Electric heating – Microwave heating – Cookware
Patent
1996-06-26
1998-03-10
Leung, Philip H.
Electric heating
Microwave heating
Cookware
219735, 426234, 426107, 99DIG14, H05B 680, B65D 8134
Patent
active
057264260
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a container for use in connection with the exposure of a product to microwave radiation, and to a method of exposing edible matter to microwave radiation.
A product which is heated by microwave radiation is heated effectively from within the body of the product. The product is exposed to air which is cool and humid, compared with that to which a product might be exposed to in a conventional oven. Moreover, the period in which a product is exposed to microwave radiation in a microwave oven is generally very much less than the period of exposure to heat in a conventional oven. As a result, it is often found that it is not possible for adequate moisture to be lost from a product which is heated by exposure to microwave radiation so that, in the case of certain products, in particular edible products which are required to have a crisp external surface layer, the surface layer can be soggy and generally devoid of crispness.
A number of packaging materials have been developed for use with microwave appliances in order to alleviate this problem. Such packaging materials include several materials capable of absorbing microwave energy, and converting that energy to heat. They are sometimes referred to as "microwave heat-reactive materials". The food product in question is covered, preferably enveloped, by the packaging material, and then sears due to exposure to the heat generated within the material by the microwave radiation.
A known such packaging material is disclosed in EP-A-270838. It comprises a plastic film having a thin metallic coating applied to it. The film has a plurality of slits in the form of broken lines, in parallel, formed in it. The slits allow the material to be deformed so as to fit around a food product. Deformation of the material causes the slits to open. This known material has been found in certain circumstances to have the disadvantage that it can be difficult for a person to position the material around a food product satisfactorily to ensure that the product within the material is heated in a controlled manner, such that the exposure of the food product to the radiation is within desired limits, and that the characteristics of the heated food product are optimised.
According to the present invention, it has been found that a food product can be exposed to microwave radiation so that the inner regions of the product are suitably heated, and that the surfaces of the product are dried and made crisp, by placing the product in a tray with a lid having a plurality of openings extending through it, and being so folded that the distance through the openings from one side to the other side of the lid is greater than the thickness of the lid material.
Accordingly, in one aspect, the invention provides a container for use in connection with the exposure of edible matter to microwave radiation, which comprises a base tray and a lid, the lid being formed from a sheet of a material which absorbs microwave radiation and is heated by it, the lid having a plurality of openings extending through it, and being so folded or constructed that the distance through the openings from one side to the other side of the lid is greater than the thickness of the material of the lid.
The container of the invention has the advantage that the external surface of a product can be exposed directly to hot dry air, which has a low relative humidity, so that evaporation of water from the surface of the product is facilitated. Water vapour which results from evaporation of moisture on the surface of a product exposed to microwave radiation can then be removed from the product through the openings in the lid so that the surface of the product can acquire a low surface moisture content, and therefore also to be crisp.
Furthermore, the presence of the base tray as a component of the container allows a food product to be packaged in the container in which it is to be prepared for consumption, so that it can be passed from the original manufacturer, through the relevant retail chain, to the person who
REFERENCES:
patent: 4835352 (1989-05-01), Sasaki et al.
patent: 5053594 (1991-10-01), Thota et al.
patent: 5132151 (1992-07-01), Graney
patent: 5310977 (1994-05-01), Stenkamp et al.
patent: 5317120 (1994-05-01), Bunke et al.
Bowler Peter
Davis Jeffrey Martin
Woods Kenneth David
Leung Philip H.
Ranks Hovis McDougall Limited
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