半干法制备两性瓜尔胶的结构及其增强性能的研究

采用半干法工艺在同一反应器内合成了粉状两性瓜尔胶,用红外光谱(FT-IR)、扫描电镜(SEM)对产物进行了结构表征。通过浆内添加研究了两性瓜尔胶的取代度、用量和浆料pH值对纸张增强性能的影响,并与非离子瓜尔胶和阳离子淀粉的增强性能进行了对比。结果表明,合成样品阳离子取代度(DSc)大于0.25,阴离子取代度(DSa)为0.05～0.10;改性剂与瓜尔胶在颗粒表面与内部都发生反应;制备的两性瓜尔胶对纸张有较好的增强效果,尤其是中碱性条件下效果显著;当两性瓜尔胶添加量为0.3%时,针叶木CTMP浆的裂断长、耐折度、耐破指数和撕裂指数分别提高了13.3%、70%、17.5%和10.1%。     

磷酸酯型两性瓜尔胶的合成及增强性能研究

以异丙醇为溶剂,采用先阴离子化后阳离子化工艺合成了含磷酸酯和季铵基团的两性瓜尔胶,并通过1H-NMR证实自制阴离子中间体和两性瓜尔胶的官能用结构.研究了反应温度,阴离子中间体、阳离子单体、碱用量对产物的磷、氮含量的影响,确定优化条件为:反应温度60℃、醚化时NaOH用晕5%、阴离子中间体及阳离子单体用量分别为15%和28%,此时产物的磷和氮含量分别为0.44%和0.8%.该新型两性瓜尔胶用于ONP浆体系,能明显提高手抄片的强度性能,当其用量为0.2%时可使印刷表面强度提高24.5%,优于工厂现用两性淀粉.     

新型两性瓜尔胶的制备及其在卷烟纸中的应用研究

采用先合成两性醚化剂中间体,再将中间体接枝到瓜尔胶上的方法制得一种新型两性瓜尔胶,并对反应产物结构进行了表征。比较了其与传统添加阳/非离子瓜尔胶的方法在卷烟纸生产中的应用效果。结果表明:DSC分析证实N,N-二甲基氨基乙酸盐酸盐已经被成功制得;红外谱图证实两性中间体已经接枝到瓜尔胶上制得了两性瓜尔胶。当阔叶木浆与针叶木浆比例为7∶3,非离子瓜尔胶添加量为0.3%、阳离子瓜尔胶添加量为0.1%,或单独添加两性瓜尔胶为0.1%时纸张性能达到最佳;单独使用两性瓜尔胶比使用阳/非离子瓜尔胶复配在白水循环系统中能更好地稳定纸张的强度和透气度。     

The viscosity of dilute solutions of guar gum and locust bean gum with and without added sugars

The apparent viscosities of dilute solutions of guar and locust bean gums have been measured. The intrinsic viscosity [n] of guar gum solution is greater than that of locust bean gum solution, but the interaction coefficient k of guar gum solutions is less than that of locust bean gum. Addition of glucose, sucrose, or glucose syrup increases the apparent viscosity of the gum solution. The intrinsic viscosity of the gum solution is decreased but the interaction coefficient is increased.     

Functional Properties of Flax Seed Mucilage

Flax seed (Linwn usitatissimum L.) mucilage was prepared by extraction of seeds with water followed by evaporation, precipitation with ethanol and freeze drying of extract. Proximate composition, solubility, foamability and moisture sorption characteristics were determined. The mucilage contained less carbohydrates, more minerals and more protein than commercial locust bean and guar gums. Its solubility, however, was higher than locust bean and guar gums, and lower than gum arabic. Flax seed mucilage exhibited good foam stability properties in aqueous solutions at 1.0% (w/v). Very diluted solutions exhibited Newtonian-like behavior while shear thinning was shown at concentrations above 0.2% (w/v). The viscosity was maximum at a pH range 6.0–8.0 and it was reduced in solutions containing NaCl.     

