Subatmospheric pressure cooking device

A method of preparing a food product is disclosed and includes the steps of placing the food product within a cooking cavity, reducing the pressure within the cooking cavity thereby creating a vacuum within the cooking cavity, heating the food product within the cooking cavity and returning the cooking cavity to atmospheric pressure. In doing so, a temperature necessary to cook the food product in the vacuum is less than that temperature necessary to cook the food product at atmospheric pressure. Consequently, the food product may be fully cooked at a temperature which does not cause the food product to dry-out or become tough.

BACKGROUND OF THE INVENTION 
The present invention relates generally to cooking ovens and more 
particularly to such an oven which cooks utilizing a variety of heating 
mediums. Preferably, the cooking is carried out at a reduced pressure and 
the oven is adapted to hold the cooked product at a preferred temperature 
in a reduced atmosphere during the cooking. 
There are a wide variety of known cooking techniques and there has been, 
within each, a great deal of experimentation with the several variables 
associated with such cooking techniques. For example, the use of steam as 
a heat transfer medium is well known. Such steam cooking devices may 
employ the steam at atmospheric pressure as in U.S. Pat. No. 4,011,805 
with convection heat transfer. Steam as the heat transfer medium at 
substantially atmospheric pressure with forced convection heat transfer is 
also known from U.S. Pat. No. 4,173,215. In this last patented 
arrangement, water is introduced into the bottom of a steam chamber and a 
heat source outside that chamber heats that water to produce steam. The 
chamber is vented so as to maintain the pressure within the cooking vessel 
at substantially atmospheric pressure. Such steam cooking devices may 
employ the steam at an elevated pressure as in the common "pressure 
cooker". U.S. Pat. No. 3,800,778 discloses a steam cooker with a valve and 
pump arrangement so that the pressure within the cooking vessel can be 
maintained either above or below atmospheric pressure. 
The stated reason for cooking below atmospheric pressure is to cook at a 
reduced temperature so that delicate foods will not be overcooked and 
their vitamins lost. U.S. Pat. No. 3,223,021 employs this same general 
concept in a coffee roasting oven which operates below atmospheric 
pressure for a period of time and then has its internal pressure 
increased. The coffee in this roasting oven is cooled after roasting and 
before the pressure is released. Finally, the concept of a food holding 
cabinet is old and disclosed, for example, in U.S. Pat. No. 4,623,780. 
This patent points out that it is difficult to maintain precooked food at 
a preferred serving temperature while maintaining its moisture content. 
The patent suggests food storage at a temperature below its cooking 
temperature and in a steam atmosphere to maintain crust crispness, for 
example, with fried chicken, while minimizing moisture loss. 
There has been a significant amount of research into eating habits as they 
relate to health. For example, in the article PREVENTION OF FORMATION OF 
IMPORTANT MUTAGENS/CARCINOGENS IN THE HUMAN FOOD CHAIN by Weisburger and 
Jones, it is pointed out that during cooking (typically frying or 
broiling) leading to the browning of meat or fish, mutagens or carcinogens 
are frequently generated. The article suggests the desirability of finding 
ways to lower or prevent the formation of these undesirable products 
during cooking. One scheme for lowering these undesirable products is to 
reduce the surface temperature during cooking. Another is by additives to 
the meat or fish prior to cooking. 
From the above article, it appears that the undesirable mutagens or 
carcinogens are generated on the food surface during cooking, for example, 
of a hamburger on a conventional hot grill and that these undesirable 
products will be scraped off the grill with the meat and placed in the 
consumer's sandwich. 
The current method of cooking a hamburger, for example, requires a lot of 
fat for three reasons. The fat acts as a release agent preventing the meat 
from sticking to the griddle. It also acts as a heat transfer medium. 
Finally the fat provides the "juiciness" in the finished sandwich. The 
undesirability of the conventional "fast food" approach to cooking beef 
for sandwiches on a hot grill should now be apparent. 
Lower cooking temperatures not only reduce or eliminate the formation of 
the above noted mutagens or carcinogens, but also provides a more 
palatable product. Exposing meat to high temperatures causes the fibers in 
the meat to shrink purging the meat of its natural juices. Such high 
temperature cooking also cooks the outer surface to its "done" state prior 
to the interior reaching that "done" condition. Thus, the outer portions 
are frequently comparatively over-cooked, dry and tough. Reduced cooking 
temperatures ensure that the food product will not be over-cooked 
regardless of the time the food product is subjected to that reduced 
temperature and that the center as well as the surface will be cooked to 
perfection. 
It is a well known phenomenon that it seems to take forever to hard boil an 
egg at high elevations, say, for example, high in the mountains, where the 
air pressure is significantly lower than it is at sea level. The reason is 
that the water in which the egg is immersed boils at a much lower 
temperature under the reduced pressure conditions and the egg never gets 
as hot as it will under similar circumstances at sea level. The present 
invention capitalizes on this phenomenon by reducing the pressure within 
the cooking vessel during cooking. Researchers have identified at least 
four compounds in cooked meats that are known carcinogens that are formed 
during conventional cooking. These compounds, known as heterocyclic 
aromatic amines, or HAAs, are formed by the heating of animal protein. 
