Chemical Modification of Guaran Gum. Part 3: Carboxymethylation in non-Aqueous Medium

Guar gum was isolated from the seeds and subjected to modification via non-aqueous carboxymethylation. Highly substituted carboxymethyl guaran derivatives could be obtained via repeating the reaction four times, where a product of degree of substitution (D.S.) 2.07 was obtained indicating that the free hydroxyl groups of both glucose and mannose (which form the main constituents of guaran) can react with monochloro acetic acid. The modification increases the solubility of the gum in cold water, and increases the stability of its pastes to microorganisms. Pastes of these derivatives are characterized by non-Newtonian pseudoplastic behaviour regardless of their D.S. or the measuring temperature, while their apparent viscosity decreases by increasing the D.S. and/or the measuring temperature.     

Chemical Modification of Guaran Gum. Part 2: Cyanoethylation

Guar gum was cyanoethylated under a variety of conditions. It is shown that the extent of reaction increases by increasing the acrylo-concentration nitrile and decreases by increasing the reaction temperature. Cyanoethyl guaran pastes are characterized by non-Newtonian pseudoplastic behaviour and may be described by the power low T = kDⁿ in which the rheological parameters k and n depend mainly on the type of the derivatives. The apparent viscosity of these derivatives depends on its nitrogen content as well as the rate of shear.     

Isolation,Chemical Modification and Rheological Characterization of Leucaena Gum. Part I: Carboxymethylation

Leucaena gum was isolated from leucaena seeds and subjected to chemical modification via carboxymethylation under a variety of conditions. Variables studied include concentration of the etherifying agents and the preparation medium. It was found that the extent of carboxymethylation expressed as DS increases by increasing the concentration of the etherifying agents. Higher DS values were obtained in non-aqueous medium. The carboxymethylated leucaena derivatives are cold water soluble and can be precipitated by ethanol. Their pastes are characterized by non-Newtonian pseudoplastic behaviour regardless of the method of preparation or DS of the products. The apparent viscosity at various rates was thouroughly investigated. The effect of storing of these pastes on the rheological properties was also studied.     

瓜尔胶的改性及其在造纸中的应用

概述了瓜尔胶的结构和性质,重点介绍了其化学改性方法及不同类型瓜尔胶衍生物在造纸工业中的应用.     

魔芋葡甘聚糖与瓜尔豆胶协同相互作用及其凝胶化研究

魔芋葡甘聚糖( 也称魔芋胶)与瓜尔豆胶均为非凝胶多糖,但二者共按一定比例共混可以得到凝胶,这是多糖分子间相互作用的结果。当总糖浓度为 1%,魔芋胶与瓜尔豆胶的共混比例为 60/40,制备温度为 80OC,体系盐离子(Ca2 )浓度为 0.1mol/L时可得到协同相互作用的最大值,从 FT-IR 谱图上分析了两种多糖分子间相互作用的机理。     

Tailoring a New Sizing Agent via Structural Modification of Pregelled Starch Molecules Part 1: Carboxymethylation and Grafting

Pregelled starch (PS) was subjected to acid hydrolysis using phosphoric acid to prepare pregelled starches having different molecular sizes. The degraded pregelled starches were carboxymethylated at different reaction times. The carboxymethyl derivatives were grafted with either methacrylamide (MAam) or methacrylonitrile (MAN) as vinyl monomers using ceric ammonium nitrate (CAN) as initiator. Suitability of the new graft derivatives of pregelled starch as sizing agent of cotton yarns was studied. It is shown by the data that the extent of carboxymethylation, expressed as carboxyl content, increases by increasing the extent of hydrolysis and reaction time. Furthermore, the graft yield, expressed as mmol MAam or MAN monomer/100 g graft copolymer (grafted carboxymethylated pregelled starch or grafted carboxymethylated hydrolyzed pregelled starch) increases with increasing extent of carboxymethylation and degree of hydrolysis and follows the order: MAam > MAN. In addition cotton yarns sized with grafted carboxymethylated hydrolyzed pregelled starch – irrespective of the grafting monomer used – have better mechanical properties (tensile strength, elongation at break, and abrasion resistance) than hydrolyzed pregelled starches, carboxymethylated pregelled starch and carboxymethylated hydrolyzed pregelled starches.     