The effect of shear rate on the viscosity of solutions of guar gum and locust bean gum

The apparent viscosities of aqueous solutions of guar gum and locust bean gum have been measured over a range of shear rates from 14 to 1142 s^?1. Comparable measurements were also made on gum solutions to which glucose, sucrose or glucose syrup had been added. For all the solutions the variation of relative viscosity with shear rate fits a power law equation. Addition of sugar has no effect on the non-Newtonian behaviour of the gum solutions. The relative viscosity of the gum in the sugar solutions is lower than in water. The ratios of the relative viscosities closely correspond with the ratios of the intrinsic viscosities. This is interpreted in terms of a smaller extension of the gum molecule in the sugar solution.     

瓜尔豆胶对锥栗淀粉糊化和流变学特性的影响

以新鲜锥栗为原料,考察了瓜尔豆胶对锥栗淀粉的糊化特性和流变学特性的影响。结果表明,向锥栗淀粉中添加瓜尔豆胶后,锥栗淀粉糊化溶液的峰值黏度和终值黏度增大,且随瓜尔豆胶添加比例的增加而增大;添加瓜尔豆胶增大了锥栗淀粉的起始糊化温度和峰值糊化温度,提高了锥栗淀粉的吸热焓,使得糊化过程更长,吸热更多。添加瓜尔豆胶后的锥栗淀粉溶液显示为假塑性流体,剪切变稀现象更为明显,具有更大的黏弹性。添加瓜尔豆胶后,混合物形成的凝胶表面空隙中填充物增多,空隙数量减少,且空隙分布更加均匀。     

Viscosity of guar gum and xanthan/guar gum mixture solutions

The viscosity of diluted guar gum solutions and the viscosity of xanthan and guar gum mixture solutions have been studied. Guar gum solutions showed pseudoplastic behaviour. Apparent viscosity increased with gum concentration and decreased with the temperature at which viscosity was measured. A maximum in the plot of viscosity versus increasing dissolution temperature was observed at 60 °C. This behaviour was related to differences in molecular structure of the polymers solved at different temperatures. Mixtures of xanthan and guar gum showed a higher combined viscosity than that occurring in each separate gum. This synergistic interaction was affected by the gum ratio in the mixture and dissolution temperature of both gums. The effect of polysaccharide concentration (1.0, 1.5 and 2.0 kg m⁻³), xanthan/guar gum ratio (1/5, 4/2, 3/3, 4/2 and 5/1) and dissolution temperature (25, 40, 60 and 80 °C for both gums) on the viscosity of solutions of mixtures were studied. The highest viscosities were observed when 2.0 kg m⁻³ gum concentration was used together with a ratio of xanthan/guar gum of 3/3 (w/w) and dissolution temperature of 40 and 80 °C for xanthan and guar gum, respectively. © 2000 Society of Chemical Industry     

Semi‐dilute solutions of hydroxypropyl guar gum: Viscosity behaviour and thixotropic properties

Semi‐dilute solutions of hydroxypropyl guar gum (HPGG), the most widely used derivative of naturally occurring guar galactomannan, were investigated with respect to their viscosity, yield stress and thixotropy. It was found that the shear‐dependent viscosity behaviour under various HPGG concentrations, added salts and temperature could be well described by the Cross viscosity model. The zero‐shear‐rate viscosity was observed to change with HPGG concentration according to a power‐law function, and decease with the increase of temperature according to an Arrhenius‐type equation. The addition of salts (KCl and CaCl₂) lowered the zero‐shear‐rate viscosity. The HPGG solutions of high concentration showed a higher degree of thixotropy while the addition of salt lowered the thixotropic property. Copyright © 2007 Society of Chemical Industry     

