【作者】 乔宇；

【导师】 谢笔钧； 潘思轶；

【作者基本信息】 华中农业大学 ， 农产品加工与贮藏， 2008， 博士

【摘要】 柑橘汁的香气是柑橘汁的重要品质之一,本研究围绕柑橘果汁香气成分这一中心课题,以我国湖北松滋和宜昌地区的三大类10种柑橘果汁为研究对象,运用固相微萃取(Solid Phase Microextraction,SPME)、气相色谱-质谱联用(GasChromatography-Mass Spectrum)和气相色谱嗅觉测量法(GC-Olfactometry,GC-O)技术对10种柑橘果汁的挥发性成分和香气活性成分(Aroma active compounds)进行了鉴定,比较了不同采收期的锦橙果实的香气成分,并对其在榨汁、巴氏灭菌、辐照灭菌过程中以及灭菌果汁在储藏过程中香气成分的变化进行了系统的研究,同时利用电子鼻对柑橘果汁的整体香气和酸橙汁加工过程中香气成分的变化进行了区分。研究结果为科学评价柑橘汁的香气品质奠定了一定的基础,对我国柑橘的生产加工和产品质量的提高也具有重要的应用价值。研究的主要内容和结果如下:1.柑橘汁挥发性物质的提取分离方法比较了同时蒸馏提取法、溶剂萃取法、顶空法和固相微萃取4种方法对锦橙汁香气成分的分离效果,其中固相微萃取法是分离柑橘汁挥发性成分的有效方法,萃取最佳条件为DVB/CAR/PDMS 50/30μm三层复合萃取头,在15mL顶空瓶中加入6mL果汁和3.6g/mL的NaCl,40℃平衡15min后萃取40min,在此条件下可以获得理想的香气化合物信息。2.柑橘果汁挥发性成分及相关理化指标的分析使顶空固相微萃取-气质联用对10种柑橘果汁的挥发性成分进行了分析,在3种温州蜜柑汁(国庆1号、宫川、大叶尾张)中分别检测到43种,47种和46种挥发性物质,2种葡萄柚汁(白葡萄柚、红葡萄柚)中分别检测到45和39种挥发性物质,5种橙汁(锦橙、哈姆林、纽荷尔、血橙、酸橙)中分别检测到54种,57种,52种,54种和44种挥发性物质,此外,不同品种的柑橘汁在固酸比、VC含量、糖含量、酸含量都存在一定的差异。3.柑橘果汁香气活性成分分析使用GC-O技术在10种柑橘果汁中分别检测到了21种(国庆1号),17种(宫川),27种(大叶尾张),34种(血橙),30种(哈姆林),30种(锦橙),26种(纽荷尔)26种(酸橙),20种(白葡萄柚),21种(红葡萄柚)气味活性物质。以血橙的气味物质最多,白葡萄柚最少。在10种果汁中共有的香气活性物质是柠檬烯。还有其他一些香气活性化合物无法被质谱检测到,暂时不能确认。通过溶剂萃取结合GC-O确认了香兰素是3种温州蜜柑中的香气活性成分。风味轮廓分析发现国庆1号和尾张中主要的是药草/青味,宫川中主要的是木头/树叶味,锦橙、哈姆林、纽荷尔和酸橙都以花香为主,血橙中最主要的气味是果香和橘香。酸橙气味轮廓图与其他四种甜橙(锦橙、哈姆林、纽荷尔、血橙)有明显的区别。四种甜橙汁有相似的轮廓图,各品种汁有较好的区分。白葡萄柚以果香为主,红葡萄柚以木头/树叶味为主。综合考虑香气成分以及相关理化指标,我国的锦橙是适合加工榨汁的品种。酸橙汁、葡萄柚汁和温州蜜柑汁可以以适当的比例添加入橙汁,来调节合适的口感和香气。4.锦橙果实不同采收期间香气成分的变化分析了不同采收期10月1日、11月1日、12月1日、12月30日的锦橙鲜果的挥发性成分,通过比较总挥发性物质及香气活性物质,可以发现总挥发性物质以及柠檬烯、芳樟醇等物质的峰面积随着果实的成熟而增加,在12月1日的果实中达到最大,12月30日的过熟果中的挥发性物质的峰面积减少。因此,12月初是最佳采果时期。5.锦橙榨汁和灭菌过程中香气成分的变化对锦橙的手工鲜榨汁、机械榨汁、果皮精油的香气成分进行了分析,并对鲜榨锦橙汁进行了巴氏灭菌和三种不同辐照剂量的处理,结果表明:机械榨汁的挥发性物质的总峰面积要高于手工榨汁,手工榨汁的挥发性成分的总峰面积经巴氏灭菌后减少了27.64%,三种辐照剂量处理后的果汁挥发性成分的总峰面积都要高于巴氏灭菌汁。在机械榨汁,手工榨汁及其巴氏灭菌汁中分别检测到了51,54和47种挥发性成分,三种果汁各有31,30,29种香气活性物质。机械榨汁除脂肪味外其他类香气均高于手工榨汁,手工榨汁经巴氏灭菌后整体香气发生了一些变化,果香,花香,橘香,药草,松油味减弱,木头/树叶味和脂肪味增强。果皮精油中共鉴定出32种挥发性化合物和22种气味物质,芳樟醇,α-蒎烯和癸醛香气强度最高,对精油香气起到主要贡献作用。6.巴氏灭菌和辐照处理的锦橙汁在储藏过程中香气成分的变化将巴氏灭菌和辐照处理的锦橙汁在4℃储藏60d,D-柠檬烯在储藏期间一直呈下降趋势,芳樟醇、松油烯-4-醇、α-松油醇、6-甲基-5-庚烯-2-酮和α-蒎烯呈先上升后下降趋势。7.基于电子鼻的柑橘汁样品的研究应用电子鼻对不同品种的橙汁和蜜柑汁进行了区分,对酸橙汁加工过程中香气成分的变化进行了监测,28°Brix、38°Brix和63.5°Brix不同浓缩度的还原汁在电子鼻上的信号经拟合后有良好的线性关系,以55°Brix还原汁为盲样,判别结果为57.95,误差为5%。更多还原

【Abstract】 Aroma has long been known to be one of the most important quality attributes of citrus juices.Encompassing the central task of characteristic aroma component of citrus juice,the ten citrus juices from three cultivars planted in Song zi and Yi chang region of Hubei province in China were chose in this paper.The volatile compounds and aroma active components of ten citrus juices were identified by SPME-GC-MS and GC-Olfactometry.The aroma constituents of Jinchen fruits at different harvested time were studied.Comparison of aroma components were extensively investigated in squeezed juice,pasteurized juice and irradiated juice from Jinchen fruit and aroma variation of aseptic juice during storage.Furthermore,the