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.     

Linear and non-linear viscoelastic behaviors of crosslinked tapioca starch/polysaccharide systems

Effects of polysaccharides on both the thickening performance and large deformation behavior of mixtures of various crosslinked tapioca starch and polysaccharide were investigated. It was found that the gelatinized crosslinked tapioca starch at 1-8% w/w in aqueous solutions behaved as swollen granules with the low-shear viscosity described by Krieger & Dougherty equation. To achieve thickening performance, 3.5% w/w starch was cooked with a range of 0.5% w/w polysaccharides, i.e. konjac glucomannan, guar gum, xanthan gum, and their 50:50 mixtures. It was shown that additions of polysaccharides greatly affected the rheological behavior of the suspensions, predominantly in the linear viscoelastic regime. The studied mixtures of starch and polysaccharides exhibited strong synergistic effects as evidenced from the increase in their consistency coefficients and the excess storage moduli calculated from the Palierne equation. Moreover, the mixtures containing xanthan gum showed weak-gel characteristics while the others demonstrated liquid-like behavior. In the non-linear viscoelastic analysis, arrangement of starch granules and specific interfacial interactions evidently affected the deformation behavior of the mixtures of crosslinked tapioca starch and polysaccharide. The mixture of konjac glucomannan and xanthan also largely improved stress susceptibility of the suspension and gave the unique shear stiffening under large amplitude oscillatory shear experiment.     

高取代度羟丙基木薯淀粉流变特性研究(I)流变特征及羟丙基取代度的影响

研究了高取代度羟丙基木薯淀粉溶液（分子取代度ＭＳ＝１．６～４．５）的流变特性及羟丙基取代度对流变特性的影响规律。结果表明，高取代度羟丙基木薯淀粉呈现假塑性流体特征，符合幂定律τ＝Ｋγｍ。ｍ值在０．７～０．８范围，表明羟丙基化使木薯淀粉偏近牛顿流体。高取代度羟丙基木薯淀粉具有触变性和剪切稀化性质，并随溶液浓度升高而增大。羟丙基取代度对木薯淀粉流变特性有很大影响，当ＭＳ≤３．５时，溶液的表观粘度和剪切稀化现象随ＭＳ的增高而减小，当ＭＳ＞３．５时，溶液的表观粘度和剪切稀化现象随ＭＳ的增高而增大。这种变化规律符合羟丙基化反应机理。     

Rheological/textural properties of starch and crude hsian‐tsao leaf gum mixed systems

The Effects of hsian‐tsao leaf gum (HG) on the rheological/textural properties of non‐waxy starches were studied. Pronounced interactions between starch and HG were observed. The rheological properties, including pseudo‐gel viscosity in the rapid visco‐analyser test, storage and loss moduli in the dynamic rheological test, as well as firmness in the texture analyser test, of the mixed gels generally improved with increasing gum concentration to a certain level, then deteriorated with further increase in gum concentration. The critical gum concentration for the development of optimal rheological properties depended on the starch type and concentration. Within the concentration range studied, mixed systems with wheat starch could generally reach the highest pseudo‐gel viscosity, firmness, and storage modulus if the starch/HG ratio was appropriate, followed by those with corn and tapioca starch. Copyright © 2003 Society of Chemical Industry     

Rheology of dairy custard model systems: Influence of milk -fat and hydrocolloid type

The influence of milk-fat content and the addition of two types of hydrocolloid (-carrageenan and a mixture of -carrageenan and xanthan gum) on the pasting behaviour, the flow and the viscoelasticity of custard model systems with modified tapioca starch at different concentrations was studied. To evaluate the pasting behaviour, apparent viscosity and temperature data were recorded over time. Flow was measured by recording shear stress at shear rates from 1 to 200 s^–1 and vice versa and viscoelasticity by performing the frequency sweeps from 0.01 to 1 Hz. Substitution of skim milk by whole milk increased apparent viscosity values during pasting. All the samples exhibited time dependence and pseudoplastic behaviour. Shear stress values increased when skim milk was substituted by whole milk, except for the custard system with 6% of starch. G, G and * values at 1 Hz resulted higher for whole milk systems although differences relatively decreased with starch concentration. The effect of hydrocolloid type was not significant (=0.05) for all the parameters studied except for the n values.     

