MXPA00009386A - A method of controlling the operation of cooking apparatus - Google Patents

Abstract

Disclosed is a method of at least partially cooking food items by exposing them to a heated liquid cooking medium supplied by cooking medium delivery means to a cooking zone of a cooker including a control unit which, during a cooking process:(a) controls the temperature of the cooking medium delivered to the cooking zone to a pre-determined setpoint specific for the food items by controlling heat output from a heat exchanger for heating cooking medium throughout the cooking process;(b) controls the rate of convective heat transfer to the food items by directly controlling a sensed condition of cooking medium delivered to the cooking zone, other than temperature which is controlled in step (a), related to the rate of convective heat transfer;and, optionally, (c) controls the rate of convective heat transfer to the food items by controlling a sensed condition of the cooking zone related to the rate of convective heat transfer. Cookers which implement the method are also described.

Description

A METHOD OF CONTROLLING THE OPERATION OF COOKING APPLIANCES FIELD OF THE INVENTION This invention relates to a method of the control of cooking appliances and in particular to the control over the rate of heat transfer to food products that are being cooked in a particular cooking appliance such as frying apparatus. Cooking appliances are also exposed to carry out the method.

PREVIOUS TECHNIQUE The cooking appliances cook food items by exposing them to a heated liquid cooking medium, such as an oil, gas or molten solid fat. The liquid can be oily or aqueous depending on the nature of the cooking process, whether it is boiling or frying. The gaseous media may include steam or heated air or other gases. Conventionally, the cooking process - achieved by the transfer of heat to the food material - is controlled by controlling two variables, the temperature of the cooking medium; and the time during which the food items are exposed to the cooking medium.

Several problems can arise with this form of control in practice. For example, although the temperature can be controlled, it has generally been controlled in a somewhat imprecise manner, with the temperature being conjectured by the operator, which is the optimum for the cooking process on the basis of minimum temperature data. A similar inaccuracy applies to the cooking operation. The duration may be approximately correct but not optimal. Then, an even higher level of complexity and a lack of precision can result if there is not a single cooking temperature that is applicable throughout the entire cooking process, but rather the temperature must be a function of time, that is, change during the whole cooking process. By way of example, the cooking of a meat article in which it is desired to seal the outer part of the article at high temperature at the beginning of the cooking process should be mentioned, the temperature then being varied downwards to a value that is then maintained for the rest of the cooking procedure. The greater variability in the cooking temperature may result from variations in temperature caused, for example, by the loading of frozen food items into the cooking chamber or the cooking zone during the cooking process. The loading operation will cause the temperature drop when contacting the frozen items with the heated cooking medium. This is a problem that needs to be addressed. A tub frying application, as commonly used in the fast service food industry, is one that employs the principle of deep frying of food items by immersing them in a body of heated cooking medium. Deep frying is a procedure of significant interest to the applicant. In that case, a difficulty arises that is greatly accepted in conventional practice, that is control over the temperature in a specific place within the body of the cooking medium. This is a compromised system in which local overheating and subheating can take place, not only compromising the efficiency and quality of the cooking process and the food items that result, but also gives rise to problems with the operation of the team itself. Even if temperature control is attempted, the thermal inertia of the tub filled with the cooking medium results in a poor control response and an unbalanced temperature profile. If there is local overheating of the cooking medium, the food items may be over sewn or may be sewn non-uniformly. If the temperature is highly local to a heating food, the food particles and crumbs in this place can be carbonized causing a cleaning problem and the quality of the cooking medium. The cooking medium can degrade, the texture of the product can be adversely affected and the oil performance to the product can be increased. The latter situation may be undesirable if one wishes to avoid the quality of the oily food product. This heating can be a particular program if the charred food particles are deposited in the ducts that knew the cooking medium both in a given cooking appliance. In the tub fryers, complete disassembly, cleaning or replacement of the ducts may be required every 3 to 5 years or even less, stopping the capacity of the cooking appliance. Either way, any deposition of "scale" interference with heating efficiency of the cooking damage with a heat exchanger and can be compensated by techniques that can actually exacerbate the problem of overheating, heating for example the heat exchange element or the heating medium at higher temperatures if the overheating becomes even more likely. Previous practice has sought to address such problems with metallic design measures, such as scrapers and drills for long elimination of crumb deposits. Devices for the removal of oil may also be preferred. For example, the fabrics may be equipped with transverse flow devices intended to cause mixing of the cooking medium and more uniform heating. Cold zones could be provided in regions in which the crumbs are likely to be deposited, so that the temperature below the carbonization temperature is maintained. The vapor test could also be used in an effort to avoid carbonization, but this technique is potentially dangerous. In addition, you can install settlement systems, such as drum filters, band filters (with paper or cloth bands) or other complex filtration systems. Drum and band filters that expose the oil to the air are undesirable.

