ZUO Weibiao, CAI Xianjie, GUAN Qi, GUO Wen, WANG Hao, XUE Chaoqun, YAN Ding, XU Chengyue, CAO Yafan, LU Xiaohua, DOU Jiayu, SONG Jizhen
It is important to explore the appearance characteristics of flue-cured tobacco of woody and honey-sweetness flavor type for excavating its application value. Based on the C2F samples of flue-cured tobacco from 6 core planting areas in the northeast plain ecological region, several classical and geostatistical methods were used to describe and evaluate the appearance characteristics, differences and spatial characteristics were analyzed, and the relationship between the appearance characteristics and the intrinsic quality of tobacco leaves was discussed. The results showed that: (1) obvious wax texture, slightly dense structure, orange or light yellow color and slightly weak color intensity (plumpness) were the relatively distinct appearance identification characteristics of flue-cured tobacco. (2) The optimal model of background color and leaf color difference between front and back was a linear model, and the indexes showed pure nugget effect and weak spatial autocorrelation. The optimal model of thickness, leaf body difference between tip and base, luster and maturity was an exponential model. The optimal model of wax texture, flexibility, leaf structure, and body and color intensity was a spherical model. The optimal model of leaf surface tissue, color depth, color and oil was a Gaussian model. The leaf surface tissue and color intensity showed moderate spatial autocorrelation, and the remaining 11 indexes showed strong spatial autocorrelation, with their nugget coefficients from 0.10% to 22.86%. The distribution of leaf structure was relatively uniform, and the flexibility, luster, color, maturity and color intensity were generally high in the middle and low in the periphery. The remaining 9 indexes generally showed a gradual upward trend from the northeast to the southwest in the whole or sub region. (3) Generally, the thicker the thickness, and the lower the maturity, the higher the starch; the smaller the leaf color difference between front and back, the lower the chlorine; the smaller the leaf body difference between tip and base, the higher the potassium/chlorine and reducing sugar/total sugar; the lighter the color, the lower the nicotine. Generally, the more the oil, the more obvious the honey-sweetness and green scents, and the better the aroma quality in the sensory evaluation; the looser the leaf structure, the more obvious the woody scent; the thicker the thickness, the more abundant the aroma and the better the aroma permeability, and the greater the smoking strength. The study firstly clarified the main appearance indexes and corresponding relationships for identifying the origin and intrinsic quality of woody and honey-sweetness flavor type flue-cured tobacco, and preliminarily explored the spatial variation and distribution characteristics of indexes. The results could provide intuitive reference for targeted development and precise purchase of feature tobacco leaves.