Continuous monitoring of dough fermentation and bread baking by magnetic resonance microscopy

The consumer quality of baked products is closely related with dough structure properties. These are developed during dough fermentation and finalized during its baking. In this study, magnetic resonance microscopy (MRM) was employed in a study of dough fermentation and baking. A small hot air oven was installed inside a 2.35-T horizontal bore superconducting magnet. Four different samples of commercial bread mixes for home baking were used to prepare small samples of dough that were inserted in the oven and allowed to rise at 33°C for 112 min; this was followed by baking at 180°C for 49 min. The entire process was followed by dynamic T₁-weighted 3D magnetic resonance imaging with 7 min of temporal resolution and 0.23×0.23×1.5 mm³ of spatial resolution. Acquired images were analyzed to determine time courses of dough pore distribution, dough volume and bread crust thickness. Image analysis showed that both the number of dough pores and the normalized dough volume increased in a sigmoid-like fashion during fermentation and decreased during baking due to the bread crust formation. The presented magnetic resonance method was found to be efficient in analysis of dough structure properties and in discrimination between different dough types.     

Effect of ultrasound-assisted dough fermentation on the quality of dough and steamed bread with 50% sweet potato pulp

Ultrasound at an intensity of 17.5, 20.0, 22.5, 25.0 and 27.5 W/L was used to assist dough fermentation to prepare steamed bread with 50% sweet potato pulp (SB-50% SPP), which was compared with SB-50% SPP without ultrasonic treatment. The dough rheology, starch–gluten network, texture characteristics and sensory quality of steamed bread with different ultrasonic power densities (UPDs) were investigated. Dough samples at UPD of 22.5 W/L showed optimal viscoelasticity. The microstructure images exhibited that the content of starch particles wrapped in the gluten network increased significantly after sonication. In addition, the reduction in free sulfhydryl (SH) content and increase in wet gluten content after ultrasonic treatment led to significantly improved dough extensibility (p < 0.05). Results exhibited that the specific volume of SB-50% SPP increased by 13.93% and the hardness decreased by 21.96% compared with the control under UPD of 22.5 W/L. This study suggested that the application of ultrasound as a green technology to dough fermentation could lead to SB-50% SPP with good quality and sensory characteristics.     

Characterization of water distribution in bread during storage using magnetic resonance imaging

A soy bread of fully acceptable quality and containing 49% soy ingredients (with or without 5% almond powder) has been recently developed in our laboratory.

An investigation on water distribution and mobility, as probed by proton signal intensity and T₂ magnetic resonance images, during storage was designed to examine possible relations between water states and hindered staling rate upon soy or soy–almond addition.

Water proton distribution throughout soy-containing loaves was found to be very homogeneous in fresh breads with and without almond, with minimal water migration occurring during prolonged storage. In contrast, traditional wheat bread displayed an inhomogeneous water proton population that tended to change (with higher moisture migration towards the outer perimeter of the slice) during storage. Similar results were found for water mobility throughout the loaves, as depicted in T₂ images. On intensity images of all considered bread varieties, the outer perimeter corresponding to the crust exhibited lower signal intensity due to decreased water content. Higher T₂ values were found in the crust of soy breads with and without almond, which were attributed to lipids.

The results indicated that the addition of soy to bread improved the homogeneous distribution of water molecules, which may hinder the staling rate of soy-containing breads. However, incorporation of almond had little effect on the water proton distribution or mobility of soy breads.     

应用ICP-MS分析猪污物中铅砷镉的形态分布

为有效控制资源化过程中畜禽污物所含重金属对环境和人类健康的危害,需要监测污物中重金属的赋存形态和浓度。采集北京昌平种猪场的猪污物样品(鲜样和干清样),用BCR提取法、硝酸-高氯酸消化法和ICP-MS仪器检测铅砷镉(Pb,As,Cd)总量及各形态含量。结果表明,猪污物中Pb,As,Cd的总量分别为29.0,28.2和0.288 mg·kg-1 DW(鲜样)以及19.7,28.2 和0.134 mg·kg-1 DW(干清样),均没有超过我国的城镇垃圾农用控制标准(As接近标准值)。两类样品中重金属的形态分布规律明显不同：鲜样中三种金属可交换态及碳酸盐结合态均超过50%,有机物及硫化物结合态则低于20%;而干清样中高生态毒性的可交换态及碳酸盐结合态和Fe/Mn氧化物结合态的比例较鲜样中都明显降低(降幅可达20%以上),表明干清样用于堆肥对农田更安全。该研究结果将为北京地区养猪场污物的资源开发和生态安全评价提供重要基础数据。     