添加剂对莲藕淀粉糊流变特性的影响

测定了不同添加物对莲藕淀粉糊剪切应力和表观黏度的影响,结果表明:添加剂不改变莲藕淀粉糊的流体类型;单甘酯、蔗糖、磷酸盐使莲藕淀粉糊的剪切应力不同程度降低,表观黏度也相应降低;CMC、食盐、黄原胶使莲藕淀粉糊的剪切应力明显提高,表观黏度稍有增大。     

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.     

Rapid Visco-Analyzer (RVA) Pasting Profiles of Wheat,Corn, Waxy Corn,Tapioca and Amaranth Starches (A. hypochondriacus and A cruentus) in the Presence of Konjac Flour,Gellan, Guar,Xanthan and Locust Bean Gums

The Rapid Visco-Analyzer (RVA) 20min test was used to study the effects of different levels of konjac flour, guar, gellan, xanthan and locust bean gums on starch cooking properties. Wheat, corn, waxy corn, tapioca and A. hypochondriacus and A. cruentus starches were affected to different degrees by different levels of the gums. Peak viscosity increased at the higher gum concentrations, especially with locust bean gum at the 0.4 g level. The increase in viscosity was more pronounced with wheat and corn starches than with waxy corn and tapioca starches which consist mostly of highly branched amylopectin thus preventing close physical association between molecules. Amaranth starches showed much lower viscosity with all the gums than the other starches. Peak viscosity, time to reach the peak and maximum setback viscosity were affected by the gums. The increase in viscosity of starch/hydrocolloid systems is due to the release of amy-lose and low molecular weight amylopectin which promotes the formation of polymer complexes and significantly adds to the viscosity of the system.     

Steady and dynamic shear rheological properties of extrusion modified fenugreek gum solutions

This study investigated the rheological properties of extrusion modified fenugreek gum solutions (0.5, 1.0, 1.5, and 2.0%, w/v) under steady and dynamic shear conditions. Fenugreek gum was extruded in a twin-screw extruder without an exit die to minimize a decrease in molecular weight of fenugreek gum during extrusion process. Both of the steady and dynamic shear rheological tests revealed that extrusion process did not substantially influence the steady and dynamic shear properties of the gum. The power law model was applied to describe the flow behavior of the extruded gum solutions. The extrusion modified fenugreek gum solutions exhibited a shearthinning flow behavior at 25°C, and the values of consistency index (K) and apparent viscosity (η_a,100) increased with an increase in the gum concentration. The magnitudes of storage modulus (G′) and loss modulus (G″) for the extrusion modified fenugreek gum solutions increased with increasing frequency (ω) and with increasing gum concentration.     

黄原胶对木薯阴阳离子淀粉糊性质的影响

本文采用Brabender黏度计和哈克流变仪研究了黄原胶对木薯阴、阳离子淀粉糊黏度、冻融稳定性及流变学性质的影响。结果表明:黄原胶使木薯阴、阳离子淀粉糊的峰值黏度和崩解值均显著增加,但其起始糊化温度有所降低;添加黄原胶后,阳离子淀粉的析水率有了一定程度的提高,冻融稳定性减弱,而阴离子淀粉的析水率下降;黄原胶的加入使两种变性淀粉凝胶的tanα值降低,储能模量(G’)增大,这使得木薯阴阳离子淀粉凝胶向趋于固性的方向发展。      

谷氨酸对木薯淀粉糊流变性质的影响

采用哈克流变仪,研究谷氨酸对木薯淀粉糊流变性质的影响。结果表明：添加谷氨酸前后的木薯淀粉糊均为假塑性流体且具有触变性,随谷氨酸添加量的增加,假塑性和触变性均先增强后减弱;淀粉糊的表观黏度随剪切速率的升高而降低,具有剪切稀化现象。添加/未添加谷氨酸的木薯淀粉糊都呈现弱凝胶行为,随着谷氨酸添加量的增加,其储能模量(G＇)和耗能模量(G＇＇)先增大后减小,损耗角正切值(tanθ)先减小后增大,最终趋向于牛顿流体的方向发展。     

