淀粉类保水剂合成过程中皂化介质对吸水性的影响

合成适用于工业生产的淀粉接枝共聚物保水剂。系统地考察了淀粉接枝共聚物在皂化过程中,分散介质对产物吸水性能的影响。     

新型淀粉吸水剂HSPANS的合成及其吸水,保水性能的研究

合成了一种比现有淀粉接枝物吸水剂吸水性能更为优异的新型淀粉吸水剂——HSPANS。系统地比较了各种淀粉接枝物吸水剂的吸湿性、吸水性、凝胶保水性能,以及溶液的pH值、分散介质、温度以及压力等因素对淀粉接枝物吸水剂吸水、保水性能的影响. 吸水、保水性能比较结果为: HSPANS>HSPAN>>CLSPAANa>SPAMS>SPAM>SMS     

魔芋接枝丙烯酸高吸水性树脂的制备及性能研究

本实验以魔芋精粉为基体,环己烷为连续相,Span-60为分散剂,硝酸铈铵为引发剂、用反相悬浮聚合法合成魔芋-丙烯酸高吸水性树脂。研究了多种因素对接枝共聚物吸水性能的影响。结果表明:反应时间为2 h、魔芋精粉与丙烯酸质量比为1∶5、交联剂用量为物料质量的0.04%、引发剂为3×10-3mol/L、丙烯酸中和度为60%、反应温度为70℃时,接枝共聚物吸水性能最优。并通过对接枝产物的红外图谱分析,证实了反应的可行性。     

魔芋葡甘露聚糖-丙烯腈接枝共聚反应的研究

本研究以硝酸铈铵作为引发剂,探讨反应时间、反应温度、引发剂浓度和单体用量对魔芋葡甘露聚糖-丙烯腈接枝共聚反应的影响;并利用扫描电镜等分析技术对接枝共聚物结构与性能的关系作了初步探。结果表明,接枝共聚物的粘度比反应前提高了2—4倍;溶胶的相对稳定性提高了近4倍;接枝共聚物成膜更为均匀、细密;且气泡明显减少。     

丙烯腈-蚕丝接枝共聚纤维的热性能研究——Ⅰ,热分析法对丙烯腈接枝的表征

采用热分析法,对接枝率(R_p为0—99.4％的丙烯腈-蚕丝接枝共聚纤维进行了表征。发现当R_p为39.4％时,接枝蚕丝开始出现明显的特征初始放热效应。随着R_p的增大,DSC、DTA的放热峰位(T_p)朝低温向移动,并与T_p成良好的线性关系,其T_p在245—275℃之间。引用表现特征放热效应的反应模式,计算出反应热焓为21.1—26.0RJ/mol,从反应热力学上初步证实了该模式的存在。还用DSC法,测定了接技蚕丝的玻璃化程度(T_g),得到丙烯腈接技链段不长的结论。     

新型共聚物淀粉接技聚乳酸的制备及其表征

采用原位熔融共聚法,以淀粉和乳酸为原料,制备改性淀粉聚乳酸接枝共聚物,对共聚反应机理进行初步探讨.结果表明,淀粉经PEG-400和马来酸酐增塑改性处理反应活性增强,与乳酸反应生成的淀粉聚乳酸接枝共聚物分子量Mw为6.921×10~4,Mn为4.789×10~4,分子量分布Mw/Mn为1.445.共聚物在PBS缓冲溶液中进行降解测试,结果为6天后质量损失一半.     

