| Upper leaf contributions greatly to the output and quality of flue-cured tobacco.The fine upper leaf,which sells extremely well in the international market,not only takes the leading role in the tobacco leaf formula of the modem Blended type cigarette and low tar cigarette,but also is very important to the fragrance style of cigarette.However,in our country there are still some problems in upper leaf of each tobacco-producing area,for example,the nicotine content of upper leaf is higher,the remaining starch is too much,the intrinsic chemical components are maladjustment,the fragrance style is not prominent,the tissue structure is close,the maturity is low,and variegated color is heavier,which give rise to the low usability and massive stocks of upper leaf.Therefore,how to improve the quality and usability of upper leaf is a urgent question which the tobacco-producing areas are facing now,that is significant to improve the tobacco overall quality and the economic efficiency too.In order to provide theory basis for improving the quality and usability of upper leaf and provide new ideas for curing technics.Effect of different harvesting methods on quality of upper leaf was conducted.The results were as follows:During the process of flue-curing,the water content of three treatments show the same tendency:the water loss rate decreased slowly during 0h-24h,and the water content and the water loss rate increased fast during 48h-72h,and after 72h the water content and the water loss rate decreased slowly again,but different treatments show the different tendency at each stage:in yellowing stage,the leaf water content of harvesting upper leaf with stalk together method almost didn't change,which remained at 77 percent;at same time the leaf water content of the commonly used picking method and the method of concentrated picking upper leaf decreased slowly; at color fixing period the water content of three treatments decreased fast,and the water content of harvesting upper leaf with stalk together method is higher than other two treatments.In the process of flue-curing,the midrib water content of three treatments varied in the same manners,which decreased continuously,and the midrib water content of harvesting upper leaf with stalk together is higher than that of the other treatments.The midrib water content of treatment three dropped slowly,in the later color-fixing period it reached as high as 81.97 percent,which dropped 6.36 percentage points compared with the beginning of flue-curing.The degradation amount of chlorophyll and carotene in upper leaf of harvesting upper leaf with stalk together(T3)is higher than the other two treatments,which is advantageous to the quality of cured tobacco because degeneration matter of the pigment relatively increased.With the process of curing,the electric conductivity rate and MDA increased gradually and the electric conductivity rate was T1＞T2＞T3 in 0h～36h,then T3＞T1＞T2 in 36h～60h;the tendency of MDA showed T1＞T2＞T3 in different treatments;the Pro content accumulated unceasingly in the process of curing,that of the commonly used picking tobacco leaf is highest compared with other two treatments.The SOD,POD and CAT activities of harvesting with stalk together method (T3)is higher than that of the commonly used picking method(T1)and concentrated picking method(T2)in yellowing stage.The yellowing stage is important time to improve the quality of tobacco,and degradation and transformation of the macromolecular substances take actively in this stage.Maintaining the protection enzyme activity in a higher level can lengthen the life of tobacco leaf,adjust the degradation of macromolecular substances,and reflected the quality of tobacco leaf.In the process of flue-curing,amylase activity of three treatments increased slightly first,then decreased slowly,and till the color-fixing time increased again, which appeared the trend of "rise-reduce-rise".But different treatments changed differently,in 0h～12h amylase activity of tobacco leaf is T1＞T2＞T3,and after 24h is T3＞T2＞T1.The yellowing stage is crucial time which the starch degrades,and in this stage amylase activity of treatment three increased.The leaf starch content of harvesting with stalk together is lowest in three treatments.Tendency of invertase activity of three treatments is consistent,invertase activity maintained a lower level during 0h～48h,and after 48h invertase activity raised suddenly.Change of each treatment has difference:leaf invertase activity of harvesting with stalk together kept rising during later curing period.Sucrose content of tobacco leaf is commonly used picking method(T1)＞concentrated picking method(T2)＞harvesting with stalk together(T3).The GOT activity of harvesting with stalk together is lower than the other two treatments,and GPT activity is higher than others.Loss of dry matter of cured tobacco is the harvesting with stalk together(T3)＞commonly used picking method(T1)＞concentrated picking method(T2).Compared with the other two treatments,the harvesting upper leaf with stalk together method could increase the filling power of tobacco leaf(6.99 cm~3/g),reduce the weight per leaf(11.2g),the weight per unit leaf area(95.59 g/m~2),and the thickness of leaf(64.22um),stem ratio(30.58%)of cured tobacco were higher than the other two treatments.The tobacco leaf area varied much in three treatments, mainly in width of tobacco leaf,the harvesting upper leaf with stalk together effected the upper leaf apparently.And the equilibrium moisture content of three treatments is similar,about 9%.The apparent quality of cured tobacco of the harvesting upper leaf with stalk together method,including grading maturity,the leaf structure,the color,oily and status,was better than other two treatments.Commonly used picking method increased the scalding leaf and the slick(rigid)leaf;and the color intensity of the harvesting upper leaf with stalk together is strong,clear and rich oil.Harvesting upper leaf with stalk could reduce the total sugar content,reducing sugar,starch,and total nitrogen content,compared with commonly used picking method the range of degradation is 9.96%,18.48%,11.83%,19.29%respectively;and compared with concentrated picking method the range of degradation is 10.10%, 14.93%,7.84%,14.41%respectively.The starch content of different treatments reached remarkably;and the difference of total sugar,reducing sugar and total nitrogen between treatment one and treatment two weren't significant,but the difference between treatment three and the other two treatments were significant.Harvesting upper leaf with stalk increased the content of petroleum ether extract, the total phenol and the chlorogenic acid content significantly,decreased the free amino acid content significantly.Difference of Rutin content between three treatments weren't significant.Compared with commonly used picking method,the total volatile aroma compounds content of harvesting upper leaf with stalk method(1188.22ug/g) increased 27.30%,and in it the content of neophytadiene,products degraded by carotenoid and products degraded by cembrane enhanced in different degree;but products of aromatic amino acid metabolism and products of maillard reaction of T3 were lower than that of CK.Harvesting upper leaf with stalk together method could improve the proportion of high grade leaves(71.8%),proportion of high and middle grad tobacco(95.6%) and ratio of yellow tobacco(99.1%),reduce the ratio of variegated leaves.Harvesting upper leaf with stalk together method increased the average leaf prices and the output compared with two other treatments,average leaf prices improved by 1.58 yuan/kg,0.83 yuan/kg and the output improved by 66.42 yuan/667m~2,37.10 yuan/667m~2 respectively,which showed harvesting upper leaf with stalk together method could increase economic value of tobacco leaf.
|
PDF Full Text Request