玉米麸皮中阿拉伯木聚糖的提取、结构及性质

采用碱-过氧化氢法从玉米麸皮中提取阿拉伯木聚糖(AX),并考察其基本性质。研究发现:0.5 mol/L Na OH溶液提取所得阿拉伯木聚糖色泽浅、产量较高且未发生降解;阿拉伯木聚糖主要由阿拉伯糖和木糖单元组成,还含有少量葡萄糖和半乳糖单元;阿拉伯木聚糖从215℃开始发生热分解,350℃时分解完全;阿拉伯木聚糖还具有一定的增稠效果;此外,AX可用来制备水包油型乳液,所制得的乳液十分稳定。     

疏水改性玉米麸皮阿拉伯木聚糖的性能研究

采用碱-过氧化氢法从玉米麸皮中提取碱溶性阿拉伯木聚糖(AX),然后分别用1-溴代丁烷、1-溴代十二烷和1-溴代十六烷对其进行疏水改性得到两亲性的烷基化阿拉伯木聚糖(C_n-AX)。利用荧光分子探针、动态光散射、扫描电子显微镜和流变仪对C_n-AX水溶液的性质进行研究,发现Cn-AX在一定质量浓度时水溶液中形成缔合聚集体。疏水缔合使C_n-AX水溶液的黏度高于AX水溶液。此外,通过制备一系列O/W型乳液,对AX和C_n-AX的乳化能力进行了评价。结果表明,乳液的稳定性受C_n-AX的烷基链长度和质量分数的影响,并且C_(16)-AX的乳化性能优于常用的Tween 80。     

玉米麸质阿拉伯木聚糖的疏水改性

从玉米麸质中提取了半纤维素阿拉伯木聚糖(AX),以1-溴代丁烷、1-溴代十二烷、1-溴代十六烷为烷基化试剂,通过醚化反应制备了疏水改性阿拉伯木聚糖(Cn-AX)。采用傅里叶红外光谱和1H NMR表征了改性阿拉伯木聚糖的结构。利用流变仪研究了改性前后阿拉伯木聚糖水溶液的粘度性质,发现疏水改性阿拉伯木聚糖水溶液由于长碳链的聚集,粘度显著升高。     

玉米麸质阿拉伯木聚糖在水溶液中的聚集和构象

从玉米麸皮中提取碱溶性阿拉伯木聚糖(AX)并用乙醇分级。用体积排除色谱-多角度激光光散射联用(SEC-MALS)和动态光散射(DLS)研究了AX的构象和聚集。碱溶性麸质AX的相对分子质量随均方旋转半径(Rg)的变化可以用Mw~Rdfg表示。玉米麸质AX分子链的分形维数(df)为1.47,其结构因子ρ=Rg/Rh为1.70。忽略分子间作用,根据"蠕虫链"模型可以估算出玉米麸质AX的持久长度(Lp)为1.72 nm。即使在很稀的溶液中,玉米麸质AX也可以形成紧密的聚集,其df在3.0左右。     

玉米麸质阿拉伯木聚糖对香豆酸酯的制备及性能研究

通过对水溶性玉米麸质阿拉伯木聚糖(CAX)进行改性,使CAX具有抗氧化性。将CAX溶解到DMA/Li Cl体系中,以三乙胺为缚酸剂,与对香豆酸酰氯进行酯化反应得到阿拉伯木聚糖对香豆酸酯(p-CA-CAX)。用红外、核磁对其结构进行了鉴定,表明对香豆酸(p-CA)以酯键的形式连接在CAX上。用高效液相色谱确定了p-CA的取代度,p-CA与CAX的糖苷键的摩尔比分别为1∶5,1∶4,1∶3,1∶2和1∶1时,取代度分别为0.38,0.51,0.63,0.83和0.94。用凝胶渗透色谱确定了不同取代度的p-CA-CAX的分子量,p-CA-CAX-0.38,p-CA-CAX-0.51和p-CA-CAX-0.63的分子量分别为3.52×10~5,3.85×10~5和3.93×10~5。脂质过氧化物的检测和抗氧化能力指数(ORAC)的测定表明,p-CA-CAX具有较好的抗氧化性,而且p-CA含量越高,p-CA-CAX的抗氧化性越好。     

紫外吸收剂阿拉伯木聚糖肉桂酸酯的合成和表征

从玉米麸皮中提取水溶性的阿拉伯木聚糖(AX),以DMF为溶剂,三乙胺为缚酸剂,醚化产物与肉桂酰氯反应,生成高分子紫外吸收剂阿拉伯木聚糖肉桂酸酯(AX-CM)。UV检测表明,AX-CM在283 nm处有较高的紫外吸收,且光稳定性良好。     

