DE3200808A1 - Process and equipment for producing smoke for smoking - Google Patents

Abstract

The invention relates to a process for producing smoke for smoking by continuous charring of comminuted wood. According to the process of the invention, the moisture content of the comminuted wood material is determined and adjusted with steam or water, and the comminuted moistened wood particles are passed to a combustion point in a combustion furnace and burned therein. The temperature in the combustion furnace is measured, and the oxygen feed is controlled as a function of the measured temperature, and the smoke formed is then passed into a smoking chamber.

Description

BES CII FRICTION

The invention relates to a method for producing smoking smoke by smoldering of shredded wood in a continuous way and a device to carry out the procedure.

Among the treatment methods for food comes smoking meat products and fish are of particular importance. These foods spoil quickly when fresh. But they can be smoked for a longer period of time be kept. The preservation effect of smoking smoke is based on condensation of smoke components on the surface of smoked goods. The ingredients of the Smoked smoke has a chemically preservative effect. They prevent that Fat oxidation and the development of a microflora, and thereby become undesirable Operations delayed.

Smoking becomes meat products and fish and, in general, luxury items also flavored. The flavoring and preservation are essential by the same components of the smoke, namely by phenols, carbonyls, Acids and alcohols. In addition to these compounds, the incense contains smoke a variety of neutral hydrocarbons, some of which are polycyclic aromatic Hydrocarbons (PAH) are undesirable because of their carcinogenic effect. Even these substances get onto the surface of the smoked goods during the smoking process.

Since it has been shown in numerous animal experiments that benzo- / aJ-pyrene (= 3,4-benzopyrene) has carcinogenic effects, numerous authors have commented on the content reported on benzo- / a ~ / -pyrene in smoked meat products. Benzo-L a / pyrene is one of the carcinogenic PAHs with which meat and fish products become contaminated in the course of the smoking process. 3,4-Benzopyrene was smoked in and grilled meat products, and it was found that the scope the contamination has a noticeable relationship to the smoking or grilling processes used (cf. Dr. L. Toth and W. Blaas "Die Fleischwirtschaft", 52.

Volume 11, Page 1419). K. Potthast recently reported (See "Fleischwirtschaft", Volume 60, November 1980, page 1941) that it is in the Federal Republic of Germany gives a number of meat products, which also after the publication of the Meat Ordinance of June 6, 1973 more than 1 ppb benzo / a / pyrene included. Of 662 samples, 21.6% contained more than 1 ppb benzo- / a ~ 7-pyrene. The amount of carcinogenic substances formed in the smoke depends on many factors, for example on the smoldering temperature, the soot contamination, the moisture content of the wood products used, the air supply, etc.

Various smoking technologies are used in industry and craft today used, namely the glow smoke, friction and steam smoke processes. at In this modern process, the smoke generator is separated from the smokehouse. The various methods come with the exception of both the steam smoking method as cold, warm and hot smoking processes. In the glow smoke process For example, the sawdust to be smoldered is initially heated on an electrically heated one Plate stimulated to glow and later in the glowing state by careful 'air dosing held.

The sawdust is supplied continuously from a storage container according to the amount of sawdust burned.

The combustion temperature in the glow zone is currently uncontrolled and often exceeds the desired temperatures of 500 to 7000C. For smoke generation Both hard and soft woods can be used.

In the steam smoke process, the pyrolysis of the wood takes place with the aid a superheated water vapor-air mixture. There- at the increases Pyrolysis temperature in the steam smoke generator to approx. 350 ° C. Here too, hard and Soft woods are used.

In the friction smoke process, friction smoke is generated.

The smoke density and smoke generation temperatures are at this Smoking process for the duration of the rotation of one with a rotating cylinder wooden stick in contact. The smoke generation temperatures lie generally usually around 400 C.

All of these known processes are used in numerous small businesses carried out and it is evident that the control of the factors responsible for the concentration of benzo- / a ~ 7-pyrene are responsible, often not sufficient is.

Studies have shown that the benzo / a-pyrene content of meat products fluctuates strongly and that especially in small businesses, such as butchers, a control of the factors that determine the benzo / a ~ / pyrene content in smoke in practice not possible.

In DE-AS 2 306 182 a device is described in which a predetermined value of the glow temperature can be maintained. This well-known However, the device has the disadvantage that it is complicated in structure and control of the glow temperature is difficult. In DE-OS 2 725 358 is a method for operating a cooking and smoking chamber described. This well-known However, the method has the disadvantage that the control of the individual process parameters is complicated and unsuitable for practical use. In the DE-AS g 948 494 finally describes a method for producing smoking smoke. The method described there has the disadvantage that precise temperature conditions Must be adhered to in order to obtain high quality smoke create. In all of these cited references, however, there is no information whatsoever as to which Measures must be taken to produce smoke! its benzo- / ag-pyrene content is as low as possible. From this known state of the art it was not possible to find any Get suggestions on what measures to take in order to cope with the usual smoking process to control the content of benzo- / a ~ -pyrene and to reduce it as far as possible.

