X射线法无损测定造纸法再造烟叶涂布率

为了建立X射线法无损测定涂布率的方法,采用X射线定量仪对不同再造烟叶样品的定量进行测定,建立了定量指示值与定量实测值的线性回归模型,通过线性回归模型计算基片和再造烟叶成品的定量求得涂布率,并对该方法与烘箱法测定涂布率一致性进行了比较。结果表明:①再造烟叶成品和基片线性回归模型R~2均大于0.9,该仪器通过线性回归模型计算的定量值与国标法测定的定量值相对误差小于2%。②同品牌再造烟叶样品不同含水率状态下建立的线性回归模型相近。③X射线法和烘箱法测定涂布率一致性较好,其中配对t检验p值0.05、组内相关系数ICC值为0.989。④X射线法测定再造烟叶涂布率重复性实验中日内RSD值范围为0.133%～0.496%,日间RSD值范围为0.223%～0.486%,说明此方法重复性和精密度较好。     

活性染料的I/O值及其与染色性能的关系

活性染料的I/O值(无机性值/有机性值)与其染色性能有着一定的关系。文中通过无机性值、有机性值及I/O值的计算,探讨了计算值与染色性能以及染料拼色中的相容性、配伍性和重现性之间的关系,从而对选用染料带来很大方便。     

PAC及其复合物电荷密度的影响因素分析

研究了聚合氯化铝(PAC)的电荷密度与盐基度的关系、PAC及其复合物电荷密度的影响因素,并用PAC及其复合物作为施胶沉淀剂,以PAC及其复合物改性阳离子松香胶和AKD为施胶剂,在中碱性条件下进行施胶。结果表明,PAC及其复合物电荷密度对施胶有较大影响,在加入相同电荷量的PAC及其复合物时,高电荷密度PAC复合物比高纯PAC获得更高的施胶pH值和更满意的施胶度,PAC及其复合物改性阳离子松香胶对AKD的施胶有增效作用。     

响应面优化超声辅助提取羊栖菜中无机砷

采用盐酸作为提取剂,超声辅助提取法对羊栖菜中的无机砷进行提取,氢化物发生-原子荧光光谱法(HG-AFS)测定羊栖菜中的无机砷。为了优化羊栖菜中无机砷的提取工艺,在单因素试验基础上,利用Box-Behnken试验设计原理和响应面分析法,以荧光强度为响应值,选取浸提液浓度、超声提取温度和提取时间3个因素,研究各因素及其交互作用对荧光强度的影响。结果显示:无机砷的最佳提取条件为浸提液浓度6.6mol/L、提取温度53.4℃、提取时间24.4min,在此条件下,检测所得荧光强度为675.51,通过计算得无机砷含量为4.78mg/kg。     

广西主要食品中砷污染及居民膳食暴露风险评估

目的掌握广西主要食品中砷污染的水平,评估居民膳食无机砷暴露量及其潜在健康风险。方法利用2010-2015年广西主要食品中总砷及无机砷含量数据和食物消费量数据,采用简单分布评估的方法 ,计算广西居民膳食中无机砷暴露水平及其分布情况,并利用暴露限值(MOE)法评估其潜在健康风险。结果 16 567份食品样品中,总砷检出率为42.71%(4 735/11 087),无机砷检出率为48.07%(2 634/5 480)。总砷平均含量以海洋甲壳类最高,其次是海水鱼类和软体动物;检测无机砷食品样品中,平均含量为0.018~0.072 mg/kg,其中以大米无机砷平均含量最高。除大米、新鲜水果、蛋及其制品、畜禽内脏直接采用其检测的无机砷结果外,其他食品均通过总砷转换到无机砷而进行暴露评估。一般人群和高消费量人群膳食中无机砷的平均每天暴露量MOE值均1,但18~34岁男性组高消费量人群每天无机砷暴露量的MOE值≤1。大米的贡献率远高于其他食物,是居民膳食中无机砷的主要来源。结论广西居民膳食中无机砷暴露风险总体上是安全的,而对于18~34岁男性组高暴露量人群可能存在一定的健康风险,大米是广西居民的主要食品,大米的安全问题需加以关注。     

