EP0113900B1 - Apparatus and method for the treatment of food with microwaves - Google Patents

Description

The invention relates to a device for the continuous, thermal treatment of foods with microwaves in a treatment room designed as a cavity system with a mechanical transport device designed for the horizontal transport of the food through the treatment room, with means for feeding the microwaves via a waveguide into the Treatment room transverse to the direction of transport, with an air conditioning system designed for air conditioning and with means for introducing air conditioned in the vertical direction.

The invention also relates to a method for the continuous, thermal treatment of foodstuffs with microwaves, in a treatment room designed as a cavity system, in which the foodstuffs are transported horizontally through the treatment room and microwaves are irradiated into the treatment room transversely to the direction of transport, and in which climate-conditioned air is also introduced into the treatment room in the vertical direction.

Such a device and such a method are known from GB-A-1 053 012.

In known devices and in known methods of this type, the means for feeding the microwaves into the treatment room consist of a waveguide which is arranged centrally above the treatment room in the longitudinal direction of the treatment room. The waveguide has transverse slots on its underside facing the treatment room, through which the microwaves can exit into the treatment room. In a cavity system of this type, slightly standing waves can form, which leads to very different field strength distributions of the microwave energy in the treatment room. While in the known device the field distribution in the longitudinal direction of the band should be uniform, an inhomogeneous field strength distribution can be expected over the cross section of the band because of the special symmetry of the arrangement of the waveguide. This could be expressed, for example, by the fact that there is a higher field strength in the middle of the band than on the edges. Depending on the reflection conditions, a different distribution would also be possible. In any case, it can happen that a food particle that moves in the peripheral region of the conveyor belt is exposed to a more intensive or less intensive radiation all the way through the treatment route than a food particle that is located, for example, in the region of the center of the conveyor belt. This can lead to overheating and heat damage to one part of the good particles and to inadequate treatment of another part of the good particles.

The invention has for its object to provide a device for the continuous thermal treatment of food, in which the end products are improved and in particular overheating and heat damage to good particles are avoided.

In a device of the type mentioned, this object is achieved in that the means for feeding the microwaves into the treatment room are designed and arranged such that the microwaves fall horizontally into the treatment room in at least two levels.

In a method of the type mentioned at the outset, the solution is achieved in that the microwaves are irradiated horizontally in at least two planes.

The measure according to the invention cannot prevent locations with concentrated microwave energy from being formed, i.e. the energy concentration fluctuates in the longitudinal direction of the treatment room. When passing through these points, however, the individual good parts are only subjected to intensive thermal treatment for a comparatively short time that can be predetermined by the conveying speed. During the crossing of the treatment room, however, a single good particle reaches both zones of high and low concentration, so that the fluctuations are balanced out along the way. Furthermore, a mutual adjustment of the radiated energy and the conveying speed ensures that overheating and heat damage are avoided.

The fact that, according to the invention, a particularly balanced and uniform treatment of the food particles is achieved, the device and the method according to the invention can advantageously be used for pasta, the treatment of which is extremely difficult to understand, very complex physical and biochemical processes leading to complete consolidation and drying.

The microwave radiation into the treatment room is preferably carried out according to two principles or a combination thereof. According to a first variant, the microwaves are decoupled from the waveguide or the microwave radiation into the treatment room, hereinafter also referred to as the cavity system, via push-pull electrodes which protrude into the treatment room. The push-pull electrodes are preferably designed as single-wire or multi-wire long-field radiators (Lecher line).

Long field radiators of this type have the advantage that they build up a predetermined field distribution within a defined space enable. If several long-field radiators are used, a desired field structure can be generated even in a room of considerable dimensions - at least in the vicinity of the long-field radiators.

The long field radiators are preferably bridged on their side opposite their microwave coupling by means of an electrically conductive tuning slide. With the aid of this tuning slide, the location of the reflection plane required to form the standing waves on the Lech line can be varied as desired.

Long field radiators of this type are particularly suitable when the mechanical conveying element guides the food substantially flatly through the cavity system. In this case, the long-field radiators are preferably arranged at a certain distance, for example from a few to 10 or more centimeters, parallel to the flat mechanical conveying element. The greater the distance from the long-range radiator, the more evenly the microwave field is distributed in the good area.

According to the second variant, the microwaves are allowed to enter the cavity system directly from the waveguide. According to a modification of this variant, the microwave waveguide can protrude a little into the cavity space and preferably have one or more passage openings in its side walls.

The advantage of this direct coupling of the microwaves into the treatment room - that is to say without the use of long-range radiators - is that, in addition to the elements required for direct product promotion, there are no additional elements in the treatment room. This minimizes the possible attachment areas for dust and other undesirable deposits, including undesired product deposits - in particular, undesired product deposits would carbonize after a short time.

According to a further preferred embodiment, the mechanical conveyor device is realized by one or more air and microwave permeable material conveyor belts, preferably endless conveyor belts. The tapes are preferably made of sufficiently heat-resistant plastics.

Instead of the belts, the mechanical conveyor can also be designed as a scale belt. Both the belts and the scale belts are suitable for the mechanical conveyance of bulk goods which are particularly sensitive to pressure and breakage, for example short pasta. Depending on the type of food to be treated, the material can be guided through the treatment room as a layer, one or more centimeters thick, evenly distributed over the width.

An advantageous, further training idea lies in the use of a bar conveyor as a mechanical conveying element. Long pasta, for example spaghetti, pasta, lasagna, can be guided through the treatment room using the rod conveyor system known per se.

In this case in particular - but also in the case of other foods, in particular pasta - the advantages of the invention, namely the controllability of the individual parameters essential for drying, can be used. This is particularly true with regard to the market trend of being able to carry out the entire pasta production within a much shorter period of time.