电感耦合等离子体质谱法测定城市污泥中重金属的活性形态

以沈阳北部、满堂河、仙女河三个污水处理厂的污泥为研究对象,选择水、醋酸和不同极性的有机溶剂对其进行浸提分离,采用ICP-MS测定了污泥中主要污染的重金属元素各活性形态的含量,并探讨了Cr,Cu,Zn,Cd和Pb随环境条件的改变其活性形态含量的变化规律及其影响因素。结果表明：城市污泥中重金属的醋酸浸提态含量较高,水溶态含量较低,二者随时间和温度条件的变化呈一致的规律性,有机浸提态重金属的含量与溶剂极性大小呈正相关性。醋酸浸提态重金属在迁移转化过程中具有较大活性,同一形态重金属的活性次序为：水溶态Zn＞Cu＞Cd＞Pb＞Cr,醋酸浸提态Cd＞Cr＞Cu＞Zn＞Pb,有机浸提态Pb＞Cd＞Cr＞Cu＞Zn。     

软玉中结构水类型和近红外光谱解析

利用傅里叶变换近红外光谱分析技术, 对源自国内外不同产地的软玉进行了测试与分析。结果表明在7 000～7 400 cm-1波数范围内,部分产地的软玉中出现四个由羟基倍频振动致近红外吸收谱带,分别归属OH(Mg MgMg),OH(MgMgFe2+),OH(MgFe2+Fe2+),OH(Fe2+Fe2+Fe2+)的倍频振动所致, 并与软玉中透闪石矿物晶体结构中M1和M3位置的Mg2+,Fe2+占位有关。随着透闪石中Fe2+/(Fe2++ Mg2+)比值的增大,亦可导致软玉中羟基NIR谱带的进一步分裂,谱带数目和强度增加,并向低波数方向位移。文中对软玉中羟基NIR光谱的产地鉴别意义一并给予了讨论。     

ICP-MS/ICP-AES测定小麦穗离体培养籽粒营养元素及重金属含量

环境中重金属污染会导致谷物营养缺乏、代谢紊乱.借助ICP-MS/ICP-AES系统和离体穗培养方法,准确测定灌浆期不同浓度铜、镉(0,5,15,45 mg·L-1)处理对籽粒营养元素及重金属元素含量的影响.结果显示,不司浓度铜、镉处理显著降低小麦粒重;外源铜促进了籽粒P,K,Mg,Ca,Na,Mn和Zn含量的增加,抑制了 Fe和B的吸收.镉的加入对小麦籽粒P,K,Ca,Mg和Mn的吸收起促进作用,然而对Na,Fe,Zn和B的吸收起拮抗作用.外源铜、镉抑制小麦籽粒对Hg的积累,但籽粒Cu和Cd含量最高分别超过国家食品卫生标准的55和62倍,存在极大安全隐患.     

Preparation and characterization of type 3 resistant starch by ultrasound-assisted autoclave gelatinization and its effect on steamed bread quality

In this study, we aimed to establish an innovative and efficient preparation method of potato resistant starch (PRS). To achieve this, we prepared type 3 resistant starch (RS3) from native potato starch (PS) using an ultrasonic method combined with autoclave gelatinization and optimized by the response surface method to study the structure and properties of potato RS3 (PRS3) and its effect on the quality of steamed bread. Under optimal treatment conditions, the PRS3 content increased from 7.5% to 15.9%. Compared with PS, the B-type crystal structure of PRS3 was destroyed, and the content of hydroxyl groups was increased, but no new chemical groups were introduced. PRS3 had a rougher surface and a lower crystallinity, gelatinization temperature, viscosity, setback value, and breakdown value. The low content (5%) of PRS3 had a stable viscosity and was easily degraded by bacteria, which can improve the quality of steamed bread to a certain extent. When the PRS3 content was over 10%, it competed with the gluten protein to absorb water, which reduced the contents of β-turn and α-helix in the dough, increased the contents of β-fold, and weakened the structure of the gluten network. It also decreased the specific volume and elasticity of the steamed bread and increased the spreading rate, hardness, and chewiness. Steamed bread prepared with a flour mixture containing 5% PRS3 was similar to the presidential acceptance of control flour. In this study, a new sustainable and efficient PRS3 preparation method was established, which has certain guiding significance for the processing of Functional steamed bread with high-resistant starch.     