可溶性淀粉合成酶与稻米淀粉精细结构关系的研究进展

支链淀粉是稻米淀粉的最主要组成部分,不同水稻品种间支链淀粉分子聚合度及分支链链长与分布有所不同,从而影响了稻米的品质。本文简要回顾了稻米淀粉的结构及其主要合成酶类,并以可溶性淀粉合成酶为重点,综述了水稻中可溶性淀粉合成酶4个亚家族不同同工型在决定淀粉精细结构中的作用,同时对相关基因的表达等方面也做了论述,旨在为水稻淀粉合成调控及品质改良提供参考。     

酶促淀粉利用和遗传工程

淀粉是植物界主要贮存性食物多糖,多见于玉米、小麦、大麦、燕麦、水稻和高粱的籽粒,以及马铃薯、竹芋和木薯的块茎或块根以及西谷椰子的髓部中。淀粉由 D-葡萄糖的直链和支链均聚物组成。直链淀粉含有由1,4-键连接的α-D-吡喃葡萄糖单位组成的多条直链,聚合度为1×10~2～4×10~3。而支链淀粉中,1,4-键连接的α-D-吡喃葡萄糖单位组成的多条短直链(含17～23个葡糖单位),靠1,6-键相互连接起来,形成一个高度分支的结构,聚合度为1×10~4～4×10~7。淀粉的分支程度和直、支链淀粉比例因淀粉来源和时基等而异。大部分淀粉被用于食品业和饮料业,主要是用其水解产物怍为饮料和甜食中的甜味剂及半固体食物如果酱、蛋奶冻、馅饼馅、甜点心中的增稠剂等。淀粉总量中有约百分之一的部     

淀粉发酵法制取甘油

随首市场对甘油(丙三醇)的需求量不断增加,且皂化甘油产量又不断下降,为缓解供需矛盾,开发甘油新来源,以淀粉为原料经酶法液化、糖化后,以亚硫酸盐诱导进行甘油发酵,再经处理分离、精制,能获得较好的甘油产品。本文介绍淀粉发酵法制取甘油的工艺及化学原理。     

用于荧光辅助糖电泳寡糖标尺的构建

荧光辅助糖电泳(FACE)是一种简洁廉价的分离糖类方法。寡糖首先与8-氨基萘基-1,3,6-三磺酸(ANTS)反应标记,然后,ANTS标记的寡糖通过在32％丙烯酰胺-2．4％双丙烯酰胺组成的分离胶上电泳从而得以相互分离。结果表明,电泳图谱能准确反映寡糖的聚合度梯度,因而,一种具有连续聚合度的淀粉水解液的荧光标记电泳图谱可以作为荧光辅助糖电泳的分子量标尺。     

Super-absorbent polymers from starch-polyacrylonitrile graft copolymers by acid hydrolysis before saponification

Graft copolymers (SPAN) of polyacrylonitrile (PAN) onto starch were prepared from gelatinized starch varieties with ammonium ceric nitrate as an initiator. The molecular weight of the PAN branches increased for the varieties of starches in the order high amylose maize starch < maize starch < waxy maize starch. SPAN samples were saponified with aqueous NaOH, and the aqueous solution of the resulting polymer (HSPAN) was cast into film in a forced-air oven at 35°C. The water absorbency of the HSPAN film formed from waxy maize starch was the highest (1200 g H₂O (g dry sample)⁻¹) and that from high amylose maize starch was the lowest (530 g g⁻¹). SPAN samples from maize starch were partially hydrolyzed with dilute hydrochloric acid. The resulting polyacrylonitriles with low molecular weight starch end groups (LSPAN) were also saponified. The resulting saponified product (HLSPAN) was cast into film. The absorbencies of HLSPAN films were found to be far larger (up to 6000 g g⁻¹) than those of the corresponding HSPAN films. The absorbency increased with increasing molecular weight of PAN in the initial SPAN up to a molecular weight of 1−1·5 × 10⁶. The absorbency decreased significantly when HSPAN and HLSPAN films were subjected to heat treatment at 135°C or above. The crosslinks present in HSPAN and HLSPAN films prepared at 35°C and those formed during heat treatment were considered to have different structures: the former formed between carbohydrate alkoxide ions and nitrile groups at the early stages of saponification and the latter formed between carbohydrate and copoly(acrylate-acrylamide) chains and/or between copoly(acrylate-acrylamide) chains.     

HRP-mediated synthesis of starch–polyacrylamide graft copolymers

Starch was reacted with acrylamide in water in the presence of horseradish peroxidase (HRP) catalyst/H₂O₂/2,4 pentanedione to give starch–polyacrylamide graft copolymers.     