electronic nose was applied to discriminate the overall aroma of different citrus juices and monitor aroma change during sour orange juice processing.The results could be benefit to evaluate aroma quality of citrus juice and provide important information about citrus processing and products quality improving.Through the studies above,conclusions were made as follows:1.Isolation the volatile compounds from citrus juicesThe volatile compounds of Jinchen orange juice were extracted by simultaneous distillation-extraction,head-space technique,solvent extraction and solid phase microextraction.The solid phase microextraction was the valid method to isolate volatile compounds.The optimum extraction condition was:6ml orange juice with 0.36g/mL NaCl, extracting 40min after equilibrium 15 min at 40℃by DVB/CAR/PDMS50/30μm fiber.2.Analysis of volatile compounds and physical and chemical propertiesThe volatile components in ten citrus juices were analyzed by headspace solid phase microextraction(HS-SPME) combined with GC-MS.The results showed that there were 43,47 and 46 aroma components in three Mandarin juices(Guoqing 1,Miyagawa Wase, Owari),respectively.In five orange juices(Jinchen sweet orange,Hamulin sweet orange, Newhall navel,Blood orange,Sour orange),54,57,52,54 and 44 volatile compounds were detected,as well as 45 and 39 volatiles in two grapefruit juice(White grapefruit and Pink grapefruit).Moreover,the difference of the radio of soluble solids and total acids,VC content, sugar content,and organic acid content were observed among the different citrus juices.3.Analysis of the aroma active compounds in citrus juices The GC-O method was performed to identify the aroma active compounds of ten citrus juices.The mandarin juice,Guoqing 1,Miyagawa Wase and Owari were characterized by 21,17,27 odorants,respectively,while the white and pink grapefruit juices,were characterized by 20 and 21 odorants.In five orange juices,such as Jinchen sweet orange,Hamulin sweet orange,Newhall navel,Blood orange,Sour orange, 30,30,26,34,30 odorants were found,respectively.The kinds of odor compounds of blood orange was highest while white grapefruit juice was least in all samples..There were some aroma active compounds not detected by GC-MS.Vanillin was confirmed to be the aroma active compound of three mandarin juice isolated by solvent extraction.The flavor profile showed that the herbaceous/green note formed the main odor note of the overall aroma of Guoqing 1 and Owari,and the main perceived note of Miyagawa Wase was the wood/leg odor.The floral note was the main perceived note in Jinchen sweet orange,Hamlin sweet orange,Newhall navel,and Sour orange.The profile of sour orange was completely different from the four sweet orange juices.Four sweet orange juices had a similar distribution of the odor note.The white grapefruit and pink grapefruit