In principle, each drying can be accelerated either by increasing the drying temperature of the surrounding air, by increasing the difference between the water content of the product and that of the surrounding air and / or by increasing the inherent temperature of the good particles to be treated.

In the case of food, however, there are now relatively narrow limits for both moisture and temperature. The transition from the liquid phase to the vapor form requires a corresponding increase in volume.

A decisive parameter for the economic operation of an entire pasta line is the conditioned air. As is known, the first phase of each drying process can be carried out in a relatively short time. In order to be able to accelerate the drying in the second phase, air has recently been used which is heated to a higher temperature.

Although the drying of pasta has long been aimed at, only limited real success has been achieved.

Accelerating the thermal treatment is countered by a qualitative influence on the properties of the treated goods, for example the cooking properties. To date, no economically satisfactory solution for the climate control from the pre-drying to the main drying of the pasta has been found.

By means of the device according to the invention or according to the method according to the invention, an acceleration of the thermal treatment of pasta can now be achieved in that both the temperature of the product and that of the climate can be controlled independently of one another, with an additional independence regarding the climate control Climate factors temperature and humidity are given - of course, only if the limits for the water saturation of air are observed.

Es hat sich gezeigt, daß die Ergebnisse bei allen Teigwaren besonders kritisch von der Einhaltung der Klimabedingungen im Behandlungsraum abhängig waren.For example, in the treatment of croissants and spirals among the The following conditions set excellent results:

It has been shown that the results for all pasta were particularly critically dependent on compliance with the climatic conditions in the treatment room.

According to the invention, the material is preferably heated directly to the desired temperature by the microwaves between a large climatic jump, regardless of the climate. For this purpose, the treatment room or the cavity system is connected between the pre-dryer and the main dryer. In the case of long goods, the bar conveyor with the pasta attached to it is guided through the cavity system in a continuous process. In certain cases it is advantageous to heat the pasta again during the final drying. As with the first climatic jump, the goods can be guided through a second cavity system with the bar conveyor or any belt. The supply of heat in the final drying process can at the same time prevent incrustation of the edge zone of each individual part of the pasta and thus also lead to a shortening of the thermal treatment time.

According to a further preferred exemplary embodiment, the mechanical conveyor device is designed as a rotatable drum. The drum is arranged wholly or partially within the treatment room.

So that the microwave energy can penetrate into the interior of the drum, it has microwave-permeable sections, so-called microwave windows. The microwave windows can be openings or holes in the drum wall. For example, the drum itself can have a sieve shape. In the case of fine powdery or dusty goods, however, it is advisable to make the microwave windows dustproof, for example by making them out of plastic. Rod-shaped or sheet-like planes formed in the drum wall are preferably used as the microwave window. The longitudinal axis of the rods or the longitudinal direction of the planes is preferably parallel to the longitudinal axis of the drum. In addition, especially in the case of comparatively short drums, microwave windows can also be arranged in the end faces of the drum. A particularly intensive, all-round microwave entry into the drum is made possible in that the drum preferably consists entirely of a microwave-permeable material, for example a suitable plastic.

However, the use of only single microwave-permeable windows in the drum enables the remaining parts of the drum to be made from steel or other highly wear-resistant materials. These versions are particularly suitable for thermal treatment in a higher temperature range, for example from 150 to 400 ° C.

According to a further preferred embodiment, the microwaves are coupled into the drum in that a long-field radiator is arranged essentially coaxially with the drum axis and projecting into it. In this embodiment, it is no longer necessary to radiate microwaves through the drum shell into the drum interior. At the same time, the arrangement of the long-field radiator along the drum axis ensures a sufficient distance between the long-field radiator and the good particles. In principle, this means that an additional treatment room surrounding the drum can also be dispensed with entirely.

If a thermal treatment in a temperature range of below 100 ° C. is required, the drum can, as already mentioned above, be made entirely of a microwave-permeable plastic.

A drum with an end product inlet and outlet and an end air inlet and outlet is preferred. At defined intervals between the product supply and the product discharge, the dwell time of the individual good particles can be controlled very precisely by controlling the drum revolutions per minute.

Conveying and lifting elements are preferably used in the drum interior in such a way that a vertical movement upwards and downwards is superimposed on the material in addition to the longitudinal movement through the drum. When emphasizing the vertical movement component, the prerequisite for an intensive interaction between the material and the direction of flow of the conditioned air is given. The air flow direction is almost transverse to the direction of movement of the goods.

In a further embodiment, the air inlet and outlet or the air duct are arranged transversely to the longitudinal axis of the drum. Depending on the type of material used, the cross section of the drum can be round or polygonal, preferably hexagonal.

A round drum cross-section allows the goods to be treated much more gently, whereas the polygon increases the movement of the goods.

According to a further preferred embodiment, the drum is divided into three sections, the two end sides each forming a cold zone which is responsible for the introduction and execution of the goods and the conditioned air.

A particularly gentle and nevertheless effective treatment can be achieved with an embodiment in which several drums are arranged axially parallel in the treatment program. The distribution of the material over several drums enables a thin layer to be maintained and thus intensive treatment by microwaves and by the conditioned air. The arrangement of several drums of small diameter has the advantage over the use of a single drum of larger diameter that the material is not raised as much by the lifting blades and accordingly falls back only over a short distance. The embodiment with several axially parallel drums is therefore particularly suitable for mechanically sensitive products.

From a design point of view, it has proven advantageous to rigidly connect the axially parallel drums to one another and to allow the system formed in this way to rotate about the common axis. The number of bearings is therefore not greater than in an embodiment with a single large drum.

The goods are fed into the individual drums via a single feed connector, which is alternately connected to the individual drums in the course of the rotation.

