【作者】 窦宏亮；

【导师】 李春美；

【作者基本信息】 华中农业大学 ， 食品科学， 2007， 硕士

【摘要】 本研究围绕绿茶饮料在贮藏期内主要生化成分和香气成分的变化及二者的相关性这一中心课题，通过对多种芳香成分提取方法的比较，确定顶空固相微萃取一气质联用（HS-SPME／GC／MS）作为绿茶饮料香气成分分析的主要方法，同时采用GC-MS／GC-Olfactometry／RI法对学院绿茶及其饮料的香气成分进行了对比分析，确定了各自的主体香气成分。并对绿茶饮料在贮藏期间主要生化成分、芳香成分的变化、二者的相关性、及其对茶饮料风味的影响进行了系统研究；同时采用模拟体系分离鉴定了绿茶饮料中儿茶素的氧化产物，探讨了儿茶素氧化对其抗氧化活性的影响。通过上述内容的研究，得出以下结论：1．绿茶饮料香气物质提取方法的选择通过对同时蒸馏萃取法（SDE）、顶空进样法（MS）、顶空固相微萃取法（HS-SPME）三中方法对饮料香气成分提取效果的比较，确定HS-SPME作为绿茶饮料香气成分的适宜提取方法。HS-SPME提取绿茶饮料香气成分的最佳条件为：选择CAR／DVB／PDMS纤维头，顶空体积为30mL，萃取温度50℃，萃取时间60min，加入饱和NaCl（0.32g／mL）。2．绿茶饮料中典型呈香成分的确定采用气—质联用技术（GC-MS），结合气相—嗅觉测量（GC-Olfactometry）和保留指数（RI），确定绿茶饮料中的典型呈香成分为：芳樟醇、芳樟醇氧化物、香叶醇、橙花醇、橙花叔醇、（Z）-2-庚烯醛、苯甲醛、己醛、苯乙酮、3，5-辛二烯-2-酮、β-紫罗兰酮、水杨酸薄荷酯、D-芋烯、2，5-二丁基呋喃。3．绿茶饮料贮藏过程中主要生化成分、香气成分的变化及其对饮料风味和感观品质的影响贮藏过程中，未添加抗氧化剂和添加抗氧化剂绿茶饮料的亮度均呈下降趋势，降幅分别为17.3％和8.84％；两者的色泽均向黄红转变；香气和滋味均在贮藏至10个月时达最佳，在贮藏的最后两个月，出现微酸的情况。绿茶饮料在贮藏过程中主要生化成分会发生显著变化。未添加抗氧化剂和添加抗氧化剂饮料中总酚含量均呈下降趋势，前者的减少率为26.6％，后者仅为9.01％；主要儿茶素EGCG含量下降趋势明显，在贮藏的第一个月，前者EGCG含量迅速下降，后者的基本不变，但随后开始大幅下降。贮藏6个月后，两种饮料中EGCG的损失率分别达57.2％和64.3％。茶饮料在贮藏过程中有H₂O₂产生。两种饮料中H₂O₂的含量均呈规律性变化，前者H₂O₂含量在第一个月时高达16.42μmol／L，随后下降，在第8个月有小幅增加，直至10个月时，无法检测到；而后者H₂O₂的含量在第一个月时仅为1.78μmol／L，此后迅速增加，贮藏两个月时即达21.09μmol／L，然后逐渐下降，从第8个月开始，H₂O₂的含量又开始逐渐上升，直至第12个月，达21.65μmol／L。两者游离氨基酸的含量也呈规律性变化。前者氨基酸在贮藏的第一个月后，含量明显下降，损失率约为68％，当贮藏4个月后，游离氨基酸总量又逐渐增加，至第6个月时开始小幅下降。而后者氨基酸含量在贮藏一个月后变化不大，而此后变化趋势与前者一致。贮藏过程中绿茶饮料中香气成分也发生显著变化。贮藏后，饮料中香气成分的种类和含量均明显增加。两种饮料中典型的呈香物质，例如芳樟醇、芳樟醇氧化物、香叶醇、β-紫罗兰酮、己醛、橙花醇、苯甲醛的含量总体上均随贮藏时间的延长呈现增加的趋势，只是在未添加抗氧化剂的饮料中己醛、橙花醇、苯甲醛的含量在贮藏10个月后有小幅下降。贮藏过程中，绿茶饮料主要生化成分的变化会导致香气成分发生变化。利用SAS软件进行相关性分析表明，生化成分的变化与典型香气成分变化呈正相关；其中，儿茶素氧化和H₂O₂含量变化导致芳樟醇、芳樟醇氧化物、香叶醇、β-紫罗兰酮、苯甲醛和橙花醇含量增加；氨基酸和H₂O₂的变化导致己醛含量增加。进一步采用多元逐步回归分析，结果表明：儿茶素氧化是导致饮料香气成分发生变化的主导因素。通过模拟体系进一步证明儿茶素氧化是导致茶饮料贮藏期间香气成分发生变化的主要因素之一。4．儿茶素氧化物的分离鉴定及其抗氧化活性的研究采用H₂O₂模拟氧化体系制备儿茶素氧化聚合物，经多级柱色谱和液—质联用分离鉴定了一种氧化物及其二聚体，结果表明：所得产物的分子量为471，是EGCG脱掉两个氢原子，加上一个氧原子形成的，其二聚体的分子量为939。测定了不同体系（甲基紫体系、2-脱氧-D-核糖体系、水杨酸体系和邻苯三酚—鲁米诺化学发光体系）中儿茶素氧化聚合物和同浓度茶多酚的抗氧化活性，结果表明：儿茶素氧化物具有很强的抗氧化活性，在前三个体系中对羟自由基（·OH）的清除率分别为：96.46％、84.8％、81.9％，在邻苯三酚-鲁米诺化学发光体系中对超氧阴离子(O₂^-·)的清除率为97.0％，均强于同一体系下等浓度茶多酚。更多还原