These compounds are formed as a normal part of the cooking process, 
whether the meat is beef, pork, chicken, or fish. This invention provides 
a method to solve this problem. It will eliminate the carcinogens that are 
formed during cooking and reduce fat by as much as 66% in such products as 
hamburgers. This invention provides a new method of cooking which improves 
the taste and nutritional value of meat and vegetables. 
SUMMARY OF THE INVENTION 
It is a primary object of the present invention to overcome the 
shortcomings of the prior art discussed hereinabove. 
A further and significant object of the present invention is to provide a 
cooking device and method for cooking a food product, particularly a meat 
product while eliminating cancer causing compounds which are formed using 
presently known cooking methods and devices. 
Another object of the present invention is to provide a cooking method and 
cooking device for reducing the fat content of meat products when such 
products are cooked while improving the overall yield of the food product. 
It is yet a further object of the present invention to improve the 
tenderness and flavor of the food product by retaining more of the natural 
juices within the food product. 
Among the several objects of the present invention may be noted the 
provision of a cooking technique which provides a moist food product, such 
as meat, without the fat normally present in such moist food products; the 
provision of an oven capable of cooking the product at a preferred 
temperature without dehydrating that cooked product; and the reduction or 
avoidance of the carcinogens and mutagens frequently associated with the 
cooking of meat on a grill. These as well as other objects and 
advantageous features of the present invention will become apparent from 
the following detailed description. 
In accordance with a first embodiment of the present invention, a method of 
preparing a food product includes the reduction of the ambient pressure 
surrounding the food product while in one embodiment allowing steam to 
surround the food product for a predetermined period of time to cook the 
food product. Thereafter, air is allowed to enter the cavity or chamber in 
which the food product is located and the food product is maintained at a 
preferred holding temperature without further cooking. With this process, 
the effective heat transfer rate to the food product is substantially 
greater during the time period of reduced pressure and is significantly 
reduced when the air enters the cavity. Reentry of air is typically 
associated with a restoration to atmospheric pressure. Preferably, to 
generate the steam, water is boiled in the range of one-hundred sixty to 
one hundred seventy degrees fahrenheit in the reduced ambient pressure. 
In one form of the invention, a cooking and holding food preparation unit 
or oven has a food receiving compartment and a door with an interposed 
gasket for hermetically sealing the compartment when the door is closed. A 
liquid receiving open-topped tray is located near the bottom of the 
compartment. The compartment itself may function as the tray. The liquid, 
typically simple tap water, in the tray is heated by electrical resistance 
strip heating elements beneath the compartment which are under the control 
of a thermostat coupled to the tray and to the heating elements so as to 
maintain the temperature of the tray at an operator selected temperature. 
The air pressure within the compartment is maintained at a subatmospheric 
level by a vacuum pump while food is being cooked. 
A vacuum release valve selectively couples the compartment to the exterior 
atmosphere and there may be a timer for measuring elapsed time after 
cooking is begun which opens the vacuum release valve upon the expiration 
of an operator determined cooking time interval. While the liquid may be 
simple tap water, aromatic materials may be added to give the food a 
particular flavor. A "smoked" flavor could, for example, be easily 
provided in this way. 
In a preferred embodiment of the present invention, a method of preparing a 
food product comprises the steps of placing the food product within a 
cooking chamber, reducing the pressure within the cooking chamber thereby 
creating a vacuum within the cooking chamber, heating the food product 
within the cooking chamber and returning the cooking chamber to 
atmospheric pressure. In doing so, a temperature necessary to cook the 
food product in the vacuum is less than that temperature necessary to cook 
the food product at atmospheric pressure. Consequently, the food product 
may be fully cooked at a temperature which does not cause the food product 
to dry-out or become tough. This can be accomplished in several manners, 
the first being by way of an oven for cooking the food product comprising 
a cooking cavity for accommodating the food product, a vacuum pump 
communicating with the cooking chamber for reducing the ambient pressure 
within the cooking cavity, a heating device for heating the food product 
in a reduced atmosphere and selectively restoring the cooking cavity to 
atmospheric pressure once the cooking of the food product is completed. In 
one embodiment the heating device includes a megnatron unit for generating 
microwave energy and directing the microwave energy to the cooking cavity. 
While in another embodiment the heating device generates an electric 
current and directs the electric current to the cooking cavity and through 
the food product. The electric current is passed through the food product 
by supporting the food product by at least one lower conductive element 
and contacting an upper surface of the food product with at least one 
upper conductive element, such that the electric current passes from the 
upper conductive element through the food product and to the lower 
conductive element. 
Additionally, the food product can be placed in a standard baking oven 
wherein the internal pressure of the oven is reduced. Reducing the 
internal pressure of a standard baking oven whether such oven be of the 
radiant, rotisserie or convection type dramatically improves the quality 
of the food product being cooked. 