Brief description of the drawings

• Figur 1 zeigt eine Ausführungsform eines Cavity-Systems mit mechanisch bewegten Trommel.
• Figur 2 stellt einen Schnitt IV-IV der Figur 1 dar.
• Figur 3 zeigt die Anwendung der Erfindung bei der Herstellung langer Teigwaren.
• Figur 4 zeigt in vergrößerten Maßstab den Behandlungsraum entsprechend Figur 3, wobei die Teigwarentransportstäbe an einer endlosen Förderkette angehängt sind.
• Figur 5 stellt eine weitere Ausführungsvariante mit im Behandlungsraum angeordneten Förderbändern dar.
• Figur 6 stellt einen Schnitt der Figur 5 dar.
• Figur 7 stellt einen schematischen Schnitt zur Veranschaulichung der Einleitung der Mikrowellen von einem Hohlleiter über Langfeldstrahler in den Behandlungsraum dar.
• Figur 8 zeigt eine Ausführungsform mit vier achsparallelenen Trommeln
• Figur 9 zeigt einen Schnitt XI aus der Figur 8.
• Figur 10 zeigt einen Schnitt XII aus der Figur 8. Die Figur 1 stellt einen Längsschnitt durch eine Einrichtung zur kontinuierlichen thermischen Behandlung dar. Die Vorrichtung besteht aus einem Metallgehäuse 1, das innen mit einer Wärmeisolation 2 versehen ist. Die Wärmeisolation 2 ist gegenüber dem Cavity-System-Innenraum mit einem Mikrowellen- reflektierenden Material, in folgendem Reflektormaterial 3 genannt,begrenzt, und zwar derart, daß ein vollständig nach außen abgeschlossener Behandlungsraum 4 gebildet wird.

The invention will be explained in more detail with reference to some exemplary embodiments with reference to the attached schematic drawings.

• FIG. 1 shows an embodiment of a cavity system with a mechanically moved drum.
• Figure 2 shows a section IV-IV of Figure 1.
• Figure 3 shows the application of the invention in the manufacture of long pasta.
• FIG. 4 shows the treatment room corresponding to FIG. 3 on an enlarged scale, the pasta transport bars being attached to an endless conveyor chain.
• FIG. 5 shows a further embodiment variant with conveyor belts arranged in the treatment room.
• Figure 6 shows a section of Figure 5.
• FIG. 7 shows a schematic section to illustrate the introduction of the microwaves from a waveguide via long-field radiators into the treatment room.
• Figure 8 shows an embodiment with four axially parallel drums
• FIG. 9 shows a section XI from FIG. 8.
• FIG. 10 shows a section XII from FIG. 8. FIG. 1 shows a longitudinal section through a device for continuous thermal treatment. The device consists of a metal housing 1, which is provided with thermal insulation 2 on the inside. The heat insulation 2 is limited in relation to the cavity system interior with a microwave-reflecting material, referred to in the following reflector material 3, in such a way that a treatment space 4 which is completely closed to the outside is formed.

In Figure 2, a magnetron space 5 is provided on the side, in which the magnetrons 6 required for microwave generation are installed. To protect against the outside space, the magnetron room is also provided with a microwave-proof outer skin. In Figures 1 and 2, only a few magnetrons 6 are schematically provided on the same side. In the case of a larger device, in particular if its length dimensions are enlarged, a larger number of magnetrons would have to be provided.

It would be expedient to arrange the magnetrons, including their microwave decoupling devices and adjoining waveguide 7, to the left and right of the treatment room 4 in a corresponding magnetron room.

An electrical supply with the devices required for the magnetron supply and control is provided below the magnetron space 5. The microwaves are coupled into the waveguide 7 by the magnetron 6 and are emitted by the latter directly into the treatment room 4 through one or more couplers 8.

Depending on the particular conditions, additional movable or immovable reflectors, which are not shown, can of course be provided in the treatment room 4. As will be shown, however, in the majority of cases, these aid measures known per se can be completely or at least largely dispensed with.

A rotatably mounted drum 9 is arranged within the treatment room 4. The drum 9 is supported on its two end sides on a drum bearing 16 and is driven by a drive motor (not shown) via a gear wheel 15. The drum 9 has a stiffening cross 10 on each end. The stiffening crosses 10 each have a tubular hub 11 guided in the drum bearings 16. On the right-hand side of the figure in FIG. 1, an air supply 13 is tubular and is guided through the hub 11 into the interior of the drum 9. An air discharge 14, in the exemplary embodiment shown in the form of a tube arranged coaxially with the air supply 13, is arranged on the end face of the drum 9 opposite the air supply 13.

The drum jacket has a larger number of holes 21 in the region of the air discharge end of the drum 9. These holes serve to discharge the product from the drum 9. Below the drum 9, in the area of the holes 21, a collecting funnel 20 is arranged for the material treated in the drum 9. The collecting funnel 20 opens directly into a rotary lock 18 which transfers the product via a connecting piece 25 downstream - not shown - away means of transport.

The product feed is located on the right-hand (referring to FIG. 1) end side of the drum 9. For this purpose, a funnel 31, a rotary lock 32 and a microwave-impermeable channel 33 are provided. The channel 33 is aligned with holes 34 in the drum shell. The bores are designed in such a way that they allow the good particles to be introduced into the interior of the drum. In the interior of the drum, namely below the holes 34, a baffle plate 35 which tapers in the shape of a truncated cone to the center of the drum is arranged. The guide plate 35 serves to deflect the product particles entering the interior of the drum from the holes 34 in the direction of the center of the drum. The purpose of the guide plate is therefore to direct the material into the interior of the drum 9 without back pressure or "dead corners".

As can be seen from FIG. 2, at least the central drum section has a hexagonal cross section. For this purpose, the drum 9 is composed of six flat or slightly curved plates 36 in its central section. In addition, longitudinal profiles 37 are arranged in the corners of the hexagon:

For the microwave treatment of the food inside the drum, for example, the plates 36 and / or the longitudinal profiles 37 can be designed as microwave windows, ie they can be microwave-permeable. Instead, longitudinal rods provided in the drum shell parallel to the drum axis can also be used as microwave windows.