BRIEF DESCRIPTION OF THE INVENTION It is an object of achieving better control over the cooking process by reducing the above problems with minimal recourse to complex mechanical arrangements that form the basis of this invention. With this object in view, the present invention provides a method of cooking food items at least partially by exposing them to a collected liquid cooking means provided by means of supplying cooking means to a cooking zone of a holder including a control unit. which, during a cooking process: (a) controls the temperature of the cooking medium supplied to the cooking zone to a specific predetermined set point for the food items, controlled the heat rise of a heat exchanger preheat the medium of cooking during the whole cooking process; (b) controls the heat preference regime converted to directly controlled food items a detected condition of the cooking medium supplied to the cooking zone, different from the temperature that is controlled in step (a), in relation to the regime converted heat transfer; and, optionally, (c) controlling the rate of converted heat transfer to the food items by controlling an infected condition of the cooking zone in relation to the convective heat transfer regime. Temperature control can be achieved throughout the cooking process by appropriately heating the cooking medium to a predetermined set point for the cooking process, using suitable heat exchangers that are operated taking into account the particular nature of the cooking medium that is heating up For example, in the case of frying, where the cooking medium is a melted oil or gauze, heating is conducted desirably in the absence of air using, for example, the flow heating arrangements as described in the Australian patent No 666944; and co-pending international patent application No. PCT / AU98 / 00552, filed July 16, 1998, the contents of which are hereby incorporated by reference herein. Such heat exchangers may include another system for cooling the cooking medium. The temperature can be varied as desired throughout the cooking process by proper control of the output of the heat exchange element. Control over the rate of heat transfer from the cooking medium to the food article can be achieved in several different ways. In establishing this control, the applicant recognized that the cooking process commonly proceeds by a convective heat transfer mechanism rather than a conductive heat transfer mechanism. The thermal conductivity of the cooking means, such as oils and fats, is considerably low. In effect, oils and fats are insulators that conduct heat only poorly to food items that are being cooked. The control mechanisms of the convective heat transfer regime, based on this understanding, should advantageously take into account the cooking process, the nature of the food items to be cooked, such mechanisms, can include the induction of turbulence in the especially local cooking means, to a food item being cooked or, particularly desirably, to control over the pressure or flow rate of the cooking medium supplied to the cooking zone or the flow rate of the cooking medium beyond of the food item. Such control can be achieved in a particularly advantageous manner independently of the control over the temperature of the cooking medium and the duration of the cooking, the last of which is also controlled. More specifically, said detected condition of the cooking medium supplied to the cooking zone is one or more of the following: supply pressure of the cooking medium, flow velocity of the cooking medium, flow velocity, density of the cooking medium, viscosity of the cooking medium and turbulence of the cooking medium; and, if step (c) is employed, one or more of the following; type of sprinkler, type of nozzle, type of hydraulic restriction, turbulence in the cooking zone, temperature in the cooking zone, duration of cooking and the frequency of shaking of the metal basket. Such control can be applied throughout the cooking process in the case of several different types of cooking appliances. Indicative of the types of cooking appliance that can be controlled according to the method are the spray cooking appliances, the tub type cooking appliances and the pressure fryers. The bleaching apparatuses can be controlled in this way. The method can be applied to other kinds of cooking appliances that can operate on the basis of cooking procedures in which the convective heat transfer mechanism is of importance. Most cooking procedures would fall into this category. In the case in which the cooking appliance is an apparatus in which the cooking appliance is an expression cooking appliance, for example a spray fryer, the flow rate of the cooking medium can be controlled in a controlled manner by means of a cooking appliance. the sprinkler nozzles to the cooking chamber, as well as the supply pressure of the cooking medium. Such sprinkler nozzles can be of different types in terms of the flow distribution of the operating pressure range. In the case where the cooking appliance is a tub cooking plant, for example a tub fryer, the turbulence or flow velocity of the cooking medium can be controlled controllably beyond the surfaces of the food article while is cooking and the energy transfer speed. Generally, increasing speed and flow results in higher connective heat transfer. In this case, the sprinkler nozzles can be replaced by hydraulic constraints, such as flow or pressure, within the means of supplying the tub with cooking means. Such restrictions, such as sprinklers and nozzles, may have different characteristics, such as pressure loading, etc. Diaphragms may be employed, for example, in tub arrangements, including transverse flow arrangements for fine adjustment of the flow of the cooking medium that can be varied through the tub during the cooking process, to substantially secure the uniform profile of the tub. temperature in it. The cooking appliance can be multi-zone in nature in that the appliance is configured to allow different cooking methodologies for the food items that advance through the cooking zones through the generic cooking mechanism, for example fryer by spraying or in tub, they can be the same for each cooking zone. This takes into account the fact that the cooking procedures change in nature during the optimal cooking of some food items. The energy and the temperature profile can be controlled through the constituent cooking zones to achieve this object. A common example applicable to meat is an initial toasting followed by slower cooking. Another type of food article that undergoes different regimes during the optimal cooking is potato chips.

Advantageously, the energy absorbed by the food items during the cooking process can be measured and used as an additional basis for controlling the operation of the cooking appliance. In particular, such addition can advantageously be used as a basis for controlling the rate of heat transfer to the food items during the cooking process. The measurement of the energy absorbed by the food items can be determined on the basis of the differential and temperature between the temperature of the cooking medium entering the cooking zone or each of them and the temperature of the cooking medium leaving the cooking zone. the cooking zone or each one of them. This difference in temperature can be multiplied by the speed of the flow of the mass of the cooking medium and by the specific heat of the cooking medium. The heat losses of the cooking zone can also be taken into account. If the temperature differential falls outside predetermined limits, then corrective action must be taken to produce the temperature differential and the energy absorbed by the food items in the cooking zone or in each of them within the desired limits. Corrective action can be taken first by altering the flow velocity of the cooking medium, thereby decreasing the error between the desired energy absorption of the food items and that actually achieved. An alarm condition can also be indicated at the same time.