These as well as additional objects and advantages of the present invention 
will become apparent from the following detailed description when read in 
light of the several figures.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
A cooking and holding food preparation unit or oven is shown in FIGS. 1, 2 
and 7 and includes a food receiving compartment 20. The compartment 
includes a door 28 and a gasket 11 for hermetically sealing the 
compartment when the door is closed. There is a liquid receiving 
open-topped tray in the form of the sealed bottom compartment region 13 
near the bottom of the compartment. This tray holds about two gallons of 
water 22. Water 22 is heated by strip resistance heating elements 18. The 
temperature of the compartment is sensed by probe 15 of thermostat 16 the 
setting of which controls energization of the heating elements 18 thereby 
maintaining the temperature of the compartment at an operator selected 
temperature. A vacuum pump 12 is provided for selectively removing air and 
reducing the pressure within the compartment 20 and a vacuum release valve 
14 selectively couples the compartment 20 to the exterior atmosphere at 
outlet 17. A timer 24 measures elapsed time after cooking is begun and 
functions to open the vacuum release valve 14 upon the expiration of an 
operator designated time interval. 
There is a start control 19 which, when depressed, initiates operation of 
both the thermostatic control of the heating elements 18 and the timer 24. 
Once started, the thermostatic control and timer operate independently of 
one another and, typically, operation of the heating elements 18 continues 
long after the opening of the vacuum release valve 14. Tray 13 may be 
filled and emptied daily and a manually operable drain valve 26 has been 
provided near the lowermost portion of the tray to facilitate nightly 
draining thereof. There are a plurality of food receiving racks such as 
21, 23 and 25 (FIGS. 1, 2, 8 and 9 respectively) supported in stacked 
relationship within the compartment 20 by sidewall pins such as 27, 29 and 
31. There is also an optional grease catching pan 40 in FIG. 3 and 38 in 
FIG. 9 which is interposed between the lowermost of the racks and the 
water evaporation tray 13. The pump 12 has an inlet 33 located near the 
top of the compartment 20 and an outlet 35 which terminates immediately 
above a moisture collection pan 37. Little moisture is collected by this 
pan and, like the tray in an automatic defrost refrigerator, evaporation 
is adequate to keep it from overflowing. A heating element 39 (FIG. 10) 
may be provided beneath tray 37 to aid evaporation if desired. 
Many of the components of FIG. 10 have already been discussed. A main fuse 
41 is placed in the hot line. When the operator depresses the ON button 
19, control relay number one is latched with its coil continuously 
energized by way of its now closed contacts 45. A fan 47 which circulates 
cooling air through the louvers such as 49 and between the oven walls is 
similarly continuously energized as is the ON indicator light 51. A second 
set of normally open contacts 51 close when coil 43 is energized supplying 
electrical energy to the thermostat 16. As long as the thermostat 16 
contacts 53 are closed indicating a below desired temperature condition, 
coil 55 of a second control relay is enabled. This second control relay 
has two sets of normally open contacts 57 and 59 which close to energize 
the heating elements such as 18. When coil 55 is on, a heaters ON lamp 57 
is also energized. When timer 24 is active, solenoid coil 14 is enabled 
and the vent closed off. At the same time the motor 59 which drives the 
vacuum pump 12 is enabled to reduce the interior vessel pressure. When the 
timer times out, the pump motor 59 and solenoid 14 are disabled opening 
the vent 17 and returning interior pressure to atmospheric. Heaters 18 
remain ON. To shut off the oven, OFF button 61 is momentarily depressed 
disabling coil 43 and causing contacts 51 to reopen. An oven temperature 
sensor 63 may effect this same turn off if the oven temperature exceeds, 
say, 230 degrees fahrenheit. 
In one embodiment, a double wall construction was utilized with about two 
inches of insulation 30 between the cooking compartment 20 and certain 
ones of the exterior walls. Typically, the door 28 and top are insulated. 
Other exterior walls such as 32 were spaced from the interior walls such 
as 34 and air allowed to circulate between the walls to maintain the outer 
walls at a safe temperature. Typically, 14 gauge stainless steel interior 
walls such as 34 and 20 gauge stainless steel exterior walls were utilized 
except for the door 28 which utilized 20 gauge stainless steel for both 
its inner and outer wall panels. 
The cooking and holding food preparation unit as described has a single 
compartment, but two compartment models are also contemplated with each 
compartment substantially as described and operable independently of the 
other. The cooking and holding food preparation unit is particularly 
suited to use in schools, hospitals and similar institutional environments 
as well as restaurants and other commercial operations. 
The method of operation of the above described device should now be clear. 
During the cooking cycle, the vacuum pump 12 is on, the solenoid valve 14 
is closed and the thermostat 16 is controlling the strip heaters 18. The 
vacuum pump removes air from the compartment 20 reducing the pressure 
therein and causing the water 22 to boil at a temperature well below the 
normal 212 degree fahrenheit boiling point. The thermostat 16 setting 
determines the temperature of the water 22 and steam within the 
compartment 20. Steam condenses on the surface of food products (or their 
containers) within the compartment adding heat thereto. This cook cycle 
continues until the timer 24 times out and converts the oven to its hold 
mode of operation. 
During the hold cycle or mode, the vacuum pump 12 is off, the solenoid 
valve 14 is open and the thermostat 16 continues to control the heaters 
18. All the heat comes through the water 12 causing the relative humidity 
within the compartment 20 to be at 100%. Because of this 100% relative 
humidity, no moisture evaporates from the food product during this hold 
mode. 
