CA1339273C

CA1339273C - Microwave steam-pressure cooking

Info

Publication number: CA1339273C
Application number: CA 569477
Authority: CA
Inventors: Stanley E. Johnson
Original assignee: Individual
Current assignee: Individual
Priority date: 1988-06-14
Filing date: 1988-06-14
Publication date: 1997-08-12
Anticipated expiration: 2014-08-12

Abstract

Microwave cooking where the foodstuff while being cooked is kept in a confined space thereby being subjected steam or vapor environment. Also, cooking takes place at a pressure slightly greater than atmospheric pressure. Apparatus for cooking includes a bag of plastics microwave safe material and is of an elastic nature so as to expand as the pressure increases. The bag can be of such material as to not exceed a predetermined pressure and/or a pressure relief valve can be used. Different valve mechanisms are disclosed some of which are selectively adjustable to vary the release pressure. Bags of different cooking pressures are provided and color coded to different preselected pressure characteristics.

Description

MICROWAVE ST~AM-~Kh~UK COOKING 13 3 9 ~ 7 3 Field of Invention;
This invention relates generally to microwave cGoking, and more particularly to subjecting foods stuffs being cooked in a microwave oven to a vapour environment and at a pressure greater than atmospheric pressure during cooking. The invention is directed to both a method of coGking and apparatus fGr use in cooking.

Back~round of Invention:
Domestic pressure food cookers are well known for cooking with convection heating apparatuses but they are not widely used. One drawback is that the pots for pressure cooking are heavy, cumbersome utensils which are hard to handle. Effectively, they are pressure vessels with a removable cover having an over pressure release blow-out type valve in the cover and a pressure control and release valve removably mounted on the cover. The seals and~or Gver pressure release valve require frequent replacement.
It is well known that foods cooked in a pressure cooker are more wholesome, and pressure cooking substantially reduces the cooking time. Pressure cooking, however, has not, to applicant's knowledge, been used domestically when cooking with microwave ovens, which, in recent years, have become very popular. As a matter of fact, cooking instructions for microwave users teach directly away from pressuri~ation by directing them to ensure containers, plastic bags and other cGoking vessels and containers be open. Microwave cooking is extremely fast, and when the food stuff being cooked is subjected to pressure greater than atmospheric pressure, it may perhaps be even faster. This however is not applicant's main concern because microwave cooking is of extremely short duration, anyway. Cooking time in microwave cooking is quite critical as a few seconds one way or the other can result in undercook or overcooking. With the present invention, from limited testing of the same it seems the cooking time is less critical than it is with conventional microwave cooking techniques.

Summary of Invention:
A principal object of the present invention is to provide improvements in cooking foodstuffs in a microwave oven.
A further principal object of the present invention is to provide apparatus for use in improving cooking in a microwave oven.
In keeping with the foregoing, there is provided in accordance with one aspect of the present invention a steam-pressure cooker for cooking foodstuffs in a microwave oven comprising a bag of flexible elastically stretchable microwave safe material and means for closing said bag.
In accordance with a further aspect of the present invention there is provided a steam pressure fGod cooker comprising a bag of flexible microwave safe material and a closure for said bag including a pressure relief valve. The valve and/or bag may be disposable or reusable and the bag preferably is made of stretchable and particularly stretchable elastic material.
In accordance with a further aspect of the present invention there is provided a cooking utensil comprising a flexible bag normally open at one end for receiving and holding foodstuffs to be cooked and means permitting the interior effective volume of the bag to increase and decrease in volume in response to pressure changes therein.
In accordance with a further aspect of the present invention there is provided a method of cooking comprising:
(a) providing a bag having an open end and made of flexible material with at least a portion being of predetermined elasticity;
(b) placing foodstuff to be cooked in said bag and closing the otherwise normally open end of the bag, and (c) placing said bag with the foodstuff therein in a microwave oven and su~jecting the same to microwave energy of selected level for a selected period of time.
A significant advantage of cooking under pressure in a microwave oven is that the food value and flavour is retained. The food is cooked effectively in a steam or vapour environment (normally from the fGodstuffs own constituents) and thus more wholesome. The foods so cooked are not dried out and thus the present invention overcomes one of the most common complaints of foods cooked in a microwave oven. It seems from preliminary use and testing of the invention the time of cooking is less critical when using the present invention compared to conventional microwave cooking. ~erhaps this is because the moisture is always present during cooking.