In addition to their already described function as a microwave window, the longitudinal bars can also perform a further function, namely to overturn the product, as is known per se from other drum applications, by the friction behavior between the product on the one hand and the longitudinal bars and the inner wall of the drum 9 on the other hand , there is a kidney-shaped movement of the product in the drum 9.

A construction has proven to be a very expedient solution in which the plates 36 are designed as microwave windows and the rest of the drum is essentially made of steel. With this solution, almost the entire drum circumference can be used for feeding microwaves from the treatment room 4 into the drum interior. Of course, the end faces can also be provided with microwave-permeable inserts 38.

According to a preferred embodiment for the treatment of very delicate products, the drum 30 is divided into three treatment zones by corresponding reflector elements 39 and 40, namely a hot zone in the middle of the drum and a cold zone adjoining it to the outside, i.e. a cold zone in the area of the product feed and the other -Product withdrawal. In the essentially hexagonal hot zone, conveyor pallets 41 can be fastened to ensure an exact dwell time of the individual good particles. The conveyor pallets 41 are preferably formed from microwave-permeable material, so that no microwave reflections occur at these points.

The device according to FIGS. 1 and 2 has the particular advantage that the two end regions of the drum 30, that is to say the cold zones, can be designed for the specific type of product. This also applies to the product locks upstream or downstream in the product flow direction. In the exemplary embodiment shown, the input lock 32 and the output lock 18 each primarily have a climate lock function. At the same time, they serve as a safety gate for a microwave outlet. It should only be mentioned in passing that microwave barriers 13 'and 14' are provided in the air supply and air discharge, which also serve as a climate barrier. For this purpose, for example, an air-permeable fine fabric or grid made of electrically conductive material, preferably metal, is suitable.

The operation of the device described so far is now as follows:

At the start of processing any bulk material, the microwave generator, i.e. H. the magnetron (s) 6 are switched on and the microwave energy is supplied to the treatment room 4 via the waveguide 7. At the same time, conditioned air is introduced into the interior of the drum 9 via an air conditioning system (not shown) through the air supply 13 and is led out of the drum again via the opposite air discharge 14. The parameters that determine the climate are preselected as a function of the other process parameters, in particular as a function of the food used, the treatment to be carried out with it or the desired end product and the irradiated microwave energy.

For this purpose, the necessary air is preferably passed through the inside of the drum in such a way that a slight negative pressure is created inside the drum. Finally, the product is fed into the interior of the drum via the feed hopper 21.

In the exemplary embodiment shown in FIG. 1, the waveguides 7 open open into the treatment room 4. The microwaves emerging from them are reflected by the microwave-reflecting wall 3 until they reach the inside of the drum through one of the microwaves. This already brings about a quasi-statistical pre-distribution of the microwave radiation or an equalization of the microwave field in the treatment room 4. Of course, the entry of the microwaves into the drum is independent of whether the drum is rotating or stationary. The rotation of the drum is essentially used to ensure movement of the good particles inside the drum and thus to prevent the burning of good particles which are stationary on the microwave windows. Since not only the entire treatment room 4 is lined with the microwave-reflecting wall 3, but also the drum bearings 16, the handle 11 and the product collecting funnel 20 are microwave-impermeable, in particular lined with microwave-reflecting material, the microwaves radiated into the treatment room 4 can no longer do so leave. All parts of it reflect back and forth until they finally enter the inside of the drum through the microwave windows. Possibly. Microwaves emerging from the inside of the drum are subject to the same fate.

Since, as is well known, every change in an electromagnetic field, in particular also in a microwave field, propagates at the speed of light, any necessary changes or interventions in the microwave field are passed on to the product particles to be treated with virtually no delay.

The drum 9 is preferably given a rotational speed of only a few revolutions per minute. The knowledge gained so far indicates that the speed can be varied as required in the range required for the industrial purpose - this with regard to the required protection of the product to be treated. For products that are particularly sensitive to breakage or friction, the speed can be varied from 1 to 10 revolutions per minute. These revolutions are particularly suitable, for example, for the thermal treatment of particularly delicate pasta parts, for example fine muesli, etc. In particular, this applies at the beginning of the drying phase, if necessary after a short drying of the pasta in a pre-dryer. Other products can be thermally treated according to the invention at 10 to 100 drum rotations per minute. This includes most foods, such as rice, barley, wheat, corn, soybeans, hazelnuts, coffee, bean flour, tobacco, etc.

As already stated, a kidney-shaped movement path is forced on the product after it enters the drum. This movement has a component pointing in the axial direction, which is determined by the degree of filling of the drum 9, the angular position of the conveying pallets 41 and in particular by the speed of the drum 9. The second movement component of the good particles runs almost vertically upwards and downwards. If one now assumes that the microwaves enter the drum 9 essentially radially, it follows that the direction of the microwave entry into the drum 9, the direction of the preferred flow of the climate-conditioned air through the drum 9 and the direction of the preferred movement of the product in the drum 9 are orthogonal to each other. It should also be noted here, however, that the micro-wave beams are in any case reflected repeatedly within the drum 9 if the parts of the drum that are not designed as microwave windows, such as the microwave-reflecting wall 3 of the treatment room 4, reflect the microwaves.

Another aspect is particularly emphasized, namely the exact possibility of controlling the dwell time of the individual particles in the drum 9. The dwell time of the individual good particles in the drum is namely determined by the aforementioned axial component of the good movement. This in turn can be controlled extremely precisely by the drum speed selected in each case.

