Effect of two drying methods on chemical transformations in flue-cured tobacco

Abstract

Tobacco leaves are flue-cured to create desired appearance and internal quality, but the effects of flue-curing on transformation of chemical substances in tobacco have not been fully studied. The half-leaf method and a mass balance approach were used to compare two drying methods (i.e., oven-drying and flue-curing) in terms of chemical substances in tobacco. These substances included: carbon, nitrogen, plastid pigments, and polyphenols and some important elements in tobacco leaves. Compared with oven-drying, starch content significantly decreased while saccharides (including total sugar, glucose, fructose, maltose, and sucrose) increased in flue-cured tobacco leaves. There was only numerical change in reducing-sugar content between two drying methods. Protein, total nitrogen, and nicotine content in flue-cured tobacco leaves significantly decreased compared to oven drying. Two important elements (potassium and chlorine) showed no significant change. Compared with oven-drying, four plastid pigments (lutein, chlorophyll A, chlorophyll B, β-carotene) significantly decreased and six polyphenol substances (neochlorogenic acid, chlorogenic acid, caffeic acid, chrysatropic acid, rutin, kaempferol) significantly increased. This research clarified the transformation mechanisms of chemical substances after flue-curing of tobacco leaves, which provides a reference for the transformation and an insight into the procedures to study flue-cured tobacco leaf processing.

KEYWORDS:

• Oven-drying
• flue-curing
• metabolites
• mass balancing

Acknowledgments

Authors thank Drs. Mark S Coyne and Yong Li for giving valuable reviews for improving the quality of this paper. Authors also thank Yunnan Science and Technology Innovation Project (2019HB068), Yunnan Ten Thousand People Program (2018-73) for supporting Congming Zou.

Disclosure statement

Jijian Zong, Xian He, Zhonglong Lin and other coauthors have no conflict of interest.

Additional information

Funding

This study was financially supported by several projects from the National Natural Science Foundation of China (No. 41601330), Yunnan Applied Basic Research Projects (No. 2017FB074) and Tobacco Monopoly Bureau China (2016YN28, 2017YN09 and 2020530000241025).