Study On Physiological And Biochemical Change Of Flue-Cured Tobacco During Nor-Midrib-Curing Of Leaves

The quality of flue-cured tobacco leaves and the change of physiological biochemistry during bulk curing of the fresh leaves nor-midrib-curing and the leaves were air-cured to some degree nor-midrib-curing were studied by using the electric-heated flue-curing barn designed and made by Henan Agriculture University.1.The trend of water's dynamic changed was the same between fresh leaves nor-midrib-curing treatment with and normal curing treatment, the water content and the water loss rate decreased slowly during 0~48h, the content of losing water was 9.94% on average, the average rate of losing water was 0.21%/ h. The water content and the water loss rate increased fast during 48~84h, the content of losing water was 52.72% on average, the average rate of losing water was 1.47% / h. Water content of fresh leaves nor-midrib-curing treatment was a little lower than that in normal-curing treatment during 0~48h. Water loss rate of fresh leaves nor-midrib-curing treatment (1.33%/h) was significantly lower than that in normal curing treatment (1.6%/h) during 48~84h, and the water content of fresh leaves nor-midrib-curing treatment was higher than that in normal curing treatment. The water content of main vein in normal curing treatment showed a slowly downtrend during the whole curing process. The trend of water's dynamic changed was the same in the three different degree of air-curing treatments: the water content and the water loss rate decreased slowly in the initial stage of curing, The water content and the water loss rate increased fast during 36~60h, the water loss rate was full yellow of air curing reaches the maximum, Seven to eight tenths yellow of air curing take second, five tenths yellow of air curing reached the minimum. The water content of these three treatment was opposite to the water loss rate.2.The content of chlorophyll and carotene reduce with the process of curing, the speed of degradation achieved the highest during 0~48h then degraded gently. On the earlier stage of curing, the chlorophyll decomposed in nor-midrib-curing of leaves was quick than that in normal curing. The variation trends of the chlorophyll content in different treat of air-curing degree are similar during the curing stage. Chlorophyll content decreased as air-curing degree increased; The degradation rate of carotenoid was far less than that of Chlorophyll. During the whole process of flue-curing, the content of chlorophyll manifested as nor-midrib-curing of leaves higher than that of normal curing. The result of the different treat of air-curing degree was that the chlorophyll decomposed fully when seven to eight tenths yellow of air curing.3.With the promotion of the curing process, the tobacco leaves level of membrane lipid peroxidation enhanced, the content of MDA increased gradually. The content of MDA was higher in Nor-midrib-curing of leaves than that in normal- cured leaves. The MDA content increased as air-curing degree increased in different treats. The activities of POD and SOD showed downtrend during the flue-curing process, that lower in nor-midrib-curing than normal curing. The activities of POD and SOD showed: five tenths yellow of air curing>seven to eight tenths yellow of air curing>ten tenths yellow of air curing.4.The activities of amylase appeared"rise~reduce~rise"both in normal curing treatment and fresh leaves nor-midrib-curing treatment. The amylase activities of fresh leaves nor-midrib-curing treatment was lower than that of normal curing during 0~48h, but opposite after 48h. from the three different degree of air-curing treatments, the activities of amylase decreased somewhat during 0~12h, then increased during12~24h, reached maximum at 24 hours, then decreased slowly, but increased quickly at the later stage. The trend of starch content was echo each other with that of the activities of amylase. The residue content of starch after curing presented: normal curing(5.32%)>fresh leaves nor-midrib-curing(4.33%)>five tenths yellow of air curing(4.02%)>seven to eight tenths yellow of air curing(3.42%)>full yellow of air curing(3.02%).5.The PAL activity of nor-midrib-curing of leaves and common curing decreased slightly during 0～24h, and after 24h PAL activity raised, reached maximum at 48 hours when common curing, then decreased slowly; the PAL activity of nor-midrib-curing of leaves continued to increase, the activity of amylase lasted for a long time. In addition, The PAL activity of different degree of yellowing by air-curing varied slightly during 0-24h, and after 24h PAL activity raised, reached maximum at 48 hours. then the PAL activity of air-curing seven to eight tenths yellow and full yellow of nor-midrib-curing decreasing, on the contrary, the amylase activity increased slowly. with the proceeding of curing, the LOX activity raised gradually, reached maximum at 36 hours. Then disappear completely. The LOX peak of fresh leaves nor-midrib-curing treatment was bigger than normal curing treatment, what's more, the amylase activity lasted longer. the tendency of LOX activity showed: seven to eight tenths yellow of air curing>five tenths yellow of air curing>full yellow of air curing.6.fresh leaves nor-midrib-curing treatment whose thickness and specific leaf weight were just decreased a little than normal curing treatment, but it was light in color. And the color,oil,body,organization structure of seven to eight tenths yellow of air curing were better than the others, in addition, filling value was increased, and the thickness was reduced.7.Seven to eight tenths yellow of air curing could decrease starch content,and increase total sugar, nicotine content,reducing sugar content and the content of total nitrogen, the chemical components of the flue-cured leaf were coordinated.8.The content of petroleum ether extract, total polyphenol, chlorogenic acid were highest of Seven to eight tenths yellow of air curing, and the difference was significant; the content of rutin was highest of common curing treatment, and the difference was significant ;the content of free amino acid was highest of five tenths yellow of air curing, and the difference was significant. Fresh leaves nor-midrib-curing treatment could decrease the contents of Volatile aroma components compared with the normal curing treatment, such as neophytadiene and the products of degraded by carotenoid, but Seven to eight tenths yellow of air curing could increase the contents of volatile aroma components. such as neophytadiene and the products of maillard reaction,degraded by cembrane and degraded by carotenoid; moreover, improve the proportion of high and middle grades cured leaves.