顶空固相微萃取法测定果酒中的挥发性成分

应用顶空固相微萃取法(HS-SPME)和气质联用(GC-MS)研究果酒中的挥发性成分.在3种果酒中共检测到95种挥发性成分,鉴定出73种;在梅酒、荔枝酒、枸把酒中分别鉴定出46种、52种、50种化合物,有23种化合物是3种果酒中共有的成分.通过TIC峰面积归一化定量发现辛酸乙酯、辛酸以及β-苯乙醇等成分是3种果酒中的主要挥发性成分.     

蓝莓酒主发酵前后挥发性成分变化的GC-MS分析

为研究蓝莓酒主发酵前、后挥发性成分的变化,采用固相微萃取(SPME)结合气相色谱-质谱(GC-MS)联用技术,分别测定了蓝莓主发酵前、后的挥发性成分。结果表明:主发酵前共检出挥发性成分36种,主要为萜类(11种)、醇类(12种)、酯类(8种)和酸类(3种)等;主发酵后共检出挥发性成分46种,主要为醇类(7种)、酯类(13种)、萜类(13种)、酸类(4种)和烃类(8种)等。与主发酵前相比,主发酵后有21种化合物消失,有31种新增的化合物,还有15种化合物在主发酵前后均有检出。研究表明,主发酵过程是完成蓝莓酒由果汁到果酒的主要香气变化阶段。     

气相色谱-质谱联用法和高效液相色谱法测定4种人参酒中的皂苷和挥发性成分

目的 探究不同种人参醇提物中皂苷和挥发性成分的差异。方法 将四种参粉碎后用乙醇浸泡后,经顶空固相微萃取 (Headspace solid phase microextraction)结合气相色谱-质谱联用法（Gas chromatography-mass spectrometry）测定其挥发性成分,再用高效液相色谱法（High performance liquid chromatography）测定其皂苷成分。结果 分别在红参、西洋参、鲜参和生晒参酒中检测出39种、28种、39种和28种挥发性成分,其中白菖烯、(E)-β-金合欢烯、表蓝桉醇为共有的挥发性成分,倍半萜类化合物是人参酒的主要化合物,相对含量分别为42.3%、37.71%、46.25%和54.68%;分别在红参、西洋参、鲜参和生晒参酒分别检测出11种、9种、13种和9种皂苷,其中Rg3仅在红参酒中检测出。结论 4种参酒中的皂苷种类和挥发性成分均有差异,红参酒和鲜参酒呈现出更多种类的皂苷和挥发性成分。     

百香果全果与果汁发酵酒滋味成分及香气成分对比

目的：提升百香果酒品质。方法：以百香果全果和果汁为原料酿制百香果酒,分别测定其有机酸、氨基酸和挥发性化合物含量,并结合电子舌试验结果评价百香果酒风味成分。结果：2种百香果发酵酒中主要有机酸为酒石酸、柠檬酸、乳酸和苹果酸,但全果酒的前3种有机酸含量均显著高于果汁酒中的（P<0.05）,全果酒和果汁酒中含量最多的有机酸分别为酒石酸（27.20 mg/mL）和柠檬酸（12.49 mg/mL）;除半胱氨酸未检出外,全果酒和果汁酒中16种游离氨基酸总含量分别为88.16,68.88 mg/100 g,且全果酒中4类呈味氨基酸含量高于果汁酒;电子舌测试发现,2种百香果发酵酒中咸味信号强度差异性最大,且全果酒中的鲜味、咸味最强,酸味、涩味和甜味最弱;HS-SPME-GC-MS共检出179种香气成分,全果酒中挥发性风味化合物种类比果汁酒多4种,但其萜烯类物质含量和种类分别比果汁酒的多1,3倍。结论：相比于果汁酒,新型百香果全果酒整体风味（鲜味、咸味、萜烯类物质等）较突出,提升了百香果资源的综合利用度。     

发酵菌种对打瓜酒风味的影响

研究采用GC-MS、电子鼻技术和感官评价结合的方法评价发酵菌种对打瓜酒风味的影响。研究分别使用红葡萄酒果酒专用酵母、果酒专用酿酒酵母、葡萄酒活性干酵母和酒曲酵母为发酵菌种,对打瓜汁进行发酵、陈酿,比较4种打瓜酒中挥发性物质组成和风味特征。结果显示4种打瓜酒中分别检测出21、23、28和18种挥发性成分,红葡萄酒果酒专用酵母发酵打瓜酒主要挥发性成分为乙酸异戊酯（17.2%）,果酒专用酿酒酵母和葡萄酒活性干酵母发酵打瓜酒主要挥发性成分为癸酸乙酯（22.7%和18.8%）,酒曲酵母发酵打瓜酒主要挥发性成分为辛酸乙酯（18.3%）;电子鼻检测发现酒曲酵母发酵打瓜酒与其它3种打瓜酒风味存在显著性差异,其油脂香和草香气较明显。结合GC-MS、电子鼻和感官评价结果,发现采用葡萄酒活性干酵母生产的打瓜酒总体风味最佳,香气浓郁、酒香和果香协调。      

