烤烟密集烘烤变黄期类胡萝卜素及其降解香气成分的变化.doc
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1、【精品文档】如有侵权,请联系网站删除,仅供学习与交流烤烟密集烘烤变黄期类胡萝卜素及其降解香气成分的变化.精品文档.烤烟密集烘烤变黄期类胡萝卜素及其降解香气成分的变化宋朝鹏1,2,武圣江2,高 远2高远的单位是不是不改为好,许自成2,张卫建1,宫长荣2(1南京农业大学农学院,南京 210095;2河南农业大学烟草学院,郑州 450002)摘要:【目的】研究密集烘烤变黄阶段烤烟类胡萝卜素组分、酶活性及其降解香气成分含量的变化,为密集烤房烘烤工艺优化和完善提供理论依据。【方法】采用河南农业大学设计的电热式温湿自控密集烤烟箱,研究不同温湿度条件对变黄期烤烟类胡萝卜素各组分降解、相关酶活性变化及其降解香
2、气成分含量的影响。【结果】变黄期类胡萝卜素(-胡萝卜素、叶黄质、新黄质、紫黄质)含量均随烘烤过程推进而逐渐降低。其中低温低湿变黄(T1)和低温中湿变黄(T2)-胡萝卜素在变黄结束时含量较低,其值分别为17.14 gg-1 FW、19.00 gg-1 FW。叶黄质、新黄质、紫黄质含量在各处理中随温湿度的降低而降低。低温变黄处理-胡萝卜素与叶黄素(叶黄质、新黄质、紫黄质)的比例和烤前相比均有所升高,高温变黄处理则与之相反。不同处理叶黄质与叶黄素的比例和烤前比均升高,而新黄质和紫黄质则与之相反。烤后烟叶T1、T2处理类胡萝卜素含量较低,尤其是T2处理,其值为76.31 gg-1。烤后烟叶类胡萝卜素降
3、解香气成分含量以T2处理最高,为87.5634 gg-1,其次为T1处理,为81.1192 gg-1,显著高于其余处理。变黄期T1、T2处理有利于脂氧合酶(LOX)、过氧化物酶(POD)活性的充分表达,使类胡萝卜素降解更充分。相关分析表明,烘烤中变黄期POD活性与类胡萝卜素各组分呈显著正相关。【结论】变黄期低温和相对较低的湿度条件下,保持相对较高的酶活性,使LOX与POD之间的协同拮抗作用达到一种动态平衡,并在3648 h适当延长相对较长的时间,对充分降解类胡萝卜素物质和改善烟叶香气品质是有利的。关键词:密集烘烤;变黄期;类胡萝卜素;降解机理;香气成分The Degradation Mecha
4、nism of Carotenoids in Flue-Cured Tobacco and the Changes of the Related Aroma Components in the Yellowing Stage During the Bulk Curing ProcessSONG Zhao-peng1,2, WU Sheng-jiang2, GAO Yuan2, XU Zi-cheng2, ZHANG Wei-jian1, GONG Chang-rong2(1College of Agronomy, Nanjing Agricultural University, Nanjing
5、 210095; 2College of Tobacco Science, Henan Agricultural University, Zhengzhou 450002)Abstract: 【Objective】 The changes of the contents of carotenoids components, the related enzymes activities, and the aroma components degraded by which in flue-cured tobacco in the yellowing stage during the bulk-c
6、uring process were studied in order to provide a theoretical basis for optimization and perfection of curing technology. 【Method】 The effects of different temperature and humidity conditions on the degradation of carotenoids, the related enzymes activities in the yellowing stage and the contents of
7、aroma components in flue-cured tobacco during the bulk curing process were studied by using the electric-heated flue-curing barn designed and made by Henan Agricultural University. 【Result】 The results showed that the contents of carotenoids (-carotene, lutein, neoxanthin, violaxthin) decreased grad
8、ually in the yellowing stage during the bulk curing process. At the end of yellowing stage the -carotene contents of low temperature with low humidity (T1) and low temperature with middle humidity (T2) treatments were lower than others and the value of them were 17.14 gg-1 FW, 19.00 gg-1 FW, respect
