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关键词： 豌豆蛋白   超声辅助pH偏移   乳化   凝胶   包埋  

摘要： 豌豆蛋白具有良好的营养价值和功能特性,在食品工业具有较好的应用价值。然而,商业豌豆蛋白的低溶解度限制了其在食品产品中的应用。为了拓展商业豌豆蛋白应用范围,可以通过一定的改性手段提高其溶解性质。本论文通过超声辅助pH偏移处理提高商业豌豆蛋白的溶解性,将改性豌豆蛋白部分替代乳清蛋白制备双蛋白乳状液用于载运白藜芦醇,并进一步将载运白藜芦醇乳液填充于乳清蛋白凝胶探讨改性豌豆蛋白在营养素包埋中的应用前景。论文主要研究结果如下:(1)首先研究了超声辅助pH偏移对豌豆蛋白功能特性、消化特性及蛋白结构的影响。以溶解度为指标考察了超声频率(单频:20、28、40、60k Hz;双频:20/28、20/40、20/60、28/40、40/60k Hz;三频:20/28/40、20/40/60k Hz)、多频超声工作模式(同步、顺序超声)、超声介入时段(偏移中、偏移后)对豌豆蛋白pH12偏移改善溶解度效果的影响。结果表明pH偏移中超声(28/40同步工作)处理7.5min改善豌豆蛋白溶解度的效果最为显著。该处理条件下豌豆蛋白的溶解度比单独pH偏移处理样品提高了79%(p<0.05)。经过超声辅助pH偏移处理的豌豆蛋白消化率比未处理样品高,消化最终(4h)产生的游离氨基比pH偏移样品提高了46%。(2)进一步通过粒度、电位、疏水性、圆二色光谱和荧光光谱以及SDS-PAGE分析了豌豆蛋白结构特征的变化。结果表明,pH偏移中超声处理7.5min处理的豌豆蛋白与单独pH偏移样品相比粒径减小,表面疏水性降低,电势绝对值提高了。SDS-PAGE结果显示超声辅助pH偏移处理使豌豆蛋白中大分子(>150k Da)聚集体和分子量在35-25k Da的亚基增多。pH偏移中超声7.5min处理的豌豆蛋白α-螺旋含量与单独pH偏移样品相比分别降低了35%。研究表明豌豆蛋白溶解度增加可能是与改性豌豆蛋白表面静电荷的增多以及表面疏水基团减少,消化率的的提高可能与其较小的粒径和部分展开同时保留一定折叠的结构有关。(3)其次,以界面张力、界面蛋白含量及组成、乳化活性和表观粘度为指标,考察改性豌豆蛋白和乳清蛋白比例对复合蛋白乳化性质的影响。结果表明,提高改性豌豆蛋白比例可以降低复合蛋白溶液的界面张力,提高复合蛋白界面吸附率、界面膜厚度、乳化活性和表观粘度。改性豌豆蛋白制备的乳液中界面蛋白吸附率比乳清蛋白制备的乳液高了139%(p<0.05)。激光共聚焦显微镜结果证实改性豌豆蛋白制备的乳液中界面蛋白膜最厚。乳化活性提高可能与复合蛋白有较好的柔性能迅速在界面吸附并展开有关。(4)接着,以粒径、表面电位、外观以及微观形态和丙二醛含量为指标,考察改性豌豆蛋白与乳清蛋白的比例对复合蛋白乳状液物理、化学稳定性的影响。结果表明,豌豆蛋白比例越高、盐浓度和温度越高复合蛋白乳状液的粒径越大、表面电位绝对值越小。复合蛋白乳状液的氧化稳定性显著高与单一乳清蛋白乳状液,豌豆蛋白与乳清蛋白比例为5:5时乳状液丙二醛含量较乳清蛋白乳状液降低了53%(p<0.05)。不同复配比例乳状液的物理稳定性和氧化稳定性与界面蛋白膜厚度和界面吸附蛋白种类有关。(5)以游离氨基和游离脂肪酸释放、表面电位、粒径和微观形态为指标,考察不同豌豆蛋白和乳清蛋白比例及胆盐对乳状液的消化特性的影响。结果表明,双蛋白乳状液游离氨基和游离脂肪酸的释放量和速率高于单一蛋白乳状液。在胃消化阶段,p:w=5:5乳液的游离氨基释放速度最快且最终释放量比乳清蛋白乳状液高42%。此时,p:w=5:5的复合乳液粒径显著增大,进一步证明了乳液表面蛋白的迅速消化。在肠消化阶段,p:w=5:5游离脂肪酸最终释放量比豌豆蛋白高48%,这可能与其肠消化阶段粒径显著减小有关。(6)通过荧光光谱、荧光猝灭机制、模拟分子对接和热重分析,探讨了白藜芦醇与不同复配比例蛋白之间的相互作用。结果表明,白藜芦醇与p:w=5:5为动态联合静态猝灭形成稳定复合物,氢键和范德华力为主要驱动力。荧光光谱结果显示,随着白藜芦醇的浓度增加,白藜芦醇与不同复配比例蛋白的复合物的荧光强度减弱,最大吸收波长红移。这表明白藜芦醇加入能改变蛋白构象,蛋白疏水基团的外露,更有利于蛋白与白藜芦醇的疏水相互作用。(7)以界面张力和界面蛋白含量、表面电位和粒径、氧化稳定性、表观粘度及微观形态为指标,考察蛋白与白藜芦醇的相互作用对载运白藜芦醇的双蛋白复合乳状液的影响。结果表明,蛋白与白藜芦醇的相互作用可以增强蛋白降低界面张力能力。与未包埋白藜芦醇的复合乳状液相比,包埋白藜芦醇的复合乳状液的界面蛋白含量增加,粒径和表面电位绝对值增大、氧化稳定性提高。p:w=10:0含白藜芦醇的乳状液催化氧化45min后,丙二醛含量比不含白藜芦醇乳液低12%。这可能是因为白藜芦醇改变了复合蛋白乳状液的界面组成、界面膜厚度和表面电荷

