The Relationship Between Maturation Process And Formation Rule Of Aroma Components In Flue-cured Tobacco

The experiment studied the changes of biological characteristics, conventional ingredients, enzyme activities and photosynthesis characteristics during the maturity of flue-cured tobacco, the change lows of pigment,petroleum ether extract, trichome, exudates and neutral aroma components during aroma components forming, and determined the contents of conventional ingredients, petroleum ether extract, protein, free amino acids and neutral aroma components in flue-cured tobacco, and quality index of sensory, analyzed the relationship between maturation process and formation rule of aroma components in flue-cured tobacco, and the effect of different harvesting time to tobacco quality. The results were as follows:1.Droop degree of the lower leaves reduced to minimum at transplanted 65d,then increased. Angle between leaf and stem increased quickly after 60d, and reached the maximum at 70d, then decreased a little. Dry weight and fresh weight reached the maximum at transplanted 60d. Ratio of dry to fresh weight reached the maximum at transplanted 65d. Droop degree of the middle leaves reached the maximum again at transplanted 65d, Angle between leaf and stem increased gradually, but increased a little after transplanted 85d. Dry weight reached the maximum at transplanted 85d, but fresh weigh increased a little after 80d. Ratio of dry to fresh weight reached the maximum at 85d. Droop degree of the upper leaves began to decrease after transplanted 90d, reduced to minimum at 100d. Angle between leaf and stem increased slowly after 100d. Dry weight and fresh weight reached the maximum at transplanted 110d. Ratio of dry to fresh weight reached the maximum at100d,then decrease.2.During the maturity of flue-cured tobacco ,the nicotine content increased at first and then decreased in the lower leaves after transplanted 45d, middle leaves after transplanted 65d and upper leaves after transplanted 85d,and reached the maximum at transplanted 65d,80d and 100d, separately. The amylose content increased at first and then decreased from global aspect, but sugar content of upper leaves increased a little after transplanted 100d.3.During the maturity of flue-cured tobacco, invertase activity of middle leaves reached the maximum at dome then decreased, which of upper leaves reached the maximum at transplanted 90d.Amylase activity was manifested as bimodal curve, especially, in upper leaves,the first peak appeared at transplanted 90d,the second at 115d.4. During the maturity of flue-cured tobacco, photosynthetic rate of every part leaves decreased with the passage of time. Intercellular CO2 concentration of lower leaves increased at first and then decreased, middle leaves appeared two peak at 65d and 90d,upper leaves decreased gradually.Stomatal conductance of lower leaves increased gradually, middle leaves and upper leaves at first decreased greatly then slowly. Transpiration rate of lower leavesand middle leaves increased at first and then decreased, but upper leaves decreased gradually.5. The content of chlorophyll a,chlorophyll b and carotenoid on flue-cured tobacco increased at first and then decreased with the passage of time, the pigment of lower leaves, middle and upper leaves reached the maximum at transplanted 55d and 80d separately. Lower leaves ratio of carotenoid to pigment reduced to minimum in transplanted 60d to 65d,then increased, middle leaves reduced to minimum at transplanted 85d then increased, reached the maximum to15.5% at transplanted 95d, upper leaves reduced to minimum at transplanted 105d then increased, reached the maximum to 19.7% at transplanted 120d,6. Petroleum ether extract content of lower leaves and middle leaves changed as"M",the two peak of lower leaves appeared at transplanted 55dand 65d seperately ,and content of NO 2 was higher. Two peak of middle leaves appeared at transplanted 70dand 90d separately. Petroleum ether extract content of upper leaves increased at first and then decreased after transplanted 75d and reached the maximum at transplanted 110d,then decreased a little.7. Solanone formation amount of tobacco trichome exudates presented as bimodal curve on middle and upper leaves(middle>upper),two peak of middle leaves appeared at transplanted 65d and 85d separately, which of upper leaves did at transplanted 85d and 105d separately, and the NO.2 peak was higher than NO.1. Alkaloids formation amount increased at first and then decreased on middle and upper leaves, and reached the maximum at transplanted 85d and 110d separately. Cembrenoids formation amount increased at first,keeping stabilization for some time then fell. Trichome exudates formation amount increased at first and then decreased on middle and upper leaves, and reached the maximum at transplanted 85d and 100d separately.8. Phenylalanine content of lower leaves decreased stage, which of middle and upper leaves decreased at first and secondly increased ,then fell. The contents of browning reaction product materials were rather low in middle and lower leaves, and showed fluctuation again during the maturity, but the contents in upper leaves were higher and decreased at first and secondly increased then fell. the contents of cembranoid in middle and lower leaves were rather low and change range was smaller, but the contents in upper leaves were higher. the contents in middle and upper leaves were manifested as bimodal curve, reached the maximum at transplanted 75d and 90d separately in middle leaves, and did at95d and 115d in upper leaves. The contents of arotenoid degradation products materials changed greatly. The contents in middle and lower leaves increased at first and then decreased, and reached the maximum at transplanted 60d and 70d separately, but the contents in upper leaves decreased at first and secondly increased then fell. The content of other kinds material rather low in middle and lower leaves, oppositely in upper leaves, the content in every leaves increased at first and then decreased. lower leaves reached the maximum at transplanted 65d, middle leaves did at transplanted 70d, upper did at transplanted 110d. The content of neophytadiene in middle and lower leaves increased at first and then decreased, and reached the maximum at transplanted 65d and 85d separately. The content in upper leaves decreased at first and secondly increased , then fell. It reached the maximum at transplanted 115d. The total content of neutral aroma components in middle and lower leaves increased at first and then decreased, and reached the maximum at transplanted 65d and 90d separately, but it in upper leaves decreased at first and secondly increased ,then fell, reached the maximum at transplanted 115d.9.12 indexes of aroma components formation and indexes of maturity on middle leaves were significant at 5% or 1% level, and 3 ones which were petroleum ether extract content,phenylalanine content and browning reaction product materials contents, were not significant. 2 indexes of maturity which were fresh weight and amylase activity and indexes of aroma components formation were not significant. 14 indexes of aroma components formation and indexes of maturity on upper leaves were significant at 5% or 1% level, and contents of arotenoid degradation products materials was not significant. Total sugar and indexes of aroma components formation was not significant.10.the nicotine content presented increasing trend with harvest time delaying, total nitrogen, petroleum ether extract and sugar content increased at first and then decreased, but variation range was little. Starch content was marginally high, and decreased with harvest time delaying. The hange law of protein content change was not obvious. The change trend of free amino acids presented as"V",when mature stages were more proper ,lower leaves in transplanted 60d to 70d, middle leaves in transplanted 80d to 90d, upper leaves in transplanted 105d to 115d. the change trend of neutral aroma components total content, neophytadiene, and arotenoid degradation products materials contents showed that best harvest time were pre-and post transplanted 65d in lower leaves, from transplanted 90d to 95d in middle leaves, from transplanted 115d to 120d in upper leaves. Sensory quality were better aroma quality, fuller aroma volume, slighter offensive odor, better aftertaste and bigger smoke consistence, but slighter irritancy and adequater physiological strength,that showed the time was better which were from transplanted 60d to 65d in lower, at transplanted 90d in middle leaves, from transplanted 115d to 120d in upper leaves..