密集烘烤过程中烤烟细胞生理和质地变化

采用河南农业大学设计的电热式温湿自控密集烤烟箱，以中烟100上部叶为材料，研究了烘烤过程中烟叶细胞生理和质地变化的规律。结果表明，烘烤中烟叶的呼吸强度在38℃时达到高峰，箱内CO₂含量为1.80%，48℃以后烟叶的呼吸作用减弱。烘烤中果胶酯酶和纤维素酶在38~54℃活性较高，其中果胶甲酯酶(PME)和纤维素酶活性42℃最高，多聚半乳糖醛酸酶(PG)活性48℃最高，PG与PME共同促进了原果胶的水解进程，烘烤中原果胶、总果胶和纤维素含量不断降低。烟叶质地(除黏聚性)在38~48℃之间发生显著变化，其中42℃硬度和咀嚼性值最大，38℃拉力和剪切力值最大，48℃黏聚性、拉力和剪切力值最小。相关分析表明，可溶性果胶与回复性呈显著负相关(P<0.05)；原果胶、总果胶及纤维素与回复性、拉力均呈显著或极显著正相关(P<0.05)。这些结果说明烘烤过程中烟叶质地的绵软在某种程度上是细胞壁物质不断降解的结果。研究表明，烘烤中烟叶剪切力的动态变化较为直观，回复性和拉力可以作为探讨烟叶细胞生理变化的参数，而烟叶细胞生理变化是导致质地差异显著的主要因素。

Changes of Cell Physiology and Texture of Tobacco Leaf during Bulk Flue-Curing

During recent years, the bulk curing barn has rapidly developed and greatly promoted the production of flue-cured tobacco in China. However, some problems, such as the lightening colours, the smoothness and close structure of tobacco leaf, occurred along with the popularizing of flue-curing barn application. In order to meet the quality requirement of the raw material of Chinese-style cigarette, it has been urgent to solve those problems for the tobacco production with high-quality. The changes of the cell wall hydrolases and components play an important role in affecting the physiological changes of post-harvest plant. The differences in the texture of tobacco leaves would affect the organizational structure, morphostructure, internal components and usability. In order to optimize flue-curing technology and to improve the usability of tobacco leaves, we conducted the experiment to investigate the changes of cell physiology and texture of upper tobacco leaves of Zhongyan 100 along with wet and dry bulb temperatures during flue-curing using the electric-heated flue-curing barn designed and made by Henan Agricultural University. The results showed that the respiration rate of tobacco leaf peaked at 38℃ with a value of carbon dioxide content of about 1.80% during curing, and then the respiration rate progressively decreased since 48℃. The activities of pectinesterase and cellulase were higher during 38~54℃ than other temperature conditions. The pectin methylesterases (PME) and cellulase activities were the highest at 42℃, while the polygalacturonase activity (PG) was highest at 48℃. The PG and PME promoted the hydrolysis process of protopectin. Meanwhile, the protopectin, the total pectin and cellulose contents steadily decreased during curing. Texture testing parameters (except cohesiveness) of tobacco leaves changed significantly at the temperatures from 38℃ to 48℃. Among them hardness and chewiness had a maximum value at 42℃, tensile and shear force got their maximum values at 38℃. Cohesiveness, tensile and shear force reached the minimum value at 48℃ during flue-curing. The correlation between the soluble pectin and resilience was significantly negative while the correlations of protopectin, the total pectin, cellulose with resilience, tensile were significantly or highly significantly positive (P<0.05). These results indicated that the texture of tobacco leaves became mealy just due to the decrease of the cell binding force in a way during flue-curing. In other words, it could be resulted from the constant degradation of cell wall substances. This research indicated that dynamic change of shear force parameter was more intuitive. Resilience and tensile could be used as texture parameters to study the change of cell physiology of tobacco leaves. The main factors to make a significant difference in texture of tobacco leaves were the changes of cell physiology during flue-curing.