N,N,N,N-tetradentate Macrocyclic Ligand Based Selective Fluorescent Sensor for Zinc (II)

N,N,N,N-tetradentate macrocyclic ligand (L) has been synthesized by the condensation of benzil and semicarbazide and characterized. On excitation by light of wavelength 350?nm, L exhibited a fluorescent peak at λ(max)?=?454?nm, which showed ca 6 times enhancement in intensity with a blue shift on interaction with Zn(2+). L has been found to act as a selective fluorescent sensor for zinc(2+) ion over a host of other metal ions such as- Cd(2+), Pb(2+), Hg(2+), Ca(2+), Fe(2+), Na(2+), Co(2+), Mn(2+), Cu(2+) and Ni(2+), in 1:1 CH(3)OH:H(2)O. A 1:1 complex formation between L and Zn(2+) was proved. The enhancement in the fluorescence could be explained on the basis of Photo induced electron transfer (PET) mechanism with log β?=?1.86.     

In-situ analysis of the water distribution and protein structure of dough during ultrasonic-assisted freezing based on miniature Raman spectroscopy

The effect of ultrasonic-assisted freezing (UAF) on the water distribution of dough and molecular structure of gluten was in-situ monitored by low field nuclear magnetic resonance (LF-NMR) and micro-miniature Raman spectroscopy in this research. The results showed that UAF treatment increased the bound water content between 5 min and 30 min, and weakened the signal intensity of hydrogen protons due to the ultrasound enhanced heat and mass transfer during the freezing process. In-situ Raman spectra analysis indicated that UAF delayed the transition from embedded to exposure of tyrosine and tryptophan residues during the freezing process. Meanwhile, UAF reduced the number of hydrogen bonds, gauche-gauche-gauche (g-g-g) conformation breakage, the degree of α-helix to random coil conversion and damage to the gluten network during the freezing process. UAF treatment reduced the water mobility and breakage of non-covalent bonds, which prevented a dramatic shift in the protein advanced conformation during the freezing process, thereby improving the quality of frozen dough.     

Mascara--an unsuspected cause of magnetic resonance imaging artifact

It is well recognised that metals, especially iron, will cause artifacts in magnetic resonance (MR) images. Hitherto it has not been recognised that some facial cosmetics contain magnetic materials, in sufficient quantities to cause artifacts. We report a case of a 25-year-old female who had MR images of her orbits made while wearing mascara eye makeup. The resultant images showed distortion of the signal over the anterior aspect of both eyes. Examination following the removal of the eye makeup resulted in the acquisition of normal images. The typical ingredients of mascara are natural and synthetic waxes, glycerine, water, kaolin, preservatives, polymer film formers and pigments. A wide range of pigments may be used, especially iron oxide, which is a constituent of both brown and blue mascara. In addition it is likely that a number of mascaras will be contaminated with heavy metals. As a result of this observation we now ensure that all patients who are undergoing MR imaging of the head, remove all facial cosmetics as well as any jewelry prior to imaging.     

Dynamic magnetic resonance microscopy of flour dough fermentation

Magnetic resonance microscopy was carried out at 9.4 T with a voxel volume of 117 x 117 x 500 microm(3) and temporal resolution was adjusted to 8.5 min for a dynamic follow-up of bread dough fermentation during 2 h at a constant temperature of 30 degrees C. An image analysis procedure based on gray levels mathematical morphology routines was performed to assess bubble distribution and cell wall thickness inside the imaged bread dough. The evolution of the extracted curves allows one to characterize quantitatively the amount of bubbles and their growth. Using this procedure, different bread doughs were examined to determine the impact of dough composition on the structure modification during fermentation.     

