Patent Publication Number: US-2012034361-A1

Title: Sous Vide Cooking Method

Description:
PRIORITY CLAIM 
     Priority is claimed to U.S. provisional patent application Ser. No. 61/370,652, filed 4 Aug. 2010, which is incorporated herein in its entirety by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The term sous vide means “under vacuum” and is a style of cooking developed in the 1970&#39;s. The basic technique involves placing a food item in a food-grade plastic bag, pumping air from the bag, sealing it, and then submerging the bag in a water bath. The process works well for steaks and chops and has many advantages in terms of the quality of the cooked items as well as convenience. The process is also used for liquids by placing the liquid into the container and then carefully pressing as much air out of the bag as possible before sealing it or by placing the liquid in an unsealed container in a vacuum chamber and then sealing the container when the pressure in the chamber is reduced. 
     SUMMARY OF THE INVENTION 
     According to its major aspects and briefly recited, the present invention is a cooking method that permits additional types of foods to be cooked using the basic sous vide method, namely, foods that may include solid, liquid or semi-solid components in a structured form, such as in layers. The method comprises the use of an inner container to hold the food in its structured configuration inside an outer container that serves as the vacuum barrier. The inner container may be a serving container. Because liquids are less tightly bound chemically than solids, pumping air from the outer container enclosing an inner container holding food that partially includes a liquid must be done with care so as to avoid pumping the food itself from the container. Accordingly, it is important to regulate the pressure applied to the inner container and to the food it contains by the outer container as air is evacuated from the outer container and causes the outer container to collapse against the inner container and onto the food itself. The use of containers preserves the structure of the food while it cooks and facilitates serving. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the figures, 
         FIG. 1A  is a side cross sectional view of a inner container inside a outer container, according to an embodiment of the present invention; 
         FIG. 1B  is a side cross sectional view of a inner container inside a outer container, according to another embodiment of the present invention 
         FIG. 2  is a side view, partially cut away showing food in its outer container inside a water bath, according the present invention; and 
         FIG. 3  is a flow chart of the sous vide method, according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     The present invention is a method for cooking food under vacuum, the so-called sous vide technique. The term “under vacuum” means under a partial vacuum, that is much but not all air is evacuated from the containers holding the food. Because the food to which the present method applies includes non-solid components, the chemical bonds holding it together are much less strong than those of the solid foods to which the sous vide method is most often applied in the prior art (such as steaks and chops). Accordingly, the vacuum pressure, while below that of atmospheric pressure, is not so far below atmospheric pressure that appreciable quantities of the non-solid components separate from the bulk of the food. The exact pressure will vary depending on the nature of the food to be cooked and will inevitably depend on a certain amount of trial and error. For example, a casserole of cheese sauce and cooked pasta can be cooked in a higher vacuum than a bowl of broth. Further description of the air evacuation process is provided below. 
     The term structured food means that the density of the food is not homogenous but may consist of different components, perhaps some being denser and others less dense, or some being more cohesive and other components being less cohesive. Those different components may be larger or smaller, distributed evenly throughout or arranged in layers. Importantly, the food preparer wishes to preserve their arrangement—inhomogeneity and order—during cooking. Of course, some foods change their character as a result of cooking, beginning as liquids and ending as solids; other foods soften as a result of cooking, such as potatoes and apples. 
     Referring now to the  FIGS. 1A and 1B , food  12 , which may contain solid components but may also contain liquid and semi-solid components is placed in a inner container  10 . Inner container  10  may be a serving container, including an individual serving container, or a pan, ramekin, or other container with sides and a bottom that are sufficiently rigid to hold the food under partial vacuum without deforming. Inner container  10  may be a disposable container. As shown in  FIG. 1B  inner container  10  may have a top or lid  14  as long as the lid  14  is not tight fitting or is vented with one or more vent holes  16  to allow air to escape from inside inner container  10 . 
     The food  12  in container  10  may be soup or a casserole or layered dish as well as food that has solid and softer foods intermingled. If food  12  is in layers and includes a solid layer, such as a layer of lasagna pasta, a solid layer is best placed on top of food  12 . 
     Next, inner container  10  is placed inside an outer container  20 . Outer container  20  is flexible and sealable and sized to receive inner container  10 . Outer container  20  may be made of food-grade plastic of a type adapted to be heat-sealed. In one embodiment, outer container  20  is a tube of food-grade plastic dispensed from a roll by a device that forms heat seals  22  in one side of the tube and in the opposing side  24  where and as instructed by the user. Other devices use a plastic bag open on one end. Examples of vacuuming sealers are sold under the trademark SOUS VIDE SUPREME VACMASTER by Eades Appliance Technology LLC and FOODSAVER manufactured by Jarden Corporation. Other brands are available as well. Plural seals on either side of the inner container  10  made in outer container  20  assure an air-tight fit that prevents the intrusion of air before or after cooking, the intrusion of water during cooking in a water bath, and the loss of moisture or cooking juices from the food before, during and after cooking. 
     Other prior art vacuum machines may be used such as those generally referred to as vacuum chambers. 