酵母及原料品种对猕猴桃酒挥发性成分的影响

以3种(红阳、徐香、金艳)猕猴桃为原料,分别接种EC1118单菌株,EC1118与FLAVIA双菌株进行发酵,利用顶空固相微萃取技术和气相-质谱联用技术(HS-SPME-GC-MS)对陈酿3个月的酒样进行测定,分析酵母和原料品种对猕猴桃酒挥发性成分的影响。结果表明,6种猕猴桃酒共鉴定出88种挥发性成分,这些物质主要是醇类、酯类以及酸类。其中,EC1118单菌株发酵制得的红阳、金艳、徐香猕猴桃酒分别检测出62种、52种、44种挥发性成分,共有成分32种;EC1118与FLAVIA双菌株发酵制得的红阳、金艳、徐香猕猴桃酒分别检测出66种、61种、53种挥发性成分,共有成分35种。双菌株产生的挥发性成分总量更高,红阳、金艳、徐香3种酒样挥发性成分总量分别为412.22、301.53、336.77 μg/L。红阳猕猴桃酒检出的挥发性成分种类高于金艳猕猴桃酒,而徐香猕猴桃酒的种类最少。因此,红阳及双菌种发酵制得的猕猴桃酒的风味更好。     

顶空-固相微萃取-气质联用分析咂酒挥发性成分

采用顶空-固相微萃取对咂酒中挥发性成分进行提取,通过气相色谱-质谱联用技术对提取出的挥发性成分进行定性和定量分析。结果表明:从咂酒中共鉴定出挥发性成分50种,其中酯类和醇类是咂酒中种类和含量最多的两种挥发性物质,分别为20种和15种。咂酒中的主要挥发性化合物有异戊醇(19.48%)、乙酸乙酯(17.78%)、丁二酸二乙酯(14.73%)、辛酸乙酯(10.95%)、乙酸戊酯(9.51%)、癸酸乙酯(5.92%)、异丁酸(5.91%)、己酸乙酯(3.07%)。     

3种酵母发酵橄榄酒的发酵规律及香气分析

以橄榄为原料,分别利用三种酵母对橄榄酒进行发酵,研究橄榄酒整个发酵过程中酒精度、还原糖及酸度的变化规律;采取顶空固相微萃取和气相色谱质谱联用法对橄榄酒的香气成分进行分析比较。结果表明:三种酵母发酵过程中橄榄酒酒精度均逐渐上升,还原糖含量逐渐降低,酸度先上升后下降;果酒干酵母发酵周期最短,最终果酒酵母1383所酿橄榄酒酒精度最高,残留还原糖含量最低,酸度最低;同时果酒酵母1383、果酒干酵母和果酒酵母1596发酵的橄榄酒分别检出50、49、52种香气成分,其中相同的有35种,三种酒样的主要香气成分均为异戊醇。初步确定果酒酵母1383酿制的橄榄酒最优。      

桑椹果酒挥发性成分的GC/MS分析

利用顶空固相微萃取方法对桑椹果酒中的挥发性成分进行提取,并用气相色谱-质谱技术(GC-MS)对化合物进行分析和分类,并经过NIST 05谱库检索对比。结果表明:在桑椹果酒中共检测出52种挥发性成分,主要有醇类9种、酯类14种、酸类8种、醛类3种、烷烃类9种、酚类2种、烯烃类2种、酮类3种及其他化合物2种。其中醇类、酯类、酸类和醛类化合物的含量最高,分别为54.26%、23.62%、11.22%和7.96%。     

不同酿酒酵母发酵桃果酒香气成分研究

采用SPME-GC-MS技术分析选育酿酒酵母J11和4株商品活性干酵母分别酿造的桃果酒,5种桃果酒共检测出100种挥发性香气物质,包括醇类、酯类、酸类、羰基化合物、苯系化合物以及萜类化合物。结果表明醇类和酯类是桃果酒挥发性物质的主要组分,异戊醇、辛酸乙酯、癸酸乙酯以及9-癸烯酸乙酯是桃果酒的主要香气物质。5种桃果酒中,选育酵母J11酿造的果酒更好地保留了桃果实自身的风味,且其香气物质的种类和含量都是最高的,证明与其他4种商品酵母比较,选育酵母J11更适合桃果酒的酿造。      

