Method of and apparatus for heating an item of food

(54) Name: Methods of cooking a heated food and therefore intended oven (56) Published publications: DE 2 541 196 (A21B 1/14), US 3 847 069 (99-443)

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IN

The invention relates to a method for heating a layered foodstuff and an oven with different strong heating, baking and roasting zones.

Hot foods, such as pizza pies, are often cooked at the place where they are eaten, where they can be so large in size that they form a single portion. If you try to bake such foods quickly, the baking becomes easily uneven. In addition, the same equipment will often be used for baking both initially frozen and frozen pizza pies, and in the first case, the degree of freezing can vary from one place to another on one pizza pie, resulting in 10 for uneven rise, uneven baking and uneven browning, and sometimes the food can also be partially burnt before it is finished eating. Excessive overheating with insufficient rise of the dough can also occur. To avoid this problem, a separate oven was previously used to thaw the dough before baking, but such an arrangement becomes difficult because the baker needs to use two ovens, must open and close the oven door several times and must be able to estimate the baking time.

A model for solving the above-described heating problem provides the furnace shown and described in U.S. Pat. No. 3,847,069. This furnace has a multi-level vertical axis line helical runway 7703823-0 path, electric heating elements between runway levels and a rotatable reel or winding for advancing circular food items or molds down the tread and over the heating elements. An epicyclic movement of the molds contributes to a uniform heating of the food.

Said patent specification discloses the heating elements arranged in two ways. According to the first, an unbroken piece of a heating element is arranged below a relatively wide, open tread, the heating element extending from the top of the tread to its lower part. According to the second method, the upper section of the tread lacks heating elements, whereas a lower section of the tread is equipped with a heating element.

However, it has been found that the known oven cannot heat either a frozen or a chilled but not frozen food in a reproducible and satisfactory manner. The known oven can not apply very strong heat but must work with rather low heat intensity, which is why each food unit requires quite a long time. Furthermore, the known furnace needs a long runway and a large furnace chamber, which means high manufacturing cost and a large heat loss through the furnace walls and consequently large power consumption and demands on power with high current. In the known oven, continuous power supply is required at a level sufficient for heating a food product regardless of whether the oven is loaded with food or not, and the heating element arrangement does not allow. nor variation of the power supply to the heating element upon increasing or decreasing the amount of food in the oven.

Furthermore, the design of the known furnace is too costly for commercial use, and the furnace is difficult to build, assemble and clean.

All food stoves are subject to splashing and accumulation of grease and cooking residues, and they must therefore be able to be cleaned periodically. Known ovens that consume energy far beyond the actual need can no longer be tolerated for economic and other reasons.

The above-described disadvantages are remedied by the present invention, the features of which are set forth in the claims and which will be explained in more detail below with reference to the accompanying drawings.

Fig. 1 shows in schematic vertical section an electric oven for carrying out the method according to the invention;

Fig. 2 is a perspective view of a food item unit cooked in the oven and an associated mold;

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Fig. 3 is a side view, partially in section, of a preferred embodiment of the oven according to the invention;

Figures 4-7 show horizontal sections along lines IV-IV, VV,

VI-VI and VII-VII in Figure 3.

The method according to the invention will be described first with reference to Fig. 1.

The oven 10 diagrammatically shown in Fig. 1 has an insulated casing 11 having an inlet 12 and an outlet 13. Inside the casing 11 is a tread 14 which serves to support food items. The tread 14 is a conveying path and in this case runs helical, but it can also be round, flat, sloping or zigzag. An electric radiant heating element 15 is mounted above the tread 14. The tread 14 has a first section 16 immediately adjacent the inlet 12 and a second section 17, which winds under the first section

16th The heating element 15 is mounted above both sections 16 and 17 and has an end 18 located above the second section 17 during the first section 16. The section of the tread 14 above which the radiant heating element 15 is arranged is also referred to here as the heating zone 15a.

The tread 14 has a lower section 20 leading to the outlet 13.

Under this lower section 20 there is a convective heating element 21, which heats air and which also to a certain extent emits radiant heat (infrared heat). A screen 22 is placed between the convection heater element 21 and the lower section 20 of the tread. The section of tread 14 above the convection heater element 21 is also referred to herein as roasting zone 21a.

