Spiral oven and method for treating food products with conditioned air

Abstract

The present invention relates to a spiral oven and a method for treating food products. The spiral oven comprises a cooking chamber and a belt conveyor for conveying the food products. A fan is provided for circulating conditioned air through the cooking chamber. A heater is provided for heating air that circulates past the heater, a steam injector is provided for supplying steam to the circulating air and a natural smoke vapor generator is provided which is connected via a duct to a smoke exhaust upstream of the steam injector and downstream of the windings of the helical conveyor path.

Description

[0001] Title: SPIRAL OVEN AND METHOD FOR TREATING FOOD PRODUCTS WITH

[0002] CONDITIONED AIR

[0003] This invention relates to a spiral oven and associated method for treating food products with conditioned air, in particular mass cooking of food products, such as the partial or complete cooking, baking, frying, drying, roasting, grilling of meat and meat products, such as optionally breaded and / or marinated hamburgers, chicken portions and other shaped products.

[0004] Such a spiral oven is well known and commercially available. In EP2111112 of the same applicant such a spiral oven is described in detail. Here, the air is conditioned by the provision of a heater inside the cooking chamber. Furthermore, it is suggested to condition the circulating air by supplying moisture to the circulating air via steam injection.

[0005] In the spiral oven described in US202040933 the heater is provided downstream from the fan. At the inlet of the fan a vertical pipe is provide with openings, which are distributed along the height of the pipe / channel. This pipe collects the air from each chamber and provides it to the inlet of the fan. Inside this pipe a smoke pipe extends, connected to a natural smoke generator. The smoke exhausted from the end of the smoke pipe immediately enters the inlet of the fan. By means of steam the dew-point temperature in the respective chamber can be influenced.

[0006] The aim of the present invention is to provide a more expedient spiral oven and associated method.

[0007] According to the present invention, this is achieved by a spiral oven for treating food products according to claim 1 and a method according to claim 6.

[0008] The invention differs at least from the prior art oven described in US202040933 in that according to the invention: the conditioned air is expelled outward from the cylinder openings onto and around food products on the windings of the helical conveyor path, the heater is provided upstream of the inlet of the fan, the steam injector and the natural smoke vapor exhaust are arranged such that the natural smoke emerging from the smoke exhaust is mixed with the injected steam ahead of being heated by the heater, prior to entering the inlet of the fan. An advantage of the smoke exhaust being provided upstream of the steam injection nozzle according to the present invention, is that the smoke is mixed with the steam within a short time, thereby ‘dissolving’ the smoke in the steam. This is advantageous in view of pollution of the oven in that the deposition of smoke as tar is reduced, preferably prevented. Such pollution has a large impact on the overall efficiency of the oven, and hence, the prevention of deposition has an important advantage in view of operating time of the oven.

[0009] The present invention provides a spiral oven and associated method for treating food products with conditioned air, in particular mass quantities of food products such as whole chickens or poultry parts such as chicken fillets, roasted duck, nuggets, hamburger patties, spareribs, sausages, fish patties, vegetable foods etcetera. The inventive spiral oven and method allow treatment of a wide range of products at high capacity. Achieving the right appearance, texture, flavour, and bite for food products relies heavily on the treatment. A suitable treatment with conditioned air advantageously results in desired degree of properties including crispness, browning and juiciness.

[0010] The spiral oven of the invention comprises a cooking chamber with conditioned air, in which the treatment with conditioned air takes place. In embodiments, the substantially closed cooking chamber has top and bottom walls, side walls and end walls defining a substantially closed vapor leak proof enclosure. Cooking chambers with a polygonal cross-section are also known in the art. The cooking chamber has an entry and an exit, preferably formed in at least one of the side or end walls thereof. In one advantageous embodiment, the cooking chamber comprises a raisable hood and a tray, with a seal such as a water trap being provided in between.

[0011] In embodiments, well known, the spiral oven comprises two adjacent cooking chambers, each having an entry and an exit, and wherein the exit of the first cooking chamber is connected via a passage to the entry of the second cooking chamber. In such embodiments, advantageously, the helical conveyor path in a first cooking chamber is upwardly directed, and a helical conveyor path in second chamber is downwardly directed. Alternatively, it is possible that one of the cooking chambers does not comprise a helical path but only a downward or upward slope. Advantageously, distinct environments are created and controlled in the two cooking chambers, to give the spiral oven versatility. E.g. the first cooking chamber is used for high dew point steaming and followed up by low dew point cooking in the second cooking chamber. Preferably each cooking chamber has independent controllers for the conditioned air in the respective cooking chambers. A temperature difference of up to 100°C between two chambers is possible.

