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Home | Latest Cigar News | CURING AND FERMENTATION OF THE CUBAN TOBACCO LEAVES
CURING AND FERMENTATION OF THE CUBAN TOBACCO LEAVES
The curing process of dark tobacco in Pinar del Rio
Generalities and classification of the curing process
The curing of tobacco is the process that takes place between the period of time of the stringing and loosening of the leaves, this process usually lasts between 40 and 50 days, the period of time in the traditional curing barns lasts between 60 and 90 days, this happens mainly when the year is very dry and having concluded the process they can not carry out the loosening of the leaves because the required humidity does not exist.
It is necessary to point out that the name of this process is curing and not drying, because in spite of the fact that in the leaf an important process of loss of water is verified (drying), prevails a highly biological, biochemical, chemical and mainly physiologic process being indispensable for its development that the cells stay alive during a period of time that oscillate between three and five days, it is common that during the curing process of Virginian tobacco that is carried out in an artificial way the process be named drying and not curing, this type of tobacco is even known as Flue Cured.
It has been demonstrated since the first decade of the XX century that the curing of tobacco is highly a biological process in which a group of reactions of decomposition are carried out (catalysis), many of them require of enzymes that are only possible in alive cells. We can consider that the initial phase of this process takes place with the maturation process.
During the curing process big changes occur, some internal ones (not visible) and others that can be appreciated at first sight. Next we offer the information related to the main changes that take place in the leaf during this process:
Loss of the green color due to the effects of an enzyme.
Substitution of green color for pigments of yellow or orange color (xanthofyll).
Loss of a high percent of water, the leaf enters with a percent between 80 and 85 and it goes out with 18 or 20 percent.
Almost total reduction of the initial contents of carbohydrates particularly starches.
Transformation of the proteins into amino acids.
Reduction of the thickness of the leaf.
Losses of dry mass.
Relative increase of the concentration of mineral substances.
Beginning of the process of reactions that in superior phases will facilitate the emergence of the aroma and other chemical components.
The increase of the contents in amino acids and simple nitrogenous substances.
Decrease of the contents of nicotine of the leaf.
The curing process depends on the occurrence of a group of factors, being some of them the following:
Chemical composition of the leaf.
Type of tobacco.
Position of the leaf in the stem.
Climatic conditions that prevail in the moment of harvesting.
Behavior of the indicators of quality of the leaf.
Curing method.
Relationship between the size of the leaf, the quantity of leaves per pole and the climatic conditions.
Average temperatures.
Presence of south wind.
Very high relative humidity (more than 90 percent) or very low (less than 60 percent)
Air speed (over 4 m/seconds).
For curing dark tobacco different technologies are used, which try to facilitate an appropriate control of the climatic conditions in order to achieve that the changes that happen during the process allow to obtain a final product of high quality, contrary to other countries, in Cuba this process is expensive and very difficult, but it allows that the intrinsic quality of the leaf be preserved.
The curing process of dark tobacco in Pinar del Rio is classified in the following way:
a) Air curing. This method is the most used in the province, it is used in a limited way in tobacco for wrappers and in almost all sun grown tobacco (strung and en palo). In this method, the natural air (its temperature, humidity and speed) is the factor that causes the curing and drying of the leaf, the constructive characteristics of the curing barns allow an appropriate use of the environmental conditions.
The disadvantage of this method is that when the environmental conditions are not favorable it is very difficult to modify them, also when peasants are going to loosen tobacco it is necessary to wait for the rain because in those months the relative humidity is very low (inferior to 60 percent).
b) Controlled curing. This method consists on using a system that allows in an automated way to have an atmosphere inside the curing barn very controlled according to the three climatic factors that influence the most during the curing process, they are: temperature, relative humidity and air speed.
This method is used exclusively in tobacco for wrappers, only the leaves from the central and central basal third of the plant are submitted to this process, therefore the leaves of the base and of the superior part which are not good for wrappers won't be submitted to the process. The system that is used in Cuba is known as kalfriza.
The controlled curing can be carried out in two variants, one of them well-known as controlled curing in modified traditional curing barns and the other one denominated controlled curing in cameras, this last one provides uniformity in the control of the climatic factors and it is also more efficient.
One of the advantages of this technology is that it allows to humidify the air and therefore to elevate the relative humidity in a controlled way so that the leaves can be manipulated and the process of loosening be verified.
c) Sun curing. This method is typical of the oriental and semi-oriental tobacco, in Pinar del Rio a variant of it is applied in the case of sun grown tobacco (en palo) that consists on leaving the poles in the sun during a period of time from three to five days until the leaves wither.
