上6片烟叶烘烤过程中水分与颜色及化学成分的协同变化

Coordinated variations of moisture content,color and chemical components of top six upper leaves during flue-curing

为优化上部烟叶烘烤技术,设置优化烘烤工艺和常规烘烤工艺2个处理,通过对烘烤过程中烟叶样品的采集分析,研究了烘烤过程中烟叶水分与颜色、内在化学成分的协同变化及烤后烟叶的品质差异。结果表明:①上部烟叶烘烤前期失水较难,叶片失水集中在变黄后期至定色期。②烘烤过程中烟叶失水与颜色及化学成分变化密切相关,随烟叶含水率由75%左右(鲜烟叶)降至60%左右,烟叶颜色由黄绿色变为浅黄色,淀粉大量降解;烟叶含水率由60%左右降至10%左右(叶片基本干燥),烟叶颜色由浅黄色变为深橘黄色,游离氨基酸含量(质量分数)明显下降。③烘烤过程中,烟叶含水率与颜色参数明度值(L值)和黄度值(b值)呈极显著正相关,与红度值(a值)呈极显著负相关,还原糖含量与颜色参数L值、b值和a值均呈显著正相关。④针对豫中产区上6片烟叶,烘烤过程中应避免变黄期不排湿、定色前期湿球温度大幅度降低而快速排湿,重视烘烤中后期的工艺参数的调控,促进烟叶内在化学成分的合理转化。

In order to optimize upper leaves during tobacco curing,two treatments(optimized curing and conventional curing)were set up.By analyzing leaf samples collected during curing,the coordinated variations of moisture content,color and chemical components of the leaves under different curing conditions and the quality differences of cured leaves were studied.The results showed that:1)The dehydration of upper leaves was relatively difficult at the early stage of curing,and it occurred mainly from late yellowing stage to color fixing stage.2)The dehydration of tobacco leaves during curing closely correlated to the variations of color and chemical components.In the process that the moisture content decreased from about 75%(fresh tobacco leaves)to about 60%,the color of leaves changed from yellow-green to light yellow accompanied by large amounts of starch degradation.In the process that the moisture content decreased from about 60%to about 10%(basically dry leaves),the color of leaves changed from yellow to dark orange and free amino acid contents decreased significantly.3)During curing,the moisture content in tobacco leaves extremely significantly positively correlated with L(lightness)and b(yellowness)values,while extremely significantly negatively correlated with a(redness)value.The content of reducing sugar had significant positive correlations with L,b and a values.4)For the top six upper leaves from central Henan tobacco-producing areas,no dehydration of leaves occurred at yellowing stage,and fast dehydration due to sharply reduce of wet bulb temperature at early color fixing stage should be avoided.The regulation of processing parameters at the middle and later stages of curing should aim to promote the reasonable conversion of chemical components in tobacco leaves.