FR2526133A1 - HOT AIR OVEN FOR PREHEATING PRE-COOKED FOODS AND RELATED HEATING METHOD - Google Patents

Abstract

THE OVEN INCLUDES A ROTATING ANNULAR TABLE ON WHICH A LOAD OF FOOD IS ARRANGED AROUND A CENTRAL ZONE 24, AN AIR HEATING ASSEMBLY AND A PROPELLER DRIVING THE HOT AIR IN A TOROIDAL MOVEMENT WRAPPING THE LOAD, A STRANGLE BEING CLEANING AT THE EXIT OF THE CENTRAL ZONE IN ORDER TO BETTER A SIGNIFICANT PART OF THE AIR COMING INTO THE CENTRAL ZONE THROUGH THE LOAD. A CURVED SCREEN 31 LONG THE INTERIOR SURFACE OF PART OF THE LOAD, PREVENTS HOT AIR FROM PASSING THROUGH THE SAID PART OF THE LOAD AND THUS DIVIDES THE OVEN INTO A HOT ZONE, AND INTO A VERY HOT ZONE, THE TEMPERATURE OF THE LATTER BEING VERY HIGHER THAN THE DESIRED TEMPERATURE FOR SERVING FOODS SO THAT THE TRANSMISSION OF HEAT BETWEEN HOT AIR AND THE FOOD, WHICH DEPENDS ON THE DIFFERENCE BETWEEN THEIR TEMPERATURES, REMAINS HIGH DURING THE ENTIRE HEATING OF THE FOODS AT THEIR SERVICE TEMPERATURE.

Description

The present invention relates generally to a technique for

  the rapid preparation of meals according to which food is first cooked, then refrigerated and stored before undergoing an operated reheating without affecting their texture, their taste or their nutritive qualities, and targets in particular a hot air oven

  for reheating food, and the corresponding process.

  To meet the growing demand for quick, inexpensive meals, fast food techniques have been developed whereby the food to be served is frozen to the core and stored and, when a customer orders a particular item listed on the menu, we extract this dish from the freezer and cook it In some cases, the frozen dish is already cooked, so that it is enough

  thaw and reheat it.

  Admittedly, known techniques of this kind make it possible to pre-

  prepare relatively inexpensive meals and serve them quickly, but often the dishes thus obtained are not very appetizing. This is so because if freezing preserves food well and prevents it from spoiling, it is often at the expense of the quality and taste of the product During freezing, the moisture contained in the food is converted into ice crystals which exert a

  destructive effect on the internal structure of the food

  What characterizes frozen food is that it

are tasteless and flabby.

  In addition, when reheating an already cooked and frozen dish, it

  is difficult to prevent the product from remaining cold inside-

  lying while the outside is hot and, if we try to do well

  heat the whole food, it risks being over-

  heating and reheating which makes it lose its nutritional value

and its flavor.

  One of the main reasons why the techniques

  adopted in self-service restaurants are unsatisfactory.

  is that the heated food is necessarily enclosed in a closed heating enclosure that must be opened to access its content In an establishment serving many meals, where it is necessary to keep hot a large number of dishes ready to be removed by consumers , this requires a complicated structure with multiple cells with individual doors that

  you have to open to remove the food, then close.

  The object of the present invention is to provide a method and an apparatus for a fast food service, such as to allow the reheating of a previously cooked and refrigerated dish and its making available to the customer without degrading the texture, the

  flavor and nutritional qualities of this dish.

  According to a process covered by the invention, the food to be served to the customer is initially fresh, uncooked. For example, it will be assumed that the serving dish includes fish and fries and that the ingredients for departure are therefore fresh cut fish

  into pieces and thinly sliced potatoes.

  We will also assume that we have to prepare a hundred port-

  tions of fish and fries, each of which must be served in an individual dish large enough to receive a full portion To this end, a quantity of freshly cut fish and potato slices is cooked sufficient for one hundred servings After

  cooking, we divide the cooked products to fill a hundred dishes -

  The dishes must then be refrigerated to keep the cooked portions until they are served, possibly several days later. The dishes are kept under refrigeration at a temperature just above their freezing point which, in practice, can be from -7 to 1 l C Indeed, when the humidity

  contained in the food is rich in dissolved salts, the point of con-

  freezing may be well below Oa C It is important that the temperature

  refrigeration is close to that of freezing, but without falling below the freezing point, this to avoid

  formation in the food of destructive ice crystals, It im-

  also covers the dishes with tight lids to avoid

  loss of moisture and volatile constituents.

