For fresh tobacco leaves, drying has four functions, one is to form the appearance quality of tobacco leaves; the other is to form the chemical quality of tobacco leaves; the third is to form the physical quality of tobacco leaves; and the fourth is to form the evaluation and absorption quality of tobacco leaves. It can be seen that drying is the key link in the formation of the quality of the tobacco leaf.
1) Appearance quality of tobacco leaf shape
The appearance quality of tobacco leaves refers to the quality factors that people can make judgments through the senses, usually by means of sight, hand touch, hearing hearing and smell of tobacco. nose. Appearance quality factors closely related to baking are mainly color, chroma, oil content, identity, residual damage and breakage, six aspects.
2) Chemical quality that forms tobacco leaves
The chemical quality of tobacco leaves is the internal factor that determines the flue gas quality and use value of tobacco leaves, and largely determines the economic value of tobacco leaves. The chemical composition of tobacco leaves is closely related to the quality of tobacco products. The chemical composition of tobacco leaves is divided into two categories: organic compounds and inorganic compounds. Organic compounds: one is carbohydrates, such as total sugar, starch, cellulose, etc.; the other are compounds that contain nitrogen, such as proteins, amino acids, etc. inorganic compounds: inorganic salts such as cl, k, mg, s, ca.
3) Physical quality of tobacco leaves in formation
The physical quality of tobacco leaves, mainly burning, moisture absorption, elasticity, filler, weight per unit area, stem content, refers to some of the physical properties of tobacco leaves in the cigarette process.
4) Evaluation and quality of absorption of tobacco leaves formed.
Tobacco leaves in the drying process, yellowing period, a series of polymer substances are decomposed into small molecular substances, forming the original tobacco aroma substances. Gluten dry period, is the decomposition volatilization of some flavoring substances, especially in the high temperature above 68°C, the volatilization of flavoring substances occurs.
According to the tobacco drying technology standard, combined with the working principle of vapor absorption heat pump system, after many experiments and demonstrations with tobacco drying technology experts, we have introduced the technology standard for drying tobacco with the following characteristics: the entire drying process is divided into three stages: the yellowing period, the fixed color period and the dry gluten period.
yellowing period
It is recommended to start the process with a temperature of around 32°C, it is heated for one hour at 35 - 36°C (keep the dry and wet temperature difference at 1 - 2°C), the temperature must be constant to perform gentle drying (generally lower leaves take 10-15 hours, middle leaves 15-20 hours, upper leaves 20-25 hours); then temp rises to 38 - 39°C, wet bulb temp stays at 36 - 37°C, constant temp helps everything turn yellow, even green bars, then wet bulb temp rises to 42 °C, the temperature is kept constant from 10 to 15 hours (Yellowing time to reach the lower leaf is generally 60 - 72 hours, middle leaf 48 - 60 hours, upper leaf 36 - 48 hours).
fixed color period
The drying room temperature is raised to 45 - 48°C at the rate of 1°C every 2 - 3 hours, and the wet bulb temperature is controlled at 37 - 39. It should then be heated to 50 - 52°C , and maintain the wet bulb temperature at 38 - 40°C for 12 hours. The wet temperature of the bulk sheet stacked furnace is determined by the minimum moisture required at the stage, and the total wet bulb temperature cannot exceed this requirement.
For tobacco leaves with a large difference in quality from fresh tobacco leaves, it is required to lengthen the time by 45 - 48 hours as far as possible, and then heat after the tobacco sinews are completely yellow, to reduce the production of green gluten-containing tobacco leaves after drying.
Completion of the process
After the tobacco leaves reach the fixed color requirement, the drying chamber temperature rises to more than 60 degrees rapidly, the maximum cannot exceed 68°C, the maximum wet bulb temperature cannot exceed 43 °C, generally should be kept at 39 - 42°C, dry until the tobacco is completely dry, generally the process takes between 30 - 40 hours.
