改性大豆分离蛋白产品功能性及机理的研究

利用氮气和谷氨酰胺转胺酶(MTG)对大豆分离蛋白(SPI)进行复合改性.复合改性SPI的吸水性、保水性和吸油性分别比对照提高了121%、222%和150%;溶解性比对照降低了36%.经MTG改性后SPI可在分子间生成共价键,形成相对分子量较大的聚合物.复合改性可在MTG改性的基础上进一步增加SPI分子间的交联程度.     

谷氨酰胺转胺酶对大豆分离蛋白改性机理的研究

利用微生物谷氨酰胺转胺酶(MTG)对大豆分离蛋白(SPI)进行改性，结果表明：SPI浓度、MTG浓度、反应温度、反应时间和pH值对SPI改性具有显著影响。改性SPI的凝胶性为11．6kcp，比对照提高了1833％。十二烷基硫酸钠-聚丙稀酰胺凝胶电泳结果表明，经MTG改性，SPI可在分子间生成共价键，形成相对分子量较大的聚合物，从而增加了SPI的凝胶性。     

氮气对改性大豆分离蛋白功能性的影响

利用氮气对大豆分离蛋白(SPI)进行改性，研究结果表明充氮气、反应温度、反应时间、充氮量四因素对SPI改性均有影响。通过正交试验确定了经氮气改性的SPI凝胶性、保水性、乳化性和乳化稳定性的4组最佳处理组合。试验表明改性后SPI的凝胶性、保水性、乳化性和乳化稳定性分别比对照样提高了100％、210％、7％和91％。     

谷氨酰胺转胺酶对大豆分离蛋白改性机理的研究

利用微生物谷氨酰胺转胺酶 (MTG)对大豆分离蛋白 (SPI)进行改性 ,结果表明 :SPI浓度、MTG浓度、反应温度、反应时间和pH值对SPI改性具有显著影响。改性SPI的凝胶性为11 6kcp ,比对照提高了 1833%。十二烷基硫酸钠 -聚丙稀酰胺凝胶电泳结果表明 ,经MTG改性 ,SPI可在分子间生成共价键 ,形成相对分子量较大的聚合物 ,从而增加了SPI的凝胶性。     

氮气对改性大豆分离蛋白功能性的影响

利用氮气对大豆分离蛋白 (SPI)进行改性 ,研究结果表明充氮气、反应温度、反应时间、充氮量四因素对SPI改性均有影响。通过正交试验确定了经氮气改性的SPI凝胶性、保水性、乳化性和乳化稳定性的 4组最佳处理组合。试验表明改性后SPI的凝胶性、保水性、乳化性和乳化稳定性分别比对照样提高了 10 0 %、 2 10 %、 7%和 91%。     

酶复合改性大豆分离蛋白相关功能性研究

利用微生物中性蛋白酶、微生物谷氨酰转氨酶(MTG)二者复合改性大豆分离蛋白(SPI),结果发现,双酶复合改性SPI的溶解性、吸水性、保水性和吸油性相关功能性显著增加,分别比对照提高了26.5%、48%、173%、35%,并经电镜观察改性SPI微观结构,探讨了SPI改性机理。     

谷氨酰胺转胺酶改性大豆分离蛋白在低能量肉制品中应用的研究

利用谷氨酰胺转胺酶(MTG)对大豆分离蛋白(SPI)进行改性,并将改性SPI应用于低能量肉制品中。实验表明:除常温黏度外,改性SPI的其他功能性明显优于市售肉用SPI;改性SPI在低能量肉制品中适宜的添加量为5%,改性SPI使产品的固体脂肪乳化稳定性、得率分别比肉用SPI提高了14%和7%,产品的感官指标也明显好于肉用SPI。     

微波处理对大豆分离蛋白某些功能性的影响

采用微波处理对大豆分离蛋白(SPI)进行改性,探讨了微波功率、微波处理时间、料液比、pH值对SPI功能性的影响。结果表明:微波处理对SPI的溶解性、乳化性、乳化稳定性影响显著。微波处理的最佳条件为:微波功率600W,反应时间2min,料液比为1:11,pH值为10。改性后SPI的溶解性、乳化性和乳化稳定性分别比对照提高32.15%、58.87%和56.54%。     

大豆分离蛋白的复合改性及其对某些功能性的影响

利用中性蛋白酶和微生物谷氨酰胺转胺酶(MTG)对大豆分离蛋白进行复合改性,通过单因素实验和正交实验研究,获得改性SPI最佳凝胶性的反应条件为:添加中性蛋白酶0.003%,水解20min;添加MTG0.5%,作用2.0h。获得最佳溶解性的反应条件为:添加中性蛋白酶0.005%,水解30min;添加MTG0.3%,作用1.0h。正交实验结果表明,双酶复合改性的最佳处理组合为添加中性蛋白酶0.005%,水解30min;添加MTG0.5%,作用1.0h,得到产品凝胶性为4226cp,比对照提高了36.3%,溶解性为70.1%,比对照降低了5.8%。     

谷氨酰胺转胺酶改性谷朊粉的研究

本文利用谷氨酰胺转胺酶(MTG)对谷朊粉(WG)进行改性,并将改性后的WG添加到低筋小麦面粉中,对面粉的流变学特性进行了系统的研究。结果表明:改性WG的凝胶性、乳化性、乳化稳定性、发泡性、泡沫稳定性分别比对照提高了96.7%、43.5%、39.1%、32.0%和75.9%。将改性谷朊粉添加到低筋面粉中,面粉的吸水率、稳定时间、形成时间、评价值、抗延伸性阻力50mm和Max处,分别比对照提高了7.2%、369.6%、121.7%、19.6%、184.3%和150.6%;软化度、延伸性分别比对照降低了63.6%和57.2%。MTG对WG中的球蛋白、醇溶蛋白、麦谷蛋白有交联作用,其中对麦谷蛋白的交联作用最明显。     

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.