[0012] A belt conveyor is provided for conveying the food products through the cooking chamber from the entry to the exit. The food products are continuously transported on the belt conveyor through the cooking chamber via a helical conveyor path with windings situated one above the other. Viewed in top view, a winding may have the shape of essentially an ellipse, a polygon, such as a triangle or rectangle. A helical conveying path in which the endless conveyor belt is guided around a cylinder or drum, with a winding essentially following the shape of a circle, is preferred. Such a spiral vertical path with a number of superimposed, helically extending tiers through a cooking chamber effects slow and thorough treatment / cooking of the food products. Commonly applied belt widths are between 700-1000mm, and the number of tiers is commonly 4, 5 or 6. Near the entry and exit, the conveying path comprises conventional straight sections which are relatively short compared to the entire length of the conveying path. The belt conveyor is designed for supporting the products and is preferably a (metal) gauze belt, which is at least partially air permeable.

[0013] In embodiments, links on either side of the belt conveyor support the windings on top of one another to provide a self-supporting conveyor belt system. The belt conveyor is suitable to convey food items through a confined space for a certain dwell time for treatment of the food products.

[0014] A rotating cylinder is provided inside the helical conveyor path, preferably a driven cylinder for driving the windings. In embodiments, a hollow cylinder is provided concentrically in the helical conveyor path, and preferably rotatably arranged around a vertical rotary shaft. In a usual way, the belt conveyor is guided around the cylinder along the conveying path and driven by slip friction between the inner edge thereof and the outer circumference of the cylinder or part thereof. A cylinder drive, such as one or more electric motors, is preferably arranged outside the cooking chamber, in particular underneath the bottom thereof.

[0015] In the inventive spiral oven conditioned air is created by regulating conditions such as temperature and / or humidity and / or smokiness of the conditioned air which is circulating in the cooking chamber. The ability to create an effective flow of conditioned air is an important aspect with such a spiral oven.

[0016] A fan, preferably a centrifugal fan, is provided for circulating conditioned air through the cooking chamber. In embodiments, the fan is provided within the rotating cylinder. The fan comprises an inlet, and comprises an outlet in communication with the rotating cylinder, the rotating cylinder having openings adapted to expel the conditioned air onto and around food products on the windings of the helical conveyor path. Air speeds of 1-7 meter / second are realistic. The inlet of the fan, such as the suction side of a ventilator, viewed in the direction of flow of the conditioned air, is arranged downstream of the heater. Advantageously, the inlet of the fan is directly or indirectly in fluid communication with the heater and adapted to suck in heated conditioned air in a vertical direction, preferably from an upper side of the cooking chamber above the helical conveyor part.

[0017] The outlet of the fan preferably allows the conditioned air to circulate through the belt conveyor and around the food products positioned on the belt in a continuous manner for efficient heat transfer from the conditioned air to the food products. E.g. a central position of the outlet of the fan within the helical conveying path makes an efficient circulation of the conditioned air and thus an effective treatment of the products possible.

[0018] The outlet of the fan may be elongated over the entire length of the helical conveyor path, or only at a part thereof, e.g. at a bottom end of the rotating cylinder. Deflector guides may be provided to guide and distribute the conditioned air which flows from the fan uniformly between the windings of the conveying path.

[0019] Advantageously, the conditioned air flows in an essentially horizontal path along the conveyor belt in a continuous manner. In order to provide continuous circulation of the conditioned air, structures associated with the belt conveyor or rotating cylinder should allow effective circulation through the helically extending tiers of the conveyor belt.

[0020] In embodiments, as described in detail in EP2111112, air-guiding means for influencing the flow of the conditioned air in a targeted manner may be present in the cooking chamber. In an embodiment a stationary tubular body is placed between the outlet of the fan and the rotating cylinder, having a vertical outflow aperture which extends at least over the entire height of the windings of the conveyor path. The conditioned air is distributed from the outlet of fan to the outflow aperture of the tubular body. Such a distribution of the air contributes to an efficient flow of conditioned air over the products which are situated on the conveying means.