双亲阳离子阿拉伯木聚糖的合成及其在香波中的应用

以玉米麸皮阿拉伯木聚糖为原料,以环氧氯丙烷和不同烷基链长的叔胺作为季铵化试剂,在碱性条件下,在水溶液体系里合成双亲阳离子阿拉伯木聚糖。通过核磁共振氢谱和碳谱对其结构进行表征。随烷基链长的增加,双亲阳离子阿拉伯木聚糖溶液粘度增加。添加了双亲阳离子阿拉伯木聚糖的洗发水有着良好的帮助硅油沉积的能力,同时有着良好的梳理性能,而且烷基链越长,取代度越高,帮助硅油沉积的能力越强,干梳和湿梳性能也越好。     

双亲阳离子阿拉伯木聚糖的合成及其在香波中的应用

以玉米麸皮阿拉伯木聚糖为原料,以环氧氯丙烷和不同烷基链长的叔胺作为季铵化试剂,在碱性条件下,在水溶液体系里合成双亲阳离子阿拉伯木聚糖。通过核磁共振氢谱和碳谱对其结构进行表征。随烷基链长的增加,双亲阳离子阿拉伯木聚糖溶液粘度增加。添加了双亲阳离子阿拉伯木聚糖的洗发水有着良好的帮助硅油沉积的能力,同时有着良好的梳理性能,而且烷基链越长,取代度越高,帮助硅油沉积的能力越强,干梳和湿梳性能也越好。     

玉米芯木聚糖的提取及特性研究

为了解玉米芯中水不溶性木聚糖在医药中的应用,采用搅拌下水浸24 h、1.5%次氯酸钠除杂、氢氧化钠碱提、乙酸中和、甲醇醇沉、甲醇及异丙醇醇洗多步法提取了玉米芯中水不溶性木聚糖.研究了所提水不溶性木聚糖的红外光谱及其粒径分布、堆积密度、振实密度、压缩指数、致密性、安息角、流变学等特性.结果表明,红外光谱可用来表征其形态结...     

玉米芯木聚糖的提取及其相对分子质量分布研究

通过碱性过氧化氢溶液提取玉米芯半纤维素,单因素试验结果表明：在1% H₂O₂、5% NaOH的碱性过氧化氢溶液中,反应温度50℃、反应时间16 h、液固比为20：1（mL：g）,木聚糖得率可达83.15%。采用梯度乙醇分级沉淀法进行半纤维素的分离实验,考察了真空冷冻和烘干方式对产物性能的影响。采用高效离子色谱测定半纤维素单糖组成,并用FT-IR、TG、¹H NMR、¹³C NMR和GPC对半纤维素进行分析与表征。结果表明：各级分由木糖、葡萄糖、阿拉伯糖等组成,玉米芯中半纤维素主要由L-阿拉伯糖-（4-O-甲基-D-葡萄糖醛酸）木聚糖构成;支化度（w（阿拉伯糖）/w（木糖））为0.17~0.52,且随着乙醇体积分数的增加而变大。干燥方式对产物的相对分子质量影响很大,真空冷冻干燥的木聚糖重均相对分子质量（M_w）为108 533~197 752,真空干燥的M_w为41 231~47 242;2种干燥方式所得12种级分中,分散系数为1.172~1.517,其中11种产物分散系数小于1.5,为分布均一的低分散度木聚糖。     

Mechanical properties and water vapor permeability of thin film from corn hull arabinoxylan

Isolated corn hull arabinoxylan was dissolved in water and provided a clear solution. Plasticizer (glycerol, propylene glycol, or sorbitol) was added to the arabinoxylan solution at 0–20 wt % (film dry weight), which was cast into stable films. Film thickness ranged from 22 to 32 μm. Mechanical properties, moisture content, and water vapor permeability (WVP) were studied for the arabinoxylan‐based films as a function of plasticizer concentration. Measured data for the corn hull arabinoxylan–based films were 13–18 wt % moisture content, 10–61 MPa tensile strength, 365–1320 MPa modulus, 6–12% elongation, and 0.23–0.43 × 10^?10 g m^?1 Pa^?1 s^?1 water vapor permeability. Plasticized arabinoxylan films produced in this study had lower WVPs than those of unplasticized films, which is likely attributable to the phenomenon known as antiplasticization. Scanning electron micrographs showed a homogeneous structure on film surfaces. Films containing sorbitol had the best moisture barrier properties. When grapes were coated with arabinoxylan and arabinoxylan/sorbitol films, weight loss rates of the fruit decreased by 18 and 41%, respectively, after 7 days. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2896–2902, 2004     