两种皂荚多糖胶流变性质的表征

采用Brookfield 流变仪研究在不同加热时间、温度、pH 值以及盐和糖质量浓度等条件下两种不同形状皂荚豆中多糖胶的流变性质。结果表明：皂荚豆胶是一种假塑性流体,测得的剪切速率和相应的剪切应力的关系符合Power-law 模型,圆皂荚豆胶具有较高的黏度,且假塑性明显高于扁皂荚豆胶。在80℃条件下加热1h 可使皂荚豆胶完全水合,胶液黏度随温度的上升而下降。在pH2～11 范围内,皂荚豆胶比较稳定,但过酸或过碱会导致黏度的下降。皂荚豆胶的黏度随NaCl 质量浓度的上升而下降,随白砂糖质量浓度的上升而略微升高。与扁皂荚豆胶相比,NaCl 对圆皂荚豆胶的降黏作用较为明显。     

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.     

Dynamic rheology of structural development in starch/decolourised hsian‐tsao leaf gum composite systems

The gelling process of decolourised hsian‐tsao leaf gum (dHG)/starch mixtures was monitored as a function of starch/gum ratio and starch type using a dynamic rheometer. It was found that the gelling process followed first‐order kinetics. At starch/gum ratios of 5:1, 4:2 and 3:3, dHG interacted with starch synergistically, resulting in a marked increase in storage modulus (G′). Both the gelling reaction rate constant and plateau G′ value as a function of starch/dHG ratio showed a maximum at a certain starch/gum ratio. These results indicated that a suitable starch/dHG ratio could facilitate the formation of a three‐dimensional network structure and the conversion of chains in the sol fraction into a gel. The maximum G′ value reached depended on the unique chemistry of each starch. Mixed systems with tapioca starch generally showed lower plateau G′ values than mixed systems with wheat or corn starch, possibly owing to the lower amylose content of tapioca starch. © 2002 Society of Chemical Industry     

Rheological Properties of Rice Starch Dispersions in Dimethyl Sulfoxide

The steady and dynamic shear rheological properties of rice starches dispersed in dimethyl sulfoxide (DMSO) solution (90% DMSO‐10% water) were evaluated at various concentrations (7, 8, 9 and 10%, w/w). Rice starch dispersions in DMSO solution at 25°C showed a shear‐thinning flow behavior (n=0.44–0.60) and their consistency index (K) and apparent viscosity (η_a,100) increased with the increase in concentration. The apparent viscosity over the temperature range of 25–70°C obeyed the Arrhenius temperature relationship, indicating that the magnitudes of activation energy (E_a) were in the range of 11.7–12.7 kJ/mol. The Carreau model provided better fit on the shear rate‐apparent viscosity data than the Cross model. Dynamic frequency sweep test showed that both storage modulus (G′) and loss modulus (G′′) of rice starch dispersions increased with the increase in concentration. G′′ showed a higher dependence on frequency (ω) compared to G′ due to the higher G′′ slopes. All rice starch dispersions showed the plateau of G′ at high frequencies. Intrinsic viscosity of rice starch dispersions in DMSO was 104.1 mL/g.     