With the device described above, excellent results have already been achieved in terms of product quality. This is due in particular to the mechanical forced conveying already described, which guarantees a very uniform drum dwell time for each individual good particle, the exposure of each individual good particle to the climate-conditioned air and the average even microwave exposure to the good particles. It should also be noted here that the climate conditioning, in particular the temperature of the climate, can be controlled essentially independently of the microwave temperature control of the individual good particles - and vice versa. In particular when the elements of the treatment room 4, but in particular those of the drum 9 - namely both the microwave window and the microwave-impermeable elements consist of appropriately temperature-resistant materials.

This device has made it possible to control all the essential parameters for the thermal treatment of bulk goods, in particular foodstuffs and luxury foods, independently of one another. For example, very high temperatures, for example 200 to 400 ° C inside the individual good particles are achieved, the temperature of the climate-conditioned air, on the other hand, is set to only about 100 ° C. and the moisture content of the climate is also optimized for the treatment required, for example from the point of view of the absorption of the water released. Such a setting of the above three parameters is suitable, for example, for roasting coffee or hazelnuts.

The device according to FIGS. 1 and 2 offers great possibilities of variation, in particular with regard to safety-related questions regarding a microwave exit. It can therefore be regarded as optimal for safety reasons.

It also has the advantage that the thermal treatment can be carried out in a device known per se, namely a mechanically moved drum. The rotary movement of the drum 9 forces the movement and mixing of the individual product particles necessary for the uniform thermal treatment and in particular also permits intensive washing of the individual product particles with the climate-conditioned air.

Another advantage is that the constant movement of the drum 9 and the aforementioned equalization of the microwave field in the treatment room 4 ensure a highly uniform exposure of the individual good particles to microwaves inside the drum 9, even then , if the "virgin" microwave field radiated directly into the treatment room 4 varies greatly.

The arrangement of the drum in a closed microwave-reflecting treatment room, that is to say in a cavity system, results in a particularly favorable field distribution of the microwaves, which penetrate radially into the interior of the drum through numerous moving microwave windows. The formation of standing waves and the associated spatial field strength differences are avoided.

The desired energy distribution in the treatment room 4 can be ensured in various ways. In a further development of the inventive concept, two options for energy supply and a combination of these two options have proven to be very advantageous.

According to the first possibility, the microwave energy is coupled out directly from the waveguide into the treatment room, that is to say without any special coupling devices being interposed.

FIGS. 3 and 4 represent a further embodiment of the invention, an entire food production line being illustrated in FIG. 3. In the exemplary embodiment shown, it is a matter of producing pasta, in particular so-called long goods, raw material, semolina, water and any ingredients are input into a mixer 50. The doughy mass emerging from the mixer 50 is brought into the desired shape of the pasta, in this case long goods, in a press 51 by means of suitable pressing tools 52. The long goods must be hung from the freshly pressed state until they dry out on rods 57 still shown. This takes place in a hanger 53. The hanger 53 conveys the rods 57 with the long goods attached to them into and through an dryer 54. In the dryer 54, a targeted stabilization of the air is aimed at stabilizing the shape of the pasta. At the same time, part of the water is removed from the pasta.

The actual pre-drying takes place in a pre-dryer 55, the major part of the water being able to be removed from the food in the pre-dryer. The temperature in the pre-dryer 55 is set according to the new solution in a range of about 80 to 100 ° C. Accordingly, relatively harsh climatic conditions, i.e. There are large differences between the absolute moisture in the pasta and the relative humidity of the air between the pre-drying and the pre-drying, for example a temperature jump of around 30 to 40 ° C and more. The core problem for overcoming such a large jump in temperature lies less in the heating of the goods themselves, but rather in the interplay between the water content of the pasta and the humidity of the surrounding climate.

Because of the described possibility of independently controlling the microwave energy supplied to the pasta on the one hand and the conditions of the climate surrounding the pasta on the other hand, such a temperature jump can be coped with without disadvantage. The mentioned control options allow the independence of the adjustability of the temperature of the goods themselves and of the temperature and the relative moisture content of the surrounding air, such that the temperature of the surrounding air can easily have a much lower value than the inside temperature of the pasta. This allows the humidity to be controlled in such a way that the dreaded sweating problems - on the one hand between the goods and the air immediately surrounding them and on the other hand between the temperature in the treatment room and the room temperature outside the treatment room - can be solved. The climate of the air surrounding the pasta can namely be controlled so that despite comparatively low temperatures Climate-conditioned air that can absorb moisture escaping from the pasta without condensation.

The fact that the temperature of the air conditioned and surrounding the pasta can be kept low also prevents the equally disadvantageous sweating in the area of the entire installation of the treatment room. Because the temperatures of the climate-conditioned air can be set to about 60 to 80 ° C, so that at the usual temperatures of 20 to 30 ° C of the outside air surrounding the treatment room, the condensation problems between the installation parts and the room air are easily solved in a manner known to me can be.

The drying described above is diametrically opposed to the current trend in climate control when drying food, in particular pasta. The current trend is pointing towards so-called overheating or super-hot air drying - in each case without the use of microwaves. This leads to considerable condensation problems, in particular also with regard to the extreme temperature differences between the treatment room and the outside space surrounding the treatment room. The formation of condensation on the installation parts in the treatment room causes the dreaded sticking of the pasta, in particular the long goods, to one another and to the installation parts.