     Before complete sealing, air is pumped from the inside of the outer container  20 . As air is removed from outer container  20 , its flexible sides will collapse to conform to the shape of inner container  10 . If inner container  10  has no top  14 , one of the sides  26  of outer container  20  will touch the surface of the food and come to apply pressure on the food. The pumping of the air from outer container  20  should be stopped while that pressure is light, that is, before the food begins to change from liquid to vapor in inner container  10  or is sucked up into an evacuation hose (not shown). Accordingly, pumping air from outer container  20  should proceed carefully, especially once outer container  20  conforms to the shape of inner container  10 . Pulsing the pumping operation provides good control and allows the atmosphere inside outer container  20  to equilibrate between pulses. 
     Once the partial vacuum inside outer container  20  is obtained, outer container  20  may be sealed. 
     Meanwhile, as seen in  FIG. 2 , a water bath  30  is heated to raise the temperature of water  32  in it to a pre-selected temperature. Once water bath  30  is at the pre-selected temperature, outer container  34  may be submerged in water bath  30 , perhaps with the assistance of a weight  38  such as a plate, and may be placed on a rack  36 . Outer container  34  remains in water bath  30  for at least a pre-selected time. Alternatively, if convenient, outer container  34  may be placed in the water bath prior to it reaching the preselected temperature. Thereafter, outer container  34  may be removed from water bath  30 , opened and the inner container removed and served, or it may, be chilled in an ice bath and then refrigerated for reheating and serving at a later time. Depending on the time between completion of cooking in water bath  30  and the reheating, outer container  34  may be refrigerated at nominal refrigerator temperatures such as 7°-13° C. or at colder refrigerator freezer temperatures, such as 0° C. or colder. 
     As an alternative to the foregoing process, after sealing the outer container, the outer container may be refrigerated to freeze it before placing it in a water bath. This freezing step may be suitable in killing parasites in certain foods such as fish. 
     Referring now to  FIG. 3 , there is illustrated a flow chart showing the present method including optional steps. As  FIG. 3  shows, the present process begins when food is placed in a container which becomes the inner container. The inner container has reasonable rigid sides and a bottom, and may have a top if the top is vented or at least is not sealed so that when the air is evacuated from outside the inner container, air is not trapped inside inner container. The inner container is then placed inside the outer container, which is a flexible, heat-proof, sealable container such as food-grade, heat sealable, heavy-weight plastic, preferably a transparent plastic. Before sealing the outer container, air is removed by pumping from the inside of outer container to create a partial vacuum. Air removal is stopped when outer container has collapsed and conformed to the exterior shape of inner container and is applying a light pressure on the surface of food that it touches. If inner container has a lid, then air removal is stopped when the outer container is applying light pressure to the surface of the lid. The outer container is then sealed so that air and water cannot intrude into outer container and food cannot escape from outer container. 
     Meanwhile, water in a water bath is heated to a pre-selected temperature. When the water has heated to the pre-selected temperature, the outer container with the food in the inner container safety sealed inside it is immersed in the water of the water bath. If the food is a liquid that has low viscosity, outer container may placed so that the inner container is right-side-up. A rack may be used to hold the outer container in the water and also to hold multiple containers with multiple food items to cook in the water bath at the same time. 
     The temperature of the water in the water bath is maintained at the pre-selected temperature for at least a pre-selected time while the food in the inner container inside the outer container cooks to doneness. The outer container may be left in the water bath beyond the pre-selected time, if convenient, as the food will not rise in temperature beyond the pre-selected temperature. 
     Once the pre-selected time has been reached, the outer container may be removed from the water bath, the seal broken and the inner container removed. If the inner container is a serving dish, perhaps an individual serving dish, such as a ramekin, it may be served directly. If not, the food may be transferred to a serving dish. 
     Alternatively, if the food will be consumed at a later date, the cooked food may be left in its inner container and in the outer container, and chilled in an ice bath. Once brought to a cold temperature, it may be refrigerated either at cold temperatures (such as 7°-13° C.) or at freezer temperatures (such as 0° C. or colder), depending on whether the food will be consumed within a few days or a longer period of time. When ready for consumption, the refrigerated, cooked food in outer container is simply re-immersed in a heated water bath and brought back up to the pre-selected temperature, and then it may be served immediately. 
     As an alternative part of the present method, after food is sealed in outer container, it may be refrigerated at cold temperatures (such as 0° C. or colder). Especially if food includes raw fish and shellfish, freezing in advance of cooking is recommended to kill parasites. When the food is to be cooked, the steps to follow are as provided above beginning with immersing the outer container in a preheated water bath. 
     The terms pre-selected times and pre-selected temperatures depend on the food being cooked. There are well known temperatures for beef, pork and poultry that identify the interior cooking temperatures that serve as the pre-selected temperatures for those foods. With a certain amount of experimentation, those of ordinary skill in the art can determine the minimum pre-selected times for achieving those temperatures in a water bath, particularly when the water bath has a temperature indicator. Additional indications of the pre-selected temperature and pre-selected time, particularly for food that is not solid and may be structured can be obtained by referring to the book SIMPLY SOUS VIDE by Cindy Kowalyk, copyright 2011 by Cinzia Enterprises LLC, which is hereinafter incorporated in its entirety by reference. 
     Many variations and modification to the foregoing embodiments will be clear to those skilled in the art of cooking from the foregoing description of preferred embodiments. For example, food cooked according to the present method but not completely consumed, may be placed within an outer container, and either refrigerated for a time or reheated in a water bath directly, as convenient. As another example, food cooked in a manner different from the present invention may be sealed in an outer container and later reheated in a water bath, according to the present method. These types of modifications and substitutions do not depart from the spirit and scope of the present invention, which is defined by the appended claims.