Major Chemical Component Changes in Upper Tobacco Leaves with Stalk during Flue-curing

The changes of major chemical components of DJ (Treatment 1, upper leaves harvested and cured with stalk) and WJ (Treatment 2, upper leaves harvested and cured without stalk) during flue-curing were studied. The results showed that: (1) the loss rate of total water in tobacco leaves with stalk was slow in the first 48 hours and then increased sharply, while the bound water decreased gradually with the proceeding of curing. The peak of free water loss came earlier than the total water. The free water increased a little from 24 to 48 hours. The ratio of total water loss in DJ was evidently lower than that in WJ between 24h and 72h, which showed that the transport of free water from stalk to leaf. (2) The content of starch in DJ was lower than that in WJ during the process, and decreased in cured leaves. The total sugar and reducing sugar in DJ increased quickly during the first 72 hours, and then decreased, whereas lower than those in WJ. (3) Little change occurred in the total nitrogen of DJ during the process, and the contents of nitrate and nitrite increased quickly in the first 72 hours followed by rapid decrease afterwards. The content of nitrate exhibited a slight decline, whereas the nitrite and potassium increased slightly.