A drying method was explored for keeping fresh tobacco leaf inclusions to a max and detecting chemical composition accurately. The effect of kill-enzyme torrefaction and freeze-drying on leaf morphology and chemical composition was investigated by half leaf method. The results showed that there was a significant difference of tobacco sample color, size, dry weight , volatile semi-volatile substances (aroma) and non-volatile substances (polyphenols) content between kill-enzyme torrefaction and freeze-drying.

Freeze-drying was a sample drying method which was suitable for detecting chemical composition accurately while it could keep inherent color, structure and inclusions of fresh flue-cured tobacco leaf. The color of fresh tobacco leaf was green by freeze-drying while the color was yellow brown by kill-enzyme torrefaction. At the same time, the tobacco leaf size by freeze-drying was 3.25 times of that by kill-enzyme torrefaction with the same weight. In the process of kill-enzyme torrefaction, 9 kinds of maillard reaction production and 8 kinds of carotenoid degradation production were generated by polyphenols and carotenoids, 11 kinds of small molecular aromatic components were lost, such as 3-methyl-butanol, 2-pentyl alcohol, 3-pentenal et al for the influence of the outside temperature stress and body water dissipation. At last, it was lower than freeze-drying, and the difference was 4.37% of dry substance content.