the degree is not necessary – as in cooking chicken or turkey, particularly dark meat cuts, which need to be cooked at least to 74C/165F but can tolerate some variation over that temperature – efforts to cook sous vide are less likely to fail. Similarly, if low temp cooking sous vide can be completed over a short period of time – generally under 30 minutes – then it may be possible to circulate the water bath by hand using a wooden spoon to avoid uneven heating. Efforts to maintain a constant temperature of 60C/140F or lower, however, are likely to fail in the absence of special equipment, and are unsafe as they may promote the rapid growth of pathogens (particularly under 55C/130F). In addition, the presence of hot or cool spots within the bath can lead to uneven cooking, contrary to one of the major goals of sous vide cooking. For this reason, most restaurant environments that employ low temp sous vide cooking use a thermal immersion circulator, which circulates the water to maintain even temperature distribution. Finally, since sous vide cooking takes place below the boiling point in a moist environment, the Maillard browning reaction does not occur. Accordingly, product prepared sous vide must be browned afterward (when necessary) by searing or finishing with a torch.

There do exist several means of regulating temperature at home. Two PID (proportional-integrative-derivative) controllers have been developed or adapted for use in sous vide cooking – one is the Sous Vide Magic and the other, which I have used for several years, is the Auber Instruments controller. These attach to a heating appliance large enough to serve as a water bath, such as a rice cooker or slow cooker, and regulate the temperature by switching the heating element on and off at intervals necessary to maintain the necessary temperature the user sets on the controller. The disadvantage to the PID controllers is their inability to circulate the water bath – for this purpose, an aquarium bubbler or similar device often is necessary.

A new product called the Sous Vide Supreme, a water bath with temperature control, is available for home cooking. Unlike the previous methods, the Sous Vide Supreme is supposed to maintain more even temperature control within the water bath. It also contains a rack setup to keep product fully immersed and avoid floatation and uneven cooking due to air discharge or water vapor formation in the bag.

If you are interested in sous vide cooking at home, consider reading Douglas Baldwin’s excellent online guide. He also has published a cookbook for home use. And definitely read the Jaime Tiampo primer on food safety and sous vide cooking before you begin. If you are interested in more advanced technique, consult the Thomas Keller opus Under Pressure: Cooking Sous Vide, published late last year.