METHOD AND INSTALLATION FOR DRYING AND THERMAL STABILIZATION OF BIOLOGICAL MATERIAL INCLUDING PLANT MATERIAL SEEDS, SESAME ESPECIALLY

Abstract

 The subject matter of the invention is a method for drying and thermal stabilization of biological material, including plant material seeds, sesame especially, in which purified material is placed in a drier chamber and subject to drying in a fluidized bed and subject to an infrared radiation, characterized by that the drying process is conducted in temperatures from 110 to 200°C with a gas stream velocity in the fluidized bed from 0.8 to 8 m/s above the sieve and in two stages lasting from 5 to 25 minutes. The gas used in the first stage is returned in 75% of the volume of entire portion of the gas used in this stage and moreover the infrared radiation of 0.8 to 6 µm wave length and adjustable electric power of an infrared illuminator (2) in range from 0.02 to 0.15 kW/kg of the material input is used. Whereas in the second stage drying is conducted with the total gas exchange and after the drying process the material is subject to immediate cooling to temperatures from 40 to 50°C and subject to thermo-biological stabilization. The subject matter of the invention is also an installation for drying and thermal stabilization of biological material, including plant material seeds, sesame especially, allowing for realization of drying according to the presented method.

Description

[0001] The subject of the invention is a method for drying and thermal stabilization of plant material with higher fat content including seeds like: sesame, sunflower, nuts, pistachio, peanuts, coffee, groats, flour, etc., as well as the installation for drying and thermal stabilization.

[0002] Stabilization in high temperature is intended to remove excess water to around 0.5 to 0.6%, which prevents unfavorable bacterial flora and fungi development. The purpose is also to achieve required biochemical changes by processing sugars contained in the dried product which improves its taste and aroma. By the Maillard reaction a taste reminiscent of a caramel is achieved from sugars which positively influences the product organoleptic properties. Simultaneously, it is important to choose the equipment and process parameters in such way not to burn the stabilized product which often takes place in case of small seeds such as sesame grains, for example.

[0003] A method and installation for drying cereal and grains with use of infrared radiation is known from the Russian patent description RU2479808 C1. A method is to dry moist material in a drier chamber, in a fluidized bed by its travel on a level sieve. The travel is possible thanks to the sieve construction with simultaneous blow of a hot air from the bottom of the sieve. There are infrared illuminators above the sieve. The material is dried in temperature from 39° to 46°C. The material after leaving the drier chamber is divided into two parts. One part is returned to the beginning of the process, to a mixer and there mixed with moist, raw grains, whereas the second part of the material after leaving the drier chamber is fed to a cooling silo. The mixture created from the first part is partly fed with a conveyor to a tempering tank for 2 to 4 hours period and from there directed to a drier loading hopper and partly returned to the mixer and mixed again with moist grains and with hot grains from the drier. The cooling silo to which the second part is fed is supplied with the fresh air supplied by a fan. In the cooling silo the material is cooled to the temperature from 4° to 6°C above ambient temperature. The grains are received from the bottom of the cooling silo and circularly returned with a conveyor and fed again to the silo from the top. This method describes also use of the air circulation which exits the drier in amount of up to 30% and its reuse in the drying process. The method and installation for drying grains according to this patent concerns low temperature drying and does not precise the drying parameters, including applied infrared radiation. The material stream is partly returned to the closed circuit before drying as well as after drying. Such solution in the industrial conditions results in a small productivity of the installation and high energy consumption recalculated per product unit while the air return during low temperature drying causes significant decrease of drying driving force. Moreover, due to a random circulation of part of the material it is not possible to ensure uniform drying level and to control the process.

[0004] In the publication of Chinese patent description CN102721271 (B) a drier for fast ginger drying was revealed. The drier has a body in which the ginger travels sequentially on the set of three belts and is dried with use of the hot air blow directed form the bottom of the upper belt. There are three dedicated zones in the drier body equipped with infrared radiation source emitting short, medium and long waves infrared radiation. The fluidized bed drying takes place in short and medium waves zone. Due to a drier construction, the dried material can be received only after passing through all three belts. This hinders control on the dried material.

