This invention relates to the field of cooking and more particularly, the field of grand cuisine or professional cooking, such as in a restaurant, for example; this is also referred to as "grand gastronomy".

Upon preparing a cooked dish, a great number of devices for preparing the dish could be used; besides tools or devices for cutting and mixing the foodstuffs to be used for preparing the dish, devices are used for cooking foodstuffs, and sometimes, for providing the foodstuffs with their final appearance, devices for surface cooking (i.e. on their surface) of foodstuffs. Cooking devices make it possible to cook foodstuffs, to medium cook them, to stew them, to boil them, etc. In all such operations, it is understood that the foodstuff as a whole is to be submitted to a heat treatment, so as to modify the state thereof. The devices for surface cooking foodstuffs are arranged so as to "mark" or "color" the surface of the foodstuffs through bringing them into contact with a surface the temperature of which is generally higher than 250 ⁰ C; in other words, the function of such devices does not consist only in cooking foodstuffs, but rather, in surface modifying their appearance, their texture, their temperature and their consistency. Such devices could comprise, for example, a heated plate, that could be grooved so as to provide foodstuffs with a special aspect, or also a heated grid. This is generally referred to as "plancha", when this is related to a plate (or grid) allowing to heat mark foodstuffs. Modern cooking, more particularly derived from molecular gastronomy, more and more uses devices or methods for modifying the appearance of prepared dishes; there are added, to this end, ingredients (alginates, liquid nitrogen, etc.) so as to provide the final composition with a particular appearance and/or texture.

The Applicant has more particularly paid attention to marking the surface of foodstuffs, in that it combines a modification of the appearance of the foodstuffs - and hence, of the cooked dish - with a surface modification of their texture, their temperature and their consistency, thus of the feeling experienced when tasting them.

Consequently, this invention relates to a device for thermally treating the surface of products to be treated, the device comprising at least a contact surface adapted to receive said products and cooling means for said contact surface being arranged so as to freeze said products on the surface thereof without freezing them inside and thus, to treat them, i.e. to treat the surface thereof.

The problem, underlying this invention, is related to surface marking of foodstuffs and this is why the device of this invention is adapted for surface thermal treating of foodstuffs.

By means of this invention, a surface change is being obtained of the appearance, the texture, the temperature and the consistency of the foodstuffs being treated. The results are astounding. Ordinary foodstuffs, treated by means of the device of this invention, achieve most original appearance, texture and consistency. This invention makes it possible to achieve the equivalent, by the cold, of already known heat marking or coloring; in other words, according to this invention, foodstuffs are struck by the cold. In a way, this invention allows for an ice-cold plancha to be manufactured.

According to a preferred embodiment, the device is arranged so that the contact surface has a temperature resulting in a frost film being formed on said surface, which does not melt upon contact with products. Such a feature is particularly valuable, in that it prevents the foodstuffs being treated by the device from adhering to the contact surface that cools them. Indeed, if the frost does not melt, it forms a barrier between the contact surface and the surface of the products and thereby prevents the latter from being stuck (adhered) on the contact surface, such a barrier remaining present throughout the whole thermal treatment since frost does not melt upon contact with the foodstuffs . According to an embodiment, said temperature is lower than -70 ⁰ C, preferably lower than -80 °C.

According to an embodiment, the device comprises a part with said contact surface adapted for receiving the products, said part comprising steel. According to an embodiment, the device comprises at least one plate with a planar contact surface.

According to an embodiment, the device comprises at least one plate with a grooved contact surface. According to an embodiment, the device comprises at least a grid comprising a plurality of bars on the surface of which the products to be treated are to be arranged. The bars (or tubes) of such a grid could be adjacent or spaced apart one from the other.

According to an embodiment, the device of this invention is integrally inserted into a kitchen stove.

According to an advantageous embodiment, the cooling means comprise a refrigerating circuit evaporator, the evaporator comprising the contact surface adapted for receiving the products.

This way, obtaining an ice-cold surface is easy and efficient.

According to a particularly efficient embodiment, the cooling means comprise two serially mounted refrigerating circuits, one of the refrigerating circuits comprising said evaporator with said contact surface .