Steady and Dynamic Shear Rheology of Fucoidan‐Buckwheat Starch Mixtures

Rheological properties of fucoidan (F) and buckwheat starch (B) mixtures (3% or 6%) at different blending ratios of fucoidans (0, 0.1, 0.2, 0.5 and 1.0%) were investigated in steady and dynamic shear. Steady shear viscosity measurement revealed that aqueous pastes of the BF blends (3%, w/v) had a pseudoplastic and shear‐thinning behavior with flow behavior index (n) values of 0.61–0.68. The substitution of starch with fucoidan polymers significantly lowered the apparent viscosities compared with the pure starch paste and, when mixed with less than 0.5% of fucoidan, the viscosities of the pastes were even lower than those of the starch pastes at the corresponding starch concentrations. According to dynamic viscoelastic measurement performed at 6% total carbohydrate concentration, buckwheat starch mixtures behaved like weak gels and the BF blends containing less than 0.5% fucoidan had considerably lower storage (G') and loss (G') moduli than the starch paste at the corresponding starch concentrations. However, the magnitude of G' increased with fucoidan concentrations over 0.5%, suggesting that a concentration of fucoidans > 0.5% might enhance the formations of three‐dimensional networks and crosslinking of the starch samples, probably because of the mutual exclusion between starch and fucoidan polymers through the phase separation process. This study indicates that it is possible to obtain the BF blends having various rheological properties by changing the concentration of fucoidan polymers.     

糖对牛奶布丁流变性的影响

奉文采用哈克流变仪研究了不同质量分数下几种糖时鲜奶布丁体系的流变学性质,所用的糖质量分数依次为2%、4%、8%和16%,未著淀耢质量分数为6%. 结果表明:牛奶布丁是-种非宾汉塑性流体,测得的剪切速率和相应的剪切应力的关系符合Casson模型. 随着糖质量分数的提高,牛奶布丁的屈服应力、表观黏度和剪切应力均随糖质量分数的增大而增大.     

Rheological properties of cereal starch gels and Mesona Blumes gum mixtures

The effect of Mesona Blumes gum (MBG) was examined on steady and dynamic shear of MBG/rice starch and MBG/wheat starch gels. In addition, stress relaxation and creep tests were performed for two types of cereal starch gels. The flow curves of both MBG/starch gels exhibited pseudoplastic behavior at shear rates between 0.01 and 10 s⁻¹, and the data were fitted into the power law model (R² = 0.91–0.98). Dynamic mechanical spectrum showed that all gels were strong gels in frequency between 0.1 and 10 Hz. Stress relaxation data at different strains indicated a strain‐softening phenomenon for both gels. Data were fitted into Maxwell model (R² = 0.91–0.98). Creep curves were conducted at the shear stress 6.4 Pa within linear viscoelastic region of both MBG/starch gels. Data were fitted into Burgers model (R² = 0.91–0.98). Apparent viscosity η, storage moduli G′, equilibrium stress relaxation modulus G_e and zero apparent viscosity η₀ of MBG/rice starch gels decreased in the following order: 6/0>6/0.5>6/0.35>6/0.1 (starch/gum w/w). Whereas η, G′, G_e, and η₀ of MBG/wheat starch gels increased gradually along side the increase of MBG contents. The stress relaxation time λ of MBG/rice starch gels increased in the following order: 6/0<6/0.5<6/0.35<6/0.1 (starch/gum w/w) while λ of MBG/wheat starch gels decreased gradually with the increase of MBG level. The influence of MBG on two examined cereal starch is totally opposite.     

Rheological and physical characterization of film-forming solutions and edible films from tapioca starch/decolorized hsian-tsao leaf gum

Rheological properties of the film-forming solutions of tapioca starch/decolorized hsian-tsao leaf gum (dHG) as well as the structural properties and viscoelasticity of the resulting films were characterized as a function of dHG and glycerol concentrations. As compared to film-forming solutions with tapioca starch alone, the apparent viscosity, storage modulus and loss modulus of starch/dHG film-forming solutions increased, and tan δ decreased with increasing dHG. After casting of the film-forming solutions, all starch/dHG films showed relatively low opacity values. SEM and X-ray diffraction analysis revealed that all starch/dHG films exhibited homogeneous and highly amorphous structure. The extensional creep compliance of starch/dHG films increased with increasing glycerol concentration, implying weaker mechanical strength and higher mobility of polymer chains by the plasticizing effect of glycerol. However, addition of dHG pronouncedly increased the mechanical and elastic properties of tapioca starch films as evidenced by a decrease in extensional creep compliance and retardation time. Such results implied that dHG may possibly modify the network structure of tapioca starch film.