Less preferably, as the cooking medium is heated in a heat exchanger to the desired temperature, the temperature in the cooking medium entering the cooking zone can be varied in order to decrease the error between the desired energy absorption of the cooking medium. the food items and the really achieved. This is a more compromised control response because the increase in temperature of the cooking medium can have disadvantageous effects on the quality of the cooking medium. It is also possible to vary the duration of the cooking, a detected condition of the cooking zone as turbulence, controlling for example the speed of the conveyor means or the supply of food products or the transfer means as a possible control response. The control responses are not exclusive. In addition, those described in any combination can be used. The control strategy can be used to check the clogging of the nozzles and other devices for the supply of the liquid cooking medium to the cooking sum. When the nozzles clog, the temperature differential varies from normal conditions. The temperature differential could be mediated between three temperature conditions of the cooking media: the liquid temperature supplied to the cooking zone; the liquid temperature in the cooking zone; and the liquid temperature that comes out of the cooking zone. As a result, the energy absorbed by the food items may fall and the food quality itself may vary, since a spray for desired distribution of the cooking medium to the cooking zones of a cooking appliance no longer occurs. Advantageously, the control strategy is carried out by an electronic control unit used for general control over the operations of the cooking appliance. It is very advantageous and desirable that the method be fully automated to achieve the best possible cooking performances. In particular, the control unit took effect the desired temperature, the flow of the cooking medium and the control of the heat transfer rate. The control unit can be programmed with temperature differentials of the target cooking medium or specific setpoint for a given cooking procedure. The set points of the temperature differential can be programmed as the time works, the speed of the flow of the cooking medium, the nature of the food article, the equal volume of transfer of the food items and / or other variables. In a second aspect of the invention, in connection with the most preferred cooking silver, a cooking appliance including a cooking zone can be used; means for supplying the cooking means for supplying the cooking medium to the cooking zone; means for removing the cooking medium to remove the cooking medium from the cooking zone; and means for conditioning the cooking means for conditioning the removed and new cooking means for supply to the cooking zone between the means include in sequence, pump means; filtration means and heat exchange means to which at least a portion of the cooking medium that is being conditioned passes. The pump means, the filtering means and the heat exchange means, which can take the form of modules containing any desired number of pump, filtration and heat units, can be composed in series or in parallel according to the invention. want. The pump means are particularly advantageously a variable speed centrifugal pump. The filtration after pumping, the pressure filtration, contrasts with the previous practice that requires a large filter area, comprising a thick primary filtration for pumping to protect the pump means and a fine secondary filtration, from the suction side of the pump. of the pumping and before heat exchange. Single-stage filtration can be employed after pumping, in accordance with the present invention, by reducing the filter area and allowing the achievement of a more compact system. The speed of the pump can be controlled by finding the pressure detected in the means for supplying the cooking medium to the cooking zone, that is to say before the flow, pressure or hydraulic restrictors, sprinklers or nozzle centered depending on the nature of the cooking appliance. The centrifugal pump is particularly suitable for this application, because the speed of the impeller can be varied to maintain the flow velocity of the cooking medium as the filter pressure increases without deterioration of the quality of the cooking medium, especially if the cooking medium is an oxidizable or otherwise degradable medium such as grease or oil. In effect, the applicant not measured a substantial deterioration of the oil cavity at pressures up to 5 bar. The flow rate of the cooking medium can be kept substantially constant or vary for any or all of the cooking zones to achieve the controlled rate object of heat transfer to all food items. The temperature of the cooking medium is likewise controlled, for example by controlling the output of the heat exchange element or the heating means of the heat exchanger to achieve the temperature by optimum temperature range for the cooking medium for the particular application during the whole cooking process. It is also possible to know the control over the flow rate of the cooking medium and the speed through the heat exchange to achieve the desired temperature of the cooking medium. It will be understood that the variables of the flow velocity, the output of the heat exchange element and the pressure and flow velocity of the cooking medium can be varied to achieve the variant rate of heat transfer during the entire cooking process if this is desirable taking into account the nature of the cooking process and / or the nature of the food items being cooked. The pressure due may typically be a function of the degree of clogging of the filter media and, even independently of the characteristics of the pump, the filtering means can be operated to allow regular cleaning procedures, such as flushing or replacement, if the pressure detected in the means for supplying the cooking medium drops below a predetermined value. These regular cleaning procedures or this replacement may be indicated if the speed of the pump impeller, increased to compensate for the descent pressure in the supply means, exceeds a predetermined value. Other techniques could be expanded to determine this point, for example the ultrasonic optical filter clogging test, etc. In the cooking appliance may include means for measuring the energy absorbed by the food items during cooking. Thus, for example, the temperature detection means for detecting the temperature of the cooking medium can be arranged in such a way that the temperature differential between the supplied and removed cooking medium can be determined and used in the calculation of the energy not absorbed as described above. The method and apparatus of the above aspects of the invention can be conveniently monitored by a control unit for the cooking apparatus that brings about the desired control of temperature, flow and heat transfer rate.; and / or the operation of the filtering means. Control can be made with reference to the nature of the food items being baked, the cooking means, the consumer's wishes of particular food products in various places in which the cooking appliance operated according to the method is located. of the invention. The control unit can be electronic and used to calculate the temperature differential and keep it within the distance limits. The method with cooking appliances other than that of the second aspect of the invention can also be used.

BRIEF DESCRIPTION OF THE DRAWINGS The various aspects of the present invention can be more fully understood by the following description of the preferred embodiments thereof made with reference to the accompanying drawings in which: Figure 1 is a flow control diagram of a fryer procedure by aspersion made and operated according to one embodiment of the invention; Figure 2 is a flow control diagram of the process of a spray fryer made and operated in accordance with a further embodiment of the invention; Figure 3 is a process flow control diagram of a tub fryer made and operated according to another embodiment of the invention; Fig. 4 is a process flow control diagram of a multi-zone tub fryer made and operated in accordance with a further embodiment of the invention; and Figure 5 is a flow chart and process control of a multi-zone spray fryer said and operated according to a fifth embodiment of the present invention.

DETAILED DEPARTURE OF THE PREFERRED MODALITIES OF THE INVENTION Referring now to the drawings as a whole, the essential components of the cooking appliance made and operated in accordance with the present invention are the cooking appliance containing the cooking zone or chamber in which the food products are to be cooked, a fluid handling system or a conditioning system that heats, filters and pumps or supplies cooking medium as required to cooking zones or chambers and a supervisory control unit and a control system that can take effect . The cooking appliance can be of the generally conventional type in terms of appearance, design of the cooking zone and adaptation to the various kinds of cooking medium. This fluid handling system and in the control unit and the control system there are significant divergences of the conventional design. However, once such modifications have been made, it is possible to retrofit design cooking appliances and other conventional manner, whether intermittent or continuous, basket or transported in order to operate according to the method of the invention.

Referring now to Figure 1, the flow diagram and process control of a spray cooking apparatus comprising a correction 29 of sprinklers 30, which for purposes of illustration are disposed above a conveyor 16 of the type shown in FIG. Endless mesh band. It could also be an angled rotating cylinder or other means that would transport food items through a cooking zone constituted by the cooking chamber 14. Thus, the cooking apparatus is arranged continuously. It could be intermittently arranged with means of stopping food, such as static or rotating baskets, trays and the like. The thicknesses 30 sprinkle in the heated cooking medium on food items that pass through the cooking zone in the conveyor in order to cook them. The preferred cooking medium can be an oil or a fat, in such a way that the cooking appliance is a fryer. However, other cooking means could be used (with the exception of deliberately supplied air) and the apparatus could be used to perform a number of cooking operations. The cooking apparatus and the components that will be described hereinafter are monitored by the control unit 100, which is preferably a programmable logic electronic control unit (ECU). It is automatically controlled as practicable of the operations of the fryer by aspersion. Manual adjustments to a minimum must be maintained to enhance the quality of food items unless safety or similar considerations dictate that a manual override method be used. The cooking medium is conditioned in the following manner. The cooking means is extracted from the main tank 150 which receives the sprayed cooking medium through the sprinklers 30; and is connected in another way to a supply of cooking means to ensure that the required volume of cooking medium is available within the system. The conditioning system also deals with the new cooking medium at startup and in the latter case. The recovery of the excess cooking medium through the duct 86 to the main tank 150 can be facilitated by the proper design of the bottom of the cooking chamber 14 and, if appropriate, the conveyor 16. A control system can be used. level of the main tank to control the supply as indicated in copending international patent application No. PCT / AU99 / 00073, filed on February 4, 1999, the content of which is incorporated herein by reference herein. The cooking medium is extracted from the main tank 150 by the operation of the centrifugal pump 40 which is driven by a variable speed motor 42. The pump 40 (commercial name?) Can be conventionally provided and selected to operate to supply desired flow rates and speeds of the cooking medium, a pressure range is given which is relevant as described below. The speed of the impeller can be controlled to achieve this object by the control unit 100.