The tread 14 also has an intermediate section 23 which is not directly exposed to either the heating element 15 or the heating element 21. This section 23 is heated by convection from the heating elements 15 and

21 and is also referred to herein as the cream zone 23a.

Radiant heater 15 has less than half the power of convection heater 21; for example, the radiant heater 15 may have an effect of 575 - 600 W, while the convection heater 21 may have a power of 2000 W. The radiant heater 15 is normally switched on and maintains the oven temperature at approx. 300-375 ° C, while the convection heater element 21 is normally disconnected. A thermostat 24, set for on and off in the specified range, is arranged to connect to the convection heating element 21 and has a sensor element 25 located in the baking zone 23a, namely immediately below the inlet 12.

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In Fig. 2, a mold 26 is shown formed by a washer with a cylindrical rim 27 and an annular flange 28. Inside the flange 28, the bottom of the mold 26 is open. A single food portion 29 during cooking is placed in mold 26 and supported by the flange

28, which is of sufficient diameter to provide sufficient support, at least for some foodstuffs. The mold 26 and the food unit 29 run through the oven 10 together.

The food item 29 is layered and has at least two layers. Examples of foodstuffs of this type are pizza pies, toast islands, pot pies, fruit pies and sandwiches. Regardless of the designation, the food product has a crust of some kind, hereafter referred to as bread, and an upper portion with a greater heat capacity. The bread can be a bread in the usual sense, either soft or hard, and made from wheat flour, maize flour, potato flour, rice flour or similar flour.

the top, which can form a filling if the bread is toasted and, for example, has the shape of a pie bottom, is usually made of tomatoes, cheese, meat or fish, fruits, vegetables, eggs and the like. All of these tops have high moisture content and require much more heat for thawing and / or heating than the bread. Because of its greater heat capacity, the filling is subjected to relatively strong heat, which would burn the bread if applied to it. The bread is heated slowly, so that its bottom remains quite porous and finally the bread is browned immediately prior to dispensing from the oven. If the bread was to be roasted first or at an early stage in cooking, it would retain the moisture that seeps into the bread from the top and this would make the bread wet, which is inappropriate.

In cooking, the food 29 is placed in the oven 10 with the bread underf and the top up. The day 10 is preheated to the vicinity of the desired one; heating temperature. For example, if the food is a pizza pie, the oven temperature is approx. 315 ° C. The oven temperature is maintained at the preheating temperature by the normally switched heating element 15. If the mains voltage is low, the convection heater element 21 can be switched on and off from time to time to help maintain the high temperature. The radiant heater element 15 is sized to provide a power sufficient to maintain the furnace at the desired temperature at normal temperature without the aid of convection heater element 21 at normal supply voltage.

In carrying out the method according to the invention, the food 29 is placed in a cooled state, either frozen or frozen, in the mold 26, which is then inserted into the oven 10 through the inlet 12 and placed on it.

7703823-0 first section 16 of the runway 14. When the food 29 is placed on the runway 14, it is immediately exposed to the warm air in the furnace 10 and also to the relatively intense or strong infrared radiant heat which is directed down from the radiant heating element 15 towards the overlay of the food item. The food item 29 is moved along the tread 14 and passes through the strong heating zone 15a below the radiant heating element 15. While the food 29 is passing through the high-heat zone 15a, the bread layer is also subjected to a certain infrared radiant heat from the heating element 15, since the end 18 of the radiant heating element 15 is below the first section 16 of the runway 14. The screen 19 serves to partially shield the bread layer from radiant heat or radish heat gets burned too soon. The strong heating zone 15a extends along one and a half turns of the tread and has the same extent along it as the heating element 15. While the food 29 moves along the first half turn of the strong heating zone 15a, it is thus subjected to strong heat (heating heat) both from the top and the bottom. thereafter, the application of radiant heat to the bread layer ceases, while the application of radiant heat to the overlayer continues. A maximum amount of radiant heat can be applied to food 29 if the time during which the overlayer is exposed to direct radiant heat is about twice as long as the time during which the bread layer is exposed to direct radiant heat in the high-heating zone.

