HU202075B - Method and apparatus for generating smoke for treating foodstuffs by smoking - Google Patents

Abstract

The invention relates to a method and a device for producing smoke for smoking foods. The smoke is produced by combustion from above, and only collected when the layer of charcoal produced on combustion of the fuel has a thickness of approx. 0.5-100 mm over the fuel layer. The layer of charcoal functions as a flow regulator for the combustion air, it being possible to cause combustion to take place at a temperature which is suitable with regard to the development of flavourings and harmful substances. The layer of charcoal also functions as a selective filter, as it removes harmful substances from the smoke. <IMAGE>

Description

The present invention relates to a method and apparatus for generating smoke for treating food with smoke.

It is a known method of preserving and flavoring food, such as meat and fish, by smoking, maturing-smoking. However, this method of treating food has the disadvantage that, when burning or heating wood for smoke production, in addition to the desired taste and aroma components, harmful substances are released, among which they have carcinogenic properties.

The problems caused by harmful substances have been known for a relatively long time and many solutions have been proposed to solve them. These methods are usually aimed at treating the smoke produced by attempting to separate the flavoring components and the harmful substances separately to produce their own fractions.

One such known process is to include cooled surfaces in the smoke flow path, assuming that the harmful substances in the smoke are condensed on these surfaces. Such processes also partially function as desired; certain harmful substances, such as tar, are separated from the smoke and remain on the condensing surfaces. Other harmful substances are condensed, however, the efficiency of these processes is not satisfactory, they are able to remove only a part of the harmful substances, but at the same time the desired flavor and residues for the smoking technology are lost, thus providing the desired taste and flavor of the final product. To be able to do this, the smoke treatment must be intensified.

More efficient methods are based 35 on the observation that flavoring substances in smoke are usually water soluble while harmful substances are generally insoluble in water.

This observation is a so-called. Led to the development of "indirect" smoking technology. The desired flavor and flavor components were selected from the smoke by washing with water. This aqueous fraction was then subjected to various physical and / or chemical processes to obtain the least harmful liquid smoke fraction, 45 which however is rich in flavor. To provide the smoking effect, the foods to be smoked are soaked in this liquid smoke fraction to give the desired flavor to the final product. After soaking, the food can even be subjected to a perfect, mild, conventional smoking operation, primarily to provide the desired appearance (color). By this method, a final product is obtained which is, at least in principle, much purer than that of a conventional cooking 55, but the treatment process itself is very complicated.

Methods are also known in which the smoke fraction removed from the smoke by washing the water is further treated for a sufficient time to obtain a dry product thereof. This substance is then used as a spice, meaning that it "smokes the food with some seasoning technology. These dry processes can also be combined with mild, conventional smoking, which in these 65 cases also improves the appearance of the final product.

Recent research into food-processing technologies for smoking has attempted to find solutions to the problem of pollutants being generated during the smoke generation process, and to find means by which the production of harmful substances can be eliminated so that the flavoring components do not lose cl. During these studies, it was found that one of the important factors influencing the composition of the smoke produced during wood burning is the temperature of combustion. It has been found that the optimum combustion temperature range is slightly below 700 ° C, ie about 650-700 ° C. Even in this temperature range, the formation of harmful substances cannot be completely avoided, but research has shown that the proportion of flavoring and flavoring components and harmful substances is the most favorable here. This ratio declines rapidly at temperatures above 700 ° C, but less rapidly at temperatures below 700 ° C (Potthast: Advances in Food Research, Vol. 29.1984).

Correct delivery of combustion air is an important factor in maintaining the aforementioned temperature range in the combustion process. In addition to the known essential role of air oxygen in the combustion process, air is directly involved in the secondary reactions following the combustion process, which play a role in the final composition of the flue gas.

Recent conclusions regarding the problem of reducing harmful substances are considered to be correct and well founded, and the benefits of taking them into account can be enhanced by the additional use of prior art techniques such as smoke condensation.