FIGS. 3, 4, 8 and 9 generally illustrate the "lean" cooking of meat with 
fat dripping away therefrom as at 42 while FIGS. 5 and 6 illustrate that 
"crispy" food products may be cooked in the unit without the direct 
application of the steam 44 thereto by enclosing them in a covered 
non-hermetic vessel 46 so that heat transfer is from the steam to the 
vessel and then from the vessel by a combination of conduction and 
convection to the food product so that the food product is protected from 
becoming too moist from direct exposure to the steam. 
It should be noted that lids 52 and 54 in FIGS. 5 and 6 extend beyond and 
below the edges of their respective vessels. Since steam is heavier than 
air, an air lock or trap is formed by the air within the underside of the 
lid effectively preventing steam from entering and condensing on the food 
products. As a specific illustration of the operation of the oven and of 
the unique cooling method herein in accordance with a first embodiment of 
the present invention, a hamburger 36 may be cooked in about 20 minutes in 
one-hundred sixty five degree fahrenheit steam. As the steam adds heat to 
the hamburger, the fat melts and drains into the catch pan 38 (FIG. 9) or 
40 (FIG. 3). 
The juice that is purged from the meat which carries creatinine, drains 
into the catch pan and the fat and juice are never consumed. In some 
cases, the juice may simply be allowed to drain back into the water supply 
22 as shown in FIG. 4. In either case, no mutagens or carcinogens are 
formed on the meat because the juice carrying the creatinine runs off and 
because the meat is never exposed to any high temperatures. The one 
hundred sixty five degree temperature is not sufficiently high to form the 
earlier discussed mutagens and carcinogens. The hamburger may be 
subsequently held ready to be served for up to several hours if desired. 
This sequence of events is illustrated generally in FIG. 11. 
In FIG. 11, a food product such as a hamburger (actually beef) patty is 
cooked in a way to significantly reduce the usual heat induced shrinkage 
by initially supporting 56 that beef patty on a plurality of relatively 
thin rails such as the extruded aluminum grill or rack 25 of FIG. 9 so 
that there are the spaces such as 76 between the rails through which the 
fat may drain. The thus supported patty is hermetically enclosed 58 within 
the oven cavity and the pressure therein reduced as indicated at 60. Steam 
generated at 62 by water boiling within the hermetic enclosure at, for 
example, 160 to 170 degrees fahrenheit surrounds the patty transferring 
heat thereto. At the desired time, the pressure is reduced at 64 and the 
cooked patty held at a preferred temperature and without significant 
moisture loss awaiting consumption. 
As a second specific illustration, consider FIGS. 5 and 6 in conjunction 
with the cooking process illustrated in FIG. 12. A food product such as 
fried chicken 50 having a surface which should be kept "crispy" is 
enclosed in a vessel 46 having cover 52. The vessel or tray 46 along with 
its cover 52 form a non-hermetic vessel in which the food is enclosed as 
indicated by 66 in FIG. 12. Thereafter, the vessel is hermetically 
enclosed (68) and the ambient pressure surrounding the vessel is reduced 
as at 70. Steam generated at 72 is allowed to surround the covered vessel 
46 or 52 for a predetermined period of time to cook the food product 
therein by the transfer of heat from the steam to the vessel (including to 
the lids 52 or 54) and then from the vessel to the food product by a 
combination of conduction and convection so that the food product is 
protected from becoming too moist from direct exposure to the steam. 
Finally, the ambient pressure surrounding the vessel is restored as at 74, 
to atmospheric pressure and the food product is maintained at a preferred 
temperature without further cooking and without the direct application of 
the steam to that food product. In FIGS. 5 and 6, the vessel covers 50 or 
52 fit over the tray 46 or 48 forming an air lock to transmit the pressure 
changes within the oven cavity to the interior of the vessel while 
substantially excluding moisture condensate therefrom. In each case, the 
steam completely surrounds the vessel transferring heat to all sides 
thereof. The primary difference between the cooking technique of FIG. 5 
and that of FIG. 6 is that the sidewalls of the container or vessel 48 are 
in direct heat conducting contact with the food product therein, e.g., a 
vegetable or pudding, while the food product in FIG. 5, e.g., a chicken 
leg 50, rests on the tray floor receiving heat by conduction therefrom, 
but is otherwise heated by convection within the vessel. 
In summary, the first embodiment of the present invention has a number of 
advantages over known prior devices. Operation is simple, just set the 
time and temperature and when the time has elapsed, the oven automatically 
goes into its hold cycle. There is no need to transfer food from a cooking 
oven to a holding oven. The 100% relative humidity during the hold cycle 
assures that the food product will not dry out. There is no boiler. About 
two gallons of water are poured into the oven at the beginning of the day 
and at days end, valve 26 is opened and the water drained. While there may 
be a drain hookup if desired, the two gallons or less of water remaining 
in the oven at days end may simply be drained into a pan or bucket. With 
no drain hookup, the oven is easily moved and located in the most 
convenient position in a kitchen or cafeteria. Daily draining and 
refilling helps prevent the buildup of lime or other minerals within the 
oven. The reduced pressure within the cooking cavity prevents the door 28 
from being opened during the cooking cycle. During the hold cycle, the 
door may be opened safely and without danger of scalding since only high 
humidity hot air is within the oven. Finally, the elimination of any 
drying of the food during the hold cycle enhances yield and reduces food 
costs. 