Phases of the curing process. Characteristics
The curing process is considered as one of the most important activities in the cultivation of tobacco, because it is the bridge between the harvested leaf and the initial fermentation. There are three phases of curing, each of them having different characteristic and peculiarities, although the process is only one these phases receive the following names:
Yellowing. It is the initial phase of the curing process, it is characterized by the loss of the green color and the beginning of the yellow color, which many times is not appreciated, because the leaves take directly a clear Brown color, the time of duration of this phase oscillates between eight and 10 days and maybe the most excellent thing is that in the first three or four days after the stringing process the cells stay alive, if this condition is not carried out the qualities of the leaf would be affected. In this phase significant losses of dry mass take place, all the carbohydrates become sugars and these in carbon dioxide and water, they also diminish drastically the contents in amino acids and increase the simple nitrogenous substances.
The climatic factors that influence the most during the yellowing phase are temperature and relative humidity, in general in this phase is considered as adequate temperature the one oscillating between 27 and 29 degrees, if temperature is under 20 degrees it diminishes the time of the process considerably and if it is under 15 it stops it. On the other hand, when the atmospheric humidity is low, the strong losses of humidity that experience the leaves in this phase cause that humidity varies between 85 and 90 percent being this the most appropriate range, if the value is under 80 percent the leaf loses humidity then very quickly and the cells die prematurely, on the other hand, if humidity is over 90 percent the leaf take a long time in losing humidity and appear favorable conditions for the emergence and attack of illnesses mainly those caused by fungi.
Limbo Curing. It is the second phase and it extends from eight to ten days up to 18 to 20 days, here the cells are dead and the reactions that happen are related to the increment of those initiated in the previous phase.
This phase requires higher temperatures than the yellowing phase and lower relative humidity. The recommended temperature oscillates between 30 and 32 degrees and the relative humidity between 70 and 75 percent. In this phase is very important to maintain an air speed between two and four meters per second and when necessary to exchange interior and exterior air.
Reduction of the central vein. Of all the phases of the curing process maybe this is the one that is more related to the concept of drying of tobacco, because in this phase new reactions don't take place but there are great quantity of losses of water in the leaf, the central objective of this phase is to eliminate the excesses of water in the central nerve and in the parenchyma of the leaf. When the leaf shows contents of humidity between 17 and 19 percent and the vein breaks when bending the leaf, then the curing process has concluded.
This phase requires higher temperatures; the recommended temperature oscillates between 32 and 34 degrees (these data refer to the controlled curing). Under conditions of natural curing temperature doesn't surpass 31 or 32 degrees and the relative humidity under 70 percent. In this phase it is very important to maintain an air speed between two and four meters per second and every time that be necessary to exchange interior and the exterior air and to apply water when humidity is very low.
The curing barns
The curing barns must be guided according to the cardinal directions, from East to West, and they will remain closed during the curing of the leaves. This approach is enough to value the importance of the curing barn in the process of the curing of the leaf of dark tobacco, it is also necessary to point out that for the correct orientation of this construction it is necessary to keep in mind direction and speed of the wind.
Many curing barns have been built with modern materials, today it is not very common to see the roofs and lateral parts built with the help of palm leaves, it is used the wooden chart and for the roof the zinc sheets and other materials, although as floor they still have the earth, they maintain the original height and the great number of windows in the lateral parts and in their fronts. In spite of the changes introduced in the last years the curing barns still fulfill the objectives for which they were conceived.
In the curing barns, the workers should watch over humidity, temperature and rains; as these factors vary, they open and close their doors. One of the first works to carry out is the stringing of the leaves; the women who carry out this task, with medium or big needles (according to the leaves: tobacco for fillers, or for wrappers), unite the leaves in pairs and place them in long poles; these poles are put on some horizontal timbers (called barrederas) where they lean on their ends; each day, about 40 or 60 poles are completed, although there are women who complete 90 or 100.
A pole is a direct stick of about 4 m; it is a very useful element in the curing process of tobacco. To obtain good poles it is necessary to cut and to maintain them in salted water during 50 days; then it is necessary to peel them, so that they don't transmit their scent to the tobacco leaves. Finally, the nodes are removed in order to avoid possible damages to the leaves.
The raw material that is used for making the Cigars is air cured, this process, long and natural, is supervised in a constant way and it assures to control temperature and humidity; the strung leaves, are put near the floor and, when they dry, they are put in the higher part of the curing barn. First the leaves acquire a yellow color due to the loss of chlorophyll and then thanks to the process of oxidation and others, they acquire the golden-reddish color that indicates that they are ready for the first fermentation.
Leaves of dark tobacco when concluding the yellowing process, in this case they are practically in the phase of the curing of the limbo (approximately between nine and twelve days after the stringing process).
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