A Study on Reaction Influencing Factors in Carboxymethylation of Leucaena glauca Seed Gum

Sodiummonochloroacetate and sodiumhydroxide were employed under different conditions to prepare and optimize the carboxymethyl derivative of Leucaena glauca seed gum. The effects of concentration of reactants, reaction temperature and time have been interpreted in terms of degree of carboxymethylation as well as efficiency and rate of carboxymethylation reaction. The formation of the proposed derivative has also been supported by providing infra-red spectral characterization.     

Interaction of Proteins with Dextransulfate in Aqueous Medium Part 2. Nonequilibrium Phenomena

The character of phase transformations and composition of the phases obtained during interaction of proteins precipitating in the vicinity of the isoelectric point with dextransulfate was investigated with the aid of nephelometric measurements and chemical analysis. Clearly expressed hysteresis of the acid-base nephelometric titration which is not observed in the presence of 7-M of urea was revealed. Composition of the phases obtained is determined by the system prehistory. The soluble protein-dextransulfate complexes are highly stable to precipitation and destruction under action of the low molecular salts.     

Rheological Properties of Leucaena glauca Gum in Aqueous Solutions

The flow properties of Leucaena glauca gum solutions were studied in the range of shear rates 1.5 to 1310 s⁻¹, using a rotational viscometer Rheotest 2. The flow behaviour of aqueous solutions of the polysaccharide is pseudoplastic, and transition from Newtonian to pseudoplastic behaviour occurs in the low shear rate range at concentrations of interest to the industry. The flow of polysaccharide solutions is described by equation of state proposed by M. M. Cross. The basic rheological parameters, like zero shear rate viscosity (η_o), infinite shear rate viscosity (ηα) and a constant associated with the rupture of linkages (α) were calculated applying simple and established relations. The effect of concentration and temperature on rheological parameters have been studied. The Cross equation is found to be applicable to the data with a good degree of accuracy over a wide range of shear rates.     

田菁胶的改性及浆纱效果

研究不同程度改性田菁胶的上浆效果.将天然高分子田菁胶通过NaClO氧化降解,使其成为分子量相对较小的分子,对降解后的不同浓度改性田菁胶的黏度进行了测试,并对比了改性田菁胶和PR-Su、PVA浆出纱线的强伸性能、毛羽数和耐磨性能.试验表明:浓度为1.5%的改性田菁胶上浆综合效果较理想.认为:田菁胶经过NaClO氧化降解后可以用于纺织上浆.     

瓜尔胶的改性及在造纸工业中的应用

结合瓜尔胶的结构特点综述了其改性方法,并对瓜尔胶在造纸工业中的应用和最新研究成果进行了介绍,阐述了瓜尔胶是一种新型环保型造纸助剂,有着广阔的应用前景。     

影响结冷胶水溶液流变特性的因素

研究了质量分数、时间、温度、柠檬酸、pH值、Na^＋、Ca^2＋对结冷胶水溶液的粘度及形成凝胶后的凝胶强度的影响.结果表明：结冷胶的粘度随着溶液质量分数的增加呈非线性增大,室温下其粘度的稳定时间大于4 h.温度、pH值、柠檬酸对结冷胶水溶液粘度有相应的影响;柠檬酸、NaCl、CaCl2溶液对结冷胶的凝胶强度有较大影响.     