According to FIG. 4, the pasta 56 on the bars 57 are continuously transferred from a first conveyor 58 from the dryer 54 to a further endless conveyor 59. The handover is carried out in a manner known per se. The endless conveyor 59 moves in a treatment room 60, in which microwave outcouplings 61, be it in the form of long-field radiators or direct outcouplings, are attached from a waveguide at suitable points. The question of the inward and outward transfer of all essential elements, i.e. the long goods and the climate-conditioned air, is particularly important in this application. The problem of introducing the long pasta has been solved in that in the area of the transfer of the rods 57 in front of the dryer 54 to the endless conveyor 59 into the cavity or treatment space 60, a vertical product entrance lock shaft 62 is passed through by the pasta. This product entrance lock shaft 62 has a length L such that no microwaves can get from the treatment room 60 into the dryer 54. The inner lock shaft wall 63 is perforated. The outer lock well wall 64 can be made of microwave absorbing or reflecting material. It is essential that the product entrance lock shaft 62 has only a width B which is only slightly larger than the corresponding transverse dimension C of the hanging goods, in this case the long goods 56. As shown, the endless conveyor 59 travels through the treatment room 60 in a plurality of loops, the climate-conditioned air used for the treatment flowing through the treatment room 60 from bottom to top according to arrow 65 in FIG.

According to FIG. 4, the air movement is forced by a fan 66, the air movement being circulated from a side blow-in shaft 67 (bottom in FIG. 4) through an outflow shaft 68 (in FIG. 4 top). Outside the treatment room 60, the - not shown - necessary elements for climate conditioning, such as air heaters, coolers, humidifiers and dryers are arranged - as well as the corresponding connecting channels. The air can be partially removed from the dryer 54 and discharged into the pre-dryer 55.

However, it is also possible to remove the air or a part of the air from the pre-dryer 55 and to mix and process it via means (not shown) via the fan 66 into the treatment room 60.

A product exit lock shaft 70 is located, according to FIG. 4, at the upper right end of the treatment room 60. The product exit lock shaft 70 has a height L and width B corresponding to the product inlet lock shaft 62; likewise a perforated sheet metal as the inner shaft wall 71 and a microwave-absorbing or reflecting outer shaft wall 72.

The rods 57 hung with the pasta 56 are taken over in the pre-dryer and moved by a further conveyor 73 in the pre-dryer 55 in accordance with the throughput time required there.

The entire treatment room 60 has an inner microwave-reflecting wall 74, an outer shell 76 and an insulation layer 75 arranged between the wall 74 and the shell 76. These measures serve to prevent a microwave leak from the treatment room 60. For this purpose, the blowing-in / out longitudinal shafts 67, 68 are also provided with the microwave-reflecting gratings already described.

This variant allows a surprisingly simple and elegant operating procedure. The two product input / output lock shafts 62, 70 have a triple function at the same time, in particular due to their narrow, vertical design. During operation, these two lock shafts 62, 70 are essentially closed by the pasta. Air conditioned to a special climate cannot escape through the two lock shafts 62, 70 Exit treatment room 60; Likewise, no (uncontrolled) outside air enters the treatment room 60 through these lock shafts. At the same time, these two lock shafts also serve as a microwave barrier.

• - mechanische Ein/Ausschleusung der Ware,
• -Luft-Ein/Aus-Schleusung und
• -Mikrowellensperre

ohne irgendwelche zusätzlichen mechanisch bedingten Teile gelöst.This is the triple problem in the simple way mentioned

• - mechanical goods in / out,
• -Air-on and off airlock and
• -Microwave lock

solved without any additional mechanical parts.

The vertical entry and exit of the goods via the product entry / exit lock shafts 62, 70 is essential. In pasta factories there is usually a sufficient room height so that the individual elements of the product processing line have or can utilize a corresponding room height, such as this is shown for example in Figure 4. The treatment room 60 essentially has a dominating vertical dimension.

Of course, it is also possible to "lengthen" the treatment room, so to speak. As a result, the triple reversal or loop formation of the endless conveyor 59 can be omitted. The design would be analogous to the element design of the dryer 54, with several elements being arranged lengthwise. In the case of long goods, it is very important that the air flow flows around the individual long goods, since otherwise there is a risk of the shape of the individual pasta deviating and sticking together.

In Figure 4, the air movement is transverse to the net direction of transport of the pasta, from left to right in the illustrated embodiment. However, if one looks at the individual sections of the pasta on the endless conveyor 59, the pasta 56 travels the longest distance in a direction parallel to the air movement.

According to Figure 3, the thermal treatment of the pasta according to the invention is not only between the pre-dryer and the pre-dryer 55, i.e. in the treatment room 60, but also between the pre-dryer 55 and a final dryer 80, i.e. namely performed a further treatment room 81. Even in the treatment section lying between the pre-dryer 55 and the final dryer 80, the main problem lies in the control of a temperature jump in the pasta or in the conditioned air. In this section in particular, the use of the thermal treatment according to the invention has proven to be particularly interesting, since the temperature of the pasta can be brought to the maximum in the vicinity of a little below 100 ° C. almost without delay. The treatment room 81 used in this treatment section corresponds to the treatment room 60 connected between the dryer 54 and the pre-dryer 55. The pasta heating by means of the microwaves here enables the pasta to be heated almost instantaneously to its maximum temperature, which is only slightly below 100 ° C. The conditioning of the air can be optimized essentially solely with regard to the removal of the water.

The further advantage of mastering the drying times as a whole should be emphasized. After traditional drying, the final drying usually takes up most of the total drying time. With the solution according to the invention, in particular the drying time in the final drying can be reduced to a fraction of the previous values. This results in a gentler product treatment since the heat supply to the pasta or the heating of the pasta takes place only for a very short time. After the temperature peak is reached, the heat is used to dry off the expelled water. Investigations by the applicant have shown that the goods treated according to the invention were of a quality which is at least equal to that of the traditionally dried goods.

The transport route of the goods through the entire drying system is illustrated in FIG. 3 by the dashed line 82.

The method according to the invention and the device according to the invention are essentially characterized by the advantages of saving time and mastering the condensation or condensation water problem achieved with them. The problems that often occur when heating or air conditioning air can also be solved in a simple manner according to the invention.