电荷检测在废纸浆造纸中的应用研究

用PCD(颗粒电荷测定仪)测定聚合物的电荷密度、浆料溶胶物质的阳离子需求量,用Zeta电位仪测定浆料的Zeta电位,并将这两种方法相结合探讨了浆料电荷特性及其影响因素.结果表明:PCD可以简单、快速,准确地测定聚合物的电荷密度;浆浓对阳离子需求有影响,PH值、离子浓度和填料都会影响旧瓦楞纸(Old CorrugatedContainers)浆料体系的电荷特性.     

评定棉丝光效果的新方法

作者用电子计算机对丝光棉织物的X射线衍射图谱进行分解,定量地计算出棉纤维在碱液作用下纤维素Ⅰ转化为纤维素Ⅱ衍射峰强度;从衍射峰强度积分面积比例和微晶取向,评定棉织物的丝光效果。通过在科研和生产实践中考验,表明这种方法是切实可行的。     

胶体金快速试纸条法测定小麦及其制品中呕吐毒素

用胶体金快速试纸条法测定小麦及其制品中呕吐毒素,方法快速,定量结果较为准确,回收率在86.67%~120%。与高效液相法进行比较,结果表明这2种方法对呕吐毒素的检测没有显著的差异,其回收率略高于高效液相法,但变异系数大。在较低浓度(1 500μg/kg)时,快速法与高效液相法有一定的线性关系Y=1.077 3X+83.786(Y为胶体金快速法测得值,X为高效液相法测得值,R~2=0.963 7)。     

高模量纤维

<正> 自从卡洛译斯二十世纪三十年代开发了可商品化的合成纤维以来,人们已认识到,其强度和模量远远低于理论最大值。该值是以计算为基础得出的,包括聚合物主链中原子的化学键力和构象力,也可以X射线数据模型计算,或者以其他资料得到。表1举例列出某些聚合物的数据。聚乙烯的模量和强度值远高于其它     

长江刀鲚呈鲜关键物质与无机离子的交互作用

为研究不同二元混合体系中长江刀鲚关键鲜味相关无机离子对关键呈鲜氨基酸(核苷酸)的增鲜作用规律,对采自江苏靖江永济港的产卵前长江刀鲚中关键鲜味相关无机离子和呈鲜组分运用不平衡完全区组设计进行二元交互感官试验,并计算各二元混合体系的鲜味强度。结果表明,其对鲜味贡献度的重要性排序为GMP (5′-单磷酸鸟苷二钠)=AMP (5′-腺苷一磷酸)相似文献   

Kinetic analysis of volatile formation in milk subjected to pressure-assisted thermal treatments

Volatile formation in milk subjected to pressure-assisted thermal processing (PATP) was investigated from a reaction kinetic analysis point of view to illustrate the advantages of this technology. The concentration of 27 volatiles of different chemical class in milk subjected to pressure, temperature, and time treatments was fitted to zero-, 1st-, and 2nd-order chemical reaction models. Temperature and pressure effects on rate constants were analyzed to obtain activation energy (E(a)) and activation volume (deltaV*) values. Hexanal, heptanal, octanal, nonanal, and decanal followed 1st-order kinetics with rate constants characterized by E(a) values decreasing with pressure reflecting negative deltaV* values. Formation of 2-methylpropanal, 2,3-butanedione, and hydrogen sulfide followed zero-order kinetics with rate constants increasing with temperature but with unclear pressure effects. E(a) values for 2-methylpropanal and 2,3-butanedione increased with pressure, that is, deltaV* > 0, whereas values for hydrogen sulfide remained constant, that is, deltaV* = 0. The concentration of all other volatiles, including methanethiol, remained unchanged in pressure-treated samples, suggesting large negative deltaV* values. The concentration of methyl ketones, including 2-pentanone, 2-hexanone, 2-heptanone, 2-octanone, 2-nonanone, 2-decanone, and 2-undecanone, was independent of pressure and pressure-holding time. PATP promoted the formation of few compounds, had no effect on some, and inhibited the formation of volatiles reported to be factors of the consumer rejection of "cooked" milk flavor. The kinetic behavior observed suggested that new reaction formation mechanisms were not likely involved in volatile formation in PATP milk. The application of the Le Chatelier principle frequently used to explain the high quality of pressure-treated foods, often with no supporting experimental evidence, was not necessary.     