  Then, when distributing pre-cooked meals to customers, the dishes are removed from the refrigerator and loaded into a heating device capable of bringing the food to a temperature of more than 60 C, sufficient for it to be eaten hot but not

  so that they undergo an annealing If some of the portions

  items in the heater are not consumed at

  during a service, the waterproof dishes can be replaced

  in the fridge and chill again until

  we need them again and we warm them up again.

  Refrigeration, being operated at a temperature just

  above freezing point, preserves food without

  improve their quality, as for the subsequent heating of the chilled dishes

  res, since it is carried out at a temperature sufficient for consumption, but lower than that of cooking, it does not

  also has no untoward effect It is therefore possible to

  put the pre-cooked dishes contained in the dishes at more than one cy-

  refrigeration-heating key without damaging them.

  During the reheating stage, the speed at which hot air transfers heat to relatively cold food in the oven depends on the temperature difference between the hot air and the food: the more this difference is great and

  the faster the heat transmission.

  Since the temperature of the hot air is almost uniform throughout the oven, heat transmission is very rapid at the start of heating, during the reheating stage where the two heating sections operate; but as the temperature difference between the hot air and the food then decreases, the heat transmission becomes increasingly slower and becomes very weak near the service temperature,

  hence an excessive duration of the reheating stage.

  The object of the invention is to overcome this drawback and propose

  to establish a heating regime in two zones.

  We will now describe the invention in more detail with reference to the accompanying drawings, in which: Figure 1 shows in perspective a dish with a sealed cover; Figure 2 shows this dish and its raised lid; Figure 3 shows in perspective a rack for receiving stacked dishes;

  FIG. 4 represents a rack loaded with dishes or

  sier garnished; Figure 5 shows in perspective a hot air oven according to the invention for the heating of lined lockers of the type shown in Figure 4; Figure 6 is a top view of the oven; Figure 7 is a longitudinal sectional view Figure 8 is a cross-sectional view; Figure 9 is a longitudinal sectional view of the lower part of the oven;

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  Figure 10 is a sectional view of the heat shield;

  Figure 11 is a circuit diagram of the electrical control

  kiln stick; FIG. 12 schematically represents a hot air oven with two zones according to the invention; Figure 13 shows in perspective the screen that divides the

oven in two zones.

  Locker In Figures 1 and 2, we see in T a dish suitable for

  refrigerate and later serve a pre-cooked dish, after reheating

  hot air in a furnace according to the invention The flat T, hexa-

  gonal, has a short rear wall Sif a long front wall

  52, two long side walls 53, 54 adjacent to the short pa-

  rear king and two short side walls 55, 56 adjacent to the long front wall The top of the dish is bordered by a rim F, on which an elastically sealed cover T of form c fits

  geometric matching that of the dish.

  The dish and its lid are both made of a plastic material.

  synthetic, such as polyethylene, approved for food and inert towards them, capable of supporting large

  temperature differences involved in refrigeration and re-

  food heating The lid T is made of less dense material than that forming the dish T, in order to be more flexible than this dish

  so that it can be detached from the latter without difficulty.

  The dishes are handled in batches and not individually.

  As illustrated in FIGS. 3 and 4, a stack of ten dishes T is fitted into a cardboard box 10, to be discarded after use, with a cross-section matching that of the dishes. The box 10 has upper walls Oa and lower lob, a rear wall 101 and two side walls 103 and 104 of lengths corresponding to those of the short rear wall 51 and long side walls 53 and 54 of the dishes, so that the stack of dishes fits exactly in

  the locker, the front 52 and side walls 55 and 56 remaining ex-

  placed so that the dishes can be easily removed from the rack

  practical, the front wall of the dish can be identified

  fication of the dish contained in the dish.

  In each of the rear walls 101 and side 103 and 104 of the rack 10 is provided a row of large Ids holes 11 intended to allow hot air to enter the rack for "hî_éa the dishes contained in the dishes that are emi Doltés La v _-, ation of

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  hot air in the rack is facilitated by the edges of the dishes, which maintain gaps between the side walls of the dishes and those of the rack, and by ribs R protruding from the bottoms of the dishes to keep these bottoms spaced from the lids of dishes under underlying so each dish in the stack is swept by

  hot air entering the locker.