The pump 40 can be a single pump, but can be considered as a pump module having a number of pumps 40 connected as desired. The pump 40 supplies the cooking medium to the filtration unit 50 which is a filter of any desired type to remove substantially all of the food particles and other solid matter before supply to the heat exchanger 240. In that respect, the filtration unit 50 has the function of preventing the formation of a quantity of solid particles, in such a way as to avoid the formation of scale in the heat exchanger conduits, carbonization. The obstruction of sprinkler nozzles. It is also important to avoid, to the maximum extent possible, that these factors have an adverse effect on the quality of the food in the form of discoloration or otherwise. The filtration unit 50 may have a number of filters arranged in parallel, any of which may be kept out of line until the work filter requires cleaning or replacement. The filters are then enabled offline. The filtration unit may be arranged to allow lump removal, backwash and other forms of cleaning. Bypass valves can be provided to facilitate cleaning. The drainage of cooking means from the filtration unit 50 can be taken into account to facilitate cleaning. The separate monitoring of the obstruction pressure in filtration unit 50 can be taken into account. Filters should not be exposed to air during operation to prevent oil degradation. The heat exchanger 240 may also include a module of heat exchangers arranged in series or parallel and having any desired means of interconnection therebetween. In a particularly preferable and advantageous manner, the heat exchangers 240 are of the type of flow heaters that allow heating of the cooking medium in the substantial absence of air or other oxidizing or degrading agents. The advantages of flow heaters are described in I Australian patent No. 666944, the contents of which are hereby incorporated by reference. A particularly preferred heat exchanger has the design described in copending international patent application No. PCT / AU98 / 00552 filed July 17, 1998, the contents of which are hereby also incorporated by reference herein. The heat exchangers 240 can supply heat to the cooking means in any desired manner and can be gas, electric or otherwise. An electric heater will have the heat output of the electric heating elements controlled to allow heating that takes into account the nature of the cooking medium and selected in particular to prevent degradation thereof. The heat output is finally controlled by the control unit 100 in such a way that a temperature of the cooking medium is supplied to the cooking chamber 14 at the desired temperature. The desired temperature is the set point predetermined by the cooking procedure. The control of the PID over the temperature is advantageous, preferably using the modulation of the pulse width of the heating element, as described in the above-mentioned international patent application No. PCT / AU98 / 00552. The control over the heating element can also be an adaptive control as described in more detail below. Reflecting the importance of the temperature of the cooking medium to bring about the desired control over the cooking process, there is a temperature probe 60 located at the outlet of the heat exchanger module 240 in the supply conduit 70. The temperature probe 60 it may be of the conventional type, but a particularly preferred type in a NTC thermistor (negative temperature coefficient). The temperature detected by the probe 60 is used to control the heat output of the heat exchange elements to achieve the desired set point temperature. The heat output varies with the capacity of the cooking appliance. Alarm conditions can be indicated and remedial action taken, as necessary, if the temperature detected in the probe 60 is outside the predetermined limits of high temperature and low temperature. The temperature detected in the temperature zone 60 can be used with that detected in the temperature zone 87, in the conduit of the excess cooking means 86, desirably of the same class as the temperature zone 60, in the control of the operation of the fryer will be described in more detail below. The supply conduit 70 supplies the pressure balancing conduit 72 which supplies a number of supply conduits 64 having sprinklers 30 located over their length. The sprinklers 30 have nozzles of the desired type and can be selected as appropriate given the position in the firing chamber 14 to ensure the desired flow distribution or supply pressure perhaps in accordance with the nature of the cooking process (to allow, for example, toasting followed by slower cooking). This requires an empirical observation procedure for the various food items and cooking procedures that serve as the basis for the proper design and control of the fryer. A pressure transducer 80 is located in the pressure balancing conduit 72. Generally, as the operation of the fryer proceeds, the filters 50 will become occluded or clogged and the pressure in the equilibrium conduit 72 will decrease. The decreasing pressure signal can be monitored by the control unit 100 and compensated by the increase in the speed of the pump impeller 40. This ensures that the required flow rate of the cooking medium to the sprinklers 30 continues to be supplied (or , depending on the design, of any sprinkler module 30) and to the cooking chamber 14. In combination with the careful control over the temperature of the cooking medium supplied by the controlled heat exchange in the heat exchangers 240, control is achieved desired temperature and heat transfer speed convectibo to the food items being cooked in the cooking chamber 14. The variable speed motor 42 of the centrifugal pump 40 is desirably operated only within certain speed limits and if the detected speed exceeds a safe speed, an alarm condition can be indicated and remedial action can be taken n necessary The safe speed can have two bands. If the speed exceeds a fixed proportion of the maximum determined speed of the pump, for example 90%, it is possible to enable cleaning or changing the filter. If the speed is too fair or exceeds the maximum determined speed, the device can be stopped. Alternatively, if the detected speed of the impeller is less than a safe speed, it may indicate a pump failure and take the necessary corrective action. The pressure detected by the occasional transducer 80 can also be used in this way. Thus, for example, if the detected pressure is below a predetermined value, the necessary regular filter cleaning procedures 50 accompanied by enabling can be brought into effect. of 50 auxiliary filters. Otherwise, the control unit 100 may indicate a need for replacement of the filter 50 or off-line cleaning. Generally, if the detected pressure decreases, the speed of the pump impeller 40 will be increased to compensate and, if increased, the speed of the impeller will be reduced to compensate.

