GB2325133A

GB2325133A - Induction heating for cooking

Info

Publication number: GB2325133A
Application number: GB9805306A
Authority: GB
Inventors: Christian Eskildsen
Original assignee: Electrolux AB
Current assignee: Electrolux AB
Priority date: 1997-03-13
Filing date: 1998-03-12
Publication date: 1998-11-11
Also published as: GB9805306D0

Abstract

In an ELF energized oven cavity, any insulating container may be used for the preparation of food when according to the invention the food in the container is covered by a ferromagnetic material. In a preferred embodiment, the material is in the form of a mail of iron rings which has a knitted covering in hydrophilic PTFE fibres. The eddy currents set up in the covering heat the same, and this heat is locally transferred to the food. Alternatively, the material may be in powder form and coat the food.

Description

A procedure for localized heating of food and an implement therefor.

The invention relates to a procedure for localized heating of food without the complexities of microwave heating. Cavities for microwave heating have to use complex electronic filters in conjunction with the oven door to avoid radiation of short-wavelenght electromagnetic radiation. It would appear much simpler to use a longer wavelenght, but then the heating cannot use the ubiquitous water content in food for dielectric heating, because the losses are too small at lower frequencies.

Induct ion heating which uses ELF energy (20kHz100kHz) would seem attractive, but it is only useable with ferromagnetic material close to the food to be heated, because it is desired to attract sufficent flux to set up eddy currents which will generate heat in the material. Until now it is only known to heat food using ferromagnetic containers, such as a baking tin or cooking pot, and the alternative in an oven cavity environment would be to use a baking plate. All of this creates complexity, and it is not possible to obtain the advantage of microwave cooking/baking that any type of insulating cooking vessel may be used.

According to the invention, these disadvantages may be avoided, in that the cooking vessel containing the food is covered with a ferromagnetic material. This may take the form of e.g. a lid, possibly a closely fitting lid with a non-stick lower surface. In such a case it is important to provide venting holes for the escape of water vapour.

In an advantageous embodiment of the invention the ferromagnetic covering is in the form of a limp iron mail interwoven with PTFE fibres of the type used in hydrophilic separation membranes. The mail, consisting of interlocking closed iron rings will conform completely to the surface of the food to be cooked, and it will follow the crust when e.g. a cake or bread raises. The PTFE fibres prevent sticking of the mail to the surface which means that it may be simply peeled off at completion of the cooking/baking.

In a further advantageous embodiment of the implement according to the invention the side of the mail facing the food has a knitted covering of PTFE fibres of the type used in hydrophilic separation membranes. This means that the separation of the covering is simplified, and the texturing of the surface is reduced. The knitting may be quite tight, because the PTFE fibres are water vapour permeable In a further advantageous embodiment, the food itself is sprinkled with ferromagnetic particles to a packing density sufficient to set up eddy currents. In case the particles are made of very finely divided iron their gradual oxidation will prevent oxidization of fats in the food, provided the finished product is encapsulated in an oxygen-impermeable container or bag shortly after the end of baking. In use, this crust may be cut off or even digested, contributing iron to the organism.

Claims

PATENT CLAIMS

1. A procedure for localized heating of food, c h a r a c t e r i s e d i n that the cooking vessel containing the food is covered with a ferromagnetic material.

2. A procedure according to claim 1, c h a r a c t e r i s e d i n that the ferromagnetic covering is a closely fitting lid with a non-stick surface.

3. A procedure according to claim 2, c h a r a c t e r i s e d i n that the lid is supplied with water vapour escape holes.

4. A procedure according to claim 1, c h a r a c t e r i s e d i n that the ferromagnetic covering is in the form of a limp iron mail interwoven with PTFE fibres of the type used in hydrophilic separation membranes.

5. A procedure according to claim 4, c h a r a c t e r i s e d i n that the side of the mail facing the food has a knitted covering of PTFE fibres of the type used in hydrophilic separation membranes.

6. A procedure according to claim 1, c h a r a c t e r i s e d i n that the food itself is sprinkled with ferromagnetic particles to a packing density sufficient to set up eddy currents.