9、ively. The contents of the lutein, neoxanthin, violaxthin decreased gradually in the yellowing stage following the decrease of temperature and humidity. The proportions of the -carotene to the xanthophylls (lutein, neoxanthin, violaxthin) of the low temperature treatments at the end of yellowing sta
10、ge were higher than fresh sample, on the contrary, high temperature treatments were lower. The proportions of the lutein to the xanthophylls of different treatments were higher than fresh sample, on the contrary, neoxanthin and violaxthin were lower. The carotenoids contents of T1, T2 treatments wer
11、e relatively lower than others, especially the T2 treatment, and its value was 76.31 gg-1 in flue-cured tobacco. The contents of aroma components of T2 treatment was the highest and its value was 87.5634 gg-1 in flue-cured tobacco while the content value of T1 treatment was 81.1192 gg-1, secondly. B
12、oth of them were higher than others obviously. The activities of lipoxygenase (LOX) and peroxidase (POD) could express fully under the T1, T2 treatments in the yellowing stage meanwhile the carotenoids degraded fully. Correlation analysis showed that the activities of peroxidase and the carotenoids
13、components were highly significant in the yellowing stage during the bulk curing process. 【Conclusion】 If the high activities of lipoxygenase and peroxidase were prolonged longer appropriately at 36-48 h under low temperature and relatively low humidity in the yellowing stage and the effect between
14、the cooperative and antagonism reach dynamic balance, it would be benefit to degrade carotenoids sufficiently and improve the aroma quality of tobacco leaves.Key words: bulk curing; yellowing stage; carotenoids; degradation mechanism; aroma components 0 引言【研究意义】密集烤房现已成为中国烤烟烘烤的发展方向。但是,过去人们过多关注于它的优势和综
15、合效益,而对密集烘烤烟叶香气质量有所降低等突出问题,没有给予足够的重视。完善密集烘烤工艺,更好地发挥密集烘烤的优势,提高烤后烟叶的香气质量,已经成为目前烟叶生产中亟待解决的问题1。类胡萝卜素是影响烟叶品质和可用性的主要成分之一,它不仅使中性香味物质总量增加,而且其降解产物继续发生转化,生成对香味物质更有用的化合物。烤后烟叶类胡萝卜素及其降解产物的含量和协调性,直接影响烤烟的香气风格、香气质和香气量2-4。因此,在国内外烟草行业中对类胡萝卜素及其降解香气成分的研究一直是个热点5-6。【前人研究进展】有关类胡萝卜色素的研究现状及结果,前人已有论述2,5,7-8。杨虹琦草药等4研究指出,烟草中的类胡