  The whole of a rack and the stack of dishes it contains will be referred to below as "fitted rack" C To facilitate handling,

  preferably surround the box lined with a material envelope

  re transparent plastic which is used to keep the dishes in the rack We remove this envelope before loading the rack

  in the hot air heating oven In practice, each

  sier garnished includes dishes containing the same dish cooked in advance,

  for example portion of spaghetti or "Chinese plate".

  To indicate that the dishes loaded in the oven are in progress

  reheating and not yet ready to be served, a strip of pa-

  pier can be stretched between the upper 10 a and lower l Ob walls of the rack, across the exposed front walls 52 of the T dishes. This strip may be marked indicating the nature of the dishes

  lining the locker The operator of the hot air oven only breaks it

  After having been informed, by a warning lamp or other means, that the dishes contained in the dishes are at the desired temperature

  to be served, hereinafter called "serving" temperature.

  The hot air oven according to the embodiment which will be described

  is suitable for eight compartments with ten dishes, four

  twenty dishes loaded with food Since the lockers are all

  garnished with different dishes cooked in advance, you can

  summing up a card listing eight dishes Even if all the dishes are not distributed during a service, there is no waste because, as we said, we can put the uneaten dishes in a cold room and refrigerate them again until needed and the

then reheat.

Hot air oven

  In FIGS. 5 to 11, an open oven can be seen according to the invention.

  tion, able to receive eight fitted lockers of the kind described above

  and bring the food they contain to a suitable temperature

  temperature, for example 770 C, then to maintain them at this temperature-

  re with minimal heat losses Thus, the energy consumption of the oven is relatively low, although the oven has

  a permanently open access bay through which one can

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  selectively milk such or such dishes.

  The oven has a circular base 12, lined with insulation

  thermal, and a circular roof 13, also provided with thermal insulation

  that the roof is supported above the base by three metal posts 14 equidistant, formed by flat bars whose lower sections are folded under the base 12, then bent downward to form feet 15 which support the base 12

above ground.

  In the middle and above the base 12 is mounted a small mo-

  tor M whose shaft is connected to a slip coupling 16 The gold

  outlet shaft of the coupling 16 is coupled to an arm 17, carrying

  both at its end a push finger 18 which, when turning, meets

  be a stop 19 provided on the underside of a rotary table 20, to drive this table -The table 20 rotates on bearings

  21 bearing on the upper face of the base 12.

  The turntable 20 has a central boss 20 A and a -

  outer periphery 20 B inclined upwards A can above the table 20, an annular console 22, carried by uprights, surrounds the central boss 20 A The console 22 defines with the table

  rotating 20 a constricted air passage 23, the inlet of which is juxta-

  placed at the 20 A central boss and whose outlet is located on the

periphery of the table 20.

  The console 22 has the dimensions required to support a ran-

  circular section of eight packed compartments C The side and rear walls of the compartments delimit, as shown in FIG. 8, a vacant central zone 24 which extends vertically above the boss 20 A and communicates with the entry of the passage of air 23, In the center and above the roof 13 is mounted a motor 25 whose armature shaft crosses the roof from top to bottom and ends with a main propeller 26, housed in the central zone 24 At the other an end of the motor shaft is fixed an auxiliary propeller 27, constituting an engine cooling fan The propeller 27 blows air in a channel formed between the roof 13 and a plastic dome 28 mounted above the roof The gap between the dome and the roof contains electrical controls

  associated with the oven and is ventilated by cooling air

  in front of the auxiliary propeller, the central cap of the dome being put

to the atmosphere.

  Hanging from the roof 13 is a heating assembly which comprises a main section 29 at high intensity and an auxiliary section at medium intensity, mounted in the vacant space between the top

  of the set of fitted lockers C and the roof 13 covering this

  seems The sections are formed by arched elements arranged on two concentric circles around the central zone 24 Thus, the air heated by the sections 29 and 30 is blown by the main propeller 26 in the central region 24, which it sweeps at high speed, making the vortex flow below

  the heating assembly, an annular inlet deflector H is sus-

hung from the roof 13 by tie rods.