The present invention is therefore based on the object of a method and to provide a device whereby smoking smoke is reproducible can be produced. The smoke should be controllable, if possible have a low content of benzo- / a-pyrene.

Furthermore, wood products with different Moisture can be used. The inventive method should be simple Wise and can be carried out without much prior knowledge. The device should be of a simple design and do without complicated measuring devices. The procedure and The device should be suitable for long-term use and designed in such a way that that they are used both for the production of incense smoke in smaller quantities as well are suitable for the production of smoking smoke in large quantities.

The invention thus provides a method for producing Smoke smoke from smoldering of shredded wood in a continuous way, which is characterized in that the moisture content of the crushed Determines the moisture content of the wood material with steam or water comminuted wood material to a value above 30 wt .-% adjusts, the comminuted directs moistened pieces of wood to a cremation point in an incinerator and burns there, measures the temperature in the incinerator and as a function of it from the measured temperature regulates the oxygen supply so that that the combustion temperature is preferably in the range from 550 to 750 ° C, and directs the smoke formed into a smokehouse.

It has surprisingly been found that when considering the moisture content the wood material, which is used to generate smoke, to a certain one Value and the combustion temperature as a function of the moisture content also regulates to a certain value, the smoke formed can be reproducibly produced and has a low content of benzo- / a / -pyrene.

Any types of wood can be used in the method according to the invention and crushed wood materials such as sawdust, wood shavings, etc. can be used. There is no restriction on the type of wood material that is crushed, and softwood (gymnosperm wood), such as fir, spruce and pine wood, and hardwood (angiosperm wood) such as beech and oak wood be used. The moisture content of the crushed wood material is increased a value above 30% by weight, generally to a value in the range from 30 to 70 % By weight, preferably 40 to 60% by weight, and particularly preferably to 50% by weight. The shredded wood material can be moistened with steam or water take place. It can be carried out batchwise or continuously. At the here before According to the embodiment, the comminuted wood material is moistened in a container, wherein the wood material is moved. The moisture of the wood material is determined with a humidity sensor, and through this the water supply is determined regulated. But you can also easily determine the moisture content of the wood, for example by simply drying in a drying oven, determine and then Add the calculated amount of water to a weighed amount of wood. The setting the moisture content of the wood poses no difficulties and, if necessary, a person skilled in the art can easily determine by means of simple preliminary tests how to proceed.

The moistening of the sawdust in the storage tank of the smoke generator has the advantage that only the required amount of sawdust for the ongoing smoking process is processed with the desired amount of moisture and thus mold sawdust that is not required is prevented.

The moistened wood is applied to the combustion point in a manner known per se a smoke generator or incinerator and there in a well-known Way, for example electrically, lit. If the combustion is in the stationary Condition expires, the temperature in the combustion chamber is measured. The temperature measurement can be done next to or in the burn site. For temperature determination you can use the usual devices that are already used in this field will. The oxygen supply is dependent on the measured temperature controlled. The oxygen supply is controlled in such a way that the combustion temperature of the comminuted moistened wood parts in the range from 550 to 7500C, preferably is in the range of 600 to 700 ° C and most preferably 650 ° C. Through the If this combustion temperature is maintained, the smoke that is formed contains only a small amount of smoke Amounts of benzo- / a ~ / pyrene.

In general, the temperature is controlled via the air supply. According to the invention, the wood to be smoldered has a uniform moisture content from - as stated above - 30 to 70% by weight, preferably 50% by weight. This lets the temperature can be easily regulated by the air supply.

A device according to the invention is shown on the basis of the accompanying drawing explained in more detail. In the attached figure, 1 means the storage container for the Chopped up wood, which is equipped with a movement device. The reservoir for the chopped wood comprises one or more water or steam supply lines 7 and a moisture meter. The water or steam is supplied accordingly the display of the moisture meter. From the shredded storage bin Wood is a predetermined amount of shredded wood, for example by means of a screw conveyor, to a combustion point 5 in an incinerator 2 directed. The incinerator is provided with an air supply duct 3 and a smoke outlet 4 equipped. In the case shown, the temperature is measured next to the combustion point by means of a temperature measuring device 8. In a preferred embodiment the reservoir 1 and the incinerator 2 are integrally connected to each other The method according to the invention and the device according to the invention have the Advantage that 1) the smoke can be produced in a reproducible manner, 2) the process is very simple to carry out and 3) the benzof a ~ pyrene content is very low.

