For fresh tobacco leaves, baking 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 baking is the key link in forming tobacco leaf quality.

 1) Appearance quality forming tobacco leaves

The appearance quality of tobacco leaves refers to the quality factors that people can make judgments through the senses, usually by the way of eye view, hand touch, ear hearing, nose smell. The appearance quality factors closely related to baking are mainly color, chroma, oil content, identity, residual injury and breakage, six aspects.

 2) Chemical quality forming tobacco leaves

The chemical quality of tobacco leaves is the internal factor that determines the quality of flue gas and the use value of tobacco leaves, and to a great extent 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 (containing c、h、o three elements), such as total sugar, starch, cellulose, etc.; the other is nitrogen-containing compounds (containing c、h、o、n four elements), such as proteins, amino acids, etc. inorganic compounds: inorganic salts such as cl、k、mg、s、ca、.

3) Physical Quality of Forming Tobacco Leaves

The physical quality of tobacco leaves, mainly burning, moisture absorption, elasticity, filling, weight per unit area, stem content, refers to some of the physical properties of tobacco leaves in the cigarette process.

4) Evaluation and absorption quality of formed tobacco leaves

Tobacco leaves in the baking process, yellowing period, a series of polymer substances decomposed into small molecular substances, forming tobacco aroma original substances; fixed color period, aroma original substances dehydration condensation, forming aroma substances; dry gluten period, some aroma substances decomposition volatilization, especially in the high temperature above 68 baking, aroma substances volatilization. The whole process of tobacco baking fixed, presented and improved the quality of fresh tobacco leaves, forming a comprehensive evaluation of the quality of raw tobacco leaves.

According to the national three-stage tobacco baking technology standard, combined with the working principle of steam absorption heat pump system, after many experiments and demonstration with tobacco baking technology experts, we have introduced the tobacco drying technology standard with the characteristics of Makku: the whole baking process is divided into three stages: yellowing period, fixed color period and dry gluten period.

 Yellowening period

Start temperature 32 degrees, heat up 1 to 35-36 per hour (maintain dry and wet temperature difference 1-2), steady temperature to leaves soft collapse frame (generally lower leaves take 10-15 hours, middle leaves 15-20 hours, upper leaves 20-25 hours); then temperature rise to 38-39, wet bulb temperature keep 36-37, steady temperature until leaves all yellow, up to yellow green bars, then heat up to 42, wet bulb temperature within 37 hours, steady temperature 10-15 hours to wet ahead, then heat into the fixed period. (yellowing time to grasp the general lower leaf 60-72 hours, middle leaf 48-60 hours, upper leaf 36-48 hours. )

Fixed color period

The temperature of the baking room rises to 45-48 at a rate of 1 per 2-3 hours, and the temperature of the wet bulb is controlled at 37-39. The change of baking to tobacco leaves reaches yellow, yellow, small rolls (the bulk-leaf-stacking oven is warm to the whole yellow leaf); then heats up to 50-52, maintains the wet bulb temperature 38-40, and heats up to 54-55(wet bulb 38-40) for 12 hours. The wet temperature of the bulk-leaf-stacked oven is determined by the minimum humidity required in the stage, and the whole wet bulb temperature can not exceed the requirement.

For the tobacco leaves with large difference in quality of fresh tobacco leaves, it is required to lengthen the time in 45-48 as far as possible, and then heat up after the whole yellow of the tobacco tendons, so as to reduce the production of green gluten tobacco leaves after baking.

 Dry tendons

After the tobacco leaves reach the fixed color requirement, the dry ball temperature will rise to more than 60 degrees quickly, the maximum can not exceed 68, the wet ball temperature maximum does not exceed 43, generally 39-42, bake until the tobacco bar is completely dry, generally 30-40 hours.