Rheology of Mixed Systems of Sweet Potato Starch and Galactomannans

The effect of galactomannans (guar gum and locust bean gum) at different concentrations (0, 0.2, 0.4 and 0.6%, w/w) on rheological properties of sweet potato starch (SPS) was studied. The flow behaviors of SPS‐galactomannan mixtures were determined from the rheological parameters of power law and Casson models. The SPS‐galactomannan mixtures had high shear‐thinning fluid characteristics (n = 0.30‐0.36) exhibiting yield stress at 25°C. The presence of galactomannans resulted in the increase in consistency index (K), apparent viscosity (η_a,100) and Casson yield stress (σ_oc). In the temperature range of 25‐70°C, the mixtures followed the Arrhenius temperature relationship. Dynamic rheological tests at 25°C indicated that the SPS‐galactomannan mixtures had weak gel‐like behavior with storage moduli (G′) higher than loss moduli (G") over most of the frequency range (0.63‐62.8 rad/s) with frequency dependency. The magnitudes of dynamic moduli (G′, G" and η*) of the SPS‐galactomannan mixtures were higher than those of the control (0% gum), and increased with an increase in gum concentration. The tan δ (ratio of G"/G′) values (0.41‐0.46) of SPS‐guar gum mixtures were much lower than those (0.50‐0.63) of SPS‐locust bean gum mixtures, indicating that there was a more pronounced effect of guar gum on the elastic properties of SPS.     

Carboxymethyl derivatives of flaxseed (Linum usitatissimum L.) gum: characterisation and solution rheology

Carboxymethyl ether moieties were introduced to flaxseed (Linum usitatissimum L.) gum (FG) by reacting gum with monochloroacetic acid (MCA). Effects of ether forming reaction conditions, temperature, NaOH concentration and molar ratio of FG (anhydroxylose equivalent) to MCA, on the degree of substitution (DS) were investigated. Treatment at 70 °C, with 7.0 m NaOH, and molar ratio of MCA to FG of 10:1 over 3 h produced a polysaccharide with a DS of 0.824 ± 0.012. Both surface morphology and thermal behaviour were modified. Solutions of FG (0.5–4.0%, w/v) exhibited shear‐thinning behaviour where viscosity decreased with decreased FG concentration. After carboxymethylation, modified polymer solutions also exhibited shear‐thinning behaviour, where dynamic viscosity was lower than that of native FG solutions at the same concentration. The dynamic viscosities were lower for solutions of modified FG with higher DS and also lower for solutions made at lower FG concentrations (0.5–4.0%, w/v). A more liquid‐like behaviour with increasing FG DS was indicated as storage modulus G′ and loss modulus G″ decreased and became more frequency dependent. The substitution of hydroxyl groups with carboxymethyl groups suppressed entanglement between FG polysaccharide chains by reducing intermolecular association.     

Influence of selected hydrocolloids on triticale starch rheological properties

The aim of the study was to define the influence of selected nonstarch polysaccharides (guar gum, xanthan gum and arabic gum) on several rheological properties of triticale starch pastes/gels, at constant polysaccharide concentration (6.5 g/100 g). These included pasting characteristics, flow curves at 50 °C and mechanical spectra at 25 °C. It was found that the presence of a gum in a system modified the rheological properties of triticale starch gels/pastes, depending on the type and concentration of the gums. In the case of guar and xanthan gums, higher pasting viscosity was observed and the shear stress was increased compared with native starch. The presence of guar gum reduced the degree of thixotropy hysteresis, negative values for this being found for systems with xanthan in spite of their shear‐thinning behaviour. Systems containing arabic gum displayed lower values of pasting and flow viscosity. The type and concentration of gums added to the polysaccharide influenced the viscoelastic properties of the gels.     

Viscosity of solutions of xanthan/locust bean gum mixtures

Xanthan and locust bean gums are polysaccharides able to produce aqueous solutions with high viscosity and non‐Newtonian behaviour. When these solutions are mixed a dramatic increase on viscosity is observed, much greater than the combined viscosity of the separated polysaccharide solutions. In this work the influences of different variables on the viscosity of solutions of mixtures of xanthan/locust bean gum have been studied. Total polysaccharide concentration, xanthan and locust bean ratio on mixture and temperature at which the gum was dissolved (dissolution temperature) for both xanthan and locust bean gums have been considered. Under these different operational mixture conditions shear rate and time have also been considered to describe the rheological behaviour of the solutions studied. The high viscosity increase observed in these mixtures is due to the interaction between xanthan gum and locust bean gum molecules. This interaction takes place between the side chains of xanthan and the backbone of the locust bean gum. Both xanthan molecule conformation in solution – tertiary structure – and locust bean gum structure show great influence on the final viscosity of the solution mixtures. Xanthan conformation changes with temperature, going from ordered structures to disordered or chaotic ones. Locust bean gum composition changes with dissolution temperature, showing a dissolved galactose/mannose ratio reduction when temperature increases, ie the smooth regions – zones without galactose radicals – are predominantly dissolved. The highest viscosity was obtained for the solution mixture with a total polysaccharide concentration of 1.5 kg m⁻³ and a xanthan/locust ratio of 2:4 (w/w) and when xanthan gum and locust bean gum were dissolved at 40°C and 80°C, respectively. © 1999 Society of Chemical Industry     