Effects of neutralization on the structure and properties of an ionomer

The structure, morphology, and properties of an ionomer, poly(ethylene‐acrylic‐acid) neutralized by zinc salts (PI) depend on the free carboxylic acid content. In this work, metal acetates (Na, Zn, and Al acetates) were used to control the neutralization levels. A wide range of techniques were used, such as spectroscopic Fourier transform infrared spectroscopy (FTIR), thermal [thermogravimetric analysis, modulated differential scanning calorimetry (MDSC), and dynamic mechanical analysis (DMA)], mechanical (tensile measurement), and small angle neutron scattering (SANS). The melt rheological properties of the samples were also examined. The results show that metal acetate neutralizes free acrylic acid in the ionomer, which has the primary role in controlling ionic association. The number of ionic groups in ionic domains and multiplets in the matrix is dependent on the neutralization level. Metal valence determines the ionic domain or multiplet structure (FTIR), further properties of PI. Dynamic mechanical properties, the ionic transition behaviour, and the mechanical properties are improved compared with PI using monovalent cation (Na⁺), but decreased using trivalent cation (Al³⁺) or shows less significant changes due to steric effects. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

测定水中石油类液液萃取仪的比较和选择

文章分别从系统误差、乳化现象、工作效率、便利性和经济实用性比较了四种商品化的液液萃取仪在测定水中石油类前处理中的应用。吹气式自动萃取仪易导致四氯化碳的挥发损失;射流萃取仪不易清洗干净;搅拌式萃取仪具有机械破乳的作用;震荡萃取仪工作效率高,但价格昂贵。最后对萃取仪的使用和选择提出了建议。     

Extraction of rice bran oil using aqueous media

Aqueous extraction of oil from rice bran was studied on a laboratory scale and the resulting product was examined. The following process parameters influencing oil extraction were individually investigated: pH of aqueous media, extraction temperature, extraction time, agitation speed and rice bran‐to‐water ratio. Extraction temperature and pH were found to be the main factors influencing oil extraction. The highest oil yield was obtained at pH 12.0, extraction temperature 50 °C, extraction time 30 min, agitation speed 1000 rpm, and rice bran‐to‐water ratio 1.5‐to‐10. The quality of aqueous‐extracted oil in terms of free fatty acid, iodine value and saponification value was similar to a commercial sample of rice bran oil and hexane‐extracted oil, but the peroxide value was higher. Furthermore, the colour of aqueous‐extracted oil was paler than solvent‐extracted oil. © 2000 Society of Chemical Industry     

Extraction and structural characterization of cellulose from milkweed floss

The aim of this study was to investigate the utilization of milkweed fruit floss residues as a source for the isolation of cellulose. Cellulose was extracted by acidified sodium chlorite and sodium hydroxide treatments. Characterization of the pristine milkweed floss and extracted cellulose was performed by chemical composition analysis, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). The extracted cellulose had mainly α-cellulose as the other components hemicellulose and lignin were significantly removed during cellulose extraction process. The FTIR spectra also indicated that the chemical treatments extensively removed hemicellulose and lignin from the pristine milkweed floss. SEM technique was used to investigate the surface morphology of the pristine milkweed floss and extracted cellulose. The intensity of the crystalline peak in the X-ray diffractograms of the extracted cellulose was higher than that of pristine milkweed. Further, the XRD results indicated a structural transformation of cellulose I (pristine milkweed) to cellulose II (extracted cellulose) because of the chemical treatments. The extracted cellulose, which is a high biomass, had better thermal stability than the pristine milkweed floss owing to removal of non-cellulosic components.     

Preparative-scale supercritical fluid extraction/supercritical fluid chromatography of corn bran

A preparative-scale supercritical fluid extraction/supercritical fluid chromatography (SFE/SFC) procedure has been developed for the removal of oil from corn bran to obtain fractions enriched with free sterols and ferulate-phytosterol esters (FPE). Operational parameters from an analytical-scale supercritical fluid fractionation technique were translated to and optimized on a home-built, preparatory-scale SFE/SFC apparatus. SFE was performed at 34.5 MPa and 40°C using supercritical carbon dioxide. These conditions did not result in exhaustive extraction of the corn bran, but yielded about 96% of the available oil. SFC was conducted in three steps, followed by reconditioning of the sorbent bed. Preparative-scale SFE/SFC of corn bran produced a fraction enriched greater than fourfold in free sterols and 10-fold in FPE, suggesting that such a scheme could be used industrially to produce a functional food ingredient.