Based on the experiments performed, it was found that the combustion process to be implemented, and the immediately following processes, are related to conditions whose proper control has a significant effect on the composition of the generated smoke, on the one hand high concentration of components.

It has also been proven that good combustion techniques are the basis for achieving positive results. Experiments have shown that, in order to obtain appropriate results, smoke generation must be based on a so-called "top-buming" technique, that is to say using a fire chamber in which a substantial portion (a portion) of combustion air is led to the fuel through a burned material layer. Although the use of such a "top-burning" technique for the development of smoke for use in food smoking is known per se, e.g. This technique can be associated with a number of measures which can influence the quality of the smoke, for example, which are not discussed and explained in this publication.

The effect of the carbon layer on the combustion process can be considered indirect because, when topburning is used, the air entering the combustion zone must flow through the carbon layer formed on the fuel surface, countercurrently to the smoke leaving the combustion zone. Thus, the carbon layer restricts the flow of combustion air and this flow limiting medium has a direct effect on the combustion intensity which in turn affects the combustion temperature and consequently the composition of the smoke produced.

On the other hand, the formed carbon layer has a significant absorption effect on the flue gases. It has been found that carbon selectively retains components from smoke, and selection is obviously based on molecular weights and polarity of the materials. However, experiments have shown that selection is advantageous when compounds found to be harmful, such as benz [a] pyrene, are more reliably bound to carbon than phenolic compounds, which are considered aromatic compounds.

In the two processes described above, the carbon layer formed on the surface of the fuel has been shown to be a significant factor that has an obvious effect on the complex process of smoke generation.

When examining the effect of the carbon layer on the combustion air stream, it is clear that the smoke flow retardant effect increases with the increase of the carbon layer thickness. When the fuel is burning, there is no carbon layer and consequently nothing prevents the combustion air from entering the combustion zone. During this phase of smoke generation, the combustion is fierce, fluttering, and the combustion temperature is too high for the formation of various compounds.

The smoke has low levels of taste and aroma components, but contains many harmful substances. However, if the fuel and its particle size (particle size) are correctly selected (this will be discussed in more detail below), the combustion becomes relatively uniform after the flame state of the flag as soon as the carbon layer begins to form on the surface of the fuel.

As far as combustion is concerned, it can be stated that a functional carbon layer must have a certain minimum thickness in order to have sufficient damping effect with respect to the combustion heat. Experiments show that this minimum carbon layer thickness is about 0.5 mm, and to some extent depends on the roughness (degree of roughness) of the fuel. To ensure the desired combustion process, the use of a coarse (rough) fuel may require a minimum carbon layer thickness of 2, After the carbon layer has formed, the combustion becomes even, the open flame ceases, and the combustion ceases without flame (glow), and visual inspection of the combustion at this stage shows a clear increase in smoke production. It was also found that at this stage the temperature in the combustion zone was stabilized within the optimum temperature range for the composition of the smoke, that is below 700 ° C, resulting in a favorable taste compared to the harmful substances. on the other hand, this ratio did not depend too much on temperature changes.

It was also found that the thickness of the carbon layer obviously influences the efficiency of the absorption of the layer. As the thickness of the layer increases, the efficiency of absorption also increases.

However, experiments also prove that the carbon film thickness also has a maximum value for lava for t effect. It has been found that as the combustion continues, and as a result, the thickness of the carbon layer increases, the amount of smoke produced decreases. Instrumental perception also revealed changes in the composition of the smoke, resulting in significant changes in the combustion process, and possibly in the post-burn process.

With respect to combustion itself, it is obvious that as the carbon layer increases, it is such a large limiting factor in the flow of combustion air that the combustion zone does not receive sufficient air to continue the combustion as desired. The combustion is delayed and the combustion temperature decreases. On the other hand, the amount of smoke produced is limited, and on the other hand, the composition of the smoke changes unfavorably due to the too low combustion temperature, that is, the amount of flavoring components relative to the amount of harmful substances.