Time resolved spectroscopic NMR imaging using hyperpolarized 129Xe

We have visualized the melting and dissolution processes of xenon (Xe) ice into different solvents using the methods of nuclear magnetic resonance (NMR) spectroscopy, imaging, and time resolved spectroscopic imaging by means of hyperpolarized 129Xe. Starting from the initial condition of a hyperpolarized solid Xe layer frozen on top of an ethanol (ethanol/water) ice block we measured the Xe phase transitions as a function of time and temperature. In the pure ethanol sample, pieces of Xe ice first fall through the viscous ethanol to the bottom of the sample tube and then form a thin layer of liquid Xe/ethanol. The xenon atoms are trapped in this liquid layer up to room temperature and keep their magnetization over a time period of 11 min. In the ethanol/water mixture (80 vol%/20%), most of the polarized Xe liquid first stays on top of the ethanol/water ice block and then starts to penetrate into the pores and cracks of the ethanol/water ice block. In the final stage, nearly all the Xe polarization is in the gas phase above the liquid and trapped inside the pores. NMR spectra of homogeneous samples of pure ethanol containing thermally polarized Xe and the spectroscopic images of the melting process show that very high concentrations of hyperpolarized Xe (about half of the density of liquid Xe) can be stored or delivered in pure ethanol.     

Solvent detection using porous silicon optical waveguides

Since the first report on the use of porous silicon as an optical waveguide medium in 1995, significant development has been made towards the understanding and applicability of such material. Here, the introduction of solvents (acetone, methanol, and propan-2-ol) into the pores is shown to dramatically reduce the loss of the waveguides, in a reversible manner. Both the magnitude and duration of this effect are sensitive to the solvent introduced. In some waveguides, for example, the measured loss (at 0.633 μm) falls by as much as 34 dB cm⁻¹ on the introduction of acetone. Theoretical estimates of the effect of solvents on the interfacial scattering loss confirm this as the origin of the observed reductions. These results, combined with the fact that a substantial portion of the guided-mode field interacts with the solvent, indicate an enhanced sensitivity for sensor applications may be achievable.     

Ultrasonically initiated emulsion polymerization of styrene in the presence of Fe2+

Ultrasonically initiated emulsion polymerization of styrene was carried out in the presence of Fe(2+). The addition of a small amount of Fe(2+) markedly enhanced the polymerization rate of styrene. In the presence of 50 microM Fe(2+), the conversion of monomer in the reaction time of 60 min was 2.4 times as high as that in the absence of Fe(2+). The increase in the polymerization rate was due to higher concentration of hydroxyl (*OH) radicals generated via Fenton reaction of Fe(2+) with hydrogen peroxide (H(2)O(2)), which was proved by a lower amount of H(2)O(2) in Fe(2+) aqueous solution compared with that in pure water during ultrasonic irradiation. However, the addition of excessive Fe(2+) had no further accelerating effect on the polymerization rate due to the reduction of *OH radicals by Fe(2+). So it is an effective way to add an appropriate amount of Fe(2+) to accelerate ultrasonically initiated emulsion polymerization of styrene.     

自蔓延高温合成掺杂SrAl2O4稀土长余辉发光粉的研究

在600℃下用自蔓延高温法制备了SrAl2O4∶Eu2+0.012 5,RE3+0.012 5(RE3+=Ce3+,Pr3+,Nd3+,Tb3+,Dy3+),SrAl2O4∶Eu2+0.012 5,M0.012 5(M=Li+,Be2+,Cd2+,Mn2+,Cu2+,Ag+,Zn2+,pb2+),SrAl2O4∶Eu2...     

Time resolved spectroscopic NMR imaging using hyperpolarized Xe

We have visualized the melting and dissolution processes of xenon (Xe) ice into different solvents using the methods of nuclear magnetic resonance (NMR) spectroscopy, imaging, and time resolved spectroscopic imaging by means of hyperpolarized ¹²⁹Xe. Starting from the initial condition of a hyperpolarized solid Xe layer frozen on top of an ethanol (ethanol/water) ice block we measured the Xe phase transitions as a function of time and temperature. In the pure ethanol sample, pieces of Xe ice first fall through the viscous ethanol to the bottom of the sample tube and then form a thin layer of liquid Xe/ethanol. The xenon atoms are trapped in this liquid layer up to room temperature and keep their magnetization over a time period of 11 min. In the ethanol/water mixture (80 vol%/20%), most of the polarized Xe liquid first stays on top of the ethanol/water ice block and then starts to penetrate into the pores and cracks of the ethanol/water ice block. In the final stage, nearly all the Xe polarization is in the gas phase above the liquid and trapped inside the pores. NMR spectra of homogeneous samples of pure ethanol containing thermally polarized Xe and the spectroscopic images of the melting process show that very high concentrations of hyperpolarized Xe (about half of the density of liquid Xe) can be stored or delivered in pure ethanol.     