Referring now to FIGS. 13-15, an alternative and preferable embodiment of 
the present invention will be discussed in greater detail. As discussed 
hereinabove, a reduction in the internal pressure within a cooking device 
has a dramatic effect on how the food cooks within the device. This is 
particularly true when cooking meat products. 
The cooking device illustrated in FIG. 13 is an industrial type microwave 
oven 100 or any type oven which cooks with electrical wave form energy 
such as microwaves, radio waves and the like, which includes a housing 102 
accommodating a control panel 104 and having a door 106 hingedly connected 
thereto by hinges 108. A handle 110 is provided for opening and closing 
the microwave oven and for permitting access to the contents of the 
microwave oven by the consumer. Unlike a conventional microwave oven, the 
oven illustrated in FIGS. 13 and 14 includes a vacuum pump 112 for 
evacuating the cavity or cooking chamber 114 within an interior of the 
microwave oven. Also provided is a solenoid valve 116 which permits a 
vacuum to be drawn within the cavity 114 and selectively subjecting the 
cavity 114 to atmospheric pressure through the solenoid valve 116. As is 
readily apparent from FIG. 14, the vacuum pump 112 includes a vacuum line 
118 which extends to a lower region of the cavity 114. The significance of 
the vacuum line extending to the lower region of the cavity 114 will be 
explained in detail hereinbelow. Also connected to the solenoid valve 116 
is an atmospheric pressure passage 120. 
As with conventional microwave ovens, the microwave oven 100 includes a 
transformer 122 and megnatron tube 124. A cooling fan 126 is also provided 
for cooling the megnatron tube 124 as with conventional microwave ovens. 
Therein, microwaves generated by the megnatron tube 124 are dispersed 
throughout the cavity 114 of the microwave oven by the microwave mixer 
128. A glass barrier 130 is also provided which permits the microwaves to 
pass therethrough while protecting the megnatron tube 124 from any 
moisture or steam which may be generated within the cavity 114 of the 
microwave oven. 
FIG. 15 illustrates an alternative embodiment of the microwave oven set 
forth in FIG. 14. Therein, the microwave oven 100' includes the door 106' 
which closes the cavity 114' of the microwave oven. As with the previous 
embodiment, a vacuum pump 112' is provided for evacuating the cavity 114' 
of the microwave oven. Likewise, a solenoid valve 116' is provided for 
selectively exposing the cavity 114' to atmospheric pressure by way of the 
passage 120'. During the evacuation of the cavity 114', a vacuum is drawn 
by the vacuum pump 112' through the vacuum passage 118' as with the 
previous embodiment. Unlike the previous embodiment; however, the 
evacuation of the cavity 114' is conducted through a top portion thereof 
rather than a bottom portion as with the previous embodiment. The 
significance of which will be explained in greater detail hereinbelow. 
Further, as with the previous embodiment as well as conventional microwave 
ovens, a transformer 122' is provide along with a megnatron tube 124' for 
generating the microwave energy for heating the contents of the cavity 
114'. Also as with the previous embodiment, a microwave mixer 128' is 
provided for dispersing the microwaves throughout the cavity 114' with the 
glass barrier 130' being provided to protect the megnatron tube 124'. 
Unlike the previous embodiment, a resistance heater 132' is provided in an 
upper portion of the cavity 114' for preheating the walls of the cavity 
114'. That is, the cooking compartment is preheated to approximately 
250.degree. Fahrenheit using the resistance heater 132'. 
Like the previous embodiment, reducing the internal pressure of the oven 
lowers the boiling point of the moisture in the food product being cooked. 
When the microwaves pass through the food product, the energy is 
transformed into heat, the heat is generated in small areas within the 
food product and subsequently dissipated throughout the food product. As 
discussed hereinabove, the problem with using microwave ovens to heat and 
cook a food product is that the heat generated within the food product is 
too hot and overcooks the product in very small areas, such that the meat 
becomes tough in those areas. It can be noted that as long as there is 
moisture in the food product, the maximum temperature of the food product 
can get to is the boiling temperature of the moisture in the food product 
which is 212.degree. Fahrenheit. Reducing the pressure within the cavity 
114 or 114' thus reduces the boiling temperature of the moisture in the 
meat and eliminates the overcooking which causes the meat to become tough. 
The ideal temperature for cooking beef is approximately 155.degree. 
Fahrenheit while the ideal temperature for chicken and pork is 
approximately 170.degree. Fahrenheit. Consequently it is desirable to 
maintain the cooking temperature within the cavity 114 or 114' in the 
range of 150.degree. to 180.degree. Fahrenheit. This can be accomplished 
by controlling the pressure within the oven. 
