Effects of the Yellowing Time and Stem-drying Temperature on the Availability of Upper Leaves of Flue-cured Tobacco

In order to study the effects of the yellowing time and stem-drying temperature the quality of upper leaves, five upper leaves of Yunyan 87 were used as the materials to study the effects of the yellowing time (40℃ for 24 h and 36 h) and stem-drying temperature (64℃ and 68℃) on the shrinkage rate, appearance quality, chemical composition and sensory evaluation quality of the upper leaves. The results showed that different yellowing time and stem-drying temperature had significant effects on the shrinkage rate, appearance quality, intrinsic chemical composition and sensory quality of the tobacco leaves. When the yellowing time was prolonged, the shrinkage rate of tobacco leaves increased, the starch content decreased, the contents of total polysaccharide and reducing sugar increased, and the intrinsic chemical composition tended to be coordinated. The stem-drying temperature had little effect on the shrinkage rate of tobacco leaves, and when the temperature of stem-drying temperature was decreased, the clear and sweet flavor type of the flue-cured tobacco leaves became more prominent, the quality of aroma was better, and the impurity gases such as withered and scorched gas were significantly reduced. The yellowing time (40℃) of the upper leaves of Yunyan 87 in the tobacco area of Longyan was prolonged for 12 h, and the temperature of killing-out was controlled at 64℃, which could effectively improve the appearance quality, more harmonious chemical composition, the sensory quality and the industrial usability.