[0005] Fluidized bed drying with use of infrared radiation as a heating medium is also presented in the publication of Japanese patent application JP2002022362 (A) p. Revealed in it drier for rice has a hopper located at the top from which the material for drying is fed. Below, in the drier body, plates with perforated surface are located at a different height. Through the perforation, the hot air is blown and this way fluidized bed drying is realized. Above each plate there are infrared waves sources installed. Drying adjustment is realized by the height adjustment of the bed on the plates. This is allowed by adjustable height dam plate fitted at the end of each plate through which the material being dried flows and falls on another plate, housed below. At the bottom of the drier body there is an outlet opening through which the dried material is received. Similarly, as in the above solution the material travels long way, during which it is subject to the heating factors influence before it leaves the drier. This extends the drying time which degrades the valuable ingredients such as: fats, proteins, starch, vitamins, organic compounds, microelements and increases the energy consumption.

[0006] Known drier according to the Polish patent application PL403771 (A) is intended for drying agri-food material in which drying process can be conducted with fluidized bed drying method of grainy and ground material and spray drying of dusty material in air-streams. Drying relays on filling measured amount of the material onto the sieve of the chamber and after drying the finished product is emptied through openable connection pipe welded to the chamber wall above the sieve.

[0007] The literature knows another way of drying called roasting in high temperature relaying on placing dried to around 8-14% moisture content raw material in a blanked heated rotating level cylinder. The cylinder walls are then heated on it external side with help of the heaters or gas burners. Due to a very hot wall of the cylinder and uneven mixing of the input the individual grains are not equally subject to a high temperature. In result ununiformly roasted material is received with not uniform organoleptic values.

[0008] From the Polish standard PN-EN 1991-4:2006 "Actions on structures - Part 4: "Silos and tanks" is known the construction of the tanks having conical bottom with a mass flow. For realization of the mass flow the half angle of the hopper top should be from 0 to 40° and a friction coefficient µ of the material against the hopper walls should be in range from 0° to 0.52. With maintaining this condition, the material flows evenly level in all volume.

[0009] The intention of this invention is to develop a method and installation which will allow for shortening the time necessary to achieve dried or roasted product with simultaneous maintaining valuable nutritional substances of the product. The process should also be more efficient.

Short description of the invention

[0010] A method for drying and thermal stabilization of biological material, including seeds of plant material, sesame especially, in which purified material is placed in a drier chamber and subject to drying in a fluidized bed and subject to infrared radiation relies on, according to the present invention, that the drying process takes place in temperature from 110 to 200°C with a gas stream velocity in the fluidized bed from 0.8 to 8 m/s above a sieve and in two stages lasting from 5 to 25 minutes. In the first stage, infrared radiation of a wave length in range from 0.8 to 6 µm and adjustable electric power of an infrared illuminator in range from 0.02 to 0.15 kW/kg of the material input is used. Drying and roasting takes place in the first stage with simultaneous drying in the fluidized bed and use of infrared radiation. In the first stage a gas circulates in a circuit repeatedly and is returned to the drier chamber for reuse, each time at least 75% of the volume of entire portion of the gas used in one circulation, remaining part is thrown out and replaced with the fresh air. Whereas in the second stage drying takes place with total gas exchange. In the second stage the radiation is not used and the material is subject to drying only in the fluidized bed. After the drying process the material is subject to immediate cooling to temperatures from 40 to 50°C and subject to a thermo-biological stabilization.

[0011] Preferably cooling is conducted in a pneumatic transport of the material to a tempering tank.

[0012] Preferably thermo-biological stabilization is conducted in the tempering tank from 15 to 60 minutes.