When the food 29 is inserted into the oven 10 it is cold, which is why it immediately starts to cool the oven air. The cooled air flows downwardly toward the thermostat sensor 25, and the convection heater element 21 is switched on. The convection heater element 21 replaces the heat loss to the food item 29 and keeps the oven 10 at the selected temperature with variations within acceptable limits. The convection heater 21 has about three times the power of the radiant heater 15 and provides a very powerful heat supply to the furnace. The oven temperature is sensed in the roasting zone 23a to control the convection heating element 21 in the roasting zone 21a.

When the food 29 reaches the end of the baking zone 15a, the overlayer is browned by the radiant heat and the bread layer is heated. The food 29 is further advanced along the tread 14 and transferred to the baking zone 23a, which is convectively heated by both heating elements 15 and 21. As the food 29 is moved through the baking zone 15a, it is exposed to hot air which gradually raises the temperature of both the overbread and the bread layer. and smoothing the temperatures therein. Thereafter, food 29 is transferred to the roasting zone

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21a, and as it passes through it, the very hot air flowing from the convection heater element 21 comes into contact with the underside of the bread layer. Due to its high power, the convection heater element 21 also emits radiant heat to some extent, and the screen 22 serves to protect the bread layer from carbonization under the influence of the Imatware exposed to the incident radiant heat. About the total time during which | the partially shielded incident radiant heat from the convection heater element 21 and the radiant heat from the first half turn of the heater element 15 is approximately equal to the time during which the upper layer is directly heated by radiation, both the overlayer and the bread layer are well and evenly browned. This result is achieved by applying less heat from the heating element 15 to the bread layer than to the overlayer. The food item should be in the strong-heat zone for a period longer than the time in either of the roasting and roasting zones in order for the overlay to be well warmed. Depending on its composition in relation to the bread layer, the overlayer should be intensively heated by radiant heat for a period of between one quarter and half of the time that the food 29 is in the oven 10.

The food 29 is advanced evenly and continuously along the tread 14 from the inlet 12 towards the outlet 13, and during the feeding, the food 29 is continuously rotated around its center as it slides forward on the tread 14. The rotation should comprise at least one lap in each of the strong-heating, baking and roasting zones. for the heating to be even.

When the food 29 reaches the end of the runway 14, it is automatically discharged from the roasting zone 21a and from the oven 10.

The above-described procedure allows and makes it possible to apply strong heat and shortens the time required for cooking the food. The method can be applied to simultaneous cooking of successive food units in the furnace 10. The radiant heating element 15 emits a predetermined radiant heating effect regardless of the temperature of the furnace 10, and the convection heater element 21 with its greater power maintains the air temperature in the oven 10 and burns bread.

Figures 3-7 show a preferred embodiment of an oven for carrying out the described method.

The furnace 30 shown in Fig. 3 has an insulated foot 31, an enclosed housing 32 having an inlet 33 and an outlet 34, and an oven chamber inside the foot 31 and the casing 32. Inside the furnace chamber 35 is an annular tread 36 with vertical axis, in this case in the form of

7703823-0 a multi-tier screw coil, and one with this coaxial reel or winding 37 with carrier 38 for advancing a food unit along the tread 36. The tread 36 has an annular support surface 39 and a flange 40 serving to retain the food unit on the support surface 39 with a portion. of the food unit projecting out over the inner edge of the carrier surface 39. The drive wind 37 is stored for rotation about the vertical geometric axis of the tread and is rotated by a motor 41. As the wind rotates, the carriers 38 move along a circular path adjacent to the inner circular edge 42 of the carrier surface 39, contacting the inwardly projecting portions of the food items and carrying them along the tread 36.

A food unit to be cooked is inserted through the intake 33 and placed on a dispensing end 43 of the tread 36, whereupon one of the drivers 38 on the wind 37 is applied to the food and feeds it around and down the tread 36 to a withdrawal end 44, where the food falls out from the tread 36 and slides down a discharge ramp 45 leaving the furnace chamber 35 through recess 34.