Influence of oat gum, guar gum and carboxymethyl cellulose on the perception of sweetness and flavour

The influence of three pseudoplastic hydrocolloids, oat gum, guar gum and carboxymethyl cellulose (CMC) on sensory perception of sweetness and flavour was studied in model systems at two viscosity levels. The sweeteners studied were sucrose, fructose and aspartame, the flavour substances ethyl caproate, a-pinene and cinnamic acid. Sweetness was best perceived from oat gum solutions and most weakly from guar gum solutions. The effect of the composition of the thickener on the perception of sweetness was greater than that of viscosity. Reduction of sweetness by hydrocolloids was weaker for aspartame than for fructose or sucrose. In the perception of flavours, both the total length of perception and the time-intensity pattern were more dependent on the model aroma substance than on the thickener. Possible explanations for the differences are discussed.     

Pasting Properties of Non‐waxy Rice Starch‐Hydrocolloid Mixtures

The swelling and pasting properties of non‐waxy rice starch‐hydrocolloid mixtures were investigated using commercial and laboratory‐generated hydrocolloids. The swelling power of the rice starch‐hydrocolloid mixtures was generally depressed at low concentration of hydrocolloids (0–0.05%), but increased directly with increasing hydrocolloid concentrations (0.05–0.1%). In gellan gum dispersion, the swelling power at 100°C was higher than that of control. The rice starch‐hydrocolloids mixtures showed shear‐thinning flow behavior (n = 0.26–0.49). Hydrocolloids except the exopolysaccharide from S. chungbukensis (EPS‐CB) increased apparent viscosity and consistency index (K) of rice starch dispersions, but decreased the n value. Hydrocolloids enhanced the trough and final viscosity of rice starch dispersions but EPS‐CB reduced the viscosity of rice starch pastes. Hydrocolloids lowered peak viscosity but addition of guar gum resulted in high peak viscosity, apparent viscosity, and consistency index of rice starch dispersions. Total setback viscosity appeared to be not affected by hydrocolloids at low concentration (0.05%). The hot and cold paste of the starch‐gellan gum mixture exhibited the highest viscosity values in the Brookfield viscometer.     

The effect of casein on the viscosity of solutions of hydrocolloids

The apparent viscosities of aqueous solutions of guar gum, locust bean gum, sodium carboxymethylcellulose and k-carrageenan have been measured over a range of shear rates from 14 to 1142 s^?1. Comparable measurements were made on solutions to which different quantities of casein (10-40 g litre^?1) had been added. For all the solutions a power law equation describes the variation of relative viscosity with shear rate. Addition of casein has no effect on the solutions of guar and locust bean gum, but does affect the rheology of solutions of sodium carboxymethylcellulose and k-carrageenan. The behaviour of k-carrageenan indicates a dependence on the polyanion:casein ratio, reaching a maximum at a concentration ratio of 1:4. The only significant solute-solute interactions in the hydrocolloid-casein solutions are electrostatic in nature.     