[0013] A process in which drying is conducted in two stages characterized by that in the first stage the additional heating of a material is applied with use of infrared radiation and the process takes place at described parameters, allows to significantly accelerate heating of the material to a given temperature. In a result the material exposition to a high temperature is shorter. Shorter total time of high temperature impact prevents form the pro-health ingredients loss, such as proteins, vitamins, organic compounds, microelements. The gas which is totally or partially returned in the first stage is subject to repeated heating to a given temperature. The process of total or partial gas return causes that the moisture removing is slower and this in turn causes that the moisture contained in the dried or roasted material moves form deeper layers to the outer surface but simultaneously creates the protective layer protecting from the valuable ingredients loss. The duration of each stage mainly depends on the input size of the dried material and the grains size. It is obvious that for a fine-grained material and a smaller input this time will be shorter and for course-grained grains or bigger input respectively longer. Application of infrared radiation of proposed wave length parameters and power of the infrared illuminator causes faster and more uniform heating of the material without heating the gas itself. The process conducted in two stages allows for drying and roasting time shortening and in effect lower losses of the valuable substances and lower energy consumption is achieved. In case of biological raw material, including grains and seeds, longer impact of high temperature causes degradation of the valuable ingredients. Immediate cooling of the dried or roasted product with a cool air to the temperature from 40 to 50°C causes interruption of the Maillard reaction and stops the processes related with this reaction, which are darkening of the grains and fats oxidation. During thermo-biological stabilization equalization of moisture and temperature as well as stabilization of physicochemical properties take place which decide about organoleptic properties such as smell, crispness, taste.

[0014] An installation for drying and thermal stabilization of a biological material, including plant material grains, sesame especially, having a drier, which has a fluidized bed sieve located in a chamber, below which there is a connection pipe supplying a gas and above the fluidized bed sieve an infrared illuminator is mounted is characterized by that the drier is connected to a gas circulation circuit and in this circuit a deduster, fan and heater are connected one by one and from the heater the gas is pumped back to the drier. Moreover, before the fan a first intake point is connected which draws the gas for the process and then this part of the fresh gas, which eventually is exchanged in the first stage of the process. Flow of the gas returned in the circuit, of the gas thrown with an ejector and fresh gas drawn with the first intake point are regulated with respective valves, which location is precisely shown in the embodiment, on the drawing. In the drier chamber, above the fluidized bed sieve the connection pipe is mounted for receiving material, to which a suction injector is connected which transports material pneumatically to a tempering tank. The suction injector is supplied with the gas pumped with the fan from the second intake point. The gas drawn from the second intake point is favorably purified in a microbiological filter.

[0015] An infrared illuminator is the illuminator with adjustable electric power.

[0016] In the drier chamber, above the fluidized bed sieve there is a stirrer is mounted.

[0017] Preferably the tempering tank has a conical bottom with a vertical angle of the hopper which half is from 0 to 40° and a friction coefficient µ of the material against the hopper walls is in ranges from 0 to 0.52.

[0018] The installation according to the invention allows for realizing presented above, two stage drying and roasting process. The first stage takes place in the gas recirculation circuit. This circuit is created by the drier, deduster, fan and heater from which the gas is pumped back to the drier. Before the fan the first intake point is connected which draws part of the fresh gas for the process. Part of the gas for exchange is thrown to the atmosphere by the ejector. Flow of the gas returned in the circuit which should not be less than 75% is regulated by the valve. Analogically flow of the gas thrown by the ejector and the fresh gas drawn with the first intake point is also regulated by the valves. The valves regulating the gas flow allow then, in the second stage, for drying and roasting with use of all fresh air drawn by the first intake point.

[0019] The suction injector allows for realization of the pneumatic transport of the material to the tempering tank. It is supplied with the gas pumped with the fan with passing the heater from the second intake point. During the pneumatic transport the required fast cooling of the material is conducted. Thanks to this the material is effectively cooled to the temperature from 40 to 50°C. The infrared illuminator with adjustable electrical power allows for drying or roasting of the material in the first stage with required power. The stirrer improves porosity of the bed, thanks to which, the intensity of the heat and mass exchange is increased and this prevents from creation of the gas bubbles in the fluidized bed. The tempering tank with the conical bottom according to present invention allows for receiving ready-made material with use of its mass flow. Above all this ensures identical time of detaining each portion of the material in identical time when they are subject to stabilization.

[0020] After roasting or drying in the dryer achieved grains gain required straw color, their consistency became crispy and delicate, the taste is improved and good aroma is achieved, excess moisture is vaporized and pasteurization of the product is conducted which guarantee elimination of the biological pathogens: salmonella, yeast, mold and other harmful microorganisms. However, in the storage tank the stabilization of achieved properties takes place, color, aroma and delicate crispness equalization.