无籽刺梨渣膳食纤维的羧甲基化改性及性质

为探究羧甲基化改性对无籽刺梨渣膳食纤维性质的影响,本文采用羧甲基化法改性无籽刺梨渣可溶性膳食纤维（Rosa sterilis Soluble Dietary Fiber,RSDF）和不溶性膳食纤维（Rosa sterilis Insoluble Dietary Fiber,RIDF）,对比分析了无籽刺梨渣膳食纤维改性前后以及羧甲基化总膳食纤维（Carboxymethylated Total Dietary Fiber,CTDF）不同混合比例的理化和功能性质。结果表明:改性后,羧甲基化可溶性膳食纤维（Carboxymethylation Soluble Dietary Fiber,CSDF）、羧甲基化不溶性膳食纤维（Carboxymethylation Insoluble Dietary Fiber,CIDF）膨胀力、持水力、持油力、吸湿性、阳离子交换力、亚硝酸盐吸附力和葡萄糖吸附力均显著增大（P<0.05）,CSDF/CIDF混合比例1:3时取代度为0.53±0.02,综合理化、功能性质为最优混合比例。红外光谱分析可知CSDF、CIDF羧甲基化修饰成功;电镜扫描分析可知两种膳食纤维结构疏松、存在大量褶皱和片状物质,CSDF/CIDF混合比例1:3时孔洞和片状结构更多;差示扫描热分析可知改性后,CSDF、CIDF贮藏稳定性均提高,CSDF/CIDF混合比例1:3热熔解温度最高为145 ℃。综上,羧甲基改性后,无籽刺梨膳食纤维性能均优于改性前且综合各项性能后,CSDF/CIDF混合比例1:3为最佳混合比。     

Rheological Properties and Emulsifying Activity of Gum Karaya (Sterculia Urens) in Aqueous System and Oil in Water Emulsion: Heat Treatment and Microwave Modification

Gum karaya is a polysaccharide gum from Sterculia urens tree. It is used as an emulsifier and thickening agent in cosmetics and pharmaceuticals. However, it has very strong swelling properties, high viscosity, and low solubility, providing the restricted applications in the food industry. The main objective of this study was to investigate the effects of different heat treatment and microwave variables (i.e., time: 8, 10, and 12 min; power: 700 and 1000 W) on the functional properties of gum karaya in the aqueous system and oil-in-water emulsion. In this regard, the rheological properties, emulsifying activity, average droplet size, and surface morphology of the native- and microwave-treated gums were analyzed and compared. Dynamic oscillatory test indicated that the microwave-treated gum karaya had more gel-like behavior than viscous-like behavior (G′ > G″) at a relatively high concentration (20% or 20 g/100 g). When gum karaya was treated by microwave for 8–12 min, both elastic (G′) and viscous (G″) moduli were declined. The native- and microwave-treated gum karaya exhibited a shear-thinning (pseudoplastic) behavior in the aqueous system and oil-in-water emulsion. The results showed that the microwave-treated gum karaya had smaller particles than the native gum in the aqueous system. On the other hand, the emulsion containing the microwave-treated gum karaya had finer emulsion droplets than the control containing the native gum karaya. This confirmed that the application of microwave treatment led to significantly (p < 0.05) improve the emulsifying activity of gum karaya.     

黄精多糖的提纯、硫酸化和羧甲基化修饰及其抗氧化活性研究

以黄精为原料,采用超声辅助法提取黄精多糖,经DEAE-52纤维素层析及葡聚糖凝胶层析柱Sephadex G-200分离纯化,得到平均分子量为21.58 kDa的纯黄精多糖(PSP1-A),浓硫酸法制备硫酸酯化多糖(SPSP1-A),氢氧化钠-一氯乙酸体系法制备羧甲基化多糖(CPSP1-A)。通过傅里叶红外光谱法对衍生物进行结构验证,并采用体外实验法对比修饰前后黄精多糖的抗氧化活性。结果表明,黄精多糖提纯修饰后得到取代度为1.44的硫酸化产物和取代度为0.49的羧甲基化产物。在最大浓度10 mg/mL时,CPSP1-A对DPPH·和·OH的清除率分别为74.69%和91.27%。与PSP1-A相比,CPSP1-A对DPPH·和·OH清除力提高,还原力增强,但对ABTS⁺自由基清除力下降;而SPSP1-A对以上三种自由基的清除作用均增强,10 mg/mL时对DPPH·、·OH和ABTS⁺·的清除率分别为98.70%、95.72%和97.87%,且还原力明显提高,在10 mg/mL时,SPSP1-A还原力是PSP1-A的三倍多。结果表明,两种修饰均是提高黄精多糖抗氧化能力的有效方法。     