  Because the air passage 23 is throttled, the heated air blown from top to bottom in the central zone cannot pass through it in its entirety and is forced back largely through the holes 11 of the lockers which delimit the central zone As shown in FIG. 8, this delimitation is ensured by the rear walls 10 of the various compartments arranged in a circle, the reentrants formed between these walls being delimited by the side walls 103 and 104 which define niches with triangular section. Thus, the air hot passes through the holes 11 not only of the rear walls 10, but also of the side walls 103 and 104 of the racks and is distributed, in each rack, in the interstices separating the stacked dishes,

  thus heating the dishes that garnish the dishes The hot air turns

  billonning enters the niches separating the lockers and re-

  set off in such a way as to heat all the dishes more or less uniformly.

  formally. In the central zone 24 is arranged vertically an arcuate screen 31 which, as shown in FIG. 8, allows only the air

  hot to enter the cartridges located on the turntable

  te, at the rear of the oven, this to minimize the escape of air through the opening in the front of the oven The screen 31 also ensures the division of the oven into two zones, as will be explained in the section of this brief entitled "Two-zone walking regime". The fraction of the hot air blown from top to bottom of the central zone 24 which is not discharged through the set of trays lined to heat the dishes crosses the inlet of the constricted air passage 23 and comes out last on the perimeter of the turntable Thanks to the suction generated by the main propeller, the air which crosses this outlet is sucked up and brought back

  in the space occupied by the heating assembly to be recycled.

  The air drawn upwards forms a cylindrical air curtain around

of the set of fitted lockers.

  Thus, the hot air presents a flow mode in the oven such that it '' describes an annular loop completely surrounding the circular row of fitted racks contained in the oven to isolate the heated dishes from the colder ambient air and minimize

  heat losses To reduce the size, we do

  te that the air curtain directly surrounds the set of fitted lockers so that it is disturbed by the air passing laterally

  between the dishes We therefore surround the air curtain with a thermal screen.

  cylindrical mique 32 This screen is preferably formed by

  inner and outer thicknesses of synthetic plastic

  transparent to support the heat of the oven, as repre-

  felt in FIG. 10 These thicknesses can be made of “Lexan” (thermoplastic polymer with carbonate bonds) and are separated by a metal or plastic fabric providing between them a layer of air. On the thersiic screen 32 is mounted, at the before

  oven, a rectangular rack frame 33 large enough to

  be to manually insert the fitted lockers to load them

on the rotating console.

  Thanks to the skating coupling training, to make a selection, you can momentarily interrupt the movement of the table by simply holding it by hand for the time being.

  wanted to remove a chosen dish, the clutch then ceasing to act

  coupling the turntable with the motor that drives it However, to load cartridges on an empty console, it takes more time in this case, it is enough to give manually to the table

  rotating a lot ahead of the knock carried by the arm: we in-

  thus breaks down the coupling between the stop of the rotary table and the rotary arm which drives it The rotary table then remains

  stationary until the rotating arm meets the bu again

  practically, therefore, assuming that the table describes a revo-

  lution every 30 seconds, it can be shifted so that

  install with a loading interval of around 15 seconds.

Ordered

  As seen in Figure 11, the two heating elements

  fants, principal 29 and auxiliary 3 fl, _nn L a Iiimenteé_s jpaze ïi conduc-

  sector 34 on which a power switch is interposed

  stop 35 ensuring the energizing of the two elements Downstream

  of switch 35, the conductor tr l: -3 e undi A-u to maxi-

  protective ma 36, then a thermosttt switch O qtij coupe

  the supply of the two heating elements if the temperature

pass a prefixed value.

  From the contactor 37, there are two branches, one of which

  serves the auxiliary heating element 30 through a thermostat switch 38 and the other of which serves the main heating element 29 through an adjustable timer 39 and a switch

  thermostat 40 A timer 41 is associated with a timer 41, normal-

  switched off and only lights up when the timed interval has elapsed The timer 39 has a control button 42 The power supply is indicated by a warning lamp 43 The timer 39, the main switch 35, the warning lamp 43 and the indicator 41

  are all mounted on the oven dome.

  When energized, the auxiliary heating element

  is immediately supplied, while the main heating element

  cipal 29 is only after pressing button 42 of the minute-

  The timer is adjustable: assuming that it takes an hour to bring the food loaded into the oven to the desired temperature, for example 660 C, using the two heating elements,

  the timer is set to one hour.

  At the end of the one hour delay, the timer 39 cuts the power

  tation of the main heating element: the light 41 then lights up to indicate that the dishes are ready to be served Then, the auxiliary heating element 30, which continues to operate under the control of the thermostat 38, set at 660 C, maintains

good temperature.