The thickness of the carbon layer can also be examined for absorption. After reaching a certain upper limit of carbon efficiency in terms of absorption, an even thicker layer no longer significantly increases the absorption of harmful substances from the flue gas. The carbon particles fill up in the upper layers, losing their effectiveness. In other words, absorption above the burning layer is only within certain limits, that is, to a limited extent.

Moreover, if the carbon layer is too thick, it will adversely affect the efficiency of flue gas cleaning. The carbon layer provides a rather efficient reaction surface for the components in the flue gases, on the one hand, for their reaction to one another, and, on the other hand, for their reaction with oxygen in the air flowing through the carbon layer. As a result of these reactions, substances that are significantly more harmful may be formed and introduced into the flue gas than the substances originally present in it. This condition after the reaction may also be significantly influenced by the fact that the uppermost carbon layers in the filter layer may begin to glow in the incoming stream of combustion air, causing a substantial proportion of the flavoring substances to be destroyed in the smoke.

Experiments have shown that the maximum thickness of the carbon layer in the combustion zone can be estimated to be about 100 mm (although the size of the fuel particles may be well below this preferred maximum layer thickness limit), preferably about 2050 mm. derived from fuel, the major portion of which is derived from grains in the size range 1252000 pjn

Made up of -3202075Β Chairs. Obviously, with a coarser fuel, the maximum thickness of the carbon layer may be slightly greater than the 100 mm mentioned.

In the circumstances detailed above, the method of generating smoke suitable for smoking the food products of the present invention involves burning the smoke by burning wood or any other material and substantially charring it according to the "top burning" technique; that is to say, finely chopped wood is incinerated by introducing combustion air c1 into the combustion zone which advances in the fuel and which passes countercurrently with the flue gas leaving the combustion fuel layer through the carbon layer formed by the combustion, and the process is characterized by used to smoke foods when the carbon layer has already formed through the combustion of the fuel and the thickness of the burn zone is about 0.5-100 mm. It is particularly advantageous to use the smoke for smoking only when the carbon layer thickness is between 2 and 50 mm above the combustion zone.

The smoking conditions are greatly improved if the carbon layer formed during combustion is kept undisturbed or maintained during the development of the smoke to be recovered.

The process according to the invention can be carried out even per serving - per filling! - it can be implemented in equipment operating in a mode of operation, which is essentially continuous. The use of per-fill smoking is advantageous in low-power equipment. The process, which is essentially continuous mode, and which can handle large-scale incineration tasks, could be developed from the per-charge method. Later, we will provide a detailed description of a continuous operation but with a charge-by-charge technique. A perfectly continuous process with respect to the combustion process may be accomplished, but the limiting step of the carbon layer is linked to processes which will be discussed later in connection with the description of another embodiment of the apparatus of the present invention.

The apparatus for carrying out the process according to the invention consists in having a smoke generating unit mounted on an endless convoy or other movable structure, in order to supply the fuel filling station, the collecting place, the smoke generating unit and the incineration unit in succession in the direction of it has a suitable fume generating site and an ash removal outlet which includes a silo and a dosimeter, and a collection point, such as a gas flame, and a separate chimney.

The invention also relates to an apparatus characterized in that it has a fire chamber through which the fuel passes substantially from bottom to top; the apparatus further comprising a fuel supply means for supplying fuel to the combustion chamber, such as a worm feed means, and a means for supplying combustion air directly to the mouth portion of the combustion chamber, e.g. having a means for removing the produced smoke and removing the ash from the apparatus, the means for conveying the smoke to the incinerator preferably being a smoke conduit and the means for removing the produced smoke a bypass line.

