Effects Of Harvest-time And Air-curing Envirionment On Content Of Neutral Aroma Components Of Burley Tobacco

Binchuan of Yunnan Province is one of the four main regions producing burleytobacco in China. Due to its climate conditions of high temperature and low humidityin Binchuan area, curing process is fast and the degradation of macromolecularmatters is not sufficient. In this experiment, burley variety TN86was used toinvestigate the effects of air-curing in different ecological environments, physicalmeasures to keep moisture, chemical measures to promote curing and fifferentharvest-time on tobacco quality and contents of neutral aroma substances, thusproviding theoretical and technical basis for the determination of suitable growingareas, and for the adoption of appropriate drying equipment and technology toimprove air-curing environment, and to promote high-quality burley tobaccoproduction.The main results are as follow.1. To explore the effect of ecological environment on the quality of burley tobaccoduring air-cured progress, burley leaves cultivated in Binchuan County and YunlongCounty of Yunnan Province were put in Binchuan County and Yunlong County toair-cure, respectively. Results showed that differences of temperature in two areaswere unapparent, while differences of relative humidity in two areas were greatlysignificant. Relative humidity of Yunlong County was higher of4.42%~16.54%thanthat in Binchuan County through the whole air-cured progress. Air-curing time inBinchuan County was less of9days than that in Yunlong County. The differences ofleaves cured in two ecological environments were markedly evident in physicalappearances. The content of left β-Carotenoid of leaves cured in Binchuan Countywas higher than that in Yunlong County. Neutral aroma components of cured inYunlong County was higher than that in Binchuan County, which was showing thataroma components of leaves that produced in Binchuan County was higher of47.31%,20.37%than that in Yunlong County, respectively.There is conspicuous correlationsbetween eco-environment and contents of plastid pigment, neutral aroma componentsof burley tobacco. Therefore it is significant to take some reasonable and scientificmeasures according to local situations in cured process to increase contents of aromaand improve quality in agricultural manufacture of burley tobacco.2.Questioning light of the problem that barns of Binchuan county lack of goodkeeping moisture, the experiment was conducted to investigate the effects of usingsunlight nets, black plastic-films and fibre nets assistant to cover around barns onair-curing progress and leave quality. Results showed that adopting physical manners of three coverings cocould increased humidity of the barns, leading to slow down thespeed of free-water of leaves,to lengthen curing time, to reduce carotenoid content, toincrease content of neutral aroma substances and make appearance of leavesbetter.The content of neutral aroma substances of upper leaves among thesetreatments was in the order of: cover sunlight nets＞black plastic-films＞fibre nets＞contrast treatment. The content of neutral aroma substances of leaves cured in coversunlight nets, black plastic-films and fibre nets was higher of102.74%，88.73%，50.24%than that contrast treatment,respectively The content of neutral aromasubstances in addition to neophytadiene of leaves cured in cover sunlight nets, blackplastic-films and fibre nets was higher of194.21%，45.90%，28.23%than that contrasttreatment, respectively.There were conspicuous correlations among humidity of curedperiod and all sorts of neutral aroma substances.3. As degradation of matirals in burley tobacco leaves during air-curing progress wasinsufficient in Binchuan area, the experiments were set up to use chemical substanceto deal with burley tobacco leaves to promote the burley tobacco leaves yellow andincrease aroma substances. Experimental results showed that the contents of moistureand dry matter in upper leaves of spraying of aqueous sodium bicarbonate was lowestcomparing with the control and blank treatments. Left carotenoid was smallest inleaves spraying aqueous of sodium bicarbonate among three treatments. The contentsof chlorophyll degradation products, carotenoids degradation products and totalneutral aroma components in leaves spraying aqueous of sodium bicarbonate werehigher of64.74%、39.00%、51.55%than that in control leaves, respectively. Thecontents of chlorophyll degradation products, carotenoids degradation products andtotal neutral aroma components in leaves spraying aqueous of sodium bicarbonatewere higher of36.15%、20.64%、18.92%than that spraying water,respectively.Moisture loss in upper stalk leaves associated with the degradation of leave dry matter.Spraying aqueous of sodium bicarbonate on leaves before air-cured could acceleratethe loss rate of of free water, increase the contents of dry matter degradation andshorten the air-cured leaves time. In leaves spraying aqueous of sodium bicarbonate,material degradation was was more totally, the contents of plastid pigmentdegradation products and the content of neutral aroma substances were more than thatthat leaves of controlling treatment.4. In order to study the effect of harvest-time on air-curing progress and quality, fiveharvest-times were set out (2weeks after topping,3weeks after topping,4weeks after topping,5weeks after topping,6weeks after topping,) to do this experiment.Resultsshowed that the air-curing time increased firstly and then decreased with thedeveloping of harvest-time after topping. The contents of plastid pigment(chlorophyll a, chlorophyll b and carotenoids) in the fresh sample reduced with thedeveloping of harvest-time after topping, while in air-cured leaves was reverse withthe developing of harvest-time after topping. The contents of plastid pigmentdegradation products firstly increased and then decreased with the developing ofharvest-time. The proportion of the content of plastid pigment degradation products inthe neutral aroma substances was biggest of all degradation products, then thecontents of plastid pigment degradation products largely determines the content ofneutral aroma substances.5weeks after topping was suitable harvest-timeand couldimprove the quality of tobacco leaves,which led to the consequence that we could getoptimum production of burley leaves that were less contents left plastid pigment andhigh content of neutral aroma substances.