As an additional safety precaution, also allowing cross-checking of the correct operation of the temperature probe 60, at least one additional temperature zone 90 may be included in the cooking chamber 14, especially when operated intermittently. The temperature of the food items can be detected. The temperature detected by probe 90 should not be used for control purposes, but comparison with the temperature detected by probe 60 can be used as a verification mechanism. If necessary, the control unit 100 could be programmed to allow control using a temperature detected by the probe 90 for a short period, as a kind of "soft home" mode. The control unit 100 facilitates the realization of the method and is programmed to achieve the desired cooking procedure. Therefore, different cooking programs can be provided for different food items, temperature-time profiles, control of multi-zone cooking apparatuses, nature of the cooking medium and physical properties and other parameters pertinent to the type of cooking appliance and the particular cooking procedure and selected by the operator accordingly. The control unit 100 is also programmed to achieve closed-loop control over the detected temperature differential between the temperature probes 60 and 87. This provides a measure of heat absorbed by food items in the fryer 10 which is also controlled accordingly . The control unit 100 is programmed with programmed search maps with set point temperature differential or energy absorption data for the particular cooking medium, the flow rates of the cooking medium, the nature of the food article and the consumption and / or the heat output of the heat exchanger. The set point data can take the form of a permissible range for the detected temperature differential and can be determined by experiment taking into account the quality of the food achieved for the various values of the temperature differential. If the detected temperature differential is outside predetermined limits, a control response can be initiated. The control response can take several forms. If the temperature differential differs from the range of set points, this may indicate that there is a fault or problem with the supply of the desired heat energy to the food items in the fryer 10. It will be understood that, often, the food items supplied to the fryer 10 will be frozen food items. Thus, in the excess cooking medium flowing to line 86 will show a significant temperature decrease from the temperature detected in temperature probe 60 by a given flow rate of cooking medium that reflects freezing and water vaporization (which allows the control unit 100). Thus, the energy of the excess cooking medium can be calculated in line 86 and checked with energy supplied in the cooking medium to the cooking chamber 14. The difference, when the correction is made, for the heat losses of the cooking chamber. cooking 14 (which can be minimized by isolation) is a value for the energy absorbed by the food items. If the measured value of the energy absorbed is less than the set point programmed to the control unit 100, a number of corrective cooking forms can be enabled. In a first control response, the flow rate of the cooking medium can be increased. This increased heat test to the cooking chamber 14 and, if the energy absorbed by the food items is recovered to the desired level, the flow rate of the cooking means can be maintained at the corrected value. In the system shown, the flow rate of the cooking medium can be increased by increasing the speed of the variable speed motor 42 of the pump 40. The heat output of the heat exchangers 240 can also be increased to heat the increased volume of the medium of cooking to the desired level as necessary. By contrast, if the value of the absorption of the energy is greater than the set point, the flow rate of the cooking medium can be reduced and / or the heat output of the heat exchangers 240 can be reduced. In a special case , the control unit 100 can be programmed in such a way that, when the supply of food items to the cooking chamber 14 ceases, for example when the operation of the fryer 10 is in "standby" mode the supply of the medium is stopped. cooking. It can be simply recirculated and cooking means, without the supply of suppressors 30, during the "standby" mode or the cooking medium can simply be stored in the main tank 150. A second possible control response, particularly which energy absorbed by the food article is smaller than desired, it caused the heat output in the heat exchangers 240 to increase at the same speed flow of the cooking medium. Such a control response is less preferred, since the overheating of the oil is not desirable due to the risk of the detrimental effect on oil quality. A less compromised response may involve small adjustments to the flow rate of the cooking medium by increasing the speed of the variable speed motor 42 and the supply speed of the centrifugal pump 40. In a third possible control response, the duration may be increased of cooking, for example by decreasing the speed of the conveyor of food items. For a given flow velocity of the cooking medium, the exposure time of the food items to the cooking medium is increased. Accordingly, the energy absorbed by the food items must also be increased. Also, the cooking duration can be reduced by increasing the consumption of the food items, for example increasing the speed of the transformer. The control responses described in any combination can be used. This gives maximum flexibility in the control response to the energy absorption variation of the food items from the set point dictated by the control unit 100.

The control unit 100 can be programmed in diagnostic mode. In such mode, the control unit 100 can use energy absorption as a means of detecting an abnormal operation, for example, failure or absorption of the means of supply of the cooking means, in this case the sprinklers 30. That is, if the Nozzles of the thicknesses 30 become clogged, a heating irregularity may result and this may lead, as a consequence, to lower levels of energy absorption by the food items. Thus, if the supply d of the cooking medium, the heat output of the heat exchanger and the supply temperature and the feed consumption is as expected, but the energy absorption measured is abnormal, the control unit 100 can indicate a possible problem with the absorption of the nozzles of the hoppers 30. In any case, if the absorption of energy as measured is outside predetermined limits, the control unit 100 can indicate such condition and the operator of the fryer 10 can be notified accordingly by a visualization and / or audible alarm. In the above embodiment, preferred locations have been suggested for temperature waves 60 and 87. However, the method can be used in some form even if the energy supplied to the cooking chamber 14 and the energy that is supplied is differently measured. comes out of the cooking chamber 14. The flow statement for line 86 may also be desired for greater accuracy, although the "lifting" of the cooking medium, if significant, in calculations could be taken into account otherwise. with the ECU 100. Referring now to Figure 2, a sprinkler fryer having an upper cooking 32 of sprinklers 30 and a lower connection 33 of sprinklers 30 is schematically shown. Instead of each connection 32 and 33 being supplied with medium of cooking through the dedicated fluid handling / conditioning systems provided for each connection 32 and 33 (although this could be done, the fluid handling system can be and including, in sequence, a single pump module 40, a single filter module 50 and only heat exchange module 240. The control of the spray fryer will be conducted in the same manner as for the apparatus of FIG. The system can be made more flexible by the production of both sprinkler collections 32 and 33. Separate flow adjustment points can be set for each collection 32 and 33. The desired cooking and food drop can be achieved with less dependence on the rotating mechanisms with this kind of sprinkler configuration. It is also possible to use the coated products in the upper part more efficiently. In this spray fryer, substantial uniformity of pressure can be achieved in the ducts that supply each series of sprinklers by producing appropriately sized ducts, so that there is minimal variation in static pressure within the ducts. The conduits may be dimensioned and provided with flow control means, including appropriate nozzles and control valves or otherwise to achieve different flow rates of the cooking medium at each outlet of thicknesses 32 and 33. This may be desirable for products Coated at the top where it may be desired to drive at a lower supply pressure and / or as nozzles of lower flow thicknesses at the point of entry or elsewhere to prevent the coating from being removed. The nozzle flow and / or the pressure characteristic can be varied or selected for each cooking procedure or during a cooking process, to achieve the same result or as desired taking into account, for example, the nature of the article food The position-dependent pressure or flow characteristic can be changed in the cooking chamber 14, so that - for example - lower flow nozzles can be used in the inlet portion of the cooking chamber and higher flow nozzles further along the cooking chamber 14. Operation ease can be achieved by making all nozzles work at the same pressure. The nozzles can be threaded or provided with quick couplings to facilitate the connection / disconnection in accordance with the operational requirements or maintenance. Means for controlling the flow in the means of supplying the cooking means may be included to allow variation in the supply behavior of the cooking medium. It will be understood that the pressure transducer 80 located in the balance conduit 172 could be the only transducer employed but, for additional control security a pressure transducer could also be located in the balance conduit 172 if desired. The heaters, including the filters, could be arranged in both members 170a and 170b of the supply conduit 170 to achieve greater heating flexibility for both series 32 and 33. All the conduits 170a, 170b, 172 and 173 are pressure balancing conduits with size large enough to have substantially the same static pressure on its length. In effect, the sprinklers 30 can be arranged in as many rows, providing the same or different flow rates or temperatures of the cooking medium as desired. If this is done, more temperature probes can be included as necessary and the probe 60 can be used for forward feed control over the temperature. Indeed, this is possible even in the simplest construction in which the temperature zone could be located in front of the heat exchanger module 240. Similarly, the spray fridges of figures 1 or 2 can be configured in the cooking mode of Multiple zones and, if necessary, the means of supply or supply of the cooking medium for each zone can cause their flow characteristics to be varied by the control valves or that the pressure or flow restrictions ensure that the speed is controlled of supply and pressure of the cooking medium to achieve particular desired energy transfer rates for the food items in each zone.