The process of constructing the device for carrying out the process is also related to general conditions that must be taken into account in the design of the device. First of all, it should be borne in mind that when the combustion chamber is made of a highly conductive material, such as metal, combustion occurs much more efficiently in the center region of the chamber than along the sides, i.e., heat loss through the walls of the combustion chamber . This phenomenon is even more evident when the fire chamber has a horizontal cross-sectional shape; in this case, the burn in the corners of the chamber is minimal. The uneven progress of the combustion front in the vertical direction is considered to be an Idros factor in terms of wood consumption, and the consequence is that this factor should be taken into account in the design of the equipment to be operated. It is advantageous if at least the vertical walls of the fire chamber are made of low-thermal conductivity material, such as ceramic, or it is desirable to insulate these walls. The problem of inconsistent combustion can be reduced by the small amount of lateral combustion air flowing through the walls of the combustion chamber, but this combustion air flow should not be so large as to interfere with the smoke generation process. Careful heating of the fire chamber wall from the outside also contributes to the even combustion.

The problem of inconsistent combustion can also be reduced by the correct choice of the shape of the fire chamber, namely that it is best to form the shape of the chamber in a circular section in a horizontal section.

If large amounts of smoke are to be developed, the design of the unit must take into account the fact that, as the combustion area increases, reverse flow of combustion air and flue gas may cause flow problems that may interfere with the operation of the fuel surface. air supply is not provided as required.

The invention will now be described in detail with reference to the accompanying drawings, in which a preferred embodiment of the invention is illustrated and a graph showing the change in temperature of the fuel over time is provided.

Figure 1 is a schematic vertical sectional view of a device operating with charges; the

Figure 2 is a schematic vertical sectional view of another embodiment of the apparatus; the

Figure 3 is a graph depicting the change in temperature of the fuel over time; the figure a

-4GB 202075Β also includes the position of the thermocouples in the fuel.

The smoke generator of the process of the present invention, shown in Figure 1, is charged, but is substantially continuous.

The apparatus has a plurality of smoke generating units 2, which are mounted on an endless horizontal convector 1, such as a chain conveyor. These smoke generator units 2 are made up of cabinets having solid walls and open at the top, the dimensions of which are selected according to the desired amount of smoke to be developed. For example, the cross-sectional dimensions of the traps may be about 0.5 x 0.5 m. The only requirement for height is that it should allow enough fuel to be placed in the cabinet. Sufficient height for the ear development process e.g. about 150 mm.

The conveyor 1 moves the smoke generator units 2 step by step, alternatively to the fuel filling station 3, the collecting station 4, the smoke generating station 5 and the discharge site 6.

At the fuel filling station 3, a sufficient amount of fuel is introduced into the fuel generating unit 2 from the silo 7 either by means of the metering device 8 or by means of a leveling device which pulls the excess fuel from the smoke generating unit 2. In the next step, the smoke generator 2 is moved to the collection point 4. Here, the flame-free layer of the fuel is ignited by flame. Preferably, a gas flame 9 is used for the emulsion, which extends over the entire surface of the smoke generator 2. After the fuel has caught fire on its entire surface, the smoldering flame is extinguished. The smoke generator 2 is held in the ignition point 4 until the fuel surface burns flaming and the desired carbon layer is gradually formed on its surface.

The smoke generated during this period is removed from the unit by a separate flue, so this smoke is not used in the smoke treatment process. During the ignition phase, the combustion process is monitored to ensure that the correct carbon layer is formed. A fairly reliable sign of the formation of the desired carbon layer is the obvious reduction in smoke formation. This stage is usually from 1 to 10 minutes.After ensuring that a sufficient carbon layer, namely at least 0.5 mm, has been formed, the smoke generator unit 2 can be transferred to the smoke generator site 5 The generator of smoke generates abundant smoke for approximately one hour. which depends to some extent on the particle size of the fuel and over which time a carbon layer is formed on the surface of the fuel which is usually 20 to 50 mm thick. In the case of coarse grade fuels, the evolution of smoke will preferably last until a carbon layer of about 100 mm thick or slightly larger is formed.

When the combustion reaches this stage, the smoke generator 2 is removed from the smoke generator 5 and transferred to the evacuation site 6 where carbon and unburned fuel are removed from the generator 2.