Change in electrical resistivity of commercial purity aluminium severely plastic deformed

Commercial purity aluminium sheets were severely plastic deformed by accumulative roll bonding (ARB). Changes in electrical resistivity at 77 K and microstructure during the ARB process were traced up to 12 cycles, which corresponded to an equivalent strain of 10. The resistivity at 77 K increased with increasing number of ARB cycles, then saturated after about the sixth ARB cycle with a maximum increment of resistivity from starting material of about 1.1 nΩ m. Since lattice defects affect the resistivity of metals, the internal dislocation density and the density of grain boundaries were evaluated from scanning transmission electron microscopy images using Ham's method and grain boundary maps obtained from electron back-scattering diffraction, respectively. The relationship between the change in resistivity and the lattice defects is discussed.     

原子吸收光谱法研究聚丙烯腈树脂对铜、铅、镉和锌的吸附性能

采用悬浮聚合法以丙烯腈和二乙烯苯交联合成聚丙烯腈聚合物微球,以原子吸收光谱(AAS)法研究了它对重金属离子的吸附性能,实验结果表明,聚丙烯腈聚合物对Cu2+,Pb2+,Cd2+和Zn2+具有不同程度的吸附容量; 酸度、吸附时间、离子浓度和温度等对其吸附性能均有一定的影响。以AAS法确定聚丙烯腈聚合物的最佳吸附条件;其对金属离子的最佳吸附容量出现在溶液pH值为5～6范围内,静态吸附时间达到1.5～2 h时吸附基本达到平衡,室温下,吸附容量较大,温度高于40 ℃时吸附容量逐渐降低,因此选择室温为最佳吸附温度。在最佳吸附条件下聚合物对Cu2+,Pb2+,Cd2+和Zn2+的吸附容量(mg·g-1)分别达到26.6,45.2,39.7和32.5。吸附时间为1.5～2 h时吸附率分别达到83.6%,87.1%,85.3%和86.7%。在5 h以上时吸附率可达到96%。选用0.1 mol·L-1盐酸溶液作为解吸剂洗脱金属离子,解吸率可达到95%。同时还探讨了聚合物的吸附作用机理。     

基于近红外高光谱成像及信息融合的小麦品种分类研究

高光谱成像技术因具有图谱合一的特点在作物品种鉴别方面具有较大潜力,但目前研究大多只提取利用了光谱信息,对图像信息没有进行有效利用。本文利用近红外高光谱成像仪采集了强筋、中筋、弱筋3个类型共计6个品种的单粒小麦种子高光谱图像,提取了长、宽、矩形度、圆形度、离心率等12个形态特征,并对图像中的胚乳和胚区域进行分割建立掩膜,提取了胚乳和胚区域的平均光谱信息。采用PLSDA和LSSVM方法建立基于图像信息的判别模型,结果表明强筋、弱筋两者二分类的识别率能达到98%以上,强筋、中筋两者二分类的识别率只能达到74.22%,说明近红外高光谱图像的形态信息能够反映品种间差异,但单独利用图像信息进行分类时准确度可能欠佳。采用SIMCA,PLSDA和LSSVM方法建立了胚乳和胚区域光谱信息的多分类模型,胚乳区域的分类效果较胚区域略好,说明籽粒不同部位的形状差异会影响分类效果。进一步融合光谱信息和图像信息,采用SIMCA,PLSDA和LSSVM方法建立融合模型,识别率较单独的图像或光谱信息模型均略有提升,PLSDA方法从原来的96.67%提升到98.89%, 表明充分挖掘高光谱图像所包含的形态特征和光谱特征可有效提高分类效果。