【作者】 周志磊；

【导师】 钟芳；

【作者基本信息】 江南大学 ， 食品科学， 2014， 博士

【摘要】 卷烟的感官感受主要包括嗅觉和味觉两方面，二者互相影响，共同决定了卷烟产品的整体可接受性。多年来研究人员对卷烟的香味进行了大量研究，但对卷烟的味觉研究较少。随着卷烟产品竞争越来越激烈，卷烟的味觉调控受到了烟草公司和烟草研究人员的重视，烤烟与其他类型的烟草（白肋烟和香料烟）相比具有典型的略酸的甜香风格，我国市场上的卷烟产品以烤烟为主，因此对烤烟的味觉进行详细研究有助于烟草研究人员更好的理解和调控卷烟产品的风味，对于提高卷烟企业的竞争力具有重要意义。本文对烤烟烟气中主要的甜味物质进行了筛选和确认，分析了它们在烟草中的主要前体物，并探讨了其形成路径。主要的研究内容和结果如下：根据甜味物质的呈味理论，初步推测卷烟主流烟气中的甜味物质主要为半挥发性醛类、酮类和酚类等中性含氧成分。首先对主流烟气成分进行了定量分析，使用全二维气相色谱（GC×GC）结合飞行时间质谱（TOFMS）对烤烟单料烟主流烟气中性和碱性成分进行了定性和定量分析。使用直接溶剂萃取法（DSE）制备样品，优化后方法的检测限、重复性和回收率都比较令人满意。DSE方法与同时蒸馏萃取法（SDE）相比，其定量结果更加稳定可靠。此外还对主流烟气中单糖、酚类、酸性成分和常规成分进行了定量分析，总共测定了48个样品164个物质的含量。将得到的主流烟气成分根据官能团和来源分成19类，加上主流烟气pH和水分确定了21个变量，利用偏最小二乘回归（PLSR）模型分析了这些变量与烟气甜味和苦味的相关性，结果表明：呋喃类、吡喃类、水分、环酮类、链酮类和酚类物质与烟气甜味显著正相关；生物碱类、吡咯类、脂肪烃类和吡啶类等物质与苦味显著正相关，呋喃类和吡喃类物质与苦味显著负相关。在此基础上，利用PLSR模型分析了酮类、呋喃类和吡喃类46个成分与卷烟甜味的相关性，有13个物质与烟气甜味显著正相关，5个成分与甜味显著负相关。通过返添加实验和甜味阈值实验对模型结果进行验证，并对这些物质对烟气甜味的贡献大小进行评估，发现烤烟主流烟气中对甜味贡献较大的物质主要有：2-糠醛、2,3-二氢-3,5-二羟基-6-甲基-4H-吡喃-4-酮（DDMP）、甲基环戊烯醇酮、果糖、菠萝酮、5-甲基-2-糠醛、对苯二酚、葡萄糖、苯酚、3-甲基-2-环戊烯-1-酮、乙基环戊烯醇酮和麦芽酚。返添加实验还证实向卷烟中添加甜味和酸味物质可以抑制烟气苦味，且这种抑制存在一定的协同作用。为了分析烟气主要甜味物质的来源和形成过程，对烤烟烟草成分与烟气成分和烟气味觉间的相关性进行了分析。对烟草挥发性中性和碱性成分的定量分析表明烟草中呋喃类、吡喃类、环酮类和简单酚类物质的物质个数和含量都远远低于主流烟气，说明主流烟气中的这些成分主要来自烟草成分在卷烟燃烧时的热裂解。使用PLSR模型对烟草成分与烟气主要甜味和苦味物质的相关性分析表明：烟气呋喃类和吡喃类物质以及5-甲基-2-糠醛和DDMP与烟草总糖、还原糖和糖氮比显著正相关，说明糖裂解和美拉德反应可能是这些物质的主要来源。烟气生物碱与烟草总氮和烟碱显著正相关，烟气生物碱主要来自烟草中生物碱（烟碱）的转移。使用PLSR模型对烟草成分与烟气甜味和苦味间的相关性进行了分析，并进行了返添加验证，结果表明：与甜味正相关的主要是烟草糖类物质，负相关的主要是钾和钾氯比，钾氯比代表了烟草燃烧性能，说明烟草燃烧性能可能对烟气甜味有重要影响。对苦味有显著影响的变量主要有：烟碱、总氮、糖碱比、糖氮比、氮碱比，其中烟碱和总氮与苦味正相关，其他三个指标与苦味负相关。说明影响烟气苦味的主要是烟草生物碱（烟碱），烟气酸碱平衡可能也对烟气苦味有重要影响。烟草部位对烟气甜味没有显著影响，对苦味有显著影响，苦味强度为：上部烟叶>中部烟叶>下部烟叶；不同产地烟叶的烟气苦味没有显著差异，甜味有显著差异，云南烟叶烟气的甜味显著高于其他产区。模型分析的结果表明烟气主要甜味物质主要来自烟草燃烧时的美拉德反应。对还原糖（葡萄糖/果糖）与脯氨酸固相美拉德反应模型中主要烟气甜味物质的形成路径和影响因素进行了研究。TG和DSC分析表明果糖比葡萄糖更容易发生热裂解，脯氨酸Amadori重排产物（Fru-Pro）和脯氨酸-还原糖混合物都在150℃左右发生了固相美拉德反应。脯氨酸-葡萄糖/果糖混合物在不同温度下的的美拉德反应产物中检测到了122个挥发性成分，生成量最大的是DDMP，其中有86个成分在主流烟气中也被检测到，尤其是酮类、呋喃类和吡喃类物质。总体来说，温度越高，美拉德反应产物的种类和生成量越大，但是DDMP在较低温度下（150℃）生成量较大。脯氨酸-葡萄糖比脯氨酸-果糖混合物生成了较多的DDMP、麦芽酚和2-乙酰呋喃等产物，同时其生成的甲基环戊烯醇酮少于脯氨酸-果糖混合物。脯氨酸与葡萄糖反应时比其他氨基酸表现出了高的反应活性，生成了较多的菠萝酮和DDMP等物质，主要原因是脯氨酸具有特殊的分子结构，是醛醇缩合反应以及美拉德反应的良好催化剂。氧气浓度对菠萝酮和DDMP的生成量没有显著影响。反应物比例对菠萝酮和DDMP的生成量影响很大，当还原糖氨基酸摩尔比高于1:1时，会促进菠萝酮、DDMP和5-羟基麦芽酚等产物的生成，且当摩尔比为2:1时生成量最大；当还原糖氨基酸摩尔比低于1:1时，会抑制这些产物的生成。DDMP生成量先随着时间增加，达到最大值后缓慢下降，峰值随着温度的升高而增加随后达到了平衡值。动力学研究表明，DDMP在初始阶段的形成符合一级动力学，反应活化能为68.8kJ/mol。更多还原

【Abstract】 The sensory of cigarette mainly consists of two aspects: olfactory sensation and taste sense.They affect each other and decide in combination the sensory acceptability of cigarettes. A lotof investigation has been done on cigarette aroma over the years but little on cigarette taste.With increased market competition, cigarette taste has garnered attention from tobaccoresearchers and companies. Flue-cured tobacco have sweet with little acidic taste and aromacompared with other tobacco such as burley and oriental tobacco. The main cigarette productsin China market are flue-cured cigarettes. Therefore, it is of great importance for cigaretteresearchers and companies to investigate cigarette taste in detail. In this work, we screenedand confirmed the main sweet compounds in cigarette smoke, analyzed their precursor intobacco and discussed their formation pathways and mechanism. The main contents andresults are as follows:According to the sweet