especially useful for the catering industry, and it excludes oxygen from food that requires long cooking and is susceptible to oxidation, e.g., fat on meat, which may become rancid with prolonged exposure to air. It also improves the transfer of heat between the water bath and food, without the thermal insulating properties of any trapped air in the bag. Apart from ensuring uniform cooking, sous vide cooking facilitates development of desired organoleptic flavors and limits off flavors due to oxidation. Temperature The degree of accuracy and constancy of cooking temperature required varies with the food cooked. In some cases, it is not critical. A -thick piece of fish will cook in 17 to 18 minutes at any temperature from to . Such food can be cooked in a switched-off slow cooker filled with hot water and a thermometer. For an egg, though, which has proteins that denature at different temperatures, maintaining precise, constant temperature is more critical. Confit egg yolks are usually cooked at , which is hot enough to cook the white without setting the yolk. Typically, the temperature of the bath is set to 64 °C, meaning that the actual cooking temperature is 63 °C. Regular cooking times are determined by when the center of the cooked item reaches a few degrees below the targeted temperature. Then heating should be stopped immediately. While the food rests, residual heat will continue to cook it for a while. If the heating continues, the food will be overcooked. The time taken for the center of food to reach the target temperature depends on the initial temperature, the thickness and shape of the food, and the temperature of the bath. Limitations One limitation of sous vide cooking is that browning (Maillard reactions) happens at temperatures above the boiling point of water. The flavors and 'crust' texture developed by browning are generally seen as very desirable in the cooking of certain types of meat, such as a steak. The flavors and texture produced by browning cannot be obtained with only the sous vide technique. In many cases, chefs will brown meats and other foods before or after sous vide cooking, using techniques such as grilling or searing on an extremely hot pan. This secondary browning is done briefly, and sometimes at higher heat than usually used, so as to affect only the surface of the food and to avoid overcooking the interior. Similarly,