[0021] The subject matter of the invention has been presented in detail on the embodiments. Examples concern a method and installation which are pictured on the drawing. Attached drawing presents the installation schematically.

Example 1.

[0022] Sesame grains in amount of 75 kg and 10% moisture content after purifying from impurities were fed to a chamber of a dryer 1 previously heated to the temperature around 150°C and then dried and roasted in the first stage in the fluidized bed with fluidization velocity around 1.5 m/s. Simultaneously grains were illuminated with infrared waves of wave length from 2 to 6 µm emitted from an infrared illuminator 2 at settings of its electrical power at 0.04 kW/kg. With help of a steam heater 3 the constant gas temperature was maintained at the level of around 145°C. The process was conducted for 15 minutes using the same portion of the air supplemented only with the fresh air from the first intake point 4 in the amount of around 20% of its total volume. Then drying and roasting was conducted in the second stage at the same temperature value for 10 minutes. This cycle was performed with total air exchange and with heat recovery in a recuperator 5. The grains were subject to additional mixing with a stirrer 6 in order to increase and equalize the porosity. Then with help of the pneumatic transport realized by an injector 7 connected with a tempering tank 8 the sesame grains were fast cooled with the cold air to the temperature around 50°C. The grains portion was kept for 30 minutes in the tempering tank 8 for thermo-biological stabilization. Roasted grains achieved characterized with straw color, had pleasant smell and crispness of the grains. The moisture content of the grains after roasting was 1%. After examination, it was organoleptically confirmed that the degree of roasting qualifies the grains for confectionery production for the halva production. Degradation of valuable ingredients, such as: fats, proteins, starch, vitamins, organic compounds, microelements was in insignificant extent, which confirms pro-health character of the process.

Example 2.

[0023] In this example, hazelnut was subject to drying and roasting. The process was conducted analogically as in the first example with the difference that the following parameters were applied:

• the process temperature was around 150°C,
• the time of the first stage was 20 minutes and the second stage 25 minutes,
• the first stage was conducted with total air return without drawing the fresh air from the first intake point 4,
• the thermo-biological stabilization time in the tempering tank 8 was 100 minutes,
• the fluidization velocity was from 6 to 8 m/s.

Example 3.

[0024] An installation for drying and thermal stabilization of a biological material including grains of plant material has a drier 1 which is supplied with the material from a charging hopper 9. A drier 1 has a fluidized bed sieve 10 located in a chamber below which there is a connection pipe 11 supplying the air and above the fluidized bed sieve 10 an infrared illuminator 2 is mounted. To the connection pipe 11 of the drier 1, a heater 3 and a fan 12 are attached. The air to the fan 12 is supplied with a channel from a deduster 13 to which the air from the drier 1 gets. Mentioned elements create the air circulation circuit and allow for realization of the first stage of drying and roasting conducted with total air return. To allow for partial air exchange the air circulation circuit before the fan 12 the channel of the first intake point 4 is connected. Simultaneously before the connection place of the first intake point 4 channel an ejector 14 is located through which the air is thrown out into the atmosphere. In this embodiment before the ejector 14 there is a recuperator 5 located which allows for recovery of the heat from removed air and heat with it the fresh air drawn with the first intake point 4. The drier 1 chamber has a valve 15 mounted above the fluidized bed sieve 10 for receiving the material to which a suction injector 7 is connected. The suction injector 7 is supplied with the air pumped by the fan 12 with passing the heater 3. The air drawn for cooling in the pneumatic transport is drawn from the second intake point 16 and purified in a microbiological filter 17. The dried material is then fed to a tempering tank 8. In the chamber of the drier 1, above the fluidized bed sieve 10 the stirrer 6 gets out. In the drier chamber wall, there is a sampling outlet 18 for quality control and control of the material drying and roasting degree. The infrared illuminator 2 is the illuminator with adjustable electric power. The tempering tank 8 is made from steel and has a conical bottom 19 which vertical angle of the hopper is α=60°. The friction coefficient µ of the material which the grains usually are against the hopper walls is in range from 0 to 0.52.
The mechanism of action of the installation is following. From the charging hopper 9 the portion of the material is fed into the chamber of the drier 1 and a valve 20 is closed. The material is dried and roasted in the fluidized bed where streams of the hot air of a given temperature rise the material particles above the fluidized bed sieve 10 and simultaneously the material in the bed is additionally heated with the infrared illuminator 2. For the fluidization process improvement, the bed is additionally cultivated with help of the stirrer 6. Moist air with an open valve 21 flows from the chamber of the drier 1 to the deduster 13 from which after purification is in the first stage returned to the fan 12. Total air return is allowed by a valve 22 which is then opened and valves 23 and 24 which are then closed. The valve 23 closes the air outflow to the ejector 14 and the valve 24 closes fresh air supply from the first intake point 4. At partial air return each valve is respectively opened: 22, 23 and 24. The air after heating in the heater 3 is pumped under the fluidized bed sieve 10 of the chamber of the drier 1. In the second stage the air is directed to the recuperator 5 with the valves 23 and 24 opened and the valve 22 closed and ejected into the atmosphere with the ejector 14. Such configuration allows for total air exchange. After drying and roasting of the grains the valve 21, a valve 25 located before the heater 3 and a valve 26 located on the recuperator 5 outlet are closed. Till closed are open: a valve 27 of the air inflow to the second intake point 16, the valve 15 for receiving of the material and a valve 28 located on the channel supplying the air to the suction injector 7. With help of the suction injector 7 dried material is drawn from the chamber of the drier 1 and cooled in the pneumatic transport to the tempering tank 8. From the tempering tank 8, thanks to an its structure allowing for mass flow out, the material is received without mixing subsequent portions with each other. The air from the tempering tank 8 is directed to the deduster 13.