In this case, the energy absorption can be calculated by the control unit 100 on a zone basis for the most efficient control. The flow rate and temperature may be varied particularly, as necessary, to respond to the measured energy absorption variation of the set point. In such a case, it may be difficult to vary the duration of cooking as a control response, particularly with the same conveyor passing through all zones. The control unit 100 can be programmed to achieve an appropriate response. Such a spray fryer is illustrated schematically in Figure 5. In the spray fryer, three cooking zones 501, 502, 503 are illustrated. Of course, any number of cooking zones could be selected, as desired. Each zone has cooking means supplied to it by the series of sprinklers 532 and 533 located above and below the conveyor 590 to transport the food items through the zones. Each surplus cooking means of each zone 501, 502 and 503 causes the temperature to be detected by the NTC thermistors 511, 512 and 513 in the branch lines 521, 522 and 523 recovering the cooking medium in excess of each zone. This is necessary in a spray fryer because the detection of the temperature of the cooking chamber itself does not allow the calculation of the absorption of energy since that temperature is almost equal to that for the supplied cooking medium. The temperature of the cooking medium supplied to each zone 501-503 is the temperature detected by the NTC thermistor 520. The thermistor 587 could be used to allow the calculation of an energy balance or cross-check but can be omitted. The control unit 100 can easily calculate the temperature differential for each zone and, accordingly, the energy absorbed by food items in each zone 501-503 can be calculated and the necessary control response can be initiated, which can be adopted. the form described in relation to Figures 1 and 2, in response to the variation of energy absorption from the range of programmed set points to the control unit 100. Although a single conveyor 590 is shown, it is to be understood that each zone 501-503 may be provided with its own conveyor. This would allow the duration of cooking to be varied as a control response to the variation of energy absorption of the set point. It also has operating advantages. If a light wire rod is to be used in order to allow the lower sprinklers to reach the food items on the band, it becomes more difficult to use a single band conveyor that travels the entire length of the cooking chamber 514 to the Same wire gauge due to load restrictions. Basically, a heavier wire gauge would be required to achieve the required strength. A modular construction avoids this problem although the driving axes of each band can be synchronized and driven by the same motor unit by means of roller chains or similar devices. If a conveyor is provided with its own motor, each being under the control of control unit 100, the speed of each conveyor for each zone 501 to 503 can be controlled to achieve the desired dwell time of the food items in each of them. the cooking zones 501-503. Referring now to Figure 3, an intermittent tub fryer of the kind typically found in fast food establishments is shown. The tub fryer could be continuous type. The same principles of operation apply as described in relation to the spray fridges of Figures 1 and 2 taking into account the following differences. The food items will generally be placed in a basket or similar device and immersed in the 120 hot oil tub. Possibly they shake from time to time. Such shaking can facilitate the transfer of connective heat. Thus, it would be preferred to control or automate the shaking, a detected condition of the cooking zone to achieve more precise control over the cooking process. The metal basket can be properly placed in a mechanical shaking device to achieve this result, the amplitude and duration of shaking being under control of the control unit 100. However, the greatest mechanism by which heat transfer will be achieved connective is through the flow rate of the cooking medium beyond the food items in the metal basket. Therefore, the means of supplying the cooking medium need to be located close to the metal basket to achieve this result. Furthermore, it is preferred that plural supply conduits are provided and the tub fryer can be operated in cross flow mode. The heating in a tub of the cooking medium desirably must be avoided, although it is not excluded. Therefore, the system for conditioning the cooking medium, including the heat exchanger module 240, can be advantageously similar to that described for the spray fryer. The flow sequences are provided in the form of diaphragms, control valves or otherwise - including nozzles - to achieve the desired flow of the cooking medium through the supply conduits of the cooking medium. The diaphragms can be constituted by thin metal washers. Such diaphragm 130 is shown located in single supply conduit 270 for purposes of illustration. The pressure transducer 80 is used in control of the operation of the pump 40 as described above. The combination of the pressure transducer 80 and the diaphragm 130 functions as a liquid flow meter and as a means by which convection can be controlled. You could also use dedicated flow and controls that use valves, etc. In that case, a similar control methodology can be expanded as described in relation to Figures 1 and 2. The temperature in the vat is measured by the NTC 90 thermistor, the outlet line 86 by the NTC thermistor 87 and the supply conduit 270 by the NTC 60 thermistor. Thus, a measure of the energy absorbed by the food items in the tub fryer can be achieved by either using temperature differential between that in the duct 270 and a) the output line 86 or b) the tub itself. If the temperature of the tub is used, it can be used alone by omitting that of the outlet line 86 using the differential and the flow outside the stipulated time. The temperature zone 87 can be detected for cross-checking purposes. The variation of the energy absorption of the set point can be treated in the same way as for Figures 1 and 2, the flow rate and the heat output of the heat exchanger being the main control variables. If the food items are transported through the tub, the duration of the cooking can be varied by controlling the speed of the conveyor. If the metal baskets are used, the cooking time can be controlled and the operator alerted accordingly by means of a visual and / or audible alarm. Referring now to Figure 4, a tub fryer 400 having a tub 480 with multiple cooking zones is shown. There are four multiple cooking zones 401, 402, 403 and 404 shown for exemplary purposes, with each of the adjacent zones being separated for flow insurers 410, although liquid transfer between the zones is provided to allow level balancing. Any desired number of zones could be provided. The food items are transported through the four different cooking zones 401, 402, 403 and 404 of the tub fryer 400 via the conveyor 430, passing the food items from left to right. Multiple conveyors or other continuous driving means could be employed and driven at the same or different speeds to achieve the desired cooking duration. Intermittent operation is also possible. Each zone is provided with a temperature zone 440 of conventional type, preferably of the NTC type. The temperature zone 440 provides temperature data for the control unit 100. Cooking means are supplied to the zones 401, 402, 403 and 404 by the supply convicts 451, 452, 453 and 454 constituting part of the supply means of the cooking medium respectively. The conduits 451 through 454 are supplied via the pressure balancing conduit 465 in which the cooking transducer 80 is located which has the same function as described above. The conduits 451 to 454 of the cooking means are provided, near the supply point to each cooking zone, with the diaphragms 461, 462, 462 and 464. The diaphragms can be exposed so that, at a given pressure drop , and the sum of the flow velocities across the multiple diaphragms is equal to the flow velocity of the single diaphragm illustrated in Fig. 3. These diaphragms could be replaced with other pressure restrictions or control valves, if desired. They can be made easily interchangeable. The cooking medium is removed from the tub 480 by operation of the variable speed centrifugal pump 40 through the conduit 86, through the pump 40, through the filtration module 50 and the heat exchanger module 240. Next from this, the cooking medium is conditioned to the appropriate temperature, flow rate and solids content, as dictated by the characteristics of the filtration unit 50 for the return supply through the conduit 470, the balancing customer conduit. pressure 465 and the cooking medium conduits 451 to 454 to the various zones 401, 402, 403, 404 of the tub 480 as described above. There are plural possible modes of operation. The diaphragms 461 to 464 should be of the same size and therefore the flow velocity of the cooking medium to each zone 401 to 404 would be the same. Then, as long as the feed rate of the food item to the cooking appliance 400 remains the same, there is a minimum total flow rate above which the temperature, as detected by the individual temperature zone 440 located in each zone 401 to 404, it's the same. The feeding speed of the food article and particularly the duration that remains in the food items in the cooking appliance can be dictated by the speed of the conveyor 430 which can also be under the control of the control unit 100. It will be understood that the speed The feeding of the food items must be controlled by other means, for example food items can be stored in storage medium provided with gate, star valves or other means that control the feeding speed of the food items either directly or indirectly to the food. conveyor.