According to a preferred embodiment in such a case, each refrigerating circuit comprises an evaporator and a condenser, the evaporator of the first circuit exchanges heat with the condenser of the second circuit and the contact surface of the device belongs to the evaporator of the second circuit. According to another embodiment, the cooling means comprise a refrigerating liquid contained and preferably circulating in an enclosure adapted for providing for heat exchanges between said refrigerating liquid and said contact surface. The refrigerating liquid could be, for example, carbon dioxide or liquid nitrogen. According to an embodiment in such a case, the device comprises at least one grid comprising a plurality of bars on the surface of which products are adapted to be located, the refrigerating liquid being driven in circulation in the bars.

This invention also relates to a cooking method for thermally treating the surface of products to be treated on a device comprising at least one contact surface adapted to receive said products and means for cooling down said contact surface arranged so as to freeze the surface of said products without freezing them inside, said method comprising the following steps:

- a product is placed on said contact surface, the product is struck by the cold and immediately frozen on the surface without being frozen inside and its surface thereof is thereby treated.

In other words, the product is taken off the contact surface before being frozen inside.

According to an embodiment, the product is placed on said contact surface during no more than a few minutes, for instance 10 minutes, preferably no more than

5 minutes. Such a time of treatment is adapted for a rather thick piece of meat for instance.

According to an embodiment, the product is placed on said contact surface during no more than two minutes. Such a time of treatment is adapted for a normal piece of meat or fish for instance, notably for a hot piece of meat or fish of which a surface is intended to be frozen. According to an embodiment, the product is placed on said contact surface during no more than 30 seconds. Such a time of treatment is adapted for a thin piece of food.

This invention further relates to the use of the device described above (according to any of its embodiments) for thermally treating the surface of products according to the cooking method above.

This invention further relates to a cooking method for thermally treating the surface of products to be treated on a part comprising at least one contact surface adapted for receiving said products, wherein said part is stored in a refrigerating compartment so as to cool it down, the part is removed out of the compartment and the products are positioned on the contact surface so as to freeze their surface without freezing them inside and thereby treat them.

Such a method is original and makes it possible to only bring on the thermal treatment location (for example, a table, a buffet, etc.) the part (for example, a plate or a stone) preliminarily cooled down so as to be able to freeze the surface of the products.

This invention will be better understood by means of the following description of the preferred embodiment of the device of this invention, referring to the appended drawings, in which: - Fig. 1 shows a schematic perspective view of a stove with a device for thermally treating the surface according to the preferred embodiment of this invention;

- Fig. 2 illustrates a bottom view of the upper surface of the plate of the device of Fig. 1; - Fig. 3 shows a schematic block diagram representing the cooling means of the plate of the device on Fig. 1; and

- Fig. 4 shows a schematic sectional view of the plate of the device on Fig. 1.

Referring to Fig. 1, a stove 1 is illustrated schematically. In the field of grand gastronomy, the term "stove" is a term being used for, generally, meaning the devices on which foodstuffs are prepared and cooked; a stove could therefore support several modules for cooking foodstuffs.

In this case, the stove 1 herein comprises two modules: a cooking plate 2 and a device 3 for surface thermal treatment of foodstuffs according to this invention, i.e. a device 3 allowing to freeze the surface of foodstuffs placed thereupon; for simplifying the explanation, such a device 3 will be subsequently called "device 3". The cooking plate 2 is conventional and will not be described in further detail; the presence thereof in the stove 1 is of course optional; it could also be replaced by any cooking module such as a gas burner or similar. In the present embodiment shown, the device 3 is described as being integrated into a stove 1; such an integration has the following advantage: foodstuffs can be prepared, cooked or treated by heat and by cold on modules being close together on one single stove or on distinct stoves; otherwise stated, the device 3 is integrated at the vicinity of the various cooking modules of the kitchen and is thus right within the latter; it is thus easily accessible and it is not difficult to submit several foodstuffs to different thermal treatments. Obviously, the device 3 could be integrated into any arrangement able to receive it or be arranged as a unit module .