16、萝卜素与烟叶的香气、色泽及质量密切相关,是影响烤烟品质的重要潜香型物质之一。烘烤中变黄期不同温湿度处理对类胡萝卜素降解机理和相关香气成分有重要影响。类胡萝卜素在烘烤开始后2448 h降解速度较快,其中以40变黄处理降解最快,但烤后烟叶质量以38变黄处理综合表现最优。低湿变黄类胡萝卜素发生快速降解较早,峰值较高,高湿变黄发生快速降解较迟,峰值也较 低9-11。但高玉珍等12研究认为,低温中湿变黄烟叶类胡萝卜素降解多,香气物质含量高,烤后烟叶质量最优。延小东13和刘海轮14研究也认为,低温条件下慢变黄使类胡萝卜素降解较充分,烟叶内能形成更多致香物质。艾复清等15研究指出,控制变黄温度在3739、相
17、对湿度83.7%90%时,有利于提高烟叶的香吃味。另外,韦凤杰等5研究指出,烤烟成熟过程中类胡萝卜素变化及其降解香气物质种类、构成比例等可能是烟叶特色品质形成的重要物质基础。脂氧合酶(LOX)是烟叶类胡萝卜素降解的关键酶。低温慢变黄能使脂氧合酶(LOX)活性增强,并且LOX脂氧合酶与类胡萝卜素的降解呈高度正相关13-14。据宋朝鹏等16报道,过氧化物酶(POD)也参与了类胡萝卜素的氧化和降解。【本研究切入点】变黄期是烟叶类胡萝卜素物质降解和转化的重要时期,不同烘烤调控措施影响烟叶内类胡萝卜素酶的活性和表达时间,从而影响香气前体物的降解转化和最终的烟叶香气质量。目前有关类胡萝卜素降解产物的研究,
18、主要集中在对香气组分及烟叶品质和评吸质量的影响上。而有关烟叶类胡萝卜素降解规律和降解机理的研究多集中在发育、成熟和醇化等时期,针对密集烘烤变黄期类胡萝卜素降解机理及其降解香气成分含量变化的研究,国内外尚不多见。【拟解决的关键问题】本试验研究密集烘烤变黄期不同烘烤工艺对烤烟类胡萝卜素各组分(-胡萝卜素、叶黄质、新黄质和紫黄质)降解规律、相关酶活性及烤后烟叶香气成分含量变化的影响,旨在为密集烘烤工艺优化和完善提供理论依据。1 材料与方法1.1 试验材料试验于20072008年进行。试验材料取自河南省宜阳县。试验田土壤质地为红黏土,土壤肥力中等。供试品种为中烟100,5月5日移栽,种植行距120 c
19、m,株距50 cm。土壤碱解氮49.52 mgkg-1,速效磷6.8 mgkg-1,速效钾145.31 mgkg-1,pH 8.49。施纯氮45.0 kghm-2,NP2O5K2O=123。田间管理按优质烤烟栽培生产技术规范进行。以中部叶(第1112位叶)为试验材料,依据成熟标准,烟叶成熟时按照叶删除位单叶采收。1.2 试验设计采用河南农业大学设计的电热式温湿自控密集烤烟箱烘烤,烘烤时装烟密度为70 kgm-3。试验共设置6个处理:T1低温低湿变黄(干球温度3638,相对湿度70%75%);T2低温中湿变黄(干球温度3638,相对湿度80%85%);T3低温高湿变黄(干球温度3638,相对湿度
20、90%95%);T4高温低湿变黄(干球温度4042,相对湿度70%75%);T5高温中湿变黄(干球温度4042,相对湿度80%85%);T6高温高湿变黄(干球温度4042,相对湿度90%95%)。分别于烘烤开始(0 h)及烘烤后每12 h取样两份,一份切去叶尖和叶基部,留叶中部分用于生理指标的测定。另一份在烘箱中105杀青5 min,60烘干、粉碎,过60目筛,用于类胡萝卜素组分的测定。各重复3次。处理结束后,按照三段式烘烤技术转入正常烘烤。烤后取C3F中桔三(C3F中桔三)烟叶用于类胡萝卜素香气成分及组分的测定。1.3 测定内容与方法1.3.1 类胡萝卜素类物质含量测定 -胡萝卜素、叶黄质、
21、新黄质、紫黄质测定方法为反相高效液相色谱法。工作条件为:Auto system XLGC配FID检测器和自动进样器(美国PE公司),Turbo Mass色质联用仪(美国PE公司),甲醇为Sigma公司生产的色谱纯试剂,异丙醇为J. T. Baker公司生产的色谱纯试剂;-胡萝卜素植物色素标准物购于Sigma公司,叶黄质、新黄质、紫黄质植物色素标准物均购于日本WAKO公司。称取不同烘烤时期烤烟叶片杀青样品1 g,放入100 mL三角瓶,用60 mL 90 %丙酮(内含0.1 % BHT)于摇床振荡萃取30 min,过滤,滤渣用10 mL 90 %丙酮(内含0.1% BHT)洗涤23次,定容到10
22、0 mL,取其中6 mL到离心管,加入0.1 g醋酸铅,10 000 r/min 4低温离心5 min,用0.45 m针头过滤器过滤。计量单位为gg-1。整个测定过程在黑暗中进行。1.3.2 酶活性的测定 脂氧合酶(LOX)活性采用许长城等17的方法,过氧化物酶活性采用愈创木酚显色法18。1.3.3 香气成分定性定量分析条件 采用内标法测定烟叶类胡萝卜素香气成分。类胡萝卜素香气物质提取及定性定量分析采用HP5890-5972气质联用仪。粉末状烟叶样品水蒸气蒸馏二氯甲烷萃取(20 g烟样+1 g柠檬酸+350 mL蒸馏水+0.5 mL内标于500 mL圆底烧瓶中,再加60 mL二氯甲烷于另一25
23、0 mL圆底烧瓶中,60水浴加热250 mL圆底烧瓶,用同时蒸馏萃取仪蒸馏萃取。)无水硫酸钠干燥有机相60水浴浓缩至1 mL左右即得烟叶的精油。经前处理制备得到的分析样品,由GC/MS鉴定结果和NIST库检索定性。GC/MS分析条件如下:色谱柱:HP-5(60 m0.25 mm id0.25 m df);载气及流速:He 0.8 mLmin-1;近样口温度:250;传输线温度:280;离子源温度:177;升温程序:50,2 min后,以每分钟上升2的速度升至120,5 min后再以每分钟上升2的速度升至240,30 min;分流比和进样量115,2 L;电离能70 eV;质量数范围50500
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