Reactions of hydroxyl radical with humic substances: bleaching, mineralization, and production of bioavailable carbon substrates

In this study, we examine the role of the hydroxyl (OH*) radical as a mechanism for the photodecomposition of chromophoric dissolved organic matter (CDOM) in sunlit surface waters. Using gamma-radiolysis of water, OH* was generated in solutions of standard humic substances in quantities comparable to those produced on time scales of days in sunlit surface waters. The second-order rate coefficients of OH* reaction with Suwannee River fulvic (SRFA; 2.7 x 10(4) s(-1) (mg of C/L)(-1)) and humic acids (SRHA; 1.9 x 10(4) s(-1) (mg of C/L)(-1)) are comparable to those observed for DOM in natural water samples and DOM isolates from other sources but decrease slightly with increasing OH* doses. OH* reactions with humic substances produced dissolved inorganic carbon (DIC) with a high efficiency of approximately 0.3 mol of CO2/mol of OH*. This efficiency stayed approximately constant from early phases of oxidation until complete mineralization of the DOM. Production rates of low molecular weight (LMW) acids including acetic, formic, malonic, and oxalic acids by reaction of SRFA and SRHA with OH* were measured using HPLC. Ratios of production rates of these acids to rates of DIC production for SRHA and for SRFA were similar to those observed upon photolysis of natural water samples. Bioassays indicated that OH* reactions with humic substances do not result in measurable formation of bioavailable carbon substrates other than the LMW acids. Bleaching of humic chromophores by OH* was relatively slow. Our results indicate that OH* reactions with humic substances are not likely to contribute significantly to observed rates of DOM photomineralization and LMW acid production in sunlit waters. They are also not likely to be a significant mechanism of photobleaching except in waters with very high OH* photoformation rates.     

亚临界水提取热稳定脱脂米糠蛋白

利用亚临界水在不同温度（100～200 ℃）和时间（0～30 min）条件下提取热稳定脱脂米糠（heat stable defatted rice bran,HSDRB）中的蛋白质。研究在不同提取条件下提取物中蛋白质含量、总糖含量、氨基酸组成、 分子质量分布以及色差。结果表明：在提取温度175 ℃、提取时间30 min时,提取物中蛋白质及氨基酸的含量最 高,分别为50%和48.6 mg/g HSDRB;在此条件下,氨基酸具有最高的疏水性（1.8 kJ/mol）以及最高的必需氨基酸 含量（14.8 mg/g HSDRB）;温度对提取物颜色具有显著影响,L*值与提取物中蛋白质含量呈负相关关系,而a*值 与提取物中蛋白质含量呈正相关关系;提取物中的疏水性成分主要为小分子物质。     

Influence of electrostatics on the oxidation rates of organic compounds in heterogeneous Fenton systems

