Tobacco leaf baking technology

According to the baking process, the baking method is introduced in stages:

1, yellowing stage

The goal to be achieved in the yellowing stage of tobacco leaves is: the leaves collapse and become soft, and the leaves turn yellow until the veins of reeds are slightly blue.

①? Basic process conditions

Dry and wet bulb temperatures. After ignition, the temperature shall be raised to 38℃ at the rate of 65438 0℃ per hour, and the error shall not exceed 65438 0℃. The temperature difference between dry and wet bulb is 2℃ ~ 3℃, and the error is less than 0.5℃. The temperature stabilization time depends on the change of tobacco leaves, generally 30 ~ 72 hours. When the tobacco leaves are about 80% yellow, the temperature is raised to 42℃ at an average speed of 4 hours, and the difference between dry and wet is increased from 2℃ to about 4℃, and the time is extended to make the tobacco leaves yellow and soft. This temperature stabilization time is about 8 ~ 12 hours.

In the yellowing stage of ventilation, continuous forced ventilation should be adhered to, and the fan should be operated at high speed for 2 ~ 4 hours first, and then at low speed continuously. Reduce the temperature and humidity difference between sheds, and make the tobacco leaves in each shed yellow and dry as evenly as possible.

②? Flexible control of factors, flexible control of heating rate, usually rainy smoke, thin smoke, over-ripe smoke, greedy smoke or in low-altitude tobacco areas, heating up faster, the low temperature stage before 38℃ should be appropriately shortened. The dry smoke, thick smoke and cooked smoke located in high altitude tobacco areas should be heated slowly, and the low temperature stage before 38℃ should be prolonged accordingly.

Flexible control of wet and dry difference For fresh cigarettes with poor quality and easy blackening, the wet and dry difference should be expanded to 3℃ ~ 5℃ to prevent the phenomenon of "hard yellowing". For fresh tobacco leaves with high quality and scorching tendency, the difference between wet and dry should be reduced and kept at about 65438 0℃, so as to eliminate the scorching phenomenon.

Flexible control of yellowing degree can increase the yellowing degree of fresh tobacco leaves with good quality and easy baking by 9 ~ 10. For fresh tobacco leaves with poor quality and difficult baking, the yellowing degree should be reduced to 70 ~ 80%, and the cyan part that has not yellowed should be dried at a higher temperature in the later fixing stage to prevent the tobacco leaves from blackening.

2. The goal of fixing color stage is to fix color in time and quickly, and improve the appearance grade quality and internal quality of tobacco leaves. It is necessary to achieve full yellow leaves at 42℃ and full yellow veins at 48℃. In terms of drying, the leaves should be semi-dry at 50℃ and completely dry at 54℃.

①? Process conditions are changed to heat. After the tobacco leaves turn yellow at a stable temperature of 42℃, they begin to increase the firepower, slowly raise the temperature, and then turn to the color fixing stage. The transformation of this process is commonly known as "turning to fire". The phenomenon of blackening or flue-cured tobacco will appear when the fire turns at the wrong time, so the early or late turning time and the fast or slow heating rate are the key links in the color fixing stage. In order to change the fire to heat up in time, tobacco farmers often adopt the method of heating up in different periods. The key points of operation are: within 65,438 0℃, the temperature rises from 42℃ to 46℃ for an average of 3 hours, and the wet bulb should be kept at 38℃ ~ 39℃. Two hours on average? The temperature rises to 65438 0℃, from 46℃ to 50℃ for about 8 hours, and the wet bulb is kept at 38℃ ~ 39℃. ? Then raise the temperature to 54℃ at an average speed of 65438 0℃ per hour, and the wet bulb should be stable between 39℃ and 40℃. Finally, keep the temperature at about 54℃ 12 ~ 20 hours to ensure the color fixation of dried tobacco leaves.

In the color fixing stage of continuous forced ventilation, the circulating fan should run continuously at high speed to ensure the smooth removal of heat supply and humid air. When the blades of each layer are basically dry, they can be turned into low-speed operation.

(2) Flexible control factors flexibly control the heating speed. For tobacco leaves that turn yellow rapidly, the temperature should be raised quickly and the color should be fixed after turning to fire. For tobacco leaves that turn yellow slowly, it is necessary to slowly raise the temperature and fix the color, so that the residual cyan after the fire is turned to yellow and fix the color through higher temperature and slower heating speed. Flexible control of wet and dry difference, for fresh tobacco leaves with high quality and great baking potential, relatively high wet bulb temperature should be adopted to ensure that the tobacco leaves change fully and perfectly, and realize yellowing, maturity and fragrance. For example, 38℃ ~ 42℃, the difference between dry and wet can reach 3℃; When the temperature is 42℃ ~ 50℃, the wet bulb is stable at 39℃; During the period of 50℃ ~ 54℃, the wet bulb stabilized at about 40℃. If the quality of fresh tobacco leaves is not high and it is not easy to bake, it is appropriate to control the relatively low wet bulb temperature.

