The surface wetting properties of paper-process reconstituted tobacco and natural tobacco leaf under different relative humidity were investigated in present study.The advancing contact angle was measured by Dynamic Contact Angle Analyzer(DCA).Scanning Electron Microscope(SEM) and Atomic Force Microscope(AFM) were also utilized to compare the surface morphology.The results showed that whether the water or essence was used as the liquid medium,the advancing contact angle of natural tobacco leaf was greater than 90°.It exhibited a hydrophobic property.While the advancing contact angle of paper-process reconstituted tobacco is less than 90°,it presents its hydrophilic surface property.For tobacco leaf,a smoother surface,and denser leaf structure were observed as compared to paper-process reconstituted tobacco.Furthermore,the surface roughness of tobacco leaf is lower than paper-process reconstituted bobacco under different relative humidity(respectively 37.23 nm,82.97 nm and 227.99 nm,105.35 nm).The coarser surface and porous structures of paper-process reconstituted tobacco verified the finding of its dymatic contact angle.

ABSTRACT In this work, the effect of oxidation pretreatment on the enzymatic hydrolysis of cellulose in tobacco stems was evaluated. A comparison was made between the effect of H2O2 pretreatment and conventional alkali pretreatment on the weight loss of cellulose, lignins and hemicelluloses of tobacco stems. The effects of H2O2 concentration, pretreatment time and temperature on the enzymatic hydrolysis of tobacco stems were investigated. This pretreatment could give a higher recovery of cellulose and better removal of lignin and hemicellulose than alkali‐only pretreatment. Compared with the untreated stems, the yield of reducing sugar pretreated by H2O2 pretreatment (pH 11.5, 0.6% H2O2) for 9 h at 60C increased 347.2%. The results of scanning electron microscope and X‐ray diffraction analysis also showed that the structural and crystalline properties of the tobacco stems were changed by pretreatment, and they were in favor of the following enzymatic hydrolysis. The optimal pretreatment conditions were 60C of temperature, 0.6% of H2O2 concentration and 9 h of time, which were calculated by orthogonal experiments. PRACTICAL APPLICATIONSPretreatment on lignocellulosic materials to disrupt the recalcitrant structure is helpful for their bioconversion into low‐molecular weight substances. The tobacco stems were pretreated by H2O2 oxidation before subjecting to enzymatic hydrolysis by cellulase in this work. This pretreatment was confirmed effectively to improve the recovery of celllulose, and helpful to remove lignin and hemicellulose. Moreover, the yield of reducing sugar produced by cellulase hydrolysis was apparently improved. These results were helpful for the extensive development of tobacco stems.

In order to investigate the effects of acidity on the pyrolysates of cigarette paper additives,the pyrolysates of potassium citrate solution of pH 3.51,8.36 and 12.14 at 300,600 and 900 ℃ in air were analyzed with pyrolysis-gas chromatography/mass spectrometry.The results showed that: 1) At 300 ℃,the major pyrolysates were ketones;while at 600 ℃ and 900 ℃,the major pyrolysates were ketones,benzenes,phenols,indenes and polycyclic aromatic hydrocarbons.2) At 600 ℃ and 900 ℃,the contents of crotonaldehyde,aldehydes,benzenes,indenes and polycyclic aromatic hydrocarbons increased,while those of ketones,furans,phenols decreased with the rise of pH value of solution.

The effects of pH value of cigarette paper additives on smoke pH, CO, TPM and sensory quality were studied.The results showed that pH value of cigarette paper additives was increased with (increasing) pH value of mainstream smoke, but the content of CO and TPM were declined,pH value of cigarette (paper) additive also affected the sensory quality,neutral solution would be better for sensory quality.

In order to improve the usability of tobacco stem,the effects of treatments with dilute NaOH and H2O2 solution on the filling power,cell wall substance and smoking quality of tobacco stem were tested. The results showed that the optimal treatment conditions were:dipping in solution of 1.0% NaOH and 1.0% H2O2 at 70 ℃ for 1.5 h,under which the contents of cell wall substances,lignin,total nitrogen and total sugar in treated stem decreased by 12.71,2.14,1.24 and 10.28 percentage points,respectively; while stem's moisture content and filling power increased by 4.02 percentage points and 10.34%,and its smoking quality obviously improved.

采用轮廓分析法对六种市场占有率较高的品牌卷烟进行评吸,并对其相应的致香成分进行了气相色谱/质谱定性定量分析,为今后研究香味感官特征与致香成分的关系提供了科学依据。