The methods and modes of roasting cocoa beans
For roasting cocoa beans the most widely used in our chocolate factories are cylindrical and ball machines.
Cylindrical fryer (Fig. 8) lined with brickwork. The main part of the device - a cylinder
-Installed door and a pair of internal blades. The hot gases generated from the fuel burned in the furnace are washed into the chimney by washing the side surface of the rotating cylinder. Cocoa beans are loaded into a rotating cylinder through a metal funnel that is integral with the front door hinged on hinges. The cylinder is loaded with 150-200 kg of beans; They do not have to fill the entire cylinder and usually occupy no more than 30% of its volume, so that during the roasting process the beans move along the inner surface of the cylinder, mixing and pouring. In this way, the danger of local overheating (beans, the heat exchange in the mass of beans and the heating of each individual bean is accelerated and the removal of moisture and volatile substances is facilitated.
Evolved from fried beans water vapor and volatiles as they accumulate in the cylinder tube sucked by a fan. Over the course of roasting observed on samples that periodically take over the work done in the door opening by means of a probe-probe.
Observing the fragility, aroma, color and taste of the fried beans extracted from the barrel by the stylus, the master determines the moment of their readiness. Too high roasting temperatures and excessive long-term effects lead to a weakening of the characteristic aroma of cocoa beans and to the appearance of an unpleasant odor of acrolein, the product of the decomposition of glycerol-containing cocoa butter. Fried beans, for these reasons, should be quickly removed from the frying bar at the end of the roasting and cooled. For this purpose, the door is opened and the cocoa beans are unloaded for cooling to the upper hole of the trolley.
At such temperatures cooling of cocoa beans through 10- 11 min. reduced to 50-60 °, and through 15-20 minutes. to 30 °.
The temperature regime of the process of roasting cocoa beans in cylindrical fryer studied the department and submitted on schedule risk 10. The first period of roasting, lasted about 10-20 minutes, characterized by a fall of temperature in the apparatus to 30-33 °. Following this, it increases for prmerno 2 ° per minute and reaches the end of the roasting 130 ° C
Fig. 10. Schedule temperature when roasting the beans in a cylindrical apparatus:
A moment of loading; At the time of discharge-beans.
As the chart above shows, roasting in the surveyed cylindrical device at the value of each zapruzki 125-130 60 kg lasted for about minutes. In accordance with this and hourly productivity cylindrical fryer is 130 kg. For vehicles, usable capacity which is 260 kg and higher hourly productivity will be increased accordingly.
The same pattern was set temperature KY Mamontov on the basis of a large number of tests carried out in the study of the work of the cylindrical apparatus obzharachnogo. The duration of roasting cocoa beans was 50-70 minutes. at the value of each load 400 kg. Fuel consumption, based on the reference fuel has been determined in these tests in 100 1 kg per ton of roasted beans.
It should be added that in the combustion chamber of the cylindrical fryer (see. Fig. 8) laid two mettalicheskie tubes in which heated air without mixing with the flue gases. Last fed to trellis rear wall, through which it is sucked into the cylinder and escapes into exhaust pipe, contributing to a better heating of beans, and roasting products removal.
Widespread our chocolate factories have the ball fryers in which the beans are roasted in the atmosphere of combustion products, mixed with air.
The main part of the device is a metal drum that rotates inside a stationary drum. Subject to roasting the beans are loaded into the hopper and from here at the opening of the damper are poured into the inner rotating bowl. Last provided LL blades which raise when rotating beans upwards from where they fall down again, the individual grains down. Strong fan sucks from the interior of the ball released from the gaseous products of beans, while sucking the mixture through the flue combustion products with air, which flows through the pipe.
The device is equipped with a pyrometer, showing the temperature in the fryer, and the probe for the selection of fried bean samples to determine their readiness.
The device has a device for the automatic control of weight loss is roasted beans; it consists in that the main shaft, and hence it fortified inner bowl contained therein is roasted beans based on the weighting mechanism. The latter is not only shows the weight loss during frying, but also signals the end of the roasting.
At the end of the roasting discharged from the roasting Bobi aid reaches the receiver located under the cooling apparatus.
As shown by the curves, the temperature in the apparatus is reduced immediately after loading the bean (point A). However, the temperature drop period duration does not exceed 6 min The temperature does not fall below 140 °.
Then she quickly rises and after 6- 7 minutes. reaches 160-170 °. Thus, in this apparatus the entire process takes place at a roasting 140-170 °
The duration of roasting not more than 12-13 minutes. Such a sharp reduction roasting time can be attributed to the rapid heating of the beans are roasted by neposredstnogo their contact with the products of combustion and the high temperature (140-170 °). In addition, fast roasting the beans in these devices linked to the energetic spilling the beans are roasted, which then rise up and fall down the individual grains. Thus each grain repeatedly comes into contact over its entire surface with the hot gases.
