Relationship between color parameters and pigment contents during flue-curing process of different-quality tobacco leaves

ObjectiveThe present study was conducted to study relationship between color parameters and pigment contents of different-quality tobacco leaves, in order to provide theoretical foundation for precise flue curing of different-quality tobacco. MethodTobacco K326 was chosen as the experiment material. Four special quality tobacco namely tender leaves at bottom part, re-greening leaves at middle part, heat-forced maturity leaves at top part and over-green and late-maturing leaves at top part were flue cured. During the procedure, color parameterssoil and plant analyzer de-velopment value(SPAD), lightness value(L*), red-green index(a*), yellow-blue index(b*) and pigment content of tobacco were measured and analyzed. ResultSPAD of four kinds of leaves dropped at fastest speed during 30-38 ℃. During flue curing process, L* , a*, b* of four kinds of leaves increased to different extent. The values of re-greening leaves, tender leaves, heat-forced maturity leaves increased most rapidly during 30-38 ℃ and those of over-green and late-maturing leaves increased most quickly during 30-42 ℃. Variation trends of chlorophyll-a and chlorophyll-b contents were similar. During 30-38 ℃, degradation amount of tender leaves, re-greening leaves and heat-forced maturity leaves reached maximum, while over-green and late-maturing leaves reached degradation amount peak during 42-48 ℃. Degra-dation amount of carotenoids contents of four kinds of leaves were relatively small. In terms of tender leaves, carotenoids contents dropped rapidly during 42-48 ℃; carotenoids contents of heat-forced maturity leaves dropped slightly both during 30-38 and 48-54 ℃; carotenoids contents of re-greening leaves and over-green and late-maturing leaves went through a slow decline. The ratio of carotenoids contents to chlorophyll contents of tender leaves, re-greening leaves, heat-forced maturity leaves and over-green and late-maturing leaves increased during 30-42, 30-38, 42-48 and 48-54 ℃, respec-tively. There was extremely significant positive correlation between SPAD and chlorophyll content in four kinds of tobacco leaves(P<0.01, the same below). There was significant negative correlation between L* and chlorophyll-a in heat-forced maturity leaves(P<0.05). In terms of other 3 kinds of leaves, there was extremely significant negative correlation between L*, a*, b* and chlorophyll contents. ConclusionDuring flue curing process, color parameters and pigment contents of different-quality tobacco leaves are closely related. Color parameters can be used to estimate pigment contents of tobacco, in order to provide theoretical foundation for handling flue-curing process of different quality tobacco.