Radiation-induced eco-compatible sulfonated starch/acrylic acid graft copolymers for sucrose hydrolysis

Radiation-induced graft-copolymers capable of hosting sulfonic groups and having more effective catalytic activity towards sucrose hydrolysis were prepared. Acrylic acid monomer (AA) was copolymerized with sulfonated starch (SS) at different compositions using ionizing radiation. Swelling behavior of the prepared copolymers at different environmental conditions was studied as well as thermal stability. The hydrolysis of sucrose to glucose and fructose by sulfonated starch/acrylic acid (SS/AA) graft copolymers was investigated. The kinetics of the reaction was determined for various (SS/AA) graft copolymers compositions and at a temperature range of 40-60 °C. The catalytic activity of the copolymers was found to be dependent on the reaction temperature and (SS/AA) graft copolymers compositions, it increases as the reaction temperature and sulfonated starch content (in the feed solution) increases. The obtained results suggest that the prepared SS/AA copolymers could be considered as catalytic reagent for sucrose hydrolysis.     

Graft copolymerization of acrylic acid to cassava starch-Evaluation of the influences of process parameters by an experimental design method

The graft copolymerization of cassava starch with acrylic acid was investigated using a free radical initiator system (Fe(2+)/H(2)O(2) redox system) in water. A comprehensive understanding of the important variables and their interaction has been obtained by applying an experimental design method. In this approach, two ('high' and 'low') values of selected variables are considered. Important result parameters are add-on and the grafting efficiency. Out of eight reaction variables, it was found that only temperature, starch concentration and the starch to monomer ratio have a pronounced influence on these response parameters. Moderate reaction temperature (40°C) and high starch concentration (10%) give relatively good results of add-on and grafting efficiency. A low starch to monomer ratio favors add-on but decreases grafting efficiency. These findings can be used to optimize the production of cassava starch-acrylate copolymers and to gain insight in the process-product property interactions, for various applications.     

Synthesis and characterization of a novel super-absorbent based on wheat straw

In order to develop an eco-friendly polymer, a novel super-absorbent polymer was prepared by graft copolymerization of acrylic acid (AA), acrylic amide (AM) and dimethyl diallyl ammonium chloride (DMDAAC) onto the pretreatment wheat straw (PTWS). The molecular structure of the super-absorbent was confirmed by FTIR. The factors that can influence absorbencies of the super-absorbent resin (SAR) were investigated, such as weight ratio between the monomers, the ratio of PTWS to monomers, the amount of initiator and cross-linker, temperature reaction time and neutralization degree of AA. The SAR has the water absorbency of 133.76 g/g in distilled water and 33.83 g/g in 0.9 wt.% NaCl solution.     

Preparation of clear noodles with mixtures of tapioca and high-amylose starches

Ways to simulate the making of clear noodles from mung bran starch were investigated by studying the molecular structures of mung bean and tapioca starches. Scanning electron micrographs showed that tapioca starch granules were smaller than those of mung bean starch. X-ray diffraction patterns of mung bean and tapioca starch were A- and C_A-patterns, respectively. Iodine affinity studies indicated that mung bean starch contained 37% of apparent amylose and tapioca starch contained 24%. Gel permeation chromatograms showed that mung bean amylopectin had longer peak chain-length of long-branch chains (DP 40) than that of tapioca starch (DP 35) but shorter peak chain-length of short-branch chains (DP 16) than that of tapioca starch (DP 21). P-31 n.m.r. spectroscopy showed that both starches contained phosphate monoesters, but only mung bean starch contained phospholipids. Physical properties, including pasting viscosity, gel strength, and thermal properties (gelatinization), were determined. The results of the molecular structure study and physical properties were used to develop acceptable products using mixtures of cross-linked tapioca and high-amylose maize starches. Tapioca starch was cross-linked by sodium trimetaphosphate (STMP) with various reaction times, pH values, and temperatures. The correlation between those parameters and the pasting viscosity were studied using a visco/amylograph. Starches, cross-linked with 0.1% STMP, pH 11.0, 3.5 h reaction time at 25, 35, and 45°C (reaction temperature), were used for making noodles. High-amylose maize starch (70% amylose) was mixed at varying ratios (9, 13, 17, 28, 37, and 44%) with the cross-linked tapioca starches. Analysis of the noodles included: tensile strength, water absorption, and soluble loss. Noodle sensory properties were evaluated using trained panelists. Noodles made from a mixture of cross-linked tapioca starch and 17% of a high-amylose starch were comparable to the clear noodles made from mung bean starch.     