List of Drawinqs:
The invention is illustrated by way of example in the accompanying drawings, wherein:
Figure 1 is a diagrammatic o~lique view of a disposable plastic bag with foodstuff therein in a microwave oven for cooking;
Figure 2 is a partial diagrammatic view of a plastic bag cooker of Figure 1 incorporating a modification;
Figure 3 is a diagrammatic view of a still further embodiment;
Figure 4 is a cross-sectional view of a pressure release valve detachably mountable on a plastic bag for relieving over pressure;
Figure 5 is a side elevational view of a modified version of the valve of Figure 4;
Figure 6 is a cross-sectional view along line 6-6 of Figure 5 illustrating a modification;

Figure 7 is a left hand end elevational view of Figure 5;
Figure 8 is a cross-sectional view similar to Figure 4 but illustrating a still further modified valve arransement;
Figure 9 is a side elevational partial sectional view of a further valve detachably mountable on a bag in accordance with the present invention; and Figure 10 is a sectional view taken alons line 10-10 of Figure 9.

Description of Preferred Embodiments:
Referring to the drawings, illustrated in Figure 1 is a plastic disposable bag 10 having foodstuffs 11 therein and located in a microwave oven 12 for cooking upon closing the oven door, making the appropriate settings and actuating the start cycle. The open end of the bag is closed using a tie or slip-type noose 13 or alternatively closed by a sealing machine or simply by tying a knot in the sleeve defining the bag. The bag 10 and tie 13 are of a plastics material and ~0 thus may ke considered as being no different than a garbage bag. Garbage bags are flexible wall containers but what the present invention provides is a flexible wall pressure cooking vessel. Cooking and garbage disposal are completely unrelated arts (or at least so they should be).

- & - 1339273 In the preferred form of the invention at least a portion of the bag wall is made of stretchable elastic material of predetermined elasticity so that it will stretch during cooking with the elasticity being such as to provide a maximum cooking pressure. Also the elasticity may, for example, be such that the maximum cooking pressure for one type of bag is two pounds greater than atmospheric pressure while that for another type of bag is three pounds, and another four pounds, etc. greater than atmospheric pressure.
These actual pressures referred to are by way of example only and have no bearing on actual cooking pressures.
Experimentation will be required to determine the most effective cooking pressures. More important than the pressure aspect is confining the cooking foodstuffs to a closed environment so that they cook in a moist environment. If desired the cooking pressure for the bag and its colour can be co-related so that one knows that if they take a red bag for example, the maximum cooking pressure will be so many pounds and another colour will be of another maximum cooking pressure. The pressure within the bag builds up during cooking from vapors given off from the foodstuff being cooked and thus the food is cooked in the presence of its own vapGur.
Figure 2 illustrates an alternative to the embodiment of Figure 1 wherein an overpressure relief reed or flap valve 20 is incorporated in the wall of the bag and covering a hole 21 so that should there be any sudden increase in pressure within the bag or should the pressure exceed that for which the bag is designed it can be released through the valve and thus prevent the bag wall from rupturing.
S In Figure 3 there is illustrated an embodiment where the bas cGoking vessel lOA is made of relatively inelastic material and communicates directly with a bag 10~ of predetermined elasticity. The bags are connected, for example, by way of a tubular coupling 14. If desired a pressure release valve 15 can be incorporated in the coupling 14 so that two way communication from one bag to the other takes place only after the pressure in bag lOA reaches a predetermined level. ~ag 10~ is effectively a stretchable balloon of predetermined strength so as to determine the cooking pressure within bag lOA holding the food content being cooked. Ideally the bag, like a balloon, requires ccnsiderable pressure to initiate stretching of the side walls but once stretched a selected amount there is little or no increase in pressure but instead substantially only a change in volume.
In the embodiments illustrated in Figures 4 to 10 a separate pressure relief valve is provided and which fits partially into the open end of the bag and the bag is clamped on to the body of the valve. In one embodiment the valve is of a simple nature intended for disposal and in other embodiments the valve is a little more sophisticated and intended for reuse. These embodiments do however have the drawback of releasing some of the cooking vapors to atmosphere the release of vapors being particularly so when using a non-stretchable bag. It is thus preferred the release valves of Figures 4 to 10 be used with bags of stretchable elastic material and normally set to blow off or release just prior to bag breakage.
Referring to Figure 4 there is illustrated a valve 30 having an outwardly flared open end 31 inserted into the open end 32 of a bag 10. The bag is clamped onto the body of the valve by an elastic 0-ring 34 or noose type plastic tie. The valve has a cylindrical recess 35 in which there is reciprocally mounted a piston 36 movable toward and away from the recess closed end 37. The cylindrical wall of the valve lS 30 has an aperture 38 which is covered and uncovered respectively by movement of the piston 36. The chamber cavity 39, between the piston and closed end wall 37, serves as an air cushion against which the piston must act in order to release pressure from the bag through valve body aperture 38. The size of the cavity 39 and longitudinal movement of the piston in the cavity can be predetermined (or a spring in such cavity can be used) to relieve pressure from the bag 33 through aperture 38 upon reaching a predetermined pressure. A compression spring such as shown in Figure 8 can be used in cavity 39 or a tension spring such as spring 40 shown in Figures 5 and 6 can be used to tether the piston.