  We have described above and illustrated a preferred embodiment of a hot air oven for racks loaded with food according to the invention,

  but it goes without saying that we can adopt many modifications.

  tions and variants without departing from the framework of Pinven-

  tion For example, lockers are not necessarily responsible for

  dishes: the food to be heated can be contained in sa-

  chets or other receptacles to be inserted in the racks It should be noted that, although at the start of the heating process, all the lined racks are filled with dishes, the gradual extraction of dishes

  does not interfere with the operation of the oven: even after removing the most

  part of the dishes, the racks which remain in place ensure

  the dispersion of the hot air towards the remaining dishes or containers. Operation in two-zone mode In an oven of the type described, a set of

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  heating comprising two zones with different intensities, so that at the start of heating, the two sections operate for an adjustable time, hereinafter called "reheating stage", sufficient to bring the food to the temperature at which it is to be served , after which the main section is switched off, while the auxiliary section, which draws less energy, then keeps the food reheated indefinitely at the right temperature for

the stadium of service.

  During the reheating stage, the speed at which the hot air transmits heat in the oven to the racks, loaded with relatively cold food, depends on the temperature difference between the hot air and the food: the more this difference is great and

  the faster the heat transmission.

  Since the temperature of the hot air is about

  uniform throughout the oven, heat transmission is very

  pide at the start of heating, during the reheating stage where the

  two heating sections operate; but as

  then the difference in temperature between the hot air and the

  heat transmission is becoming slower and slower

  comes very low near the service temperature.

  Supposing that the food is in the lined racks at an initial temperature of around 40 C, that it is necessary to bring it to serve it at a temperature of around 660 C, and that the hot air is at 740 C approximately, there is at the beginning of reheating a strong

  temperature difference which makes heating very fast Any-

  times, as this temperature difference decreases with

  during the reheating stage, the rate of heat transmission

  their fall For example, when the temperature of food reaches 540 C, the temperature difference with hot air is only 200 C, and it takes a relatively long time for food to reach the "serving" temperature of 660 C, which marks the end of the reheating stage and the beginning of the service stage, at which a single heating section operates to ensure maintenance at

operating temperature".

  Thus, if we trace the temperature curve of the garnished dishes

  a locker (4 to 660 C) as a function of time for the recovery stage

  heating, we note that, for a hot air temperature of 740 C, this curve rises with a steep slope from 6 to 380 C in a fairly short time, then gradually flattens during more gradual heating from 380 C to 660 C It follows that the duration of the stadium

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  heating is excessive which, in some cases, can

  practically a drawback.

  In order to establish a heating regime with two zones eliminating this drawback, the arcuate screen 31 shown separately in FIG. 13 is placed vertically in the central zone 24 of the oven, which follows the limit of the central zone and leaves the air hot circulate only in the lockers present, on the turntable, in the rear sector of the interior of the oven, in order to minimize air leaks through the access bay 33 provided in the front sector

from the oven.

  The screen 31 occupies in the central zone 24 a fixed position, indicated in FIG. 4, such that the external face of the screen is very close to the rear walls of the packed compartments C arranged

  in annular row on the turntable So and as schematically-

  shown in Figure 12, the heated air blown through the central area

  trale can only cross the holes It drilled in the walls of lockers running through the rear sector not intercepted

from the oven.

  As seen in Figure 12, the two sections concentrate

  triques 29 and 30 of the heating assembly are arranged so that their input terminals are located in the anterior sector of the furnace Due to the gap separating these terminals, the heating sections generate less heat in this region of the furnace

  that at the level of their uninterrupted parts located in Se sec-

back of the oven.

  Thanks mainly to the presence of the screen 31 and, to a lesser extent, to the interruptions of the concentric heating sections 29 and 30, the rear sector of the oven becomes significantly hotter than the front sector. Thus, the shield actually divides the oven into two zones: a hot front zone which presents the access bay 33 and a very hot rear zone During each revolution, the dishes T loaded in the racks cross the two zones, hot

and very hot.

  Practically, when the two heating sections operate during the reheating stage, the parameters are such that the temperature is, in the hot zone, from 66 to 71 ° C and exceeds, in the very hot zone, 880 C. The prevailing temperature in the hot zone significantly exceeds the "serving" temperature of the food, which is approximately 660 ° C., and

  may also exceed the softening point of the plas-

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  tick forming the dishes, depending on the nature of this material If the dishes are made of polyethylene, their softening point is 740 C Since food should never be brought to a

  temperature higher than that of "service", to avoid their re-

  cooking, it is not annoying in this regard that the dishes have a softening point of 740 C, because this value is sufficiently

  higher than normal "serving" food.