Preparation, characterization, and in vitro drug release behavior of biodegradable chitosan-graft-poly(1, 4-dioxan-2-one) copolymer

A novel copolymer of chitosan-g-poly(p-dioxanone) (CGP) was synthesized in bulk by ring-opening polymerization of p-dioxanone (PDO) initiated by the hydroxyl group or amino group of chitosan using SnOct₂ as catalyst. The chemical structure was determined by ¹H NMR. It was found that the feed ratio of chitosan to PDO had a great effect on the degree of polymerization (DP) and the substitution (DS) of PDO. The thermal stability and crystallization behavior of graft copolymer CGP were closely related to the values of DP and DS. When the resulting copolymer was used as Ibuprofen carrier, the release rate of Ibuprofen decreased compared with that of pure chitosan carrier. The drug release behavior was also influenced by the structure of graft copolymers.     

Analysis of nonstructural carbohydrates in storage organs of 30 ornamental geophytes by high-performance anion-exchange chromatography with pulsed amperometric detection

A comprehensive analysis of nonstructural carbohydrates in storage organs (bulbs and corms) of 30 ornamental geophytes was conducted by employing a variety of extraction techniques followed by high-performance anion-exchange chromatography with pulsed amperometric detection (HPAE-PAD). Among species, starch, fructan, glucomannan and soluble sugars accounted for 50-80% of storage organ dry weight (DW). Starch ranged from 24 to 760 mg g(-1) DW, fructan (commonly occurring with starch) from 25 to 500 mg g(-1) DW, and glucomannan from 15 to 145 mg g(-1) DW. An acid hydrolysis protocol for concurrent determination of fructan and glucomannan was developed. The average degree of polymerization (DP) of ethanol and water-soluble fructan and the man : glu ratio of glucomannan also varied between species. The 80% ethanol fraction contained soluble sugars and short-chain fructans (< 25 DP), whereas water extracts contained soluble sugars, fructans (both short- and long-chain, 相似文献   

PAN- b- PEG- b- PAN 两亲性嵌段共聚物的合成及热稳定性

以2-溴丙酰溴封端的聚乙二醇（PEG2000）为大分子引发刺,溴化亚铜（CuBr）为催化剂,2,2＇-联吡啶（bpy）为配体,碳酸乙烯酯（EC）为溶剂,采用原子转移自由基聚合（ATRY）法合成了两亲性嵌段共聚物PAN-b-PEG-b-PAN。通过FTIR、^1HNMR和GPC对产物的结构进行了表征,并运用TGA对PAN-b-PEG-b-PAN两亲性嵌段共聚物的热稳定性进行了研究。结果表明：PAN-b-PEG-b-PAN的热稳定性较纯PEG要高,且随着PAN-b-PEG-b-PAN两亲性嵌段共聚物的分子量的增加,此嵌段共聚物的热稳定性增强。它的起始的分解温度为275℃,在275℃-450℃失重较少,失重率约为15％,在400℃-450℃迅速分解,失重率为60％左右。     

Recent advances in chemistry and biotechnology of starch derivatives

The review focuses on the most important studies performed during the last eight years on the physical and chemical modifications of starch, starch graft copolymers, and starch ethers; on the development of biodegradable starch-based materials; and on various applications of numerous starch derivatives. An analysis of the recent publications allows the conclusion that considerable advances have been made in the chemistry and technology of starch derivatives as biodegradable “green” reagents and products, which are becoming increasingly important for technological applications due to the wide occurrence of starch, the ease of its processing, and its nature as a renewable resource.