' 1339273 The embodiment illustrated in Figures 5, 6 and 7 is essentially the same as that illustrated in Figure 4 except that the air cushion chamber 39 is disposed of and in place thereof is an elastic member 40 used to tether the piston.
The elasticity of member 40 is chosen such as to allow piston 36 to move releasing pressure from within the container 33 through aperture 38 when the pressure in the cooking vessel reaches a predetermined level. The elastic member 40 can be fastened to the valve body and piston in any convenient manner. In the embodiment illustrated in Figures & and 7, the elastic member 40 is an endless elastic band looped around tabs 51 and 52 provided by notches in the sidewall of the valve casing. The endless band 40 passes under a lug 53 attached to the piston 36. In this embodiment elastic bands of different strength can be provided for cooking at different pressures such bands, if desired, being colour co-ordinated to the different strength characteristics.
Another form of valve is shown in Figure 8 which is a variant of the valve shown in Figures 5, 6 and 7. Referring to Figure 3 there is illustrated a sleeve 60 flared outwardly as indicated at 61 at one end and threaded as indicated at 62 at the other end. A cap 63 threads onto the stem and holds captive therebetween a disc valve 64 and compression spring means 65. The spring means 65 may be a piece of resiliently compressible foamed plastics material. The disc 64, may be a separate element or integral with the foamed plastic spring 65 1~39273 and bears against an annular ring 66 projecting from the stem.
The ring 66 can be a separate element or integral part of member 60 and is of smaller outside diameter than the latter.
Such arrangement provides an air chamber 67 that opens to atmosphere through one or more apertures 68 through the cap wall. In this embodiment the valve release pressure can be varied by turning the threaded cap 63 and thus changing the force of spring 65 on the disc valve 64.
A further embodiment of a valve is illustrated in Figures 9 and 10. Referring to these there is illustrated a sleeve 70 having a piston 70A reciprocal therein and abutting a spring means 71. Spring means 71 (a plastics material coil spring or plug of foamed plastics material) bears against a lug 72 projecting from a threaded cap 73 that screws on the end of the sleeve.
The piston moves in response to changes in pressure in the cooking bag 10 and at a predetermined pressure uncovers one or more apertures 74 through the stem. When there is more than one aperture they can, if desired, be offset from one another along the a~is of the stem.
In the embodiment of Figures 9 and 10 the stem 70 tapers slightly inwardly as indicated at 75. This tapered end projects into a hole 81 in a plate 80 and clamps therebetween an end portion of the bag 10. This closes the open end of the bag and places the end of piston 70A in communication with the interior of the bag via central passage 76 in the sleeve.