The process is carried out in perfect operation throughout the cycle, and the combustion conditions at the smoke generation site 5 during the ignition phase must already be predetermined in order to prevent interruption of smoke generation. If this is our intention, the smoke development may be performed in stages to provide the smoke in successive sugars at intervals.

The process can be controlled by an appropriate automatic system, but manual control is not excluded.

Once it has been determined that the fuel to be used has an advantageous maximum film thickness, such as 50 mm thick, the fume generator unit 2 must be filled with a suitable fuel layer, such as 70-80 mm, at the fuel filler space 3. The fuel layer that remains at the bottom of the smoke generator 2 after the smoke generation phase is completed has its own significance because the layer absorbs all the tar fractions that may be distilled during the heating phase.

During the development phase of the smoke, the calcareous combustion air is supplied to the fuel surface by an air blower 11; it is expedient that the volume of air supplied by this device be controlled. Air should be evenly distributed over the entire surface of the fuel. It is also possible to use natural draft for the supply of combustion air, which should be a regulated pond.

The smoke generator unit 2 may also include a heat exchanger 12, which may be a cooling or cooling device. A refrigeration appliance can be used to condense any contamination in the flue gas. In case of hot smoking, the temperature of the flue gases can be increased by means of a heat exchanger.

During the emptying phase, the ash discharged from the smoke generator unit 2 is discharged into a suitable container 13 or convector at the emptying station 6.

Figure 2 shows another embodiment of the apparatus for carrying out the process according to the invention. In principle, this equipment operates continuously, although its operation involves aspects which, as will be explained below, require intermittency.

The apparatus of Figure 2 has a fire chamber 15, the upper portion of which is surrounded by a jacket 14. The apparatus also has a 16-screw feed device for injecting fuel into the lower portion of the combustion chamber 15. For the introduction of combustion air into the mouth portion of the combustion chamber 15, combustion air supply ducts 17 are provided. The apparatus further comprises a smoke conduit 18 through which the smoke enters the smoke furnace. The bypass line 18 'and the closure 18' provide a by-pass flow of smoke. Finally, the pre-removal device 19 may assist the device in removing the combustion residues.

The construction of the jacket 14 of the apparatus may be relatively simple, in principle it is made of sheet metal 5

-5EN 202075Β as it is not subject to significant thermal deformation during operation. The A15 fire chamber, on the other hand, has much higher design requirements. Because of the circumstances detailed above, it is preferable that the fire chamber 15 is circular in cross section and that the lower portion 15 'may be formed by a metal tube. However, in the actual 15 ”range of the combustion zone, the fire chamber must be made of heat-insulating material or may have a low thermal conductivity, such as ceramic.

The fuel is introduced into the lower part of the combustion chamber 15 by means of a suitable feeding device, for example a screw feeding device 16. To supply combustion air to the mouth portion of the combustion chamber 15, the apparatus may be provided with a separate combustion air supply duct 17, or alternatively, the combustion air may be introduced into the housing 14 through a suitably sized opening. Preferably, the combustion chamber 15 has a thermometer 20 located substantially at the level of the desired combustion zone.

The operation of the apparatus of Figure 2 is as follows:

feeding the finely divided wood into the fire chamber 15 by means of a 16 screw feeder until it is filled to the brim with this wood. The fuel is then ignited over its entire surface and sufficient air is supplied to the fuel for combustion. The flue gas generated during this stage is discharged from the unit, for example through a bypass (branch line) 18 'which exits the smoke conveying line 18; thus, the smoke generated during the ignition phase is not utilized. Once the combustion has stabilized, which is fairly reliably detectable, for example, based on the amount of smoke generated, the flue gas is fed to the smoke treatment unit and allowed to continue for a predetermined period of time (1-10 minutes). The fire front has been found to advance 30-50 mm in depth during this period, and in some cases about 100 mm. The by-pass line 18 'is then opened and the auger 16 is suddenly actuated. The new fuel entering the combustion chamber 15 pushes the fuel column upward, whereupon the ash layer in the lateral regions of the combustion chamber 15 drops from the mouth of the combustion chamber 15 to the bottom of the shell 14 and can be discharged from the apparatus.

