Freshly harvested tobacco leaves cannot be used for making tobacco products, because they do not have required technological properties yet. To become the raw material for manufacturing tobacco products, freshly harvested tobacco leaves undergo post-harvest processing. The latter consists of a sequence of technological processes, first of all – curing and fermentation.
The main purpose of the post-harvest tobacco processing is not only to preserve those indicators of the quality of the raw material that were formed during the process of growth of a tobacco plant in the field, but also to enhance its quality by increasing useful features and eliminating harmful ones. Post-harvest tobacco processing techniques may significantly improve the quality of the harvested leaves. And, vice versa, poor knowledge may result in a worse or even destroyed quality.
Curing is the most important stage in the post-harvest tobacco processing. Curing determines the quality of the raw material, its color, partially taste and aroma, as well as prevents mold growth.
We use flue curing, when tobacco is processed in special isolated chambers to exclude direct contact of the fuel combustion products with the raw material. In this case, the temperature is artificially increased with the help of hot air. This method perfectly preserves the color of tobacco leaves and various types of sugars, reduces the amount of tar and nicotine, and also reduces the acidity of the product.
After curing, the tobacco leaf undergoes fermentation – this is the main technological process, during which the raw material acquires its unique smoking properties.
Fermentation is a chemical reaction during which, under the influence of humidity and temperature, organic matter is converted into inorganic, thus forming new compounds. The lack of fresh air launches the process of fermentation of tobacco; that is, the leaves get suffocated in their own vapors while the humidity and temperature rise.
The fermentation process is the final stage in the post-harvest tobacco processing. The nicotine and tar content is reduced, new aroma and flavor compounds are formed, the taste becomes softer, and the aroma is enhanced. Fermented tobacco is ready for long-term storage, and it can be used for manufacturing the tobacco products.