[0021] In embodiments, a rotary shaft of the fan coincides with a shaft of the rotating cylinder, so that the distance of the fan to the circumference of the cylinder is constant. Alternatively, the fan is arranged eccentrically with respect to the vertical shaft of the cylinder. This is particularly advantageous if it is intended to allow the conditioned air to flow out only over a part of the circumference of the windings of the conveying path.

[0022] Usually a fan drive unit, such as an electric motor, is provided outside the cooking chamber, e.g. underneath the bottom of the cooking chamber.

[0023] Advantageously, due to turbulence generated in the fan, it is possible in this way for the conditioned air, which may have non-uniform conditions as a result of the configuration of the conditioning means, to be mixed downstream of the air-conditioning means and thus to be homogenized, so that any local deviations resulting from the conditioning of the air are removed. Thus, the fan may serve a double purpose: on the one hand to circulate the conditioned air and on the other hand to mix and thus homogenize the air conditioned in the air-conditioning means.

[0024] According to the invention, seen in the direction of the circulating air, a heater is provided upstream of the inlet of the fan, a steam injector is provided upstream of the heater, a natural smoke vapor generator which is connected via a duct to a smoke exhaust is provided upstream of the steam injector and downstream of the windings of the helical conveyor path, such that the natural smoke emerging from the smoke exhaust is mixed with the injected steam ahead of being heated by the heater, prior to entering the inlet of the fan.

[0025] Preferably, the heater, the steam injector and the smoke exhaust are provided outside the cylinder.

[0026] A heater is provided upstream of the inlet of the fan for heating a fluid mixture that circulates past the heater. A conditioned fluid mixture is generated of a temperature set by the heater. In embodiments, the heater is provided inside the cooking chamber, but embodiments wherein the heater is provided outside the cooking chamber are also conceivable. Commonly applied heating elements provide 15-25kW / m2. Common temperatures of conditioned fluid mixture are between 100-240°C. Advantageously, the heater is provided at an upper region of the cooking chamber, above the helical conveyor part.

[0027] A steam injector is provided for supplying steam to the circulating fluid mixture, provided upstream of the heater. The steam injector preferably comprises nozzles in communication with a water supply, preferably a hot water supply, preferably a source of water under pressure. Steam is usually generated by vaporization of water through steam injection nozzles, e.g. series of nozzles provided in a steam bar. Each nozzle is such that it will eject water as a cone of fine spray or mist with an apex angle of e.g. 70-100°. The steam bar with steam injection nozzles is provided in the cooking chamber, while the water source is preferably provided outside the cooking chamber.

[0028] A natural smoke vapor generator is provided which is connected via a duct to a smoke exhaust, upstream of the steam injection nozzle and downstream of the windings of the helical conveyor path. Natural smoke means that the smoke is not supplied as a liquid, but that the smoke is produced in a smoke generator using wood species such as hickory, applewood, pecan, oak, maple etcetera, for example using woodchips. Natural smoke vapor generators are known in the art and comprise a burning chamber and an inlet for feeding wood, e.g. wood chips, e.g. into the top of chamber. In embodiments an auger is provided for pulling wood chips into burning chamber. A burner plate is advantageously provided in chamber upon which the wood chips are burned. Generally a wiper is provided for pushing ashes off of burner plate. An air inlet is furthermore provided through which sufficient air enters burning chamber to support the burning process. A blower can be provided for pulling air into, and pulling smoke product out of, burning chamber to the duct.

[0029] As indicated above, an important advantage of the smoke exhaust being provided upstream of the steam injection nozzle is that the smoke is mixed with the steam within a short time, thereby ‘dissolving’ the smoke in the steam. This is advantageous in view of pollution of the oven in that the deposition of smoke as tar is prevented. Such pollution has a large impact on the overall efficiency of the oven, and hence, the prevention of deposition has an important advantage in view of operating time of the oven.

[0030] Advantageously, the steam injection nozzle is provided at an upper region of the cooking chamber, and the smoke exhaust is provided at a lower region of the cooking chamber, generating conditioned air with a mixture of steam and natural smoke.