The following table I shows the benzo / a / pyrene contents that were found in a number of commercial products: Table I: Benzo / a / pyrene contents in smoked meat products from the trade (Benzo - [a] pyrene content in / ug / kg (ppb)) Designation n range in ppb xs n>1%> 1 Boiled sausage 79 40.1 - 3.59 0.42 0.63 7 8.9 Cooked sausage 19 (0.1 - 6.15 0.69 1.35 1 5.3 Raw sausage 186 <0.1 - 51.0 0.53 3.76 5 2.7 cooked ham (light noise 14 nn - 3.1 0.82 1.05 4 28.6 chert) cooked ham (dark-168 nn - 300.0 4.44 24.35 78 46.4 smokes) Raw ham (light noise 30 40.1 - 3.16 0.55 0.69 3 10.9 chert) Raw ham (dark-152 <0.1 - 56.04 2.54 6.22 47 30.9 smokes) n = number of samples examined x = mean value s = standard deviation n = = samples with more than 1 ppb benzo / a / pyrene nn = not detectable As can be seen from the table, the meat regulation of June 6th 1973 regulated maximum amount of benzo- / a ~ / -pyrene of 1 ppb in a large number of samples exceeded significantly. It is noticeable that the excesses occur particularly in dark-smoked products. Among these products, the hot-smoked samples (boiled ham, dark-smoked) were particularly heavily contaminated with benzo- [a] -pyrene. This shows that the smoking processes currently used in industry and craft cannot be controlled precisely enough, as would be required for a defined composition of smoking smoke with a low benzo / a / pyrene content. Hams smoked by the process according to the invention generally showed very low levels of benzo - / - a / - pyrene contamination, as can be seen from Table II below.

Table II: Bacon with smoking according to the invention Benzo- / a / -pyrene content in / ug / kg (ppb) Number of benzo- / a ~ -7-pyrene content- 8th It was noticeable with these products that, despite their intense dark color, they contained significantly less than 0.1 ppb benzo- / a / -pyrene and, in terms of taste intensity, were to be equated with strongly smoked specialties on the market. An explanation for the low contamination of the hams with benzo- / a / -pyrene according to the method according to the invention resulted from the study of the temperature dependence of the benzo- / a / 7-pyrene formation during the pyrolysis of wood. These studies were carried out with the help of a laboratory smoke generator that worked according to the following principle.

A laboratory smoke generator was used, which is based on the principle of a modern technical glow smoke generator was recreated. It consisted of one outer heat-insulated metal shell with an output nozzle for the generated Smoke and a sound insert, which is from the heat-insulated envelope by an approximately 2 cm wide air layer separated was. The clay body was in regular Drilled through at intervals, which enabled the glow smoke to be drawn off. Around The laboratory smoke generator was used to prevent the smoke from being drawn off to the outside with a funnel-shaped lid with an approximately 15 mm thick through-hole for the air inlet closed. The suction nozzle of the laboratory smoke generator was with connected to a two-necked round-bottomed flask, which in turn is connected to six Wash bottles was connected. The wash bottles were filled with water or cyclohexane or propylene carbonate to capture the smoke ingredients to about a quarter their volume filled. In the transfer nozzles were used to destroy the particle phase Glass wool plug inserted.

An adjustable one was used to regulate the smoke generation temperatures Used vacuum pump connected to the last wash bottle. the The temperature in the smoke generator used was checked with thermocouples.

While the smoke was being generated, the Liebig cooler was filled with tap water chilled. As a result, much of the smoke generated was already in the round bottom flask collected, which was downstream of the smoke generator. Most of all it was in this Vessel largely deposited the tar phase. In the downstream washing bottles with organic and aqueous media, the more volatile constituents of the Incense smoke is collected, provided that it does not condense on the glass wool plug. The condensate from the two-necked round bottom flask and that in the subsequent washing bottles Trapped smoke ingredients were combined and shaken out with cyclohexane. The combined washing solutions and condensates were aliquots of each 100 ml analyzed.

The results obtained are shown in Table III below.

Table III: Benzo / a / pyrene contents in liquid smoke condensates from a laboratory smoke generator Combustion temperature / µg benzo-a ~ 7-pyrene / 100 g (Oc) wood approx. 400 5 approx. 600 10 approx. 800 15 approx. 1000 20 The values in Table III show that the formation of benzo- / α-7-pyrene increases linearly with increasing smoke generation temperature. It follows that smoking must be carried out at the lowest possible temperature. From studies of other ingredients of the smoking smoke it follows that a temperature range of 650 to 7000C is optimal, because in this temperature range the desired components of the smoking smoke outweigh the undesired (benzo- / a / -pyrene) considerably (K. Potthast: "Newer Results on the benzo-a-pyrene content of meat products ", Fleischwirtschaft, 60th year, 1941-1949, 1980).