关键词： Ion mixing   Optical properties   Spectroscopic ellipsometry   Auger electron spectroscopy   Silicon carbide   Protective layer   Depth profiling   Physicochemical analysis  

摘要： Protective SiC-rich nano layer was created by ion beam mixing of Si/C multilayers. The transformation of the Si and C layers into a homogeneous SiC layer was analyzed using complementary depth profiling by spectroscopic ellipsometry (SE) and Auger electron spectroscopy (AES). The distribution of elements and their chemical states was revealed by AES, whereas SE measured the accurate thicknesses, density, crystallinity, and the distribution of different phases. The optical properties of the created SiC layer determined by SE were almost identical to that of ion implantation-amorphized SiC. Amorphous Si and void formations were revealed by SE. The void profile determined by SE correlated well with the Xe distribution measured by AES. The complementary capabilities of SE and AES for a detailed chemical investigation were pointed out, such as the atomic (AES), structural (AES and SE) and non-destructive depth profiling (SE) features. It was shown that besides the synergism that the two methods reveal, SE is capable of a quick, sensitive and non-destructive testing of such layer structures and materials.

关键词： TiO2 nanotube   Crystal phase   Mechanical properties   Corrosion resistance behavior   Wettability   Hemocompatibility  

摘要： In recent years, TiO2 nanotube has presented great potentials in blood-contacting implants. However, considering the reliability and safety of the application and complexity of coagulation mechanism, the physicochemical property and hemocompatibility of phase dependent TiO2 still need to be investigated deeply. In this research, the wettability, electrochemical properties, mechanical properties, and whole blood coagulation response of phase dependent TiO2 nanotubes were systematically evaluated. First, the surface topography and crystal phase of regular self-ordering TiO2 nanotubes arrays were characterized, some significant changes including fracture, collapse and micropores appeared with the increase of annealed temperature, which mainly caused by transformation of crystal structure. Secondly, the physicochemical properties were analyzed, which presented that the superhydrophilicity, hardness, elastic modulus, adhesive strength of TiO2 nanotubes gradually decrease with the increase of annealed temperature;the mean coefficient of friction increases when the crystal phase of TiO2 nanotubes transferred from amorphous into anatase, whereas it decreases with the increase of rutile phase content;and the rutile phase displays excellent resistant element precipitation due to the increase of grain boundary density and close packed crystal structure. Finally, the whole blood was applied to evaluate the hemocompatibility of phase dependent TiO(2 )nanotubes by in vitro experiment. The deteriorative surface morphology and lower interfacial tension of nanotubes array composed of rutile phase can effectively avoid adhesion and activation of platelets. This research can provide a useful guide to design theTiO(2) -nanotube-based blood compatible biomaterials.