Figures 5 and 6 show a further embodiment of the invention. The thermal treatment of the bulk material is carried out on two endless conveyor belts 100 and 101. These conveyor belts are located in their entirety in a treatment room 102, which (in the direction from the inside to the outside) is delimited from the outside by a microwave-reflecting wall 103, an insulation 104 and an outer shell 105.

A product feed 106 is shown on the upper left edge of the figure in FIG. From this product feed, the material is metered directly onto the conveyor belt 100 via a rotary lock 107. The rotary lock 107 prevents both the entry / exit of false air and an undesired microwave exit. As an additional safety measure, the product feed 106 can also be equipped with a microwave-absorbing material 108 over a length designed for this purpose. The two conveyor belts 100 and 101 are driven by (not shown) motor means and can in their Speed can be set to the desired dwell time. The product is transferred from the lower conveyor belt 101 via a discharge lock 109 from the treatment room 102 to a further conveyor belt 110.

The direction of movement of the climate-conditioned air is illustrated in FIGS. 5 and 6 by a number of arrows 111 pointing upwards. It is particularly important that the climate-conditioned air is guided evenly through the belts 100 'and 101' made of breathable material. According to FIG. 6, the conditioned air is conditioned in an air conditioning system arranged on the side of the treatment room 102. The air flowing out of the treatment room 102 is conducted via a duct 112 to the air conditioning system. In the air conditioning system, the air is passed through a heating element 113, a humidifier / dryer 114 and a cooler 115 and then blown back into the treatment room 102 via a duct 116. A fan 117 is installed in the duct 116, which maintains the pressure for the necessary air circulation. For economic operation of the system, part of the used air is released to the outside via a flap 118. It is possible to draw in fresh air 119 via a flap. The two flaps 118, 119 are preferably controlled by the actual climate regulation; likewise the heating element 113, the humidifier / dryer 114 and the cooler 115. Depending on the particular use and the necessary width B of the air-permeable belts 100 'and 101', it can be advantageous to introduce the air conditioned on both sides of the treatment room 102 into the latter. For this purpose, an additional air conditioning system, indicated by the dashed line 120, is particularly suitable, which is arranged on the opposite side of the previously mentioned air conditioning system with respect to the treatment room.

According to FIGS. 5 and 6, a plurality of magnetrons 121 and waveguides 122 are arranged outside the treatment room, more precisely below the same and laterally offset from the belts 110 and 101. The microwaves generated in the magnetrons 121 are coupled out into the waveguide 122 in a conventional manner and fed to the treatment room 102 via the latter. The magnetrons are supplied with energy and controlled via corresponding electrical supply means 123.

In FIGS. 5 and 6, the treatment room occupies approximately the upper half of the picture. This is followed by a second process zone arranged in the lower half of the figure, into which the product coming from the treatment room 102 enters. The product cools and / or stabilizes on the conveyor belt 110 arranged in this process zone. The air conditioning required for the cooling and / or stabilization zone is not shown. If the exemplary embodiment of the invention shown in FIGS. 5 and 6 is used for drying short pasta, it is necessary to stabilize the pasta beforehand in a shaker dryer. Apart from this predrying, in this case the entire drying and stabilization of the pasta is carried out in a single unit.

• - die horizontal geführte Bewegung der Ware auf den Förderbändern 100 und 101,
• - die senkrecht zur Warenbewegung, quer durch die Förderbänder 100 und 101 gerichtete Führung der klimakonditionierten Luft und
• - die horizontale, quer zur Bewegungsrichtung der Förderbänder 100 und 101 gerichtete Einstrahlung der Mikrowellen.

With a corresponding ^"device notifier the performed tests led to very good results, especially regarding the quality of food. The control of the following three basic parameters has proven to be a very important point:

• the horizontal movement of the goods on the conveyor belts 100 and 101,
• - The guidance of the climate-conditioned air and perpendicular to the goods movement, directed through the conveyor belts 100 and 101
• - The horizontal radiation of the microwaves directed transversely to the direction of movement of the conveyor belts 100 and 101.

In addition to and / or in addition to the waveguide direct coupling 124 shown in FIGS. 5 and 6, the long-field radiator 125 shown in FIG. 7 has proven to be particularly advantageous for the microwave feed. The long-field radiators 125 have the advantage that the microwave field they set up is relatively uniform in the direction of the wire conductor even after a relatively short distance from the wire conductors - the distance was measured in the radiation direction.

In the exemplary embodiment illustrated in FIGS. 5 and 6, a plurality of long-field radiators 125 are guided in parallel over the surface of the strips 100 and 101, the individual long-field radiators 125 being arranged offset with respect to one another (FIG. 5).

The treatment room 102 represents a cavity system in that a considerable part of the microwaves is reflected in the microwave-reflecting wall 103 one or more times. These reflections result in a relatively even distribution of the microwave energy throughout the treatment room.

Experiments have shown that with this solution different foods could be successfully subjected to different thermal treatments, in particular soybeans could be treated or debittered or peeled. Excellent results have also been achieved in the treatment of bean flour. In addition, snacks or z. B. Tobacco ribs are successfully puffed.

In the exemplary embodiment in FIG. 6, the long-field radiator is designed in the manner of a Lech line system.

In Figure 7, the decrease in energy from the individual magnetrons 145 via the waveguide 132 and a coupling bar 133 shown in elevation.

However, the main advantage of using long-field radiators is that the energy distribution can be adjusted over a relatively large length dimension.

As can be seen from the aforementioned exemplary embodiments, it is also important that the microwave is introduced into the treatment room in a given definable and, if necessary, adaptable direction.

The electromagnetic field vibrates according to the frequency of the electromagnetic radiation. This frequency is preferably 2450 MHz or 915 MHz. It can be seen from this that the energy input of the microwaves can take place continuously or intermittently by means of an appropriate electronic circuit. With intermittent feeding, any interval game can be selected in order to control the short or medium-term energy output to the product in this way.