红枣多糖羧甲基化修饰及其抗氧化活性研究

本研究对红枣多糖进行羧甲基化修饰,探究羧甲基化修饰红枣多糖的结构特征及抗氧化活性变化。以红枣粗多糖为原料,采用Sevage法脱蛋白,大孔树脂AB-8脱色处理,对除杂后的多糖进行羧甲基化修饰。以羧甲基取代度为指标,通过单因素和响应面试验对NaOH浓度、一氯乙酸添加量及温度进行优化,以修饰前后多糖对DPPH、羟基自由基的清除能力及其还原力和对Fe2+的螯合能力为指标,探究羧甲基化修饰对红枣多糖抗氧化特性的影响。结果显示,羧甲基化修饰最佳工艺参数为:反应温度70 ℃,一氯乙酸添加量3.5%,NaOH浓度3 mol/L,此条件下羧甲基化红枣多糖分子修饰取代度高达1.157。浓度5 mg/mL时,羧甲基化修饰的红枣多糖DPPH和羟基自由基清除率达93.83%和44.7%,还原力和对Fe2+的螯合能力分别为0.462和44.05%。红枣多糖抗氧化性的显著提升表明羧甲基化修饰可改善多糖的抗氧化性,可为红枣多糖的深入研究提供一定的理论依据。     

产黄原胶发酵培养基的优化工艺研究

本实验研究不同培养基成分及不同添加量的碳源、氮源等营养物质对黄原胶产量及其黏度的影响.在其他营养物质一定的情况下,利用单因素实验分别对培养基中碳源、氮源、无机盐等进行了初步筛选,得到的最佳碳源是玉米淀粉,氮源是豆饼粉,加入磷盐、镁盐、钙盐等有利于黄单胞菌的生长及其代谢产物-黄原胶的分泌.最后利用正交实验确定了碳源、氮源...     

Intrinsic Viscosity and Flow Behaviour of Arabic Gum Aqueous Solutions

The intrinsic viscosity and flow behaviour of aqueous solutions of different concentrations of Arabic gum were studied. The molecular weight of this polymer was calculated using the value of the intrinsic viscosity, employing both Huggins and Kramer and Mark-Houwink equations. The value of the apparent viscosity and the influence of the shear rate on the rheological behaviour of different polymer concentrations in aqueous solution were determined. The effect of temperature over the flow behaviour was also studied. The Ostwald model has been employed to fit the experimental data and model parameters have been obtained.     

Chemical Modification of Proteins Part 6. Further Studies on Gelation of Casein after Modification by Dialdehyde Starch

The physical and chemical changes in casein during the gelation owing to the chemical modification by dialdehyde starch (DAS) in 8–10% solution were studied using electron-microscopy, measuring the mechanical properties (shear deformation), turbidimetric titration, and determination of amino groups. The gelation which proceeds during a storage time of 2 weeks is accomplished by the formation of a super-molecular network structure. Depending on the conditions of modification (pH, percentage of DAS, protein concentration) a more or less dense network is formed. An increase of pH (in the range of pH 6,3–9,7) leads to an increase of gelation speed, which favours the formation of irregular network structures. The denser the network formed the smaller is the shear deformation measured by the device of Tolstoi. During the storage of the gels the plastic component of compliance decreases to a greater amount than the elastic one. Therefore the relative amount of elastic component increases. During the reaction with DAS the maximum of turbidity of the protein (solubility minimum) shifted to lower pH owing to a blockage of positively charged groups. On the contrary to the changes measured by physical methods, this shift is complete soon after a 1 day storage. Similarly the blockage of amino groups is finished in the most cases this time too.