关键词： Oxides   Metals   Ligands   Metal clusters   Electrical conductivity  

摘要： The chelating catechol/oxime ligand 2,3-dihydroxybenzaldehyde oxime (H-3 dihybo) has been used to synthesize one titanium(IV) and two zirconium(IV) compounds that have been characterized by single-crystal X-ray diffraction and H-1 and C-13 NMR, solid-state UV-vis, and ESI-MS spectroscopy. The reaction of TiCl4 with H-3 dihybo and KOH in methanol, at ambient temperature, yielded the hexanuclear titanium (IV) compound K-2[Ti-6(IV) (mu(3)-O)(2) (mu-O)(3)(OCH3)(4)(CH3OH)(2) (mu-Hdihybo)(6)]center dot CH3OH (1), while the reaction of ZrCl4 with H(3)dihybo and either (Bu4NOH)-Bu-n or KOH also gave the hexanuclear zirconium(IV) compounds 2 and 3, respectively. Compounds 1-3 have the same structural motif [M-6(IV)(mu(3)-O)(2) (mu-O)(3)] (M = Ti, Zr), which constitutes a unique example with a trigonal-prismatic arrangement of the six zirconium atoms, in marked contrast to the octahedral arrangement of the six zirconium atoms in all the Zr-6 clusters reported thus far, and a unique Zr-6 core structure. Multinuclear NMR solution measurements in methanol and water proved that the hexanuclear clusters 1 and 3 retain their integrity. The marriage of the catechol moiety with the oxime group in the ligand H(3)dihybo proved to be quite efficient in substantially reducing the band gaps of TiO2 and ZrO2 to 1.48 and 2.34 eV for the titanium and zirconium compounds 1 and 3, respectively. The application of 1 and 3 in photocurrent responses was investigated. ESI-MS measurements of the clusters 1 and 3 revealed the existence of the hexanuclear metal core and also the initial formation of trinuclear M-3 (M = Ti, Zr) building blocks prior to their self-assembly into the hexanuclear M-6 (M = Ti, Zr) species. Density functional theory (DFT) calculations of the NICSzz scan curves of these systems revealed that the triangular M-3 (M = Ti, Zr) metallic ring cores exhibit pronounced metalloaromaticity. The latter depends upon the nature of the metallic center with NICSzz(1) values equal to -30 an

关键词： copolymers   grafting   polysaccharides   swelling  

摘要： kappa-Carrageenan-graft-poly(dimethylaminoethyl methacrylate) (CRG-g-PDMA) was synthesized via free-radical copolymerization under microwave irradiation.C-13-Nuclear magnetic resonance spectroscopy (C-13-NMR), fourier-transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and X-ray diffraction (XRD) methods were used for characterization of the CRG-g-PDMA structure. The effect of reaction variables including the concentrations of the initiator and dimethylaminoethyl methacrylate (DMA) as well as the microwave irradiation time and power on graft ratio and conversion was investigated, and their highest values were obtained to be 179 and 76%, respectively. The lower critical solution temperatures (LCSTs) of the CRG-g-PDMA copolymers were determined at various pH conditions, and their value in distilled water was found as 47 degrees C. Besides, the swelling capacity of the copolymers under different pH levels was investigated and it was seen that the swelling capacity of the copolymer increased with the decrease in the pH value of the medium. The CRG-g-PDMA copolymer exhibited excellent swelling performance in acidic pH conditions and possessed responsiveness to pH and temperature stimuli.

关键词： Anionic surfactant   Sugar-based surfactant   Glycolipid   Foaming properties   Cytotoxic activity   Irritation potential  

摘要： Surface-active compounds derived from biomass, especially sugar-based amphiphiles, have received wide attention regarding their biodegradability, low toxicity and ecological acceptability. Compared to nonionic sugar based surfactants, the anionic ones show significantly better solubility, higher surface activity and foaming performance. Thus they are largely used in personal care formulations and many technological applications. However, anionic surfactants are well known to induce skin and eye irritation. In this study, three sugar-based anionic surfactants, bearing a lipidic chain grafted to the anomeric position of a monosaccharide (glucose or xylose) and a sulfate group on the primary hydroxyl, were synthesized: 6-O-sulfoN-(beta-D-glucopyranosyl) dodecanamide (GlcNC12S), N-dodecyl-6-O-sulfo-D-gluconamide (GlcCC12S) and N-dodecyl-6-O-sulfo-D-xylonamide (XylCC12S). These molecules were investigated in details for their self-assembling behavior, foaming properties and biological effects. All their properties were compared to those of two commercially available anionic surfactants, sodium laureth sulfate (SLES) and sodium dodecylsulfate (SDS). Results revealed that the three anionic glycolipids show surface properties and foaming behavior comparable to those of SDS. Furthermore, their cytotoxic and irritation potentials are significantly lower compared to commercial molecules, which make these renewable molecules potential candidates for replacement of petroleum-based compounds.