theory, the main sweet compounds were preliminarily estimated asneutral oxygen compounds which mainly include semi-volatile aldehydes, ketones andphenols. We firstly quantitatively analyzed the mainstream constituents. Comprehensivetwo-dimensional gas chromatograph (GC×GC) coupled to time-of-flight mass spectrometry(TOFMS) was used to analyze the neutral and alkaline compounds. Directed solventextraction (DSE) method was chosen to prepare the sample and the limit of detection,repeatability and recovery were all satisfactory after the method was optimized. Comparedwith simultaneous distillation and extraction (SDE), the quantitative results from DSE weremore reliable. Furthermore, the monosaccharides, simple phenols, organic acids and tobaccoroutine compounds were also quantitatively analyzed and156compounds for48sampleswere finally analyzed.The obtained compounds were classified into19groups according to their origin andfunctional groups,21variables were obtained including these19groups and smoke pH andwater. A partial least squares regression (PLSR) model was established to analyze thecorrelation between these smoke variables with smoke sweet and bitter taste. A positivecorrelation was observed between furans, pyrans, water, cyclic ketone and phenols withsmoke sweet taste. Smoke bitter taste was found to positively correlative with smokealkaloids, pyrroles, aliphatic hydrocarbons and pyridines, and negatively correlative withfurans and pyrans. The relationship between46ketones, furans and pyrans compounds andsmoke sweet taste was then investigated with PLSR model,13compounds were found topositively correlative with sweet taste and5compounds negatively correlative with sweettaste. The standard-spiked experiments and threshhold test were performed to confirm theresults from PLSR model and to evaluate the contribution of various compounds to smokesweet. We found that the main sweet compounds in cigarette smoke were:2-furfural,2,3-dihydro-3,5-dihydroxy-6-methyl-4H-pyran-4-one (DDMP), methyl cyclopentenolone,fructose, furaneol,5-methyl-2-furfural, hydroquinone, glucose, phenol,3-methyl-2-cyclopenten-1-one, ethyl cyclopentenolone and maltol. The standard-spikedexperiment also showed that smoke bitterness could be supressed by adding sweet and acidcompounds to cigarette, and the supression was synergetic to some extent. The relationship between tobacco components with smoke compounds and taste wasinvestigated in order to evaluate the origin and formation procedure of cigarette compounds.The neutral and alkaline volatile compounds in tobacco were quantitative determined andtheir contents were much smaller than those in smoke, this indicated that the furans, pyransand simple phenols in cigarette smoke were mainly formed from the pyrolysis of tobaccoconstituents. The relationship between tobacco compounds and smoke sweet and bittercomponents was investigated with PLSR model, the results showed that furans, pyrans,5-methyl-2-furfural and DDMP in cigarette smoke were positively correlative with tobaccototal sugar and reducing sugar, this suggested that these compounds are produced from sugarpyrolysis or Maillard reaction. Smoke alkaloids were positively correlative with tobacco totalnitrogen and nicotine, smoke alkaloids were mainly derived from