[0031] Advantageously, a control system is provided to control the properties of the conditioned air in the cooking chamber. In embodiments with two cooking chambers, the control system preferably controls the properties of each chamber individually. Preferably, the control system comprises a temperature controller for controlling the heater, and / or a humidity controller for controlling the steam injection, and / or an airflow controller controlling the fan, and / or a smokiness controller controlling the natural smoke supply. The control of these properties provides flexibility to produce an array of products with unique flavour, texture, and colour characteristics.

[0032] The invention is further elucidated in relation to the drawing, in which:

[0033] Fig. 1 represents a cross section of a spiral oven of the invention.

[0034] In fig. 1 a cross section of a spiral oven 1 for treating food products of the invention is shown, comprising a single cooking chamber 10. An entry 12 for the food products is shown at the left-hand side of the drawings. The exit 14 for the food products is shown at the right hand side, at an upper part of the spiral oven 1. In fact, the spiral oven 1 as shown is suitable to be equipped with yet another cooking chamber provided adjacent the shown cooking chamber 10. This second other cooking chamber can then receive the products from the exit 14 of this first cooking chamber.

[0035] The food products are conveyed within the cooking chamber from the entry 12 to the exit 14 on a belt conveyor 5. The belt conveyor has straight path sections at the entry and exit. In the cross-sectional view of fig. 1 , in particular the windings of a helical conveyor path 5a are visible, here 4 windings. Via the windings the food products are transported upwardly inside the cooking chamber.

[0036] Inside the helical conveyor path 5a a rotating cylinder 20 is provided. The conveyor is advanced by slip friction through the hollow cylindrical drum 20 which is driven by a motor 22, here provided below the cooking chamber 10. The rotating cylinder 20 has longitudinal openings 21 adapted to expel the conditioned air onto and around food products on the windings of the helical conveyor path. As explained in detail in EP2111112, these openings, also referred to as conduits, advantageously extend over the height of the windings of the conveyor path.

[0037] A fan 30 is provided in the shown embodiment concentrically within the rotating cylinder 20. The fan 30 is driven by a motor 33 provided below the cooking chamber and the rotating cylinder. The fan is provided for circulating conditioned air through the cooking chamber 10. A funnel-shaped inlet 31 of the fan is here provided at an upper end of the rotating cylinder 20, such that the direction of airflow into the fan is essentially vertical. An outlet 32 of the fan is in communication with the rotating cylinder and provides a horizontal direction of airflow, which via the openings 21 in the rotating cylinder advantageously expels the conditioned air onto and around food products on all of the windings of the helical conveyor path, in the direction of the arrows to the right-hand side of the drawing. In the shown embodiment, additional openings 2T are provided diametrically opposite the outflow openings 21.

[0038] According to the invention, seen in the direction of the circulating air, a heater 40 is provided upstream of the inlet 31 of the fan, a steam injector 45 is provided upstream of the heater 40, a natural smoke vapor generator 51 which is connected via a duct 52 to a smoke exhaust 50 is provided upstream of the steam injector and downstream of the windings of the helical conveyor path, such that the natural smoke emerging from the smoke exhaust is mixed with the injected steam ahead of being heated by the heater, prior to entering the inlet of the fan.

[0039] Heater 40, here heat exchange elements 40, is here provided at an upper part of the cooking chamber, situated above the helical path 5a.

[0040] Steam injector 45 is provided upstream of the heater 40, also at an upper part of the cooking chamber. In fig. 1 a nozzle is schematically shown, suitable for expelling hot water under pressure and as such generating steam in the left hand upper part of the cooking chamber 10. In embodiments, a bar of nozzles extends in the cooking chamber.

[0041] Upstream of the steam injector 45, in an area of the cooking chamber horizontally adjacent and downstream of the windings of the helical path 5a is provided a smoke exhaust 50, which is connected via a duct 52 to a natural smoke vapor generator 51 provided adjacent the spiral oven 1.

[0042] In the inventive spiral oven, the food products are transported through the cooking chamber 10 on the belt conveyor 5 by a drive, including operation of the cylinder drive 22. The belt conveyor 5 transports the food products from the entry 12 of the spiral oven to the exit 14 thereof, which exit 14 is advantageously connected to the inlet of a second cooking chamber.

[0043] In the cooking chamber conditioned air is allowed to circulate, as indicated by the arrows, here in a clockwise direction. The fan 30, operated by a motor 33, sucks in air via inlet 31 and expels air via outlet 32 to effect such circulation.