【Abstract】 Focusing on the change of the main biochemistry and aroma ingredients of green teabeverage, along with their correction, during storage.The following research works havebeen conducted: （1）The comparative study of the extracting method of aroma compoundsand HS-SPME was choosn as the best extracting method of aroma compounds fromgreen tea beverage. （2） The typical aroma compounds of XueYuan green tea and freeshgreen tea beverage was analysed and identified by GC-MS/GC-Olfactometry/RI methods.（3） The change of the main biochemistry and aroma ingredients of green tea beverage ,aswell as their correction and and their effect on the flavor of green tea beverage duringstorage. （4）Separation and analysis of the oxidation products of catechin in model systemand the effect of catechin oxidation on its anti-oxidant activity were also carded out,Themain results were as follows:1.The best extracting method and the optimum extracting conditionAmong the tested extracting methods of Simultaneously Distillation-Extraction（SDE）,Head Space （HS） and HS-SPME, HS-SPME was the best for extracting aromacompounds from green tea beverage and the optimum extraction condition wasCAR/DVB/PDMS of extracting fiber,50"Cof extracting temperature, 60min ofextracting time, and 0.32g/mL of added sodium chloride, and 30mL of the head spacevolume.2.The typical aroma component of green tea beverageThe typical aromatic component of green tea beverage were: Linalool、Linaloloxide、Geraniol、Nerol、Nerolidol、（Z）-2-Heptenal、Benzaldehyde、Hexanal、Acetophenone、β-Lonone、Methyl salicylate、D-Limonene、2,5-Dibutyl-furan,which wereidentified by GC-MS/GC-O/RI methods. 3.The change of the main biochemistry and aroma components of green teabeverage,as well as their correction and their effect on the flavor of green tea beverageduring storage.The brightness of two kinds of green tea beverage （one added antioxidant, namedbeverage A,and the other wasn’t, named beverage B） descended during storage, droped17.3% and 8.84%, respectively. Colour of the two kinds of beverage became yellow red;and the aroma of the beverages all reached the best in the 10th month of storage.Thebeverages appeared slight sourish odor in the last two months of storage.The main biochemistry ingredients of green tea beverage changed prominentlyduring the storage.The relative concentration of total polyphenol of beverage A andbeverage B decreased 26.6% and 9.01%, respectively,The concertration of EGCG alsodescended obviously.In the first month of storage,the concentration of catechin inbeverage A droped rapidly.However, it almost did not change in beverage B,but afterstoring for 6 months,the loss ratio of catechin in beverage A and beverage B were 57.2%and 64.3% respectively. During storage, there were amount of H₂O₂ produced in bothbeverages, and the concentration of H₂O₂ changed regularly. Which may be corrected tothe oxidation of catechins;The concentration of dissociative amino acid （AA） in twokinds of beverage changed regularly,too. After storage for one month,the concentrationof AA in the beverage A descended obviously, about 68% of which was lost. However, itincreased after the 4th month of storage.For beverage B, the change trend of AA wasconsistent with that of beverage A after the first month of storage, except that it changedindistinctively in the first month of storage.The main aroma components of green tea beverage also changed prominentlyduring storage.After storage,the kinds and concentrations of aroma components of bothbeverages increased obviously, and the relative contents of the presentative aromaticcompounds in both beverages increased dramatically.For example all of, the relativecontents of Linalool、Linalol oxide、Geraniol、β-Lonone increased dramatically duringthe whole storage time.However, the concentration of Hexanal、Benzaldehyde and Nerolof the beverage A descended smally in the 10th month.Correction between the change of the main biochemistry ingredients and the change of aroma of green tea beverage during storage was analysis by SAS software, and theresults showed that they had positive correlation. The oxidation of catechin and thechange of H₂O₂ lead to the increase in concentration of Linalool、Linalol oxide、Geraniol、β-Lonone、Benzaldehyde and Nerol;The change of AA and H₂O₂ lead to theconcentration increase of Hexanal. The oxidation of catechins was confirmed as adominant factor which lead to the change of aroma of tea beverage during storage bymultiple gradually regression analysis,and model system.4.Separation and analysis of the oxidation products of catechin in model system andthe effect of catechin oxidation on its anti-oxidant activityOne oxidant product （m/z471） and its dimer （m/z939） of tea catechin was wereseparated from H₂O₂ model oxidation system by multiple multistage columnchromatograph.HPLC-MS analysis showed that it was a product of EGCG by theelimination of 2H and adding a atom of oxygen.The anti-oxidized activity of oxidation products and tea polyphenol in differentsystems were mensurated. The results showed that the oxidant products of catechin hadvery strong antioxidant activity in all tested systems.The scavenging effect of the oxidantproducts on hydroxyl free radical（·OH） in methyl violet color metric system、DR system、salicylic acid system were 96.46%、84.8%、81.9%,respectively;The scavenging effect ofthe oxidant products on superoxide anion (O₂^-·) in luminescence of Pyragollicacid-Luminol system was 97.0%. and the antioxidant activity of the oxidant products wasmuch stronger than that of tea polyphenol in the same concertration in all tested systems.更多还原