During the fresh fuel supply period, the inevitable exposure to the coal layer on the combustion layer is such that during the mixing and subsequent period of combustion stabilization, the smoke must flow out of the incinerator through the bypass line 18 '. Once the combustion has stabilized, the smoke can be reintroduced into the incinerator. The operation is repeated several times to produce a suitable pile of fuel at the mouth of the combustion chamber 15, and the surface-free layer of the pile is substantially completely discharged each time fresh fuel is supplied. In principle, continuous flue gas generation can be achieved by the apparatus, although subsequent stabilization of mixing and combustion results in interruption of the development of usable smoke.

Said period of fresh fuel feeding, preferably continued for at least a few feeding periods, must be long enough to extend the fresh fuel layer to the surface of the burner. In this case, the tar fraction may also be removed from the apparatus, which fraction is removed by distillation before the combustion front and is concentrated in the fuel below. After such a feeding period, the fuel pile must be re-ignited as described above.

Unlike the above, the apparatus may also be fitted with a suitable pulling device which removes the hammer chain from the mouth of the fire chamber after each feeding period. In this case, the smoke is used through the main bypass.

The operation of the unit can be controlled relatively reliably manually, based on monitoring of smoke evolution and, accordingly, control of fuel supply. However, operation can also be automated in a relatively simple manner by placing thermometers 20 in and immediately adjacent to the combustion zone so that the length and frequency of the required fuel supply periods can be determined by simple logic based on information from the thermometers 20, and it can be ensured that the combustion zone remains at a desired distance from the mouth of the combustion chamber 15.

The invention will now be described in more detail by way of example.

Example 1

This example illustrates the invention in the context of an experiment in which the combustion process was investigated by observing the combustion temperature of a pile of fuel.

In the experiment, a smoke generator (oven) for domestic use was used, which had the following external dimensions: width 400 mm, depth 450 mm, height 700 mm.

In the upper part of the smoke-generating space, a short chimney was installed to discharge the smoke. In the lower part of the stove there was a fire chamber and it was lockable with a door. The cross-sectional size of the cabinet was 130x140 mm. The combustion air was introduced into the combustion chamber through the opening that was used to push the firebox.

In the experiment, fuel from beech sawdust was placed in the firebox. The particle size of the sawdust was as follows:

particle size (μιη) % 4000-2000 1.0 2000-1000 9.4 1000-500 27.3 500-250 34.4

-6EN 202075Β

250-125 22.0

125-74 4.6

J 1.2

The sawdust had a bulk density of about 270 kg / m and a moisture content of 7.2%. In the firing experiment, 200 g (wet weight) of sawdust was used, which was filled into the cabinet to form a pile of fuel. The height of the pile at its centerline was about 86 mm.

For temperature monitoring, a temperature detector (NiCr-Ni thermocouple, type K, wire length 0.25 mm) was used, located at different levels (heights) in the center of the cabinet. The height of the detectors from the bottom level of the cabinet was as follows:

detector height above bottom (mm)

85

69

51

40

24

At the beginning of the experiment, the sawdust pile was lit over its entire surface using a soldering gun. After the rabbit had disappeared from the pile surface, the cupboard was placed in the fire chamber of the stove. With the help of natural draft, a sufficient amount of combustion air was supplied to the combustion through the cupboard opening.

During the course of the experiment, temperature changes at various measurement points as a function of time were observed as the front advanced in sawdust. The result of the experiment is illustrated in the graph of Figure 3, which also includes the arrangement of the thermocouples.

