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The mechanism of carotenoid degradation and the changes in the activities of related enzymes in flue-cured tobacco at the leaf-drying stage during the bulk-curing process were studied in order to provide theoretical basis for optimization of curing technology.The effect of different rising speeds of temperature on the carotenoid degradation and the related enzymes activities at the color-fixing stage during the bulk curing process was studied by using the electric-heated fluecuring barn designed by Henan Agricultural University,China,based on curing technology with yellowing at low temperature and moderate humidity and leaf drying at moderate humidity.The results showed that the carotenoid degradation components(β-carotene,lutein,neoxanthin,and violaxthin)decreased gradually at the color-fixing stage during the bulk curing process.The carotenoid degradation components viz.,β-carotene,lutein,neoxanthin,and violaxthin at the slow heating curing(T1)were relatively higher than the rapid heating curing(T2)accounting for 10,2,32 and 32%respectively,but there were no differences among treatments(P>0.05).The effect of different conditions of curing on the activities of enzymes related to carotenoids degradation were significant.The lipoxygenase,phenylalanine ammonialyase,peroxidase,and polyphenol oxidase enzymes had a bidirectional effect on the quality of tobacco leaves and it was beneficial to form more premise matter of aroma based on the higher enzyme activities at the early leaf-drying stage.The slow heating could regulate the change in various enzymes' activities reasonably,making cell redox reaction to reach the dynamic balance and make the degradation of carotenoids adequately.Meanwhile,it could avoid the occurrence of browning reaction and provide foundation for improving the quality of tobacco and optimization of technology for bulk curing and further enhancing aroma.