[0044] Within the essentially closed cooking chamber 10, the air expelled by the fan 30 at the outlet 32 thereof is allowed to flow onto and around food products positioned on windings of a helical conveyor path 5a of the belt conveyor 5. The rotating cylinder 20 has openings 21 to allow the air to be distributed over all windings.

[0045] This air thus treats the food products and will have a decreased temperature and contain less moist and smoke than prior to passing the food products. Having past the windings, this depleted air flow passes a natural smoke exhaust 50, where the air flow is provided with smoke to generate conditioned air comprising natural smoke.

[0046] Hereafter the air flow passes the steam injector 45 to receive steam, so as to generate conditioned air comprising a mixture of natural smoke and steam. The provision of the steam injector in the vicinity of the smoke exhaust results in mixing of the smoke and steam in a short period of time. The application of a smoke and steam mixture is advantageous over the application of pure smoke, both in view of pollution of the oven and health of the consumer of the food products, as smoke ‘dissolved’ in steam has proven to create less oven pollution and contains less carcinogenic contents. In addition, the transfer of smoke onto the food products to be treated is advantageously faster and more uniform, without negatively affecting the products. These advantages will also attribute to cost effectiveness of the treatment.

[0047] After the steam injector 45 the conditioned air flow with a mixture of natural smoke and steam passes heater 40 to generate conditioned air comprising a mixture of natural smoke and steam of a temperature set by the heater. The provision of the steam injector downstream of the heater is advantageous as the steam injector is able to increase the temperature of the air flow prior to the heater, thus saving energy.

[0048] After having past the heater the conditioned air is of a desired temperature and has a desired composition of steam and smoke. This conditioned air is sucked in by the fan to be expelled onto the food products, where steam and smoke and heat are transferred onto the food products. The ‘depleted’ air flow then circulates, via the smoke exhaust, steam injector and heater to be ‘complete’ for the next batch of food products.

Claims

CLAIMS1 . Spiral oven (1) for treating food products, comprising: a cooking chamber (10) having an entry (12) and an exit (14), a belt conveyor (5) for conveying the food products through the cooking chamber from the entry (12) to the exit (14) via a helical conveyor path (5a) with windings, a rotating cylinder (20) provided inside the helical conveyor path, a fan (30) for circulating conditioned air through the cooking chamber, comprising an inlet (31), and comprising an outlet (32) which is in communication with the rotating cylinder, the rotating cylinder having openings (21) adapted to expel the conditioned air outward onto and around food products on the windings of the helical conveyor path, wherein, seen in the direction of the circulating air, a heater (40) is provided upstream of the inlet (31) of the fan, a steam injector (45) is provided upstream of the heater (40), a natural smoke vapor generator (51) which is connected via a duct (52) to a smoke exhaust (50) is provided upstream of the steam injector and downstream of the windings of the helical conveyor path, such that the natural smoke emerging from the smoke exhaust is mixed with the injected steam ahead of being heated by the heater, prior to entering the inlet of the fan.

2. Spiral oven according to claim 1 , wherein two adjacent cooking chambers (10) are provided, each having an entry (12) and an exit (14), and wherein the exit of the first cooking chamber is connected via a passage to the entry of the second cooking chamber.

3. Spiral oven according to claim 1 or 2, wherein the fan (30) is provided within the rotating cylinder (20).

4. Spiral oven according to any of the preceding claims, and wherein the heater, the steam injector (45) and the smoke exhaust (50) are provided outside the cylinder.

5. Spiral oven according to any of the preceding claims, wherein a control system is provided to control the properties of the conditioned air in the cooking chamber.

6. Method for treating food products in a spiral oven with a cooking chamber, preferably a spiral oven according to any of the preceding claims, wherein conditioned air circulates through the cooking chamber, and wherein the conditioned air repeatedly: is expelled by a fan to flow onto and around food products positioned on windings of a helical conveyor path of a belt conveyor; passes a natural smoke exhaust to generate conditioned air comprising natural smoke; - passes a steam injector to generate conditioned air comprising a mixture of natural smoke and steam; passes a heater to generate conditioned air comprising a mixture of natural smoke and steam of a temperature set by the heater; and is sucked in by the fan.

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