mainly presented fruity odor and wood/leaf odor,respectively.Considering the aroma components and chemical and physical properties,Jinchen is the feasible fruit for processing.Sour orange juice,grapefruit juice and mandarin juice could be added to orange juice to improve their odor and taste.4.Comparison of volatile compounds in Jinchen fruit at different harvested timeThe volatile compounds of Jinchen fruit harvested on Oct.1st,Nov.1st,Dec 1st,Dec. 30th were analyzed.The results showed that the peak area of total volatile compounds and aroma active compounds such as limonene and linalool increased with the fruits development.The total peak areas reached highest in fruits harvested on Dec.1st and reduced in the fruits from Dec.30th5.Change of aroma compounds in Jinchen orange juice after squeezing, pasteurization and irradiation.The volatile compounds analysis of hand extracted juice,mechanically extracted juice and peel oil were performed.The fresh Jinchen juices were treated with pasteurization and irradiation with three different doses.According to the results,total peak areas of volatile compounds in hand extracted juice were lower than mechanically extracted juice and decreased 27.64%after pasteurization.The irradiated juices with three different dose treatments were found at higher peak area than pasteurized juice.Total of 51 volatile compounds identified in mechanically extracted juice,as well as 54 in hand juice,47 in pasteurized juice.Meanwhile,there were 51,54 and 47 active aroma compounds identified in those three different juices.Major group odor of mechanical extracted juice presented higher than hand extracted juice except fatty note. The overall aroma of hand juice changed after pasteurization due to decrease of fruity note,floral note,citrusy note,herbaceous note,piney note and increase of wood/leaf note, and fatty note.In peel oil extracts,a total of 32 compounds were identified in the volatile fraction and 22 aroma active compounds were perceived.Linalool,α-pinene,and decanal with the greatest aroma intensity gave the predominant contribution to peel-oil odor.6.Change of aroma compounds of Jinchen juice during storageThe Jinchen orange juice treated with pasteurization and irradiation stored in 4℃for 60d,D-limonene decreased throughout the whole storage,meanwhile,linalool, 4-terpinenol,α-terpineol,6-methyl-5-hepten-2-one,andα-pinene showed the increasing trend and then declined.7.Research of electronic nose for citrus juicesThe electronic nose was applied to discriminate the overall aroma of different citrus juices and monitor aroma change of sour orange juice during processing.The electronic signal was linear with different reconstituted concentrated juice.The 55°Brix reconstituted concentrated juice was chosen as unknown sample to discriminate the concentration.The discriminate result is 57.95 and RSD is 5%.更多还原