Claims

1. A method for drying and thermal stabilization of biological material, including plant material seeds, sesame especially, in which purified material is placed in a drier chamber and subject to drying in a fluidized bed and subject to infrared radiation, characterized by that the process of drying is conducted in temperatures from 110 to 200°C at a gas stream velocity in the fluidized bed from 0.8 to 8 m/s above a sieve and in two stages lasting form 5 to 25 minutes and the gas used in the first stage is returned in 75% of the volume of entire portion of the gas used in this stage and moreover the infrared radiation of 0.8 to 6 µm wave length and adjustable electrical power of an infrared illuminator (2) in range from 0.02 to 0.15 kW/kg of the material input is used whereas in a second stage drying is conducted with the total gas exchange and after a drying process the material is subject to immediate cooling to a temperature from 40 to 50°C and subject to a thermo-biological stabilization.

2. A method according to claim 1 or 2, characterized by that cooling is conducted in a pneumatic transport of the material to a tempering tank (8).

3. A method according to any of previous claims, characterized by that the thermo-biological stabilization is conducted in the tempering tank (8) for 15 to 120 minutes.

4. An installation for drying and thermal stabilization of a biological material, including plant material seeds, sesame especially, having a drier, which has a fluidized bed sieve located in a chamber below which there is a pipe connection supplying a gas and above the fluidized bed sieve an infrared illuminator is mounted, characterized by that the drier (1) is connected into a gas circulation circuit and in this circuit there are sequentially connected a deduster (13), fan (12) and a heater (3) from which the gas is pumped back to the drier (1) and before the fan (12) the first gas intake point (4) is connected and the gas flow returned in the circuit, the gas ejected with an ejector (14) and the fresh gas drawn with the first intake point (4) are adjusted respectively with valves (22, 23, 24).

5. An installation according to claim 5, characterized by that the drier chamber (1) has a valve (15) mounted above the fluidized bed sieve (10) for receiving the material to which a suction injector (7) is connected which pneumatically transports the material to a tempering tank (8).

6. An installation according to claim 5 or 6, characterized by that the infrared illuminator (2) is the illuminator with adjustable electric power.

7. An installation according to any of claims from 5 to 7, characterized by that in the chamber of the drier (1), above the fluidized bed sieve (10) a stirrer (6) gets out.

8. An installation according to any of claims from 5 to 8, characterized by that the tempering tank (8) has the conical bottom (19) with vertical angle (α) of the hopper, which half has values from 0 to 40° and the friction coefficient µ of the material against the hopper walls is in range from 0 to 0.52.

Drawing