Electrostatic effects influence the oxidation rates of charged dissolved organic compounds in systems where the hydroxyl radical (*OH) is produced by the iron oxide-catalyzed decomposition of hydrogen peroxide (H2O2). Experiments were performed using goethite and the *OH probes 14C-labeled formic acid, 2-chlorophenol (2-CP), and nitrobenzene. At pH 4 and an ionic strength of 0.01 M, formic acid (pKa = 3.745) detected a steady-state concentration of *OH ([*OH]ss, calculated as a solution average) approximately 50 times higher than the two neutral probes did in the same systems, indicating significant enrichment of formate at the surface of the positively charged iron oxide where the *OH is being produced. Increasing the pH and ionic strength decreased formic acid oxidation rates by factors consistent with predicted decreases in electrostatic effects. In the presence of high 2-CP concentrations, the [*OH]ss measured by formic acid decreased with time, and goethite coagulation increased, due to loss of positive charge on the oxide surface as the oxidation products of 2-CP complexed surface Fe species. The [*OH]ss detected by 2-CP did not change significantly, indicating that neither goethite coagulation nor surface complexation of 2-CP oxidation products interfered with the rate of *OH generation; however, such an effect could have occurred in experiments using dissolved Fe instead of goethite. Model predictions of organic compound oxidation rates in mineral-catalyzed Fenton-like systems were improved by taking electrostatic effects into account.     

Humic substances are soft and permeable: evidence from their electrophoretic mobilities

Due to the complexity of the humic substances (HS), mathematical models have often been employed to understand their roles in the environment. Since no consensus exists with respect to the structure and conformation of the HS, models have alternatively given them properties corresponding to impermeable hard spheres or fully permeable polyelectrolytes. In this study, the hydrodynamic permeability of standard HS (Suwannee River fulvic, humic, and peat humic acids) are evaluated as a function of pH and ionic strength. A detailed theoretical model is used to determine the softness parameter (lambda0), which characterizes the degree of flow penetration into the HS on the basis of measured values of electrophoretic mobilities, diffusion coefficients, and electric charge densities. Their motion in an electric field is evaluated by a rigorous numerical evaluation of the governing electrokinetic equations for soft particles. The hydrodynamic impact of the polyelectrolyte chains is accounted for by a distribution of Stokes resistance centers and partial dissociation of the hydrodynamically immobile ionogenic groups distributed throughout the polyelectrolyte. The results demonstrate thatthe studied HS are small (radius ca. 1 nm), highly charged (500-650 C g(-1) when all sites are dissociated), and very permeable (typical flow penetration length of 25-50% of the radius, depending on pH). The HS also coagulate slightly when lowering the pH of the solution. Modeling of the HS as hard spheres with a charge and slip plane located at the surface is thus physically inappropriate, as are a number of analytical theories for soft particles that hold for low to moderate electrostatic potentials and large colloids. The shortcomings of these simpler approaches, when interpreting the electrophoretic mobilities of HS, are highlighted by comparison with rigorous theoretical predictions.     

Properties of low methoxyl pectin‐carboxymethyl cellulose based on montmorillonite nanocomposite films

In this study, the low methoxyl pectin‐carboxymethyl cellulose‐based montmorillonite (LMP‐CMC‐MMT, LCM) nanocomposite films with nine ratios of LMP:CMC (from 10:0 to 0:10) and different MMT contents (1–8 wt%) were prepared. The mechanical properties, colour, opacity and water vapour permeability (WVP) of composite films were investigated. The maximum of tensile strength (TS) of composite films was 39.85 ± 2.51 MPa at LMP:CMC ratio of 4:6 and 4 wt% MMT (LCM47), which indicated the formation of hydrogen bonds between MMT and LMP‐CMC. The reduction of WVP of the LCM47 composite film was 333% of that of the CMC film due to the tortuous path caused by MMT incorporation. LCM composite films had the higher b*‐ and ΔE*‐values and lower L*‐values in comparison with LMP‐CMC (LC) composite films. The LCM composite films showed a decrease in transparency as MMT content increased.     