The result shows that after the development of the flame-free (glowing) burning property (measuring point 2 in Figure 3), the temperature in the combustion zone increased to slightly above 500 C and slightly higher in the following measuring points. . The maximum was reached at 4 points after approximately 80 minutes. At this stage, however, the smoke generation had begun to decline and continued to decrease, although the temperature had increased at the 5 measurement points, but less rapidly. It is believed that the obvious reason for the delay is the flow resistance caused by the carbon layer formed on the surface of the fuel pile, which delayed the penetration of the combustion air into the burning layer.

Using the device and firing technique described above, we also carried out test smokes, which were fish smoked. The smoked product was determined to contain benzo [a] pyrene, which indicates that it contains harmful substances in the smoke. A number of trial smokes were performed, varying to some extent the conditions of the smoke treatment; for example, by the choice of the firing phase in which the firebox was pushed into the furnace, the concentration of benzo [a] pyrene in most of the samples tested was below the detection limit, while the highest concentration was 0.05 µg / kg.

For the sake of comparison, a trial smoking was also conducted in which the fuel was burned with free-flowing air supply. For this test smoke, the concentration of benzo [a] pyrene in the test sample was 0.5 mg / kg.

The correct choice of the fuel used is also important for the process and the operation of the equipment. Examples of usable fuels are alder, which is traditionally used to treat foods by smoking. Beech and juniper, and in some cases peat, can be used well. Of course, mixtures of the above materials can also be used, especially if they are to be prepared in a variety of flavors and flavors. The moisture content of the afa-fuel shall be considered satisfactory if it is "air dry". Drier fuels may be used, but higher moisture fuels may cause difficulties.

It has been found that the particle size of the fuel also has an influence on the control of the combustion process and it is possible to use the term "sawdust" as a general definition of the particle size. Classification tests have shown that for a well-functioning fuel the predominant particle size range is in the 125-2000 μΐη range.

The greatest advantage of the invention is that the process smoked products have significantly less carcinogenic material than the conventional smoked products.

Claims (6)

A method of generating smoke by burning wood or other material and treating foodstuffs in a substantially appropriate manner by smoking food, comprising burning finely divided wood by introducing combustion air into the combustion zone, and combining the combustion air with the flue gas leaving the combustion fuel layer. passing through the coal layer, characterized in that the smoke formed during combustion is only used to smoke the food, the coal layer being branded at the time of combustion of the fuel and having a thickness of about 0.5 to 100 mm above the combustion zone. Method according to claim 1, characterized in that the smoke is used for smoking food only when the thickness of the carbon layer above the combustion zone is between 2 and 50 mm. Method according to claim 1 or 2, characterized in that the smoke is passed through a continuous (undisturbed) carbon layer to smoke the foodstuff. Apparatus according to Claim 1, characterized in that the process is: -7EN 202075Β, characterized in that it has at least one cabinet-like smoke generator unit (2) mounted on an endless conveyor (1) or other movable structure and that the unit is arranged in a fuel-sequential manner in the movement direction of the smoke generator unit (2). charging station (3); a firing point (4), a smoke generating site (5) for generating smoke and obtaining smoke to be conveyed to the incinerator, and a discharging site (6) for removing ash, which is a fuel filling station (4), a silo (7) and a dosimeter (8); and (4) comprising an ignition means, such as a gas flame (9), and a separate horn (10). Apparatus for carrying out the process of claim 1, characterized in that it has a fire chamber (15) through which the fuel passes substantially from bottom to top; and a fuel supply means for supplying the combustion chamber, such as a auger supply means (16), and also a means for supplying combustion air in the immediate vicinity of the mouth portion of the combustion chamber (15), for example a combustion air supply line (17) a jacket (14) surrounding the upper portion and a means (19) for conveying the generated smoke to the incinerator, removing the produced smoke and removing the ash from the apparatus, and a means (18) for conveying the smoke to the incense, and the means for removing the produced smoke is formed by a shroud (18 '). Apparatus according to claim 5, characterized in that one or more means, such as a thermometer (20), for detecting the temperature to determine the location of the combustion zone and to control the feed to the fuel, are located in the combustion chamber (15).