Tobacco is a botanical variety that is selected and classified through the assessment of certain characteristic standards. The level of quality of the tobacco is the result of a series of factors, such as:
- genetic characteristics of the seed;
- climate conditions (characteristics of the soil and climatic conditions) of the cultivation region;/li>
- practices of cultivation, harvesting and care that occur on the farm producing;
- pre-manufacturing stage in which the leaf tobacco is examined before being sent to manufacturing plants.
The main parameters, through which the tobacco is classified, are the position of the leaf on the plant, the quality of the tissue, the midrib and the veins, the colour, the smell and, finally, the level of maturity.
With the change in position of the leaf on the plant, the physicochemical constitution of the leaf tissue, its consistency and thickness, its size and the amount of midribs and veins, is also affected. For example, in the case of Virginia, the nicotine contained in the leaves increases rising from leaf to the apex, the contrary occurs with the contents of sugar and this causes clearly different characteristics of smokes between them.
The quality of the tissue may vary from the “substantial” to “soft” depending on the its stalks. The soft tissue, which is responsible for a greater and more complete combustibility, is typical to medium-low stalks, becoming substantial in higher stalks. Other standard of quality is the “grain” of the tissue that must be opened. One refers to grain-open tissue when the tissue presents a little roughness to the touch. The grained closed tobacco, that is smooth to the touch, burns with difficulty and is the cause of defects in taste and aroma.
The main components of the leaf are the midrib and the veins that form the structure which allows the leaf to resist the action of the wind during the step of vegetation in the field, besides constituting the reserve system and distribution of fluids that feed the leaf blade. In the pre-manufacturing stage of tobacco the midribs, that have a high cellulose content, are separated from the blade because it might cause difficulties during the following stages, in which the tobacco is examined for the production of cigarettes, and might even have, if excessive, a negative effect on the final taste of the product.
The colour plays a major role in the judgement of quality, being related to other elements that are not detected to a cursory look. A lively colour is a proof that the tobacco has a good provenance, collected at right time of maturity and well-treated, from the grain-open tissue.
The smell (which is different from the aroma that the tobaccos develop during combustion) indicates the state of conservation: the healthy tobacco has a sharp smell. The tobacco has the particularity of easily absorbing, not just the humidity, but even the smells of the environment in which is planted.
The level of maturity is finally the last important standard for the classification of tobacco.