Fresh tobacco leaves quality and curing characteristics of light-aroma flue-cured tobacco varieties from Sichuan

【Objective】To study the fresh leaf quality characteristics and curing characteristics of the Sichuan light-aroma flue-cured tobacco varieties, which could provide reference basis for the precise formulation of its curing process.【Method】Taking Yunyan 87 as the control，a comparative analysis was conducted on Zhong-chuan 208 in terms of SPAD values，water content，pigment content， and polyphenol content of mature fresh tobacco leaves，yellowing and browning characteristics，water loss properties under dark box conditions，and post-curing leaf grade structure.【Result】Compared with Yunyan 87， the carotenoid to chlorophyll ratio and total polyphenol content of Zhongchuan 208 lower leaves were significantly reduced by 11.11% and 4.91% respectively （P<0.05， the same below）， while the total water content significantly increased by 4.25%. There was no significant difference in the carotenoid to chlorophyll ratio and total water content of the middle and upper leaves between the two varieties （P>0.05， the same below）. The total polyphenol content of the middle leaves of Zhongchuan 208 was significantly decreased by 2.78% compared with that of Yunyan 87， while that of the upper leaves was significantly increased by 4.55%. There was no significant difference in SPAD values between the two varieties in each position. Under dark box conditions， the yellowing degree of the lower leaves of Zhongchuan 208 reached nearly 100% at 132 h， and browning was obvious at 60 h. The yellowing index and browning index were significantly reduced by 17.31% and 10.94% respectively compared with Yunyan 87. Moreover， the yellowing rate lagged behind the water loss rate the coordination index of yellowing and water loss （K1） was 0.38， and the coordination between yellowing and water loss was worse than that of Yunyan 87. The yellowing degree of the middle leaves reached 100% at 96 h， and browning was obvious at 84 h. The yellowing index and browning index were significantly reduced by 6.03% and 78.01% respectively compared with Yunyan 87. Moreover， the yellowing rate was much faster than the water loss rate （K1 was 1.56）， coordination between yellowing and water loss was also worse than those of Yunyan 87. The ye-llowing degree of the upper leaves reached 100% and browning was obvious at 48 h. The yellowing index and browning index were significantly increased by 3.77% and 47.13% respectively compared with Yunyan 87. The yellowing rate was faster than the water loss rate （K1 was 1.88）， but the coordination between yellowing and water loss was better than that of Yunyan 87 （K1 was 2.50）. Compared with Yunyan 87， the proportions of medium and superior tobacco rate of Zhongchuan 208 in the lower， middle， and upper positions after curing were significantly reduced by 16.24%， 8.72%， and 4.17% respectively. For the lower and middle position leaves of Zhongchuan 208 after curing， the proportion of variegated leaves was significantly reduced by 36.15% and 41.83% respectively. However， the proportion of greenish tobacco in the upper position leaves of Zhongchuan 208 after curing was significantly reduced by 14.35%.【Conclusion】Compared with Yunyan 87， easy-baking properties of lower and middle leaves of Zhongchuan 208 are poor， while the curing tolerance is fine； easy-baking property of upper leaves is fine， while the curing tolerance is poor. Therefore， the curing process of Zhongchuan 208 should be further optimized based on the quality and curing characteristics of each position of the tobacco leaves to fully utilize the quality potential of the tobacco.