The tread 36 may have a flat support surface 39 in the form of a ring or part of a ring, and if it extends helically, it may comprise a single lap. Furthermore, the carriers 38 can move outside, above or through a slot in the carrier surface 39. Regardless of the shape, a conveyor moves the food along a path inside the oven chamber and through different heating zones.

An important characteristic of the furnace 30 is that it has different strong heating, baking and roasting zones, where the strong heating and roasting zones have their own heating elements. A radiant heating element 46 is mounted above the carrier surface 39 and forms a strong heating zone 46a, over a first section of the carrier surface 39. The radiant heating element 46 extends midway across the runway end 43 of the runway and extends therefrom about one and a half turns along and above the carrier surface 39, and thus extends for approx. a half turn under the carrier surface 39. As can be seen in Fig. 4, the radiant heating element 46 has a curved end 47 where it turns half a revolution to return along the tread 36. The inlet 33 lies between the loading end 43 and the radiant heating element 46. At the bottom of the furnace chamber 35, a convection heating element 48 emits a limited amount of radiant heat. Immediately above the convection heater 48 is the lower portion of the carrier surface 39, which forms a roasting zone 48a. Between the strong heating zone 46a and the roasting zone 48a, an intermediate section 39a of the support surface 39 forms a cure zone 39b which lacks

7703823-0 heating elements but heated by convection from both heating elements 46 and 48. Each zone 46a, 39b and 48a comprises at least one turn or level of the carrier surface 39. A thermostat 49 with a sensor 50 regulates the oven 30 within those limits and in that way. as indicated above the oven 10.

The tread 36 is preferably made of perforated metal sheet (see Fig. 4), with the support surface 39 having holes 39c having a total surface of between 40 and 60% of the surface of the support surface 39.

Fig. 5 shows the rotation of the reel 37 with the carriers 38 abutting the food molds 26 containing the foodstuffs 29, the flange of the tread 40 retaining the molds with the foodstuffs on the carrier surface 39 while the carriers 39 move the molds and the foodstuffs along the tread 36. shape 26 with the food 29 also around its own geometric axis.

Figures 6 and 7 show the structure of the convection heating element 48. This heating element 48 is in the form of a semicircular C-shaped loop with an arc length of less than 360 ° and a pair of spaced apart ends 54 and 55, which form an intermediate opening to the discharge ramp 45 and the outlet 34. The ramp 45 and the outlet 34 are both below the heating element 48, so that hot air from the heating element cannot flow upwardly through the outlet 34.

Another important characteristic of the furnace lies in the design of a helical tread with minimal dimensions and an oven casing of similarly minimal dimensions.

As can be seen in Figures 3 and 4, the helically extending tread 36 has support members 51 which are disposed outside the tread. At least two such support members 51 are needed, and preferably there are three. The support members 51 have their lower ends attached to the furnace bottom 31 and support the tread 36. The electric radiant heating element 46 has low-resistive connection portions 52, which descend to the outside of the tread 36 to the furnace bottom 31, where they are!

electrically connected to an electrical power source. The oven cover 32 has an internal cylindrical wall 53 which is positioned as close to the support member 51 and the element connections 52 as possible. This design gives the minimum possible diameter and surface of the wall; -53.,. and thus the heat transfer surface becomes the smallest possible. The heating elements of the heating element 52 are located radially between the base elements 5Ί.

The operation of the furnace 30 will be readily apparent from the foregoing description. Since the heating capacity of the oven chamber is low, the heating element 48 is switched on each time a food unit 29 is inserted. When the convection heater 48 is switched on, the temperature down in the furnace chamber 35 exceeds the temperature in the upper portion of the furnace chamber by at least 111 ° C, and the warm air exiting the heater 48 flows upwardly around the tread 36 and also through the holes 39c in the tread 39. Thermostat encoder 50 is shielded from both heaters

46 and 48 of a turn or layer of the carrier surface 39. In the oven described, a frozen pizza pie can be baked and roasted in 2 minutes, and a frozen pizza pie can be thawed, baked and browned in 3 minutes; the longer time is obtained by decreasing the rotational speed of the wind 37. The oven 10, 30 gives very good results even with patches of fish, meat and poultry, potatoes, eggs and omelettes when using closed bottom molds.

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