Abstract:

To optimize the curing process of the upper leaves of flue-cured tobacco， ‘Yunyan 87’ was used as the experimental material. The local conventional curing process was control （CK）， and the 2 variable temperature treatments （T1： temperature variation amplitude ±1 ℃， temperature variation frequency 3 h； T2： temperature variation amplitude ±1.5 ℃， temperature variation frequency 5 h） were set in the yellowing period of tobacco leaf curing. The synergistic relationship between the color parameters and pigments of tobacco leaves was systematically analyzed using correlation analysis and stepwise regression. And the effect of temperature change was study on the appearance quality of tobacco leaves during the curing process. The results showed that the variation trends of lightness value （L）， redness value （a）， yellowness value （b）， chroma value （C）， hue angle （h）， color ratio （H）， and color difference value （ΔE） during the curing process of tobacco leaves treated with CK， T1， and T2 processes were basically consistent， and the degradation laws of intrinsic pigments in tobacco leaves were also consistent. At the end of curing， there were significant differences in L， a and b values of the tobacco leaves treated by different processes. The L and b values of T1 treatment were the largest， and a value was the smallest， which indicated that the tobacco leaves treated by T1 treatment had better yellow value， color saturation and glossy. The correlation analysis showed that there were significant or extremely significant positive correlations between the L value and a， b， C， H values， there were significantly or extremely significantly negatively correlated between the values of L， a， b and the contents of chlorophyll a and b. The regression equation between contents of chlorophyll a （?₁）， chlorophyll b （?₂）， carotenoid （?₃） and various color parameters of tobacco leaves treated with T1 process during the curing process were followed. ?₁=-0.158-0.013a+0.005h_{（R²=0.931， F=122.08）， ?2=0.148-0.189H （R²=0.808， F=79.97）， ?3=0.051-0.003a+0.001b（R²=0.754， F=27.59）， which indicated a， b， h and H had significant synergistic relationship with the pigment content of flue-cured tobacco leaves. The contents of reducing sugar， total sugar and starch of T1 treatment were reduced， and the starch content was 4.65%， which was close to the starch content requirement of high quality tobacco leaf （2%~4%）. The proportion of high-grade tobacco smoke and medium high-grade tobacco smoke of T1 treatment were the largest， and the appearance quality and sensory quality were significantly improved. In conclusion， based on the constant temperature yellowing at 38 ℃， the temperature change controlled by a sinusoidal program with an amplitude of ±1 ℃ and a frequency of 3 h could promote the synergistic change of upper leaf color parameters and pigment content， and improve the quality of cured tobacco leaves.}

Key words: flue-cured tobacco, curing process, color parameters, pigment, relationship

摘要：

为优化烤烟上部叶烘烤工艺，以‘云烟87’为试验材料，当地常规烘烤工艺为对照（CK），分别在烟叶烘烤过程中的变黄期设置变温处理（T1：变温幅度±1 ℃，变温频率3 h；T2：变温幅度±1.5 ℃，变温频率5 h），利用相关性分析和逐步回归对烟叶颜色参数及色素的协同关系进行系统分析，研究烟叶烘烤过程中变温处理对烟叶外观质量的影响。结果表明， 3种工艺处理烟叶烘烤过程中的明度值（lightness value， L）、红度值（redness value， a）、黄度值（yellowness value， b）、饱和度值（chroma， C）、色相角（hue angle， h）、色泽比（color ratio， H）和色差值（color difference， ΔE）的变化趋势基本一致；烟叶内在色素的降解规律也较一致。当烟叶烘烤结束时，不同工艺处理烟叶的L、a、b值均存在显著差异，T1处理的L和b值最大，a值最小，即T1工艺处理变黄结束时及烤后烟叶的黄度值较好，烟叶颜色饱和度高，富有光泽。相关性分析表明，烟叶L值与a、b、C和H值呈显著或极显著正相关；L、a、b值与叶绿素a和叶绿素b呈显著或极显著负相关。T1工艺处理烟叶的叶绿素a（?₁）、叶绿素b （?₂）和类胡萝卜素含量（?₃）与各颜色参数的回归方程分别为?₁=-0.158-0.013a+0.005h（R²=0.931，F=122.08），?₂=0.148-0.189H（R²=0.808，F=79.97），?₃=0.051-0.003a+0.001b（R²=0.754，F=27.59），a、b、h和H与烟叶色素含量协同关系较大。T1工艺处理的还原糖、总糖及淀粉含量均降低，其中淀粉含量为4.65%，与优质烟叶淀粉含量要求（2%~4%）较为接近；烤后烟叶的上等烟和中上等烟比例均最大，外观质量和感官质量得以明显改善。综上所述，在38 ℃定温变黄的基础上采用幅度±1 ℃，频率3 h的正弦式程序控制的温度变化，能够促进上部叶颜色参数与色素含量协同变化，并提高烤后烟叶的质量。

关键词: 烤烟, 烘烤工艺, 颜色参数, 色素, 相关性