vaporization of tobaccoalkaloids (nicotine). A PLSR model was used to investigate the relationship between tobaccocomponents and smoke sweet and bitter taste, and the standard-spiked experiment was alsoperformed to verify the results form this model. Smoke sweet taste was positively correlativewith tobacco sugar and negatively correlative with potassium and ratio of potassium tochlorine which reflect the combustion quality of tobacco. This suggested that combustionquality of tobacco might significantly influence smoke sweet taste. Smoke bitter was foundpositively correlative with tobacco nicotine and total nitrogen and negatively correlative withratio of sugar to nicotine ratio, sugar to total nitrogen and total nitrogen to nicotine. Thisindicated that the main factor that affects smoke bitter taste was tobacco alkaloids (nicotine),the smoke acidic alkaline balance might also played important impact on smoke bitterness.Stalk position played no significant influence on smoke sweet and played significant effectson smoke bitterness. No significant difference was observed between smoke bitterness oftobacco from different production areas. Significant difference was observed between smokesweet of tobacco from different production areas. The sweet taste of tobacco smoke fromYunnan province was significantly higher than those from other production areas.Most of the main sweet compounds in cigarette smoke were Maillard reaction products, theformation pathway and influence factors were investigated in a solid-phase Maillard reactionmodel between reducing sugar (glucose/fructose) and proline. TG and DSC investigationindicated that fructose was more sensitive to thermal degradation than glucose, the prolineAmadori rearrangement product and proline-reducing sugar mixture all underwentsolid-phase reaction at around150℃.122Compounds were identified in the reactionproducts from proline-furctose/glucose mixture conducted under different temperature, and86of the122compounds was also detected in cigarette smoke, especially ketones, furans andpyrans. In General, the higher the temperature, the higher the product number and content.However, DDMP was efficiently produced in lower temperature. Compared withproline-fructose mixture, proline-glucose mixture produced more DDMP, maltol and2-acetylfuran, and less methyl cyclopentenolone. Proline showed higher reactivity than other aminoacids when reacted with glucose and produced major furaneol and DDMP, this mainlyattributed to the special molecular structure of proline. Proline is good catalyst for aldolreaction as well as Maillard reaction. Oxygen concentration played no obvious effects onfuraneol and DDMP formation. Reaction ratio played significant influence on furaneol and DDMP formation. Their formation was greatly enhanced when reducing sugar was excessiveand reached the highest level with a molar ratio of reducing sugar to proline at2:1. Theirformation was supressed when proline was excessive. DDMP yield increased with time at firstand then slowly decreased after the peak was achieved. The peak value increased withtemperature and then seemed to achieved a plateau. The kinetics research showed that DDMPformation in the initial stage followed the first order kinetics with an activation energy of68.8kJ/mol.更多还原