The device 3 comprises a plate 4 arranged and fixed on a base 5. The plate 4 has an upper surface 6 onto which foodstuffs are to be placed so as to be surface frozen. Referring to Fig. 2, the upper surface 6 is in this case grooved, i.e. it is shaped so as to have a plurality of grooves 7 parallel one to the other. The function of such grooves 7 is to give a particular appearance to the foodstuffs that are positioned on the plate 4 and are submitted to the thermal treatment; indeed, as the foodstuffs are not in contact with the plate 4 at right angle with the grooves I ₁ their appearance is not modified as the level of the relevant surfaces but is modified at the level of the contact surfaces with the upper surface 6 of the plate 4. As can be seen on Fig. 2, the grooves 7 are only arranged, in this case, in some areas of the surface 6 of the plate 4 (in such a case, in a central position) , allowing, if desired, to place some foodstuffs on wholly planar surfaces, in which the contact can occur, between the foodstuffs and the surface 6, along such continuous planar surfaces.

The device 3 comprises means 8, 9 for cooling the contact surface 6 with the foodstuffs. Such means comprise more particularly a first refrigerating circuit

8 and a second refrigerating circuit 9, both circuits 8,

9 being mounted in cascade. As known, each refrigerating circuit 8, 9 comprises, respectively, a condenser 8a, 9a, a pressure reducer 8b, 9b, an evaporator 8c, 9c and a compressor 8d, 9d. A refrigerating agent or fluid is driven, in a closed loop, in each circuit 8, 9 in the direction of the arrow 8e, 9e, respectively, i.e. from the condenser 8a, 9a towards the evaporator 8c, 9c in a liquid form, passing through the pressure reducer 8b, 9b and from the evaporator 8c, 9c to the condenser 8a, 9a in a gas form, passing through the compressor 8d, 9d.

In the described embodiment, the refrigerating fluid of the first circuit 8 is the fluid known by the refrigerant code R404A (this is a composition of R143a (trifluoro-1, 1, 1-ethane) , R125 (pentafluoroethane) and R134a (1, 1, 1, 2-tetrafluoro-ethane) and the refrigerating fluid of the second circuit 9 is the fluid known under the reference R23 (trifluoromethane) .

The various elements of each circuit 8, 9 operate as follows. In the condenser 8a, 9a, the refrigerating fluid releases heat, which it exchanges with a secondary fluid (water, air, ...) , switching from the gas state to the liquid state. The pressure reducer 8b, 9b reduces the pressure of the refrigerating fluid, in the liquid phase. In the evaporator 8c, 9c, heat is removed from a secondary fluid for vaporizing the refrigerating fluid. Finally, the compressor 8d, 9d, operated by an electric motor, increases the pressure and the temperature of the gaseous refrigerating fluid, by- compressing it. More specifically, as the circuits 8, 9 are mounted in cascade, the evaporator 8c of the first circuit 8 exchanges heat with the condenser 9a of the second circuit 9; otherwise stated, the secondary fluid with which the refrigerating fluid of the first circuit 8 exchanges heat at the level of the evaporator 8c thereof is the refrigerating fluid of the second refrigerating circuit 9. Such a heat exchange could occur via any appropriate means; more specifically, the evaporator 8c of the first circuit 8 and the condenser 9a of the second circuit 9 are arranged in the same heat exchanger 10, that could structurally have any appropriate shape (plate exchanger, coaxial tube exchanger, etc.); the refrigerating fluid of each circuit 8, 9 flows through a circuit being distinct from the exchanger so as to exchange heat with the refrigerating fluid of the other circuit 9, 8. Moreover, the plate 4 of the device 3 here forms one of the walls of the evaporator 9c of the second circuit 9; thus, the secondary fluid with which the refrigerating fluid of the second circuit 9 exchanges heat at the level of the evaporator 9c thereof is room air. Heat is more particularly exchanged through the plate 4, thereby cooling down the contact surface 6 with the foodstuffs .

