Abstract:

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

Key words: bulk curing, leaf-drying stage, carotenoids, degradation mechanism, enzyme