Curing of tobacco
From leaf to smoke, tobacco goes through a long journey, lasting months or even years.
The steps are numerous: drying, fermentation, curing, blending and, eventually, flavoring.
In this article we want to focus on tobacco curing, which is absolutely crucial in the smoking experience.
Tobacco curing: what it is
Tobacco leaves, once developed, are harvested one by one, or sometimes all together with the stem, for curing.
This is the first process to which tobacco leaves are subjected and it is very important because it determines, irrevocably, the basic characters of tobacco. Incorrect curing can never be corrected.
It consists of the method of drying the leaves, but it is not limited to only that.
Simply put, it involves slowly dying the leaves under special conditions, different for each type of tobacco, so as to encourage the release of all its aroma, fragrance and taste.
The most noticeable phenomenon of the cure is the loss of green color and, more importantly, of water, which drops from 80% to 15%, greatly reducing the weight of the leaves. This occurs as a result of water evaporation.
Let us now see how the cure varies according to the type of tobacco.
Sun cured
The oldest and simplest cure, as well as a natural one, is typical of Oriental tobaccos and is called sun curing.
Basically, rows of about two hundred leaves are formed, strung in garlands, which are kept in the dark for a while until they turn completely yellow.
These leaves are then placed on frames and exposed to the sun during the day, to be covered at night.
After 15 to 30 days, the leaves are ready for baling and fermentation stage.
Air cured
Another natural cure is air curing. The leaves are allowed to dry by hanging them on poles for a few days and then they are gathered in rows and brought to factory premises, arranged on racks or hung from ceiling beams.
These rooms always have large windows, which must be opened and closed continuously to promote proper ventilation. In fact, a draft is enough to irreparably impair leaf drying.
There is also a second method of air curing, carried out with the entire tobacco plant. Here, too, there is brief drying in the field, then hanging the plant in the premises with the leaves pointing down.
This second method involves deeper chemical transformations because there is an exchange of soluble constituents between leaf and stem.
Air curing is used for fine and light tobaccos, particularly Burley and Maryland, and lasts between 30 and 60 days.
Fire cured
Fire curing, also called “direct fire curing,” is typical for Kentucky tobaccos.
It consists of the leaves arranged in large rooms in which hardwood, sawdust or charcoal fires are lit and regulated.
Water vapor from the leaves escapes through the windows and roof of the rooms, and in a few days the leaves begin to turn brown and become brittle.
The process takes 3 to 4 months, until the leaves turn a dark color.
Flue Cured
Also called “indirect fire curing,” this is the “most industrial” cure and was adopted many years ago to fix the yellow color of Virginia tobaccos.
The leaves are harvested when their vitality is very low, to be engulfed and left to dry in rooms, less large than the previous ones, heated by pipe systems that convey air from boilers underground.
Afterwards, the leaves are left to hang to regain moisture.
The temperature reaches as high as 80°C, but regulation is key. In the case of Virginia Bright, you cannot have a leaf that is too dark, partly because of the aroma it would develop.