Although less common, the magnetron's energy output can be regulated by regulating the current consumption.

A further exemplary embodiment of the invention is shown in FIGS. 8 to 10. This embodiment also has a treatment room 4, which consists of a metal housing 1, thermal insulation 2 and a microwave-reflecting layer 3. The microwaves are introduced into the treatment room 4 via waveguide outcouplings 8. An inlet funnel 31, a rotary lock 32, a channel 33 or a collecting funnel 20, a further rotary lock 18 and an outlet port 25 serve for feeding and discharging the goods, as in the exemplary embodiment in FIG. 1. The space 5 containing the magnetrons is only strong indicated in simplified form in FIG. As in the exemplary embodiment in FIG. 1, a connecting piece 13, which is sealed with the aid of a grating 13 ′ against the escape of microwaves, is used to supply climate-conditioned air. A nozzle 14 serves to discharge the air. The nozzles 13 and 14 are rotatably supported by means of bearings 16 in opposite walls of the treatment room 4 and carry the transport device. In this respect, the exemplary embodiment in FIG. 8 corresponds to the exemplary embodiment in FIG. 1, so that reference is made to the exemplary embodiment in FIG. 1 for further details of the components mentioned.

1, the transport device of the embodiment of FIG. 8 consists of four drums 9 arranged axially parallel. The drums 9 are each rigidly connected to one another at their front ends by a cover-shaped closure 43, 44.

The two lid-shaped cylindrical ends 43 and 44 are each connected in the center to the rotatably mounted connecting pieces 13 and 14, so that the conveyor device can be rotated about its central longitudinal axis. Baffles 35, which are star-shaped in cross section, as can be seen in FIG. 10, ensure the uniform distribution of the climate-conditioned air entering via the connection 13 and the uniform distribution of the product entering via the duct 33 to the individual drums 9. The one closest to the feed point Lid-shaped closure 43 has a plurality of radial bores 34 through which the feed channel 33 is alternately connected to the individual drums 9 in the course of the rotation of the conveying device and the material is introduced alternately into these drums. By rotating the conveying device about its central longitudinal axis, the material is conveyed in the longitudinal direction (based on FIG. 8 from right to left) by the action of the conveying bars. Thereafter, the four streams of material from the drum 9 combine in the outlet-side cover 44. The feed of the material through holes 21 of the cover 44 and the collecting funnel 20 takes place in the same way as in the exemplary embodiment in FIG. 1, so that a new description is dispensed with can.

The fact that the material flow in this embodiment is distributed over four smaller drums results in a smaller layer thickness, so that even microwaves of shorter wavelength can penetrate the material safely. In addition, the falling distance of the goods lifted by the conveyor strips 28 is smaller, so that pasta which are sensitive to mechanical stress can also be treated satisfactorily. The fact that the individual drums 9 not only rotate about their own longitudinal axis, but rather run through almost the entire treatment area through the rotation of the entire conveying device, any field inhomogeneities are compensated for and it is ensured that the entire material is treated evenly.

As in the embodiment of FIG. 1, zones of different temperatures can be provided in the device according to FIG. 8.

Claims (10)

1. Equipment for the continuous thermal processing of foodstuffs by means of microwaves, in a processing chamber (4; 60; 80; 102) constructed as a cavity system, having a mechanical conveyor (9; 30; 59; 100; 101) designed for conveying foodstuff horizontally through the processing chamber, means for supplying the microwaves to the processing chamber via a wave-guide across the direction of conveyance, an air-conditioning system designed for climatically conditioning the air, and means for introducing the climatically conditioned air in a vertical direction, characterized in that the means (8; 61; 125) for supplying the microwaves to the processing chamber (4; 60; 80; 102) are so designed and arranged that the microwaves are incident horizontally in at least two planes in the processing chamber (4; 60; 80; 102).

2. Equipment according to Claim 1, characterized by a microwave switching device for switching the microwaves into the processing chamber (4; 60; 80; 102) alternately from left and right.

3. Equipment according to Claim 2, characterized in that the microwave switching device has push-pull electrodes (140), which are constructed as longitudinal field radiators and project into the processing chamber (102).

4. Equipment according to at least one of the previous claims, characterized in that the mechanical conveyor (59; 100; 101) consists essentially of one or more air-porous belts (100'; 101'), articulated belts or rod conveyors, and is guided through the processing chamber (102) on a pluralicy of planes.

5. Equipment according to at least one of the Claims 1 to 3, characterized in that the mechanical conveyor (9; 30) is constructed as a rotatable drum, and the drum (9; 30) has microwave windows (12; 26; 36; 37) in the drum envelope (9') and/or at the end faces of the drum.

6. Equipment according to Claim 5, characterized in that the drum (9; 30) consists essentially of a material (plastic) transparent to microwaves.

7. Equipment according to Claim 5, characterized in that the drum envelope (9') consists essentially of steel.

8. Equipment according to at least one of Claims 5 to 7, characterized in that for switching in the microwaves at least one longitudinal field radiator (125) is provided, arranged essentially coaxially with the drum axis.

9. Process for the continuous thermal processing of foodstuffs by means of microwaves, in a processing chamber (4; 60; 80; 102) constructed as a cavity system, in which the foodstuff is conveyed horizontally through the processing chamber and microwaves are directed into the processing chamber across the direction of conveyance, and in which, further, climatically conditioned air is introduced into the processing chamber in a vertical direction, especially by means of the equipment according to at least one of the previous claims, characterized in that the microwaves are directed horizontally in at least two planes.

10. Process according to Claim 10, characterized in that to accelerate the drying and/or stabilizing of long farinaceous products (56), the latter are guided hanging through the processing chamber (60; 80).

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