By way of an example, the temperature of the fluid in the condenser 8a of the first circuit 8 could be equal to about 45 ⁰ C, the temperature of the fluid in the evaporator of the first circuit 8 being then equal to about -20 °C and exchanging heat with the fluid of the condenser 9a of the second circuit 9 that can show a temperature equal to -10 ⁰ C, so as to obtain a temperature of the fluid in the evaporator 9c of the second circuit 9 approximately equal to -85 °C. Thus, the temperature of the external surface 6 of the plate 4 that is achieved is approximately -85 ⁰ C.

Referring to Fig. 4, the evaporator 9c of the second circuit 9 will be now described in further detail.

The evaporator 9c is arranged so as to define an enclosure 11 in which the refrigerating fluid can switch from its liquid state to its gaseous state. A liquid supply line 16 of the enclosure 11 opens into the enclosure 11 through the base 5 (it opens into the lower part of the enclosure 11 so as to be always immersed in the liquid) , while a line 17 for venting the gas out of the enclosure 11 opens in the enclosure 11 through the base 5 (it opens into the upper part of the enclosure so as to be always contained in the gas volume) . The liquid supply is schematically represented by the arrow 16a and the gas venting is schematically represented by the arrow 17a. Naturally, the supply and venting lines 16, 17 could open into the enclosure 11 through other parts of the evaporator, for example, through the side walls of the base 5. Thus, the enclosure 11 is partially filled with liquid 12, the remaining of the space being filled with gas 13. The enclosure 11 is bound, in its upper part, by the plate 4 of the device 3 and, in its lower part, by the base 5 of the device 3. The plate 4 and the base 5 are fixed together via any appropriate means, here along a peripheral side welding line 14 ensuring, in addition to a function for fixing the plate 4 to the base 5, a tightening function between the enclosure 11 of the evaporator 9c and the room air, at the level of the side walls thereof. The refrigerating fluid exchanges heat with the room air; in order to enhance such exchanges through the plate 4, grooves 15 are arranged on the lower surface of the plate 4, for increasing the exchange surface thereof. Obviously, the flow rates of the refrigerating fluids in the circuits 8, 9 are adjustable depending on the temperature required for the external surface 6 of the plate 4 of the device 3 for contacting the foodstuffs. Such a temperature is preferably here lower than -70 ⁰ C, more preferably lower than -80 ⁰ C. The different elements of the circuits 8, 9 could be replaced by any means filling an equivalent function.

The plate 4 is made in a both mechanically strong and thermally conductive material; typically, the pressure the material should be able to withstand is, for the present desired temperature range, between 50 and 60 bars. More particularly, the material is steel. The base 5 is here also made in steel. The steels are preferably stainless, so as to avoid any oxidation risk despite the presence of liquid. It could be contemplated, in an embodiment, to provide the base 5 made in a mechanically strong, but not thermally conductive or badly conductive material, the heat being then exchanged preferably through the plate 4. More specifically, the dimensions of the plate 4 are, as seen from underneath, 60 cm x 40 cm. The operation of the device 3 will be now described in further detail.

The refrigerant circuits 8, 9 are operated and allow for quickly reaching an (ice) cold temperature for the upper surface 6 of the plate 4. In the here described preferred embodiment, such a temperature ranges between -85 ⁰ C and -70 ⁰ C. Because of the very cold temperature of the plate 4, frost 20 is formed on the surface thereof 6. A foodstuff product 18 - for example, a piece of fish 18 - is then placed on the upper surface 6 of the plate 4. The surface 19 of the product 18 is thus in contact with the external surface 6 of the plate 4, the frost film 20 being interposed between them. As the temperature of the surface 6 of the plate 4 is very low, the frost does not melt upon contact with the product 18 to be surface frozen; thus, the product 18 does not stick to such a contact surface 6 (or freezing surface 6) . Indeed, should the frost turns into water, there is the risk of the product 18 sticking to the surface 6 of the plate 4, whereas if it remains in an iced form, it creates a barrier between the surface 6 of the plate 4 and the product. Because of the very cold temperature of the surface 6 of the plate 4, the product 18 is struck by the cold and immediately frozen on the surface. As a result, the aspect, the texture, the temperature and the consistency of the product 18 are astoundingly surface modified. Thus, the device 3 could be advantageously used as a kitchen module for finalize dishes just before they are tasted. By way of an example, it could be given the shape of a piece of fish grilled on one side of the cooking plate 2 and then frozen on the other side on the device 3, creating a "hot-cold" taste effect; numerous examples could be given, including elaborating very thin slices of surface frozen tomatoes so as to rigidify them, surface frozen meat chips, etc. As the foodstuffs are not generally very inert to the cold, they could perfectly be surface frozen without being frozen inside, so that the person eating them will not have a toothache while biting into them.