  However, this softening point of polyethylene is not

  below the temperature prevailing in the very hot zone, which must be taken into account Because the dishes alternately reach and leave the hot zone, the temperature of which is a few degrees lower than the softening point of the polyethylene, their average temperature doesn’t never reaches the softening point during the brief heating allowed by dividing the oven in half

zones.

  At the end of the reheating stage, the main heating section is switched off and the temperature then obtained is that

  (about 660 C) to keep dishes at serving temperature

  this "sufficiently lower than the softening point of the material-

* re plastic.

  It is obvious that if the plastic dishes were kept in the two-zone oven during a reheating time

  prolonged, the plastic material-could eventually soften-

  read to an inadmissible degree due to the high temperature prevailing in the very hot zone However, the reheating stage according to

  the invention has a relatively short duration.

  If the reheating stage is abbreviated, it is because the heat transmission is not, as in an oven not divided into two zones, rapid only at the start of reheating when the temperature difference is large, to become more and more slowly as the food approaches the "serving" temperature: it remains fast during all the time taken by the food to

  go from a low initial temperature to the "service temperature"

  high "defect reached at the end of reheating.

  Because the hot air is, in the very hot zone, at a temperature (of 880 C) much higher than that (of 66 to 7 C) of the food, the temperature difference between the hot air and the food, although maximum at the start of reheating, never becomes weak because, when the food is

  "operating" temperature, for example 570 C, the difference between

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  the temperature which they present then and that which reigns in the

  very hot area remains quite large, so that the trans-

  heat mission is still very fast.

  Thus, the temperature curve of food as a function of time, for the reheating stage, is no longer abrupt during

  of the first 15 minutes or so of reheating to flatten out

  following the point that a long delay is necessary to obtain the "serving" temperature of the food: with the division into two zones according to the invention, the curve is a little less steep when approaching the temperature " but "does not reflect any

  moment slow heating As a result, for a feed charge

  given, while total reheating may require more than an hour in the absence of division into two zones, this delay may, depending on

  the invention, to be only an hour or less.

Claims (5)

  1 Hot air oven for heating food, of the type comprising a rotating annular table on which a load of food is arranged so that its inner surface delimits a central zone, an air heating assembly and a propeller driving the hot air in a toroidal movement enveloping the load, a throttle being provided   at the exit of the central zone in order to deflect a notable part   ble of the air arriving in the central zone through the load, oven characterized in that it comprises a curved screen (31) along the internal surface of a part of the load, which prevents hot air from passing through said part of the load, and thus divides the oven into a hot zone, and into a very hot zone, the temperature of the latter being very much higher than the temperature desired for serving food so that the heat transmission between hot air and   food, which depends on the difference between their temperatures, de-   dies high while reheating food until their serving temperature.   2 Oven according to claim 1, characterized in that.   said hot zone is maintained at a temperature close to that of food service.   3 Oven according to claim 1 or claim 2, characterized in that said air heating assembly is constituted by strong (29) and weak (30) sections with powers   different heaters, all used for heating   food, only then operating the weak section to keep food at its serving temperature. 4 Oven according to claim 3, characterized in that said sections are formed by concentric circular heating elements whose connection terminals and   interstices between terminals are located in said hot zone.   Oven according to any one of claims 1 to 4,   characterized in that the food is in large dishes   plastic with a lower softening point   at the temperature prevailing in said very hot zone, the   ree of the reheating stage and the temperature of the hot zone being such that the dishes never reach their point of   softening during this stage.   6 Method of heating precooked food from a low starting temperature to bring it to a temperature   below their annealing temperature, charac-   terrified in that, according to a predetermined frequency, one subjects   foods have hot air puffs running along them   with a relatively high speed, alternating with intervals without flow during which heat transfers take place in the food, the temperature of these puffs of hot air being higher than the temperature   food service, so the food temperature   quickly rises to operating temperature, without   however significantly exceed it.   7 Method according to claim 6, characterized in that, after the heating phase of the food, the food is subjected to a circulation of hot air whose temperature is lower than said annealing temperature, so as to substantially maintain the food at their serving temperature. 8 Method according to claim 7, characterized in that the hot air follows a path enveloping the food,   creating a curtain that isolates food from the air.