挂面生产工序能力分析

为确定挂面生产线存在的质量波动和分析工序能力,测定生产过程中面团、面带、湿切面、干面条、成品挂面的质量性状.通过控制图分析其质量波动,计算受控工序的过程能力指数,确定质量波动点和过程能力不足的工序段.结果显示,监测18天内,面团水分含量和水分均匀度、面带③(压延结束后的面带)色泽a*值均匀度、成品挂面水分含量均有2次超出了控制图的控制限,面带③色泽a*值有3次,面条②(烘房二区运行后的面条)的水分含量有4次,干面条抗弯强度有6次超出了控制限;这7个指标存在异常质量波动.面带①(面团熟化复合形成的面带)的水分均匀度、面带②(二次熟化后的面带)的水分均匀度、面带③色泽L*值及其均匀度、面带③色泽b*值及其均匀度、挂面烹调时间及烹调损失均处于受控状态;面带①水分均匀度、面带③色泽b*值均匀度及挂面烹调损失过程能力指数分别为0.93、0.4和0.99,均小于1,工序能力不足.结果认为,挂面生产过程中,面团水分含量及其均匀度、面带③色泽a*值及其均匀度、干面条抗弯强度及成品挂面水分存在异常波动;面带①水分均匀度、面带③色泽b*值均匀度工序能力不足.     

卡拉胶和黄原胶对转谷氨酰胺酶处理PSE兔肉糜蒸煮损失与成胶能力的影响

通过添加卡拉胶和黄原胶以及转谷氨酰胺酶（transglutaminase,TG）处理,改进PSE兔肉糜的持水力和热诱导凝胶性质。以正常兔肉为对照,分别研究不同质量分数卡拉胶和黄原胶对TG处理PSE（肉色苍白、柔软、汁液渗出）兔肉糜蒸煮损失、热诱导凝胶强度以及色泽的影响。结果表明：添加质量分数为0～0.8%的卡拉胶对0.3%TG处理PSE和正常兔肉糜热诱导凝胶强度的提高作用没有显著影响,而蒸煮损失随卡拉胶质量分数的增加显著下降,L*值和a*值均明显下降;随着黄原胶质量分数的增加,PSE和正常兔肉的蒸煮损失显著减少,但凝胶强度均呈下降趋势,L*值和a*值均明显下降。在0.3%TG处理肉糜中分别添加质量分数为0.8%的卡拉胶或质量分数为0.05%～0.10%的黄原胶可显著降低蒸煮损失,并获得较好的凝胶效果。     

Effect of sunflower cake supplementation on meat quality of indigenous goat genotypes of South Africa

The effect of four castrated goat genotypes and sunflower cake supplementation on goat meat quality was determined. Supplemented Boer (BOR) and Xhosa-Boer cross (XBC) goats had significantly higher (P < 0.05) SLW and CDM than non-supplemented groups. The Xhosa lop-eared (XLE) and Nguni (NGN) goats had higher pH24 (P < 0.05) than BOR and XBC goats. For each genotype, the sunflower cake supplemented and non-supplemented goats had similar a* values, except for the XLE goats. In the XLE goats, the a* values were lower in the sunflower cake supplemented goats. Sunflower cake supplemented BOR goats had higher L*values than their non-supplemented counterparts (P < 0.05). The sunflower cake supplemented BOR and NGN goats also had higher b* values as compared to their non-supplemented counterparts. In comparison with the Boer goat, the XLE and NGN goats had lower CDM, L* and WBF values but generally had higher CL and a* values. Sunflower cake supplementation improved meat quality attributes of the goats.     

EFFECT OF ADJUNCTS ON THE COLOR STABILITY OF BOLOGNA AND FRESH BEEF SAUSAGES

Alpha tocopherol (a-T), sodium tripolyphosphate (STPP), ascorbic acid (AA), copper gluconate (CG), sodium suljite (SS), sodium erythorbate (SE), citric acid (CA) and tetrasodium pyrophosphate (TS) were added in various combinations to formulations of fresh beef sausage and bologna. Fresh beef sausages containing SS had higher (P < 0.05) Hunter a* values during storage under light at 4C. Bologna containing AA + CG had higher (P < 0.05) Hunter a* values, lower (P < 0.05) Hunter L* and b* values and hue angle, and a slower (P < 0.05) decline in a* and increase in b* values and hue angle during storage. Bologna containing AA + CG had a lower (P < 0.001) cook yield and higher (P < 0.05) compressive strength. Bologna containing phosphates had a higher cook yield and pH, and lower (P < 0.05) compressive strength.