关键词： Pristine graphene   Cement mortar   Mechanical properties   Acceleration   Microstructure  

摘要： This paper aims to study the effect of the size of pristine graphene (PRG) particles on the compressive and tensile strengths of cement-based mortars and to gain better understandings of the mechanism behind the enhancement of these properties. PRG industrially manufactured by the electrochemical process with a variety of particle sizes including 5 mu m, 43 mu m, 56 mu m, and 73 mu m was used at the optimal dosage of 0.07% by weight of cement binder. The results indicate that mechanical strengths of cement mortars at 7 and 28 days considerably depend on the size of PRG. The mixes with size 56 mu m and 73 mu m show significant influence on both compressive and tensile strengths of cement mortars, which increase approximately 34.3% and 30.1% at 28-day compressive strengths, and 26.9% and 38.6% at 28-day tensile strengths, respectively. On the other hand, the mix with size 43 mu m of PRG addition exhibits a significant increase only in tensile strength, and there are no significant effects on either compressive strengths or tensile strengths of the mix containing 5 mu m particles. The observed enhancement in the mechanical properties of cement mortars by large PRG sizes is attributed to the improvement of cement hydration level, the reduction of cement particles' distance in cement gels because of the effect of van der Waals forces between PRG sheets, and the mechanical adhesion forces between PRG sheets and cement gels. The results from this study indicate that PRG is not only a promising additive in practical application for building materials to improve the current drawbacks of cement composites, but also a feasible option to support the reduction of cement mass used in cement composites, which could reduce the CO2 footprint and amount of CO2 emission into the atmosphere. Crown Copyright (C) 2020 Published by Elsevier Ltd. All rights reserved.

关键词： Wastes   Chromatography   Food   Pyrolysis   Gasification  

摘要： This study compares the physicochemical properties and steam gasification reactivity of the chars produced from the pyrolysis of the raw and torrefied food wastes at 800 degrees C, including leftover rice (LR), leftover pork (LP), leftover cabbage (LC), and watermelon peel (WP). Particularly, the release and transformation of various forms of alkali and alkaline earth metallic (AAEM) species during the pyrolysis of the raw and torrefied food wastes are studied in details. Steam gasification results of the chars from the raw food wastes indicate that the LC and WP chars have much higher gasification reactivity than the LR and LP chars, mainly as a result of the higher char surface areas, higher contents of AAEM species, and less condensed carbon structures for the LC and WP chars. However, the gasification reactivity of the torrefied LR and LP chars is reduced, mainly as a result of the decreased surface areas and increased large aromatic ring (>= 6 rings) structures as well as the decreased active K content for the torrefied LP char. In contrast, the gasification reactivity of the torrefied LC and WP chars is slightly increased, most likely as a result of the less condensed carbon structures and increased contents of active AAEM species for those chars. The results demonstrate that the effect of torrefaction on char gasification strongly depends upon the type and properties of food waste, especially the contents of active AAEM species (i.e., the water- and CH3COONH4-soluble AAEM species) in food waste. For the food wastes of low contents of active AAEM species, such as LR and LP, co-torrefaction with other food wastes of high contents of active AAEM species is an important strategy to enhance the overall gasification efficiency of all food wastes.

关键词： Cold plasma   Surface decontamination   Food safety   PCA  

摘要： Cold plasma is a novel technology for surface decontamination. Almond slices can be contaminated with different microorganisms during their production. In the current research, the atmospheric argon plasma treatment (5, 10, 15, and 20 min) was used to decontamination of almond slices surface. Microbial load, Color, peroxide value, hardness, and sensory properties of slices was comprised with untreated samples (control). Descriptive sensory evaluation about color, flavor, crispiness, crunchiness, and hardness of almond slices were performed. According to the results of the microbial tests, Total count, molds and yeasts, and Staphylococcus aureus of almond surface decreased about 2.95 log cfu/g, 1.81 log cfu/g, and 2.72 log cfu/g after 20 min of plasma treatment, respectively, provided that microbial reduction increased more by increasing the treatment time. Coupled with the color evaluation, peroxide value and sensory attributes didn't change during plasma treatment. Having said that, the hardness of slices was changed by increasing treatment time. Furthermore, Principal Component Analysis and cluster analysis were performed for sensory evaluation. In light of the consumer's point of view, firstly 10 min and secondly 15 min plasma treatment can be more desirable.