Reducing the internal pressure by way of the vacuum pump 112 or 112' in the 
preceding embodiments also removes the air from the cavities 114 and 114' 
thus the cavities become filled with saturated steam. Saturated steam is 
steam that is at its condensing temperature. When the cavity 114' is 
filled with saturated steam, all internal surface temperatures are equal 
to or above the condensing temperature of the saturated steam. In order 
for there to be a surface temperature lower than the condensing 
temperature of the steam, there would have to be a pressure difference 
within the cavity 114'. Because all surface temperatures are the same or 
greater, the possibility of one piece of meat within the cavity being done 
before another is eliminated because the moisture on the warmer piece of 
meat would boil and absorb heat and then transfer such heat in the form of 
steam and condense on a cooler piece of food within the cavity 114' and 
subsequently dissipating such heat to the cooler piece. 
Referring again to FIG. 14, during the cooking cycle, the vacuum pump 112 
is turned on and the solenoid valve 116 is closed. With a food product, 
such as a hamburger or other product containing moisture placed in the 
cavity 114, the megnatron tube 124 is activated so as to generate 
microwave energy which travels through the tunnel 132 and is reflected 
down into the cavity 114. The food product may be placed on a rack 115 or 
on a separate support within the cavity 114. A microwave energy passes 
through the glass barrier 130 and is mixed throughout the cavity 114 by 
the microwave mixer 128. The microwaves are permitted to bounce around 
within the cavity 114 until they are absorbed by the food being cooked and 
subsequently changed into heat. Removing air and steam from the bottom of 
the cavity 114 by way of the port 134 causes the cooking compartment to be 
filled with low pressure air. When the microwaves heat the food to the 
point where the moisture in the product boils, the steam rolls off the 
product and is evacuated from the bottom of the cooking compartment 114 by 
the vacuum pump 112. Because the heat transfer medium is the food product 
itself, an abundance of steam is undesirable. Consequently, because steam 
is heavier than the air within the cooking compartment, the steam is 
easily removed from the lower part of the compartment. Thus by withdrawing 
steam from the bottom of the cavity 114, any condensation on the walls of 
the cavity 114 or the food product can be avoided. Accordingly, by 
reducing the pressure within the cavity 114, the temperature at which the 
food item and particularly meat is cooked within the cavity 114 is reduced 
to a point where the product is cooked without achieving a temperature 
which creates carcinogens. 
With respect to FIG. 15, when cooking a product within this unit, the walls 
of the cavity 114' are preheated to approximately 250.degree. Fahrenheit 
using the resistant heater 132'. Moreover, the air and steam are removed 
from the top of the unit. When the microwaves raise the temperature of the 
food product enough to cause the moisture in the product to boil, the 
steam will leave the product and fill the cavity 114'. Because the surface 
temperature of the cavity 114' is above the condensing temperature of the 
steam, no steam will condense on the surface of the cavity 114'. This unit 
is particularly suitable for commercial applications in that continuous 
use of the device will not cause moisture to build up on the walls of the 
cavity 114'. Moreover, because the walls of the cavity 114' are preheated, 
the only surfaces which are cool enough to condense the steam which is 
generated from the product is the cooler surfaces of the food product 
itself and consequently such device is very effective in cooking a variety 
of food products and particularly leafy vegetable products. 
Accordingly, as can be appreciated from the forgoing discussion with 
respect to the device illustrated in FIGS. 13-15, the microwave energy 
generated by the megnatron tube 124, 124' heats the product itself. 
Consequently with these embodiments it is the temperature of the food 
product itself which is controlled and not the temperature of a separate 
heat transfer medium such as steam. This is the case because it is the 
food product itself which is the heat transfer medium in the embodiments 
illustrated in FIGS. 13-15 as well as that illustrated in FIG. 16. 
While the foregoing embodiments are described in the context of two 
separate units, an oven may incorporate all the features from both the 
device illustrated in FIG. 14 as well as that of FIG. 15 as is illustrated 
by the hidden lines of FIG. 15. Therein, a valve 136' is provided to 
selectively change the point of removal of the air and steam from the 
cavity 114' thus the air and steam may be removed from either the bottom 
or top of the unit and the resistant heater 132' may be selectively 
operated to heat the walls of cavity 114' only when steam and air are 
removed from the top of the cavity 114'. In the illustrated embodiment, 
the valve 136' is preferably a solenoid valve; however any suitable valve 
may be used. Further, each of the devices illustrated in FIGS. 14 and 15 
may be operated in a manner substantially similar to that of existing 
microwave ovens. That is, the food product may be heated by using time to 
control the temperature or by using a temperature probe within the food 
product itself. 
Further, in addition to the foregoing, a small amount of water may be 
provided in a tray 138' at the bottom of the cavity 114 or 114' below the 
rack 115 or 115' respectively. Thus, more heat can be applied to the 
product being cooked in that a portion of the microwave energy is 
dissipated into the product itself while the balance is dissipated into 
the water which boils and changes into steam with this steam then 
condensing on the surface of the food product thus adding heat to the food 
product being cooked. Consequently, the product cooks not only from the 
microwave energy being dissipated therein but also from the added steam 
and yet no part of the product can get over the boiling temperature of the 
moisture in the compartment. In doing so, frozen foods may be thawed or 
cooked using either of the foregoing devices. Further, rather than placing 
water within the tray 138', a susceptor material which absorbs microwave 
energy and becomes hot may be placed in the tray 138'. Thus, when the 
natural juices of the meat drip down to the susceptor, the high surface 
temperature of the susceptor will boil the natural juices of the product 
which subsequently condense on a surface of the food product and adds heat 
to such product much like using water. However, food products steamed 
using their natural juices retain more of their natural flavors than food 
products which are cooked with steam and microwave energy alone. 