Steady-shear flow of semidilute guar gum solutions with sucrose, glucose and sodium chloride at different temperatures

Steady-shear flow curves of aqueous solutions of guar gum at 0.22% at different temperatures (5-65 °C), guar gum (0.22%) with sugars (sucrose or glucose) at different sugar/water ratio (0.10, 0.20 and 0.40) at 5 °C, guar-sugar (at 0.40 sugar/water ratio) at different temperatures (5-65 °C) and guar gum and guar-sucrose (0.40 sucrose/water ratio) with NaCl (1%) at 5 °C, were determined using a controlled-stress rheometer over a wide range of shear rate (1-1000 s⁻¹). Apparent viscosity increased with decreasing temperature and increasing sugar content independent of sugar type. Synergic effect on apparent viscosity due to sugar addition was found and was correlated with sugar content. Salt addition decreased slightly the apparent viscosity and increased the shear-thinning behaviour of the guar gum solution. Steady-shear flow curves were satisfactorily described by the Cross model. Semi-empirical correlations of Cross model parameters with sugar content and temperature were obtained.     

Steady and Dynamic Shear Rheology of Rice Starch‐Galactomannan Mixtures

Rheological properties of rice starch‐galactomannan mixtures (5%, w/w) at different concentrations (0, 0.2, 0.4, 0.6 and 0.8%, w/w) of guar gum and locust bean gum (LBG) were investigated in steady and dynamic shear. Rice starch‐galactomannan mixtures showed high shear‐thinning flow behaviors with high Casson yield stress. Consistency index (K), apparent viscosity (η_a,100) and yield stress (σ_oc) increased with the increase in gum concentration. Over the temperature range of 20–65°C, the effect of temperature on apparent viscosity (η_a,100) was described by the Arrhenius equation. The activation energy values (E_a = 4.82–9.48 kJ/mol) of rice starch‐galactomannan mixtures (0.2–0.8% gum concentration) were much lower than that (E_a = 12.8 kJ/mol) of rice starch dispersion with no added gum. E_a values of rice starch‐LBG mixtures were lower in comparison to rice starch‐guar gum mixtures. Storage (G′) and loss (G′′) moduli of rice starch‐galactomannan mixtures increased with the increase in frequency (ω), while complex viscosity (η*) decreased. The magnitudes of G′ and G′′ increased with the increase in gum concentration. Dynamic rheological data of ln (G′, G′′) versus ln frequency (ω) of rice starch‐galactomannan mixtures have positive slopes with G′ greater than G′′ over most of the frequency range, indicating that their dynamic rheological behavior seems to be a weak gel‐like behavior.     

RHEOLOGICAL PROPERTIES AND APPLICATIONS OF MESQUITE TREE (PROSOPIS JULIFLORA) GUM. 1. RHEOLOGICAL PROPERTIES OF AQUEOUS MESQUITE GUM SOLUTIONS

The viscosities of aqueous mesquite gum solutions were measured at gum concentrations extending to 16.7% (w/v). Very dilute solutions exhibited typical polyelectrolyte behavior with respect to the influence of gum concentration on the reduced viscosity in the absence and presence of electrolyte. Shear thickening was exhibited at concentrations of 1–16.67% (w/v) when the shear rate exceeded ∼100 s⁻¹, whereas shear thinning was exhibited at lower shear rates. Shear thickening was attributed to configurational changes in the gum molecules at high shear rates. Electrolytes (0.1N NaCl and 0.1N CaCl₂) reduced the viscosity of concentrated solutions at high shear rates to a larger extent than increasing the pH. Charge screening by electrolyte permits the gum molecules to assume a more compact configuration.     

The effect of shear rate on the viscosity of solutions of sodium carboxymethylcellulose and k-carrageenan

The apparent viscosities of aqueous solutions of sodium carboxymethylcellulose (NaCMC) and k-carrageenan have been measured over a range of shear rates from 14 to 1142 s^?1. Comparable measurements were also made on gum solutions to which glucose, sucrose, or glucose syrup had been added. For all the solutions the variation of relative viscosity with shear rate fits a power law equation. Addition of sugars to the most concentrated solutions of NaCMC has no effect on the non-Newtonian behaviour but addition of glucose syrup to the most dilute solutions of NaCMC decreased the non-Newtonian behaviour. However, the general pattern of behaviour showed close similarity with that of guar gum and locust bean gum. In the more concentrated glucose and sucrose solutions the non-Newtonian behaviour of k-carrageenan was increased appreciably. There was no comparable effect on k-carrageenan in glucose syrup solutions. This different behaviour of k-carrageenan is attributed to the development of solute-solute interactions.