Below the minimum flow velocity, a temperature variation would be established that would increase from zone 401 to 404. Thus, the different temperature profiles across the zones could be converted into a desired control parameter compensated in the variations of the product feeding speed by controlling the total flow rate in such a way that the desired temperature profile is maintained, particularly in intermittent commercial fridges. The control unit 100 which monitors the control over the temperature profile can be programmed with search maps that can indicate the alarm condition or the out-of-order condition, if the temperature waves 440 are giving abnormal readings, for example values outside the allowable temperature limits of the set point for house zone 401 to 404. A similar proposal can be provided if the temperature profile through the cooking appliance 400 is outside the allowable limits. The operation of the pump 40 can be similarly monitored and controlled as described above with reference to the sprayers. Desired limits and correlation rules can be programmed to the control unit 100 to achieve this object. The temperature sensed by the temperature zone 460 located after the heat exchanger module 240 can also be monitored in the same way. It can also be compensated, as appropriate, for the discrepancy between this value and those detected by the temperature zones 440 in each zone 401 to 404 of the cooking appliance 400.

The correlation rules and the limits of the control unit 100 may be such as to allow cross-checking of the correct operation of the temperature waves. That is, if the temperature detected by one or more zones is incompatible with the speed of the feeding of the products and / or the heat input rate of the heat exchanger and / or the flow of the cooking bath or the flow to each zone 401 to 404, the ECU 100 may indicate that temperature zones 440 are not operating correctly and that service or replacement is required. The control unit 100 functions, as for the apparatus shown in Figures 1 to 3 and 5 to control the amount of energy absorbed by the food items. Being a multi-zone fryer, control is better directed on a zone basis, which will be previously described the control response. As the flow characteristics are identified for each zone, as described above, a measure for the energy absorbed in each zone can be calculated by the control unit 100, using a temperature zone 487 in line 486 and realizing an energy balance . However, the cooking appliance 400 may be designed with a main outlet duct to which the cooking means is supplied in excess of each of the zones 401-404. A branch conduit connects each zone to the main outlet conduit and a temperature zone would be located in each branch conduit, in such a way that the energy absorbed for each zone can be specifically measured. A control response can then be initiated by varying the flow of the cooking medium to each zone. The cooking duration in each zone can be controlled as a response to each error in the absorption of energy, controlled the conveyor speed separate conveyors are provided for each zone 401 to 404. In an alternative mode, it may be possible to use the profile of temperature through zones 401-404 to identify problems with the absorption of energy by food items. Thus, if the profile varies from the programmed to the control unit 100, a control response can be initiated to correct the temperature profile. The pressure transducer 80 measures the pressure in the equilibrium conduit. The speed of the centrifugal pump 40 can be varied by a variable speed motor 42 in which the pressure varies to maintain the desired flow rate. If the pressure drops below a permissible level and / or the pump speed increases above a certain level, the control unit 100 may indicate that the filtration units 50 require cleaning or replacement. A regular cleaning procedure can be carried out automatically, as described above. If the speed of the pump exceeds a safe level, detection can be carried out. Another mode of operation contemplates that diaphragms 461 a 464 are of different sizes, so that the desired proportioning of the flow rate of cooking medium to each zone 401 to 404 can be achieved. This can also be achieved by replacing the diaphragms with speed control valves ensuring that achieves the desired proportion. It will be understood that such proportioning can be controlled, such that equal flow velocity of the cooking medium occurs to each zone, thus also covering the first mode of operation as described above. This mode of operation is particularly suitable for the nature of the typical cooking process in which most of the energy in the vaporization of water is consumed at the beginning of the cooking process when food items, especially frozen food items, are supplied, to the cooking zone of the cooking appliance. In such cases, for a substantial portion, up to 75% of the cooking time, there is little absorption of fat to the food items due to the intense flow of water leaving the food items. In such cases, it is inferred that a relatively high amount of energy is needed at the beginning of the cooking process and a relatively small amount towards the end of the cooking process. The ECU 100 will allow this. Cooking at constant temperature can be achieved by selecting the size of the diaphragms, in such a way that the ratio of the desired energy transfer rate between the zones, as desired for example in the case of the cooking process of the type described above, be equalized by the ratio of liquid flow through the diaphragms.