In the foregoing embodiments the mcvable piston can be provided with any convenient well known 3ealins means, for example an O-ring, not shown, fitting partially into a groove circumscribing the piston alternatively one or the other, or both ends of the piston can be provided with a thin outwardly flared rib i.e. ribs 36A and 36~ in Fisure 4.
As a final and extremely simple embodiment pressure relief from the bag can, with reference to Fisure 4 take place between the sleeve 30 and the wall of the bas throush the bag end 32. In this case the strength of the elastic O-ring 34 can be such as to provide the desired release pressure. In such embodiment it would be preferred to have no folds in the wall of the bag where it engages the sleeve.

Claims

1. A method of microwave cooking comprising (a) providing a bag having an open end and made of non perforate flexible material with at least a portion being of predetermined elasticity;
(b) placing foodstuff to be cooked in said bag and closing the otherwise normally open end of the bag whereby the foodstuff is in a completely sealed enclosure, and (c) placing said bag with the foodstuff therein in a microwave oven and subjecting the same to microwave energy of selected level for a selected period of time during which time the bag's elasticity determines the maximum cooking pressure.

2. A method as defined in claim 1 wherein the elastic characteristic of the bag is such that after reaching a predetermined pressure within the bag further increase of pressure volume is reflected essentially by only an increase in volume.

3. A cooking utensil comprising a flexible bag normally open at one end for receiving and holding foodstuffs to be cooked, said bag being of non perforate material and means permitting the interior effective volume of the bag to increase and decrease in volume in response to pressure changes therein without discharging to atmosphere.

4. A cooking utensil as defined in claim 3 having a predetermined maximum cooking pressure and wherein said maximum pressure is determined by expansion of the utensil.

5. A cooking utensil as defined in claims 3 or 4 wherein said bag is made of flexible elastic material.

6. A cooking utensil as defined in claims 3 or 4 wherein said means comprises a separate balloon made of flexible elastic material sealingly connectable to the cooking bag opening by a coupling having a passage therethrough communicating with the interiors of the bag and balloon.

7. A cooking utensil as defined in claim 6 including a pressure release valve in said passage dumping into said balloon.

8. A cooking utensil as defined in claim 7 wherein said pressure release valve remains open after release permitting flow in either direction through the passage.

9. A steam pressure food cooker comprising a bag of flexible microwave safe material and a closure of microwave safe material for said bag, said closure having a passage communicating with the interior of the bag and discharging to atmosphere and a pressure relief valve permitting air pressure in the bag to escape through said passage upon reaching a predetermined pressure, said closure being made entirely of plastics material and comprising a sleeve having a piston reciprocally mounted therein respectively to cover and uncover an aperture in a wall of the sleeve and spring means resisting movement of the piston in a direction to uncover said aperture.

10. A cooker as defined in Claim 9 wherein said spring means is a compression spring.

11. A cooker as defined in Claim 10 wherein said spring means is a tension spring.

12. A cooker as defined in Claim 11 wherein said tension spring is an endless loop of elastic material anchored respectively to the sleeve and piston at spaced apart positions.

13. A cooker as defined in Claim 12 wherein said loop of elastic material is of selected predetermined strength.

14. A cooker as defined in Claim 12 including a supply of endless loops of elastic material with some of said loops being of different strength characteristics than the others.

15. A cooker as defined in Claim 14 wherein said elastic loops are color coded in co-relation to their strength characteristics.

16. A cooker as defined in Claim 9 wherein said bag is of elastic material so as to vary in volume in response to changes of pressure therein.

17. A pressure relief valve for use in microwave cooking comprising a body having a valved passageway therethrough, means for sealingly closing the open end of a plastics bag with said body so that the bag is vented to atmosphere through said passageway, said valve being a pressure relief valve and including a piston reciprocally mounted in said passageway and responsive to variations in pressure within the bag selectively to cover and uncover an air release aperture, means selectively to vary the release pressure of said valve, said device being made of microwave cooking safe material.

18. A device as defined in Claim 17 wherein said body comprises a sleeve flared outwardly at one end, said one end being insertable into the open end of the cooking bag.

19. A device as defined in Claim 17 wherein said body is a sleeve an end portion of which is insertable in the bag and including clamping means to secure said bag to said sleeve.

20. A device as defined in Claim 19 wherein said clamp comprises an elastic O-ring.