Abstract:

【Objective】 The changes of the contents of carotenoids components, the related enzymes activities, and the aroma components degraded by which in flue-cured tobacco in the yellowing stage during the bulk-curing process were studied in order to provide a theoretical basis for optimization and perfection of curing technology. 【Method】 The effects of different temperature and humidity conditions on the degradation of carotenoids, the related enzymes activities in the yellowing stage and the contents of aroma components in flue-cured tobacco during the bulk curing process were studied by using the electric-heated flue-curing barn designed and made by Henan Agricultural University. 【Result】 The results showed that the contents of carotenoids (β-carotene, lutein, neoxanthin, violaxthin) decreased gradually in the yellowing stage during the bulk curing process. At the end of yellowing stage the β-carotene contents of low temperature with low humidity (T1) and low temperature with middle humidity (T2) treatments were lower than others and the value of them were 17.14 μg?g-1 FW, 19.00 μg?g-1 FW, respectively. The contents of the lutein, neoxanthin, violaxthin decreased gradually in the yellowing stage following the decrease of temperature and humidity. The proportions of the β-carotene to the xanthophylls (lutein, neoxanthin, violaxthin) of the low temperature treatments at the end of yellowing stage were higher than fresh sample, on the contrary, high temperature treatments were lower. The proportions of the lutein to the xanthophylls of different treatments were higher than fresh sample, on the contrary, neoxanthin and violaxthin were lower. The carotenoids contents of T1, T2 treatments were relatively lower than others’, especially the T2 treatment, and its value was 76.31 μg?g-1 in flue-cured tobacco. The contents of aroma components of T2 treatment was the highest and its value was 87.5634 μg?g-1 in flue-cured tobacco while the content value of T1 treatment was 81.1192 μg?g-1, secondly. Both of them were higher than others obviously. The activities of lipoxygenase (LOX) and peroxidase (POD) could express fully under the T1, T2 treatments in the yellowing stage meanwhile the carotenoids degraded fully. Correlation analysis showed that the activities of peroxidase and the carotenoids components were highly significant in the yellowing stage during the bulk curing process. 【Conclusion】 If the high activities of lipoxygenase and peroxidase were prolonged longer appropriately at 36-48 h under low temperature and relatively low humidity in the yellowing stage and the effect between the cooperative and antagonism reach dynamic balance, it would be benefit to degrade carotenoids sufficiently and improve the aroma quality of tobacco leaves.

Key words: bulk curing, yellowing stage, carotenoids, degradation mechanism, aroma components