It will be understood that variations in the amount of product introduced into the cooking appliance cause variations in the heat energy requirements. Temperatures can be maintained substantially constant in all zones by appropriate variation of the total flow rate of the cooking medium with input of the product amount. The requirement of the cooking medium can then be used, since only that desired flow rate will be required to achieve cooking at the heat transfer rate and the desired temperatures. The consequent reduction of the total flow rate of the cooking medium allows for a smaller fluid handling system, smaller filtration area and smaller cross-sectional area for the flow path through the heat exchange module. The diaphragms 461 to 464 of the tub cooking apparatus can be resized, as necessary, so that the desired heat exchanger outlet temperature and total flow rate, the desired temperature and the transfer rate can be achieved. of energy for each zone 401 to 404. By analogy, the same methodology can be applied to the single-zone cooking appliance. In single-tub intermittent cooking, the constant temperature can be achieved by varying the flow rate of the cooking medium through the tub 480 during the cooking time. The advantage of a better quality of the food products and the consistency in terms of color, texture, flavor and oil content (if the cooking medium is oily) can be achieved with the technological flexibility of the products. food in the adaptation of the cooking procedure, as required for various kinds of food item. The skilled reader can make modifications and variations to the cooking apparatus and control methods of the invention with consideration of exposure. It is conceived that such modifications and variations are within the scope of the present invention. In particular, it is not conceivable that the mechanisms of enhancing the collective heat transfer described herein are limiting and other mechanisms may be used instead., or in addition, of those described. For example, in the case of the tub fryer, mechanisms could be included for stirring the cooking medium in the different design tub over the supply ducts of the cooking medium. The cooking medium could be selected taking into account its physical nature in such a way that it is a means more conducive to the transfer of convective heat to foodstuffs, thus one can consider the thermal conductivity, the viscosity profile and temperature and / or density-temperature of the cooking medium for the purpose of selecting the most appropriate cooking medium. Any kind of cooking appliance can be controlled by the method of the present invention. For example, the cooking apparatus set forth in Australian Provisional Patent Application No. PP5623, filed September 1, 1998, may also be operated.; and Australian Provisional Patent Application No. PP5622, filed September 1, 1998, the content of which is hereby incorporated by reference herein, in accordance with the method of control exposed.

Claims (24)

NOVELTY OF THE INVENTION CLAIMS

1. - A method of cooking at least partially food items, by exposing them to a liquid or heated cooking medium supplied by means of supplying cooking means to a cooking zone of a cooking appliance that includes a control unit which, during a cooking method: (a) controls the temperature of the cooking medium supplied to the cooking zone to a specific predetermined set point for the food items, by controlling the heat output of the heat exchanger to heat the cooking medium throughout the cooking procedure; (b) controls the speed of the convective heat transfer to the food items, directly controlling a detected condition of the cooking medium supplied to the cooking zone, different from the temperature controlled in step (a), in relation to the speed of convective heat transfer; and, optionally, (c) controlling the convective heat transfer speed of the food items, by controlling the detected condition of the cooking zone related to the convective heat transfer rate.

2. The method according to claim 1, further characterized in that the energy absorbed by the food items is measured and used to control the cooking appliance according to at least one of steps (a) to (c) ).

3. The method according to claim 1 or 2, further characterized in that, in step (b), said detected condition of the cooking medium supplied to the cooking zone is one or more of the following: supply pressure of the cooking means, flow velocity of the cooking medium, density of the cooking medium, viscosity of the cooking medium and turbulence of the cooking medium; and, if step (c) is used, one or more of the following: type of sprinkler, type of nozzle, type of hydraulic restriction, turbulence in the cooking zone, cooking zone temperature, cooking duration and frequency of agitation of the metal basket.

4. The method according to any of the preceding claims, further characterized in that the cooking appliance has multiple cooking zones that have a cooking means supplied to each by the means of supply of the cooking medium.

5. The method according to claim 4, further characterized in that at least one variable related to the convective heat transfer is controlled for each cooking zone to achieve a desired energy profile through the multiple cooking zones.

6. The method according to claim 4 or 5, further characterized in that the temperature is controlled for each cooking zone to achieve a desired temperature profile through the multiple cooking zones.

7. The method according to any of claims 2 to 6, further characterized in that the temperature differential between the supplied and the removed cooking medium is detected and used for the control of the cooking appliance according to at least one from step (a) to step (b).

8. The method according to any of claims 4 to 7, further characterized in that said means of supply of the cooking means includes at least one of the sprinkler nozzles and flow restrictions.

9. The method according to claim 8, further characterized in that the means of supply of the cooking means for controlling the cooking process is controlled according to at least one of the step (a) to step (b).

10. The method according to any of the preceding claims, further characterized in that it is controlled that the temperature and the convective heat transfer speeds are variants with respect to time during a whole cooking process.

11. The method according to any of claims 1 to 9, further characterized in that it is controlled that the temperature and the convective heat transfer rates are constant throughout a cooking process.

12. - The method according to any of the preceding claims, further characterized in that said cooking means is an oil or fat and the heating of the cooking medium is conducted outside the cooking zone in the substantial absence of air.

13. The method according to any of the preceding claims, further characterized in that the cooking apparatus is a tub fryer.

14. The method according to any of the preceding claims, further characterized in that the cooking appliance is a spray fryer.

15. The method according to any of claims 7 to 14, further characterized in that said control unit is programmed with set point temperature differentials data for particular cooking processes.

16. The method according to claim 15, further characterized in that said set point temperature differential is a function of one or more of: cooking duration, flow rate of the cooking medium, nature of the food article and consumption of the food. food article.

17. The method according to any of claims 12 to 16, further characterized in that energy absorption is measured to detect the abnormal operation of said means of supply of the cooking medium.

18. - A cooking appliance operated according to the method according to any of the preceding claims.

19. A cooking appliance operated according to the method according to any of claims 1 to 17, including: a) at least one cooking zone in which the food items are cooked; b) means for supplying the cooking means for supplying the cooking medium to each cooking zone; c) means for removing the cooking medium to remove the cooking medium from the cooking zone; and d) conditioning means for conditioning the removed or new cooking means for supply to each cooking zone, wherein the conditioning means include, in sequence, pump means, filtering means and heat exchange media to which it passes. successively at least a portion of the cooking means.

20. The cooking appliance according to claim 19, further characterized in that said pump means is at least one variable speed centrifugal pump.

21. The cooking appliance according to claim 19 or 20, which includes means for measuring the energy absorbed by said food items during cooking.

22. The cooking appliance according to any of claims 19 to 21, further characterized in that said means of supply of the cooking means includes a pressure sensor, detected pressure that is used to control the speed of said centrifugal speed pump variable.

23. The cooking appliance according to any of claims 19 to 22, including multiple cooking zones. 24.- The cooking appliance in accordance with the claim 23, further characterized in that the means for supplying the cooking means are arranged to establish the desired profile of temperature or energy through the constituent cooking zones.