3. The main goal of the dry gluten stage is to ensure that all the healthy tobacco leaves are dried and baked thoroughly, and there is no wet gluten, wet slices and no gluten.

①? Controlling the temperature and humidity of the process conditions, the dry-bulb temperature is increased from about 54℃ to 68℃ at the speed of 65438 0℃ per hour. Among them, when the temperature rises to 60℃, it is necessary to adjust the fire moderately and stabilize the temperature, and then continue to heat up after the tobacco leaves in the low-temperature area of the whole kang are completely dried and immobilized. When the temperature reaches 68℃, the temperature is stable 12 ~ 20 hours. In the process of stable temperature, when there is only about 3 cm left in the tobacco stem, which is not completely dry, but has shrunk to purple, coal feeding can be stopped, and the blower still needs to run continuously for about 6 hours before it can stop working. The adjustment method of wet bulb temperature is to gradually close the inlet and outlet of wet bulb from the beginning of dry consolidation period, so that the wet bulb temperature can be quickly adjusted to 465,438+0-42℃, with the highest temperature not exceeding 43℃ and the lowest temperature not lower than 465,438+0℃. Until the dry tendons are over. Reduce forced ventilation, keep the circulating fan running at high speed at the initial stage of dry reinforcement, and ensure smooth heat supply and humid air discharge. When the blades of each layer are basically dry, they can be turned into low-speed operation. Only when the fire goes out and the temperature in the curing barn is lower than 50℃ can it be closed to prevent the fan motor from being damaged and the tobacco leaves on the ceiling from being damaged by local overheating in the curing barn.

4, special process measures

① Low-temperature fixation During baking, the residual cyan should turn yellow at a higher temperature, and the time should be fully extended at 47℃, and the wet bulb temperature should be kept at 34℃ ~ 36℃. Low temperature and strong ventilation can dry tobacco leaves to more than 60%, ensuring the safe color fixation of tobacco leaves.

(2) When the wet bulb is used to bake thin and light-colored tobacco leaves, the wet bulb temperature should be kept between 35℃ and 38℃ before the dry bulb temperature reaches 50℃ to ensure that the tobacco leaves are dried into small rolls. When the dry bulb temperature is 50℃ ~ 54℃, a higher wet bulb temperature, about 39℃ ~ 465438 0℃, should be adopted. This can not only fix color smoothly, but also improve the quality of tobacco leaves.

The production process of flue-cured tobacco can be roughly divided into three stages: seedling raising, field growth and tobacco curing.

One is intensive and efficient curing barn.

With the continuous development and innovation of flue-cured tobacco production concept and technology, the traditional natural dehumidification curing barn, which has been used for many years, has been gradually transformed and replaced. In recent years, with the technical guidance and financial support of tobacco management departments at all levels in the country, some intelligent, intensive and efficient curing barns have developed rapidly and shown their unique advantages. The emergence of new curing barn and its supporting new technology has brought tobacco production into a new field of intelligence, scale and specialization. From the beginning, it shows the clue that tobacco production is integrated into modern agricultural production mode.

Second, the harvesting of mature tobacco leaves.

Because the harvesting quality of tobacco leaves is closely related to the final baking quality, the baking technology of tobacco leaves should be introduced from the picking of tobacco leaves.

The yellowing and water loss rates of immature and over-ripe tobacco leaves are quite different from those of normal mature tobacco leaves, and they are easy to be baked into green, black or variegated tobacco leaves. It has a serious impact on tobacco quality. Therefore, it is a basic skill that tobacco farmers must master to accurately identify the maturity of tobacco leaves and pick them in time.

According to the different position and maturity of tobacco leaves on tobacco plants, we divide tobacco leaves on tobacco plants into lower leaves, middle leaves and upper leaves. The whole harvesting process takes about two months from the lower tobacco leaves to the upper tobacco leaves.

Third, weave and load cigarettes.

Tobacco weaving and loading are two important processes before baking. Reasonable tobacco weaving and loading can ensure the uniformity and consistency of the required temperature of similar tobacco leaves. If the density and position of tobacco weaving and filling are unreasonable, the problems of baking slag and baking green are easy to occur during baking.