Arsenic(III) oxidation by iron(VI) (ferrate) and subsequent removal of arsenic(V) by iron(III) coagulation

We investigated the stoichiometry, kinetics, and mechanism of arsenite [As(III)] oxidation by ferrate [Fe(VI)] and performed arsenic removal tests using Fe(VI) as both an oxidant and a coagulant. As(III) was oxidized to As(V) (arsenate) by Fe(VI), with a stoichiometry of 3:2 [As(III):Fe(VI)]. Kinetic studies showed that the reaction of As(III) with Fe(VI) was first-order with respect to both reactants, and its observed second-order rate constant at 25 degrees C decreased nonlinearly from (3.54 +/- 0.24) x 10(5) to (1.23 +/- 0.01) x 10(3) M(-1) s(-1) with an increase of pH from 8.4 to 12.9. A reaction mechanism by oxygen transfer has been proposed for the oxidation of As(III) by Fe(VI). Arsenic removal tests with river water showed that, with minimum 2.0 mg L(-1) Fe(VI), the arsenic concentration can be lowered from an initial 517 to below 50 microg L(-1), which is the regulation level for As in Bangladesh. From this result, Fe(VI) was demonstrated to be very effective in the removal of arsenic species from water at a relatively low dose level (2.0 mg L(-1)). In addition, the combined use of a small amount of Fe(VI) (below 0.5 mg L(-1)) and Fe(III) as a major coagulant was found to be a practical and effective method for arsenic removal.     

Iron(VI) and iron(V) oxidation of copper(I) cyanide

Copper(Il) cyanide (Cu(CN)4(3-)) in the gold mine industry presentsthe biggest concern in cyanide management because it is much more stable than free cyanide. Cu(CN)4(3-) is highlytoxic to aquatic life; therefore, environmentally friendly techniques are required for the removal of Cu(CN)4(3-) from gold mine effluent. The oxidation of Cu(CN)4(3-) by iron-(VI) (FeVIO4(2-), Fe(VI)) and iron(V) (FeVO4(3-), Fe(V)) was studied using stopped-flow and premix pulse radiolysis techniques. The stoichiometry with Fe(VI) was determined to be 5HFeO(4-) + Cu(CN)4(3-) + 8H2O - > 5Fe(OH)3 + Cu2+ + 4CNO- +3/202 + 6OH-. The rate law for the oxidation of Cu(CN)4(3-) by Fe(VI) was found to be first-order with each reactant. The rates decreased with increasing pH and were mostly related to a decrease in concentration of reactive protonated Fe(VI) species, HFeO4-. A mechanism is proposed that agrees with the observed reaction stoichiometry and rate law. The rate constant for the oxidation of Cu(CN)4(3-) by Fe(V) was determined at pH 12.0 as 1.35 +/- 0.02 x 10(7) M(-1) s(-1), which is approximately 3 orders of magnitude larger than Fe(VI). Results indicate that Fe(VI) is highly efficient for removal of cyanides in gold mill effluent.     

Mind the (yield) gap(s)

This paper explores the origin of the notion of ??yield gap?? and its use as a framing device for agricultural policy in sub-Saharan Africa. The argument is that while the yield gap of policy discourse provides a simple and powerful framing device, it is most often used without the discipline or caveats associated with the best examples of its use in crop production ecology and microeconomics. This argument is developed by examining how yield gap is used in a selection of recent and influential agricultural policy documents. The message for policy makers and others is clear: ??mind the (yield) gap(s)??, for they are seldom what they appear.     

Supercritical fluid extraction (SFE) of 4(5)-methylimidazole (4-MeI) and 2-acetyl-4(5)-(1,2,3,4)-tetrahydroxybutyl-imidazole (THI) from ground-coffee with high-performance liquid chromatographic-electrospray mass spectrometric quantification (HPLC/ESI-MS).