Supplied Our experiments have shown that when the ambient temperature maintained at 145 °, the temperature in the center of the bean, surrounded on all sides of beans reached 100 ° after 35 min., And if the test grain was on all sides surrounded by hot air, then it took only 6 min., ceteris paribus.
The fuel used in ball apparatus coke combustor that burns in the flame short, and hardly contaminates the soot combustion products. Firewood as a long-flaming fuel at roasting cocoa beans in ball machines do not apply, and only used for roasting in cylindrical apparatus where the flue gases are not in contact with the fried product.
Due to the complete gasification for a number of confectioneries gas used for combustion in furnaces fryer. Combining the use of gas with the installation of the furnaces in the flameless burners, we not only improve the sanitary conditions of work, but also significantly improve the efficiency of the roasting process.
Consumption of equivalent fuel for ball machines is 25-35 1 kg g fried beans.
The duration of the download bean ball fryer is 25-30 sec., And the duration of the discharge 40-50 seconds. The weight of the load for vehicles with an internal diameter of the sphere equal to 1000 mm is 160 kg, hourly productivity is 600-800 kg.
The loss of dry matter during roasting not exceed 0,5%. Thus, the total amount of the loss in weight during roasting of cocoa beans may be taken as 4,5-5% by weight have been added to beans apparatus at an initial moisture unroasted beans about 6-6,5%.
Ball fryers in the presence of well-known advantages over cylindrical and have a number of disadvantages associated with short-acting high temperature
roasting adversely affect the taste of the flavor of chocolate and chocolate.
Data on adverse effects on the quality of chocolate products at a high temperature roasting, and the desire to preserve the enzymes that contribute to the oxidative processes in the production of chocolate led to the use of thermal processing cocoa beans softer modes.
Kafka BV Experiments have shown that chocolate prepared from the dried cocoa beans have normal taste qualities.
And now on the factories of the cocoa beans are dried by means of a shaft dryer, dryer consists of a drying chamber, two steam air heaters, blower, loading mechanism.
The drying chamber having a parallelepiped shape 3600 mm height, width and length 1350 2330 mm mm vertically divided into 30 horizontal planes (tiers), spaced from one another by 100 mm.
Each plane includes 15 plates. Each plate (1000 mm length, width 110 mm) can povertyvatsya around its longitudinal axis 90 °.
Each tier plate by springs held in a horizontal position forming a plane on which lies the cocoa beans. At regular intervals using a special device the plate is inverted on 90 ° and with them the product falls out on the following underlying plane.
Thus, the cocoa beans are loaded on the upper tier, periodically are poured from one tier to another. The cycle begins povertyvaniya plates alternating with the lower layer, from which the discharged dried beans.
The drying chamber is divided into 6 zones (in 5 tiers in each zone), which sequentially, starting with the bottom Zoni, passes the air blowing fan (TsAGI number 5) through the heater.
Electromotive method of roasting
The prototype of the electromotive unit for processing cocoa beans, shown in Fig. 15, it made ratikami Minsk confectionary factory and has been in operation for many years.
Each of the two heating drums is a steel pipe wrapped on the aluminum wire insulation. Top coil is also covered with insulation
When winding is included in a network, eddy currents heating a steel pipe from which heat is transferred to it while it is in the product.
Fig. 15. Electromotive device for roasting cocoa beans:
1-motor; 2-reducer; 3-elevator; 4-heating drums; 5-
screw; 6-pipe; 7-cooling device; 8- cyclone; fan; 10-hopper.
Last loaded into the hopper 10, 3 from a bucket elevator is fed into the heating drums. Along the pipe product moves screw 5.
Cooling unit represents a steel pipe 7, on which roasted product moving towards the screw air sucked fan 9 and 8 ejected through the cyclone, which traps air entrained particles and dust husk.
Roasting їv this unit being to a moisture content of cocoa beans 3%, unit performance 100 kg / hour, the temperature of the cocoa beans after roasting їv about 110 °; roasting duration 30 minutes
Roasting high-frequency currents
Recently, for a uniform preheating of dielectrics and semiconductors, the high-frequency heating method is quite widely used, in which molecules of a dielectric or semiconductor placed (in an electric field are polarized and as a result tend to orient in accordance with the direction of the field.
The electric field generated by the high frequency unit, changes direction several million times per second, the same time and change their orientation in the molecules by intermolecular friction material is heated uniformly throughout the thickness.
MTIPPa Department in conjunction with the Energy Institute experiments on high-frequency current cocoa bean roasting were conducted.
On the basis of these experiments, which gave positive results, on the instructions of technical documentation production plant for roasting cocoa beans in the field of high frequency currents.
Unlike existing batch fryer, this plant is continuously operating. In it there (possibility of quick frying regime change (through the generator configuration changes), as well as the precision of a given regime that ensures uniformity of roasting and prevents burnout fried product.
Chocolate from beans roasted high-frequency current, has good taste
It is believed that it will implement this method of roasting cocoa beans in the near future.