Another proof of the low formation of benzo- / a / -pyrene at Low smoke generation temperatures could be achieved with the help of an electrically heated one Pyrolysis furnace are provided. This smoke generator consists of a screw conveyor for supplying the electrically heated pyrolysis oven with sawdust. The generator can be closed by caps are protected from the ingress of air. This has the advantage that the pyrolysis is carried out exclusively by means of electrical heating can be regulated, provided that nitrogen is used as the carrier gas for the pyrolytically generated smoke is used.

However, if the nitrogen is enriched with air, the pyrolysis temperature depends also depends on the amount of air added.

When using nitrogen as the carrier gas, smoke generation temperatures of 3500C, when using nitrogen with an air addition 4500C pyrolysis temperature achieved.

Table IV: Benzo- / a ~ 7-pyrene contents from smoke condensates from an electrically heated pyrolysis furnace Temperature of air supply benzo- / a ~ / -pyrene (, puff / 100 g sawdust) 350 0C none 0 450 ° C low 4 With the help of the laboratory smoke generator and the electrically heated pyrolysis furnace, only small quantities of smoke condensates could be obtained, which only allowed the study of the temperature dependence of benzo- / a / -pyrene and other constituents of the smoke.

Meat products could not with the help of these smoke generators to be smoked. Technical smoke generators such as described below, applied. These smoke generators also enable profit tion of smoking smoke at the lowest possible temperatures, which means that it is low in benzo- g a-pyrene is. However, this method has the disadvantage that it is used to obtain Smoking smoke consume energy, while according to the method according to the invention energy is released.

a) Friction smoke generator The friction smoke generator is is a smoke generator in which the smoke is generated by friction. A Wooden beams loaded by gravity and an additional weight is pressed onto a rotating toothed wheel. This wheel is switched on an interval switched on and off, so that at the contact surface between wood and wheel a Temperature arises, which depends on the speed of rotation and the duration of the movement depends on the wheel. As the bike runs at intervals of around 20 seconds and 40 seconds Seconds pause is switched on and off, the smoke generation temperatures are hardly above 450 ° C. An exact temperature measurement was not possible because it was in the wood dust Introduced thermocouples destroyed on contact with the rotating wheel became.

b) Steam smoke generator When generating smoke with the help of the steam smoke generator a mixture of superheated steam and air is forced through sawdust. The pyrolysis temperature that is set depends on the amount of superheated steam and air that is used in this process. With help of the steam smoke generator can therefore set the temperature fairly precisely to a certain one Value can be adjusted. In the tests carried out here, the steam smoke generator driven at 3500C.

Table V: Benzo- / a./- pyrene contents of meat products, smoked with friction and steam smoke -Number of maximum- Kind of the number of x worth exceeding Smoking samples X (ppb) Steam smoke 36 0.24 2 1.2 Friction smoke 121 0.43 5 4.56 In terms of their sensory properties, products smoked in glow smoke are superior to meat products smoked with friction smoke or steam smoke. The glow smoke process according to the invention has the advantages of precisely controllable combustion temperatures (as in glow smoke and friction smoke generators) and stands out from these processes through the more favorable sensory quality features.

Claims (8)

Method and device for producing smoke P A T E N T A N S P R Ü C H E 1. Process for the production of incense smoke by smoldering of shredded wood on a continuous path, which means that it is not indicated n e t that the moisture content of the shredded wood material is determined, with steam or water the moisture content of the shredded wood material sets, the shredded, moistened wooden parts to a burn-out site passes into an incinerator and burns there, the temperature in the incinerator measures and regulates the oxygen supply depending on the measured temperature and directs the smoke formed into a smokehouse. 2. The method according to claim 1, characterized in that g e k e n n -z e i c h n e t that the moisture content of the crushed wood material to a value above 30 wt. Is set 3. The method according to claim 1 or 2, characterized It is noted that the moisture content of the shredded wood material is set to a value in the range of 30 to 70% by weight. 4. The method according to any one of claims 1, 2 or 3, characterized g e k e Note that the combustion temperature is in the range of 550 to 7500C lies. 5. The method according to any one of claims 1 to 4, characterized g e k e n n indicates that the combustion temperature is in the range of 600 to 700 ° C. 6. The method according to any one of claims g to 5, characterized g e k e n n notices that the temperature measurement next to or in the combustion point is made. 7. Device for performing the method according to one of the claims 1 to 6, not shown by an air- and moisture-tight seal Storage container for shredded wood (g), an incinerator (2) with a Air supply line (3) and a smoke outlet (4) of a combustion point (5), one Feed line for shredded wood material and a temperature measuring device (8th). 8. Apparatus according to claim 7, g e k e n n z e i c h -n e t through a moisture meter (6) and a water or steam supply line (7).