Two polar analytes, 4(5)-methylimidazole (4-MeI) and 2-acetyl-4(5)-(1,2,3,4)-tetrahydroxybutyl-imidazole (THI), were extracted with supercritical carbon dioxide (CO2) modified with aqueous methanol. The method was applied to a roasted coffee powder with good recovery rates. Method efficiency was compared with that of solid-phase extraction using SCX Disc cartridges and validated for spiked solid matrix. The analytes were determined using isocratic liquid chromatography-mass spectrometry (LC/MS) on an Atlantis HILIC Silica column (150 x 2.1 mm, 3 microm) with 80% methanol and 20% 0.01 mol l-1 ammonium formate as the mobile phase. The limit of quantification was around 1.5 pg for 4-MeI and 2.0 pg for THI. The linearity of the calibration curves was satisfactory as indicated by correlation coefficients of >0.999. The coefficient of variation for the intra-day and inter-day precisions was <4% (n = 6). Accuracy was in the range 98-101%; recovery rates were > or = 98 and > or = 99% for THI and 4-MeI, respectively. Several samples of Arabica coffee from various locations and commercially available 'off-the-shelf' coffee products (Arabica/Robusta mixtures) were analysed to test the method.     

Reduction of Tc(VII) by Fe(II) sorbed on Al (hydr)oxides

Under oxic conditions, Tc exists as the soluble, weakly sorbing pertechnetate [TcO4-] anion. The reduced form of technetium, Tc(IV), is stable in anoxic environments and is sparingly soluble as TcO2 x nH2O(s). Here we investigate the heterogeneous reduction of Tc(VII) by Fe(II) adsorbed on Al (hydr)oxides [diaspore (alpha-AlOOH) and corundum (alpha-Al2O3)]. Experiments were performed to study the kinetics of Tc(VII) reduction, examine changes in Fe surface speciation during Tc(VII) reduction (M?ssbauer spectroscopy), and identify the nature of Tc(IV)-containing reaction products (X-ray absorption spectroscopy). We found that Tc(VII) was completely reduced by adsorbed Fe(II) within 11 (diaspore suspension) and 4 days (corundum suspension). M?ssbauer measurements revealed thatthe Fe(II) signal became less intense with Tc(VII) reduction and was accompanied by an increase in the intensity of the Fe(III) doublet and magnetically ordered Fe(III) sextet signals. Tc-EXAFS spectroscopy revealed that the final heterogeneous redox product on corundum was similar to Tc(IV) oxyhydroxide, TcO2 x nH2O.     

优质农业生产管理指导手册

优质农业生产管理体系(GAP)概念提出的目的在于确保烟叶生产的持续、健康发展,可以将GAP定义为:在保护、维持或增强土壤、水源、空气、动植物生命和环境的同时,在确保农业生产可持续发展的条件下,推行一系列农业措施,生产出一定产量和质量的优质农作物.     

优质农业生产管理指导手册(二)

4病虫害综合防治 病虫害综合防治(IPM)是烟叶生产的一项系统体系,利用病虫害预测预报系统,提供最好的病虫害综合防治决策,重点是协调应用一切可行的办法.病虫害综合防治并不意味着完全排除使用农药,而是在使用其它办法不能使病虫害的种群数保持在可接受的范围时适当使用农药.施用农药的地方应确保安全,并遵守一切法律法规.     

优质农业生产管理指导手册(三)

7 烘烤（调制）和烤房管理 烟叶的正确烘烤和烤房管理对优化烟叶的产量、质量和产值来说是非常关键的因素。烟叶烘烤是保持烟叶产量、质量的最后一道环节。烟叶质量会因烘烤不当而降低，而正确进行烘烤能确保烟叶质量的稳定。然而，若将劣质的鲜烟叶或烟株放入烤房，则不可能提高最终的烟叶质量。     

Reactivity of Pb(II) at the Mn(III,IV) (oxyhydr)oxide--water interface

In this study, the reactivity of lead (Pb(II)) on naturally occurring Mn(III,IV) (oxyhydr)oxide minerals was evaluated using kinetic, thermodynamic, and spectroscopic investigations. Aqueous Pb(II) was more strongly adsorbed to birnessite (delta-MnO1.7) than to manganite (gamma-MnOOH) under all experimental conditions. The isoteric heat of Pb adsorption (delta HT) or birnessite was 94 kJ mol-1 at a surface loading of 1.1 mmol g-1, and decreased with increasing adsorption density. This indicated that adsorption was an endothermic process and that birnessite possessed heterogeneous sites of reactivity for Pb. X-ray absorption fine structure (XAFS) spectra revealed that Pb was adsorbed as inner-sphere complexes on both birnessite and manganite with no evidence to suggest oxidation as an operative sorption mechanism. Lead appeared to coordinate to vacancy sites in the birnessite layer structure with concurrent release of Mn to solution, which resulted in a greater number of second shell Mn scatterers in Pb-birnessite when compared to Pb-manganite samples. The difference in Pb coordination apparently explained the contrasting desorption behavior between the two Mn minerals. These results have significant implications for Pb partitioning in soil environments containing solid-phase Mn(III,IV) (oxyhydr)oxides.