Referring now to FIG. 16, a further alternative embodiment of the present 
invention will be described in detail. Again, with the device illustrated 
in FIG. 16, a device and method of cooking food products such as meats or 
vegetables that significantly reduce the amount of fat in the cooked 
product while retaining more natural juices and eliminating carcinogens is 
disclosed. In this case, electric resistance is used to generate heat to 
cook the food product retained therein. The device 200 includes two metal 
sheets or screens 210, 212 and a supporting metal sheet 215 between which 
the food product 214 is placed. A positive current is connected to the 
metal sheet 210 while a negative current is connected to the metal sheet 
212. The electric current travels through the food product, in this case a 
hamburger patty and is changed into heat due to the electrical resistance 
of the water within the food product 214. Consequently, the food product 
is cooked by the heat generated within the food product itself. 
The electrical current travels through the water in the patty and not the 
meat fiber or the fat. When the electrical current raises the temperature 
of the water to a boiling point, the water changes to steam and no longer 
transfers electricity. This reaction causes the hamburger to cook evenly 
and at the boiling temperature of the water retained within the food 
product 214. The device 200 includes a housing 216 which receives a holder 
218 for retaining the metal plates and food product as well as a drip tray 
220 for retaining drippings during the cooking of the food product 214. 
Communicating with an interior of the housing 216 by way of passage 222 is 
a vacuum pump 224 for reducing the pressure within the housing 216. As 
discussed hereinabove, the normal boiling point of water is too high, that 
is, 212.degree. Fahrenheit is too hot for cooking most food products and 
in the case of an hamburger would cause the hamburger to be tough and 
rubbery, the internal pressure of the cooking chamber is thus lowered by 
way of the vacuum pump 224 to reduce the boiling temperature of the water 
retained within the food product. This pressure reduction permits the 
hamburger or other food product to be cooked at a lower temperature, a 
temperature between 150.degree. and 180.degree. Fahrenheit. The 
temperature at which the food product within the housing 216 is cooked may 
be readily controlled by the pressure reduction within the housing 216 
which is created by way of vacuum pump 224. In doing so, carcinogens which 
were previously present during the cooking of the food product are 
eliminated in that the maximum temperature to which the food product is 
exposed is approximately 180.degree. Fahrenheit which is not hot enough to 
form any cancer causing compounds. 
With further reference to FIG. 16, a food product such as a hamburger patty 
214 is placed on the plate 215 and the lid 217 is closed. The top plates 
210 and 212 are connected to the lid and the closing action places these 
plates in contact with the top surface of the food product 214. Once the 
lid is closed, the vacuum pump 224 is started to reduce the pressure 
within the housing 216 and an electric current is supplied to the metal 
plates. It should be noted that the container is hermetically sealed 
between the lid 217 and the housing 216 by way of gasket 219. The current 
thus flows through the top plate 210, down through the food product to the 
bottom plate 215 and subsequently up through the adjacent food product to 
the metal plate 212. This operation continues for a predetermined period 
of time which may be in the range of 30 seconds to 2 minutes and generally 
approximately 60 seconds. At the end of the cooking cycle, the vacuum is 
released and the lid is opened, such that the food product can be removed. 
A valve may be used to release the vacuum or the vacuum may be released 
simply opening the lid. Drippings from the food product are caught in the 
tray 220 which is periodically empty. 
FIG. 17 illustrates yet another embodiment of the present invention wherein 
the food product 300 to be cooked is placed in a baking oven 302 of the 
radiant or convection type wherein such baking oven 302 includes a system 
304 for reducing the internal pressure of the baking oven 302. The baking 
oven is of the conventional type including insulated side walls 306, an 
insulated top wall 308, an insulated bottom wall 310 as well as an 
insulated door 312 which is hingedly connected to the bottom wall 310 by 
way of hinge 314. The door 312 when closed seals about its perimeter by 
seal 316. The baking oven may be of either the electric type including 
electric heating elements 318 and 320 as shown in FIG. 17 or may be heated 
by way of gas (not shown) or other known source of producing heat energy. 
As is noted hereinabove, the baking oven 302 includes the system 304 for 
reducing the internal pressure of the baking oven 302. This system being 
similar to that illustrated in FIGS. 14 and 15. The vacuum system includes 
vacuum pump 322 for evacuating the cooking cavity 324 of the baking oven 
302. Also provided is a solenoid valve 326 which when closed permits a 
vacuum to be drawn within the cavity 324 and when opened selectively 
subjects the cavity 324 to atmospheric pressure through the solenoid valve 
326. As may be readily apparent from FIG. 17, the vacuum pump 322 includes 
a vacuum line 328 which extends to a lower region of the cavity 324 and 
includes inlets 330 and 332. The particular positioning of the inlets 330 
and 332 are shown as being in an upper and lower portion of the cavity 
324, however a multiple number of outlets or a single outlet may be used 
with the position of such outlet being determined in accordance with the 
food product to be cooked within the baking oven 302. Additionally, each 
of the inlets may include a separate valve for controlling the flow of air 
through such inlet. The significance of the positioning of the inlets is 
similar to that set forth hereinabove and shall be explained in greater 
detail hereinbelow. Additionally, as with the vacuum system illustrated in 
FIG. 14, the vacuum system 304 includes an atmospheric air passage 334 
connected to the solenoid valve 326 for selectively subjecting the cavity 
322 to atmospheric pressure. The oven itself as well as the vacuum system 
may be readily controlled by a control panel 336 which is positioned in an 
easily accessible portion of the front of the baking oven 302. 
