Electric heating – Heating devices – With power supply and voltage or current regulation or...
Patent
1997-01-13
1998-07-14
Paschall, Mark H.
Electric heating
Heating devices
With power supply and voltage or current regulation or...
219497, 219707, 99325, 236 44C, H05B 102
Patent
active
057808180
DESCRIPTION:
BRIEF SUMMARY
It is a know fact that one by preparing food in an oven for each individual food product must set the temperature and time controls. These parameters vary according to the type of product placed in the oven and its volume. Additionaly the temperature of the foodproduct when starting the process affects the amount of time necessary for the process. The setting of these two basic parameters is generally a matter of subjective judgement and/or based on experience. The oven temperature is mostly controlled by a temperature controlling device with the purpose of keeping the set cooking temperature as constant as possible.
Apart from these basic settings there is often a need for, when processing certain types of foodproducts, removing water in the form of water vapour, and again in other cases adding water vapour. The settings of these parameters are mainly done manually by a through the entire cooking process engaged function of removing or adding water vapour. The settings can also be in advance fixed controlling programs.
These drawbacks are particularly troublesome when repetitly processing varying volume of the same type of foodproduct. This is the case often found in catering environments.
As one example among many others the course of events when processing french fries can be described as follows;
In a rotating hot air oven a continuously varying volume of french fries is processed in hot air. Initially the french fries being cooked gives off large amounts of water vapour that helpes thawing by allowing increased heat transport, but at a later stage the vapour can prevent a crisp surface being reached. The time of processing varies in accordance to the volume of french fries being processed and the amount of water vapour given off. The amount of water vapour given off is dependent on how the frozen or refrigerator chilled french fries is manufactured, frozen or stored. It is obvious that it is virtually impossible to manualy set all the required parameters needed for reaching a nicely tasting product.
Having to do this by subjective judgments in a stressful work environment very often results in mistakes giving that given quality demands is not reached or even that the food product is destroyed.
The present invention eliminates demand for continous new settings and thereby the risc of failure.
The invention is based on the fact that a food product to be cooked in heat always starts off at a lower temperature than the temperature of the heat transportation medium into which the food product is placed. This results in caracteristic changes in shape of the temperature curve of the heat transportation medium when the food product is placed into it.
On the enclosed drawings,
FIGS. 1 to 3, curves are shown illustrating temperature changes over time.
FIG. 4 shows a general outline of an oven for processing chilled or frozen food e. g. french fries.
The caracteristic changes in shape of the temperature curve is seen as breaking points which depend on differences in the initial temperature of the food product, the water content in the form of water or ice, the specific heat of the inserted food products or a combination of these different properties. When a frozen product is placed in the oven, two very characteristic breakpoints, 2 or 3 together with 4 or 5, are obtained. Where the first one, 2 or 3 appears the ice transites into water (melting point) and where the other, 4 or 5, appears, the water transites into steam (boiling heat). These break points can therefore be used for controlling amongst other things a device which regulates the amount of water vapour in the heat transportation medium circulating in the oven compartment. Most food products are in the initial stages of the cooking process, especially when frozen but even cold, almost unaffected by a heat transportation medium saturated with water vapour. A heat transportation medium saturated with watervapour is able to carry larger amounts of heat compared to a dry heat transportation medium. These conditions can be used to rapidly raise the temperat
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