It is to be noticed that the plate 4 shown on Fig. 2 comprises a peripheral channel 21 for recovering foodstuff residues.

The invention has been described referring to its preferred embodiment, but it is obvious that different embodiments could be contemplated overall or for each of the components of this invention.

In particular, the cooling means 8, 9 comprise, in the present embodiment, a cascade of refrigerant circuits with a simple structure. Other refrigerant circuits could be implemented, for example, a device with a cascade of more than two refrigerant circuits or even a device with a single refrigerant circuit.

Naturally other means for cooling the contact surface 6 of the device 3 could additionally be contemplated, if they allow for the desired temperature to be reached; such a temperature should, anyway, be lower than 0 ⁰ C in order to allow for frost to be formed at the surface 6 of the plate 4. The lower the temperature, the more quickly the foodstuffs are frozen and hence cold struck; in addition, foodstuffs adhere even less to the plate 4 as the temperature of the surface thereof 6 is lower, since the frost between the foodstuffs and the plate 4 is at a sufficiently low temperature for preventing the risk of turning to water upon contact with the foodstuffs.

According to a non shown embodiment, the cooling means comprise a refrigerant fluid or agent (for example, carbon dioxide or liquid nitrogen) contained and preferably circulating in an enclosure arranged for allowing said refrigerating liquid to exchange heat with the contact surface adapted to receive the products. For example, the device could comprise a plate under which there is provided an enclosure for circulating such a refrigerating liquid, the latter being able to be circulated in the enclosure by means of a pump. According to another example, the device comprises a grid comprising a plurality of hollow bars; the products to be treated are provided to be placed on an upper surface of the bars, while a refrigerating liquid is circulated inside the bars. The refrigerating liquid exchanges heat with the contact surface of the bars so as to cool it down and maintain it at a sufficiently low temperature for surface freezing the products when they are placed on it.

According to another embodiment, the cooling means comprise a refrigerating compartment in which a part could be stored, for example, a plate or a stone, having a contact surface for the products, the compartment being adapted so as to maintain such a contact surface at a temperature lower than or equal to the temperature required for freezing the surface of products during their treatment. A method could thus be implemented, wherein the plate or the stone is stored in a refrigerating compartment so as to be cooled down, it is removed from said compartment when it is to be used and products are arranged on it for freezing their surface. Such a surface treating method comprises the use, during cooking, of a hot stone; this is here an ice- cold plate or stone.

Whatever the selected embodiment for the cooling means, it is important, in order to freeze foodstuffs with the device 3, that the latter comprises a surface 6 being sufficiently cold for freezing the surface of the products . Such a cooled surface 6 could be supported by parts with different structures. In the preferred embodiment according to this invention, the surface 6 is the upper surface 6 of a plate 4, with a grooved shape. Obviously other shapes are contemplated for the surface 6 of the plate 4; thus, the plate 4 could be planar, could comprise grooves, different patterns, several types of patterns on different areas of the plate 4, etc. Moreover, it is possible to provide not a plate but a grid with bars in which a refrigerant product is circulated, the products being positioned on the grid and struck at the level of their contact surfaces with it; the bars of the grid could be spaced apart or adjacent one relative to the other. Other parts comprising a freezing surface cooled down by adequate cooling means could be contemplated.

This invention has been set forth in the field of a direct contact between the surface of the foodstuffs and the contact (freezing) surface of the plate (the frost only optionally interfering) . It is obviously possible to provide for an indirect contact for example, through the interposition of a film such as greaseproof paper.