FIG. 18 illustrates an alternative embodiment of the baking oven set forth 
in FIG. 17. The baking oven includes all of the components of the baking 
oven 302 with the addition of a rotisserie 338 provided within the cavity 
324. The baking oven 302' includes insulated back wall 306' as well as 
insulated top and bottom walls 308' and 310' respectively. Similarly, an 
insulated door 312' is provided and hingedly connected to the bottom wall 
310' by way of hinge 314'. 
The oven 302' likewise includes a vacuum system 304' which includes vacuum 
pump 322' and vacuum passage 328' for producing a reduced pressure within 
the cavity 324'. Additionally, the vacuum system 304' includes solenoid 
valve 326' for selectively subjecting the cavity 324' of the baking oven 
302' to atmospheric pressure by way of a passage 334'. As with the 
previous embodiment, electric heating elements 318' and 320' are provided 
for heating the cavity 324' of the baking oven 302', however any 
alternative source of heat energy may be used as discussed hereinabove. 
Additionally, control panel 336' is provided for controlling the 
temperature of the cavity 324' as well as the vacuum system 304'. 
When a turkey is cooked in a standard oven, portions of the turkey are 
overcooked while waiting for the remaining portions of the turkey to get 
up to the necessary temperature. For example, in a conventional baking 
oven, the breast meat of a turkey will get to 195.degree. F. before the 
thigh meat gets to the requisite 165.degree. temperature. Breast meat is 
ideally done at 165.degree. F., thus, by cooking the breast meat to 
195.degree. F., the breast meat will dry out and toughen. Consequently, by 
cooking a turkey in the oven illustrated in FIGS. 17 and 18 with a reduced 
internal pressure, the breast meat will not get above 165.degree. F. In 
that the water in the breast will boil and absorb the heat rather than 
permitting the temperature of the meat to rise. The reduced internal 
pressure is thus regulated so as to cause the water within the turkey to 
boil at 165.degree. F. The reduced internal pressure can be regulated to 
cause the water to boil at any predetermined temperature. However, as 
discussed hereinabove the ideal temperature for chicken and turkey 
products is between 165.degree. and 170.degree. F. When the temperature of 
the meat is raised above 170.degree. F., the fiber in the meat shrinks and 
causes the juices to be purged out. Far less juice is lost from the meat 
when boiling and holding the temperature at the reduced level as compared 
to permitting the temperature to rise. 
As discussed hereinabove, the inlets for the vacuum system may be 
positioned in any position within the cooking cavity 324 however because 
the water within the meat boils generating steam, which would rise within 
the oven cavity, it may be desirable to position the inlet in the upper 
portion of the cavity 324 to draw off this steam which is generated during 
the cooking of the meat product. However, as discussed hereinabove because 
the meat product itself is the coldest surface within the oven, by drawing 
the vacuum from a lower portion of the cavity the steam would be drawn 
back into contact with the meat product with some of the steam condensing 
on the product thus providing additional heat transfer medium for heating 
the food product. The particular positioning of the vacuum system inlet 
would thus be chosen depending upon the character of the product being 
cooked. 
Similar to the foregoing example, when cooking a pot roast in a standard 
oven the gravy and other juices boil at 212.degree. F. which for cooking 
meat and vegetables is too hot thus resulting in the overcooking of the 
meat and vegetables. Accordingly, by reducing the internal pressure of the 
cooking cavity 324 of the baking oven 302 to achieve a boiling point of 
175.degree. F., the meat and vegetables would not be overcooked and the 
meat would remain tender. Again, the particular boiling point of the gravy 
and juices can be controlled by controlling the internal pressure of the 
cooking cavity 324. 
While the foregoing examples are directed to meat products, the oven 
including a vacuum system is also highly beneficial when cooking fruits 
and products containing fruits. For example, when baking an apple pie in a 
conventional oven, the juices boil at 212.degree. F. which rapidly cooks 
the apples. As discussed hereinabove, most fruits like most meats and 
vegetables are overcooked at 212.degree. F., thus, reducing the internal 
pressure of the cavity of the baking oven would permit a cook to select 
the internal temperature of pies, casseroles, pot roasts and many other 
dishes so as to retain much of the natural juices of the product while 
eliminating the creation of harmful carcinogens. 
From the foregoing, it is now apparent that a novel cooking technique as 
well as novel food preparation ovens have been disclosed meeting the 
objects and advantageous features set out hereinbefore as well as others, 
and that numerous modifications as to the precise shapes, configurations 
and details may be made by those having ordinary skill in the art without 
departing from the spirit of the invention or the scope thereof as set out 
by the claims which follow.