西米淀粉糊流变特性研究

利用Brookfield旋转粘度计研究西米淀粉糊流变性、抗剪切能力、触变性以及温度、浓度和剪切速率对表观粘度的影响,为西米淀粉在食品行业的应用提供理论上的依据。结果表明:西米淀粉糊属于非牛顿流体。温度、浓度、剪切速率对流变性质均有影响,在同一浓度和剪切速率下,表观粘度随温度的增加而减小;在同一温度和剪切速率下,表观粘度随浓度的增加而增加;在同一温度和浓度条件下,淀粉糊的表观粘度随剪切速率的增加而减小。西米淀粉糊属于剪切稀化体系,抗剪切能力优于马铃薯淀粉糊和木薯淀粉糊;淀粉糊粘度随剪切速率增大的上行线与随剪切速率减小的下行线之间存在滞后圈,说明西米淀粉糊具有触变性。     

对聚酯切片流变行为的研究

利用Hakke流变仪、以连续的方法研究了聚酯 (PET)熔体在从毛细孔挤出时的流动活化能、表观粘度等流变性质。结果表明 ,聚酯在熔融状态下表现出假塑性流体的性质 ,表观粘度随剪切速率的提高而降低 ;其流动活化能随剪切速率的提高而降低 ,而在低剪切区域和高温下显示出趋向牛顿流体的行为。     

海棠汁的流变特性研究

采用LVDV-III+型流变仪对不同温度、百利糖度下的海棠汁的流变特性进行研究,研究发现海棠汁随着剪切速率增大,表观粘度逐渐增大,剪切应力随之增大;同时随着剪切速率的逐渐增大,表观粘度大小的变化趋势较小但表现出较微的上升趋势。海棠汁流变特性符合胀塑性流体的基本特征,通过Herschel-Bulkley方程拟合,相关系数R2都在0.99以上,并就方程中参数的变化进行了解释说明。     

离心对澄清海棠汁流变特性的影响

采用LVDV-III+型流变仪对不同离心速度、离心时间下的海棠汁流变特性进行研究,研究发现海棠汁随着剪切速率增大,表观粘度逐渐增大,剪切应力随之增大;同时随着剪切速率的逐渐增大,表观粘度大小的变化趋势较小但表现出较微的上升趋势。通过Herschel-Bulkley方程拟合,R2都在0.99以上,并就方程中参数的变化进行了解释说明,流动指数n值大于1,海棠汁流变特性符合胀塑性流体的基本特征。     

PP-COPET-ZnO三元共混物流变性的研究

采用CFT-500型毛细管流变仪测试了PP-COPET-ZnO三元共混物的流变性能.结果表明: 在230 ℃,250 ℃下,随γ增大,共混物的σ12 增大.PP-COPET-ZnO三元共混物的非牛顿指数n均小于1,随COPET含量的增大,温度的提高,共混物的非牛顿指数n增大.在测试的剪切速率范围内熔体表观粘度随剪切速率的增加而下降,为典型的假塑性流体.共混物的η0和Δη0随COPET含量的增加而减小.温度提高,共混物的表观粘度下降,下降幅度与剪切速率有关.     

海藻酸钠原液流变性能的研究

采用TR-1型毛细管流变仪对海藻酸钠原液的流变性能进行了研究。通过实验得出在不同浓度、不同温度的条件下,原液表观粘度相剪切速率之间的关系,通过数据处理,求得了不同浓度原液的非牛顿指数n、结构粘度△η、粘流活化能△E等流变参数;讨论了温度和浓度对原液流变性能的影响。结果表明:通过调节原液的浓度、温度和切变速率,可以改善原液的流变性能和可纺性。从而为纺制海藻酸盐纤维提供了理论依据。     

乳酸乙醇酸共聚物(PLGA)熔体的流变性能

采用直接法熔融缩聚制备了L-乳酸和乙醇酸共聚物PLGA ,并用锥板流变仪对PLGA的流变性能进行测试。结果表明 :PLGA熔体属于切力变稀流体 ,PLGA熔体的非牛顿指数值大于聚乳酸PLLA熔体的对应值 ,其表观粘度对剪切速率的依赖性小 ;PLGA熔体的表观粘流活化能较高 ,且在同样的切变速率下 ,PLGA熔体的表观粘流活化能大于PLLA熔体的对应值 ,其表观粘度对温度的敏感性大于PLLA熔体。     

单一胶粘剂对涂料流变特性的影响

单一胶粘剂对涂料流变特性的影响颜进华陈克复华南理工大学制浆造纸工程国家重点实验室１前言涂料流变特性是指涂料受剪切时剪切应力、剪切速率及表观粘度的相互关系，涂料流变特性既控制着涂料的质量及其中间产品，也影响涂布加工纸的涂布工艺及其涂布纸质量。随着涂布...     

亲水聚酯流变性能的研究

本文将亲水聚酯品种与普通PET品种的流变性能进行了对比,得出在相同测试温度下,亲水聚酯的流动性能优于普通PET;其在低剪切速率(γ1×10~2s~(-1))下,表现为牛顿流体的特征,而在高剪切速率(1×10~2s~(-1)-1×10~4s~(-1))下,表现为假塑性流体的特征;随测试温度的升高,亲水聚酯的非牛顿指数趋近于1,表观粘度对剪切速率的依赖减小,接近于牛顿流体;相比于普通PET,亲水聚酯的表观粘度受到温度的影响较小。.     

番茄汁液流变性质的关联

对经45、32、24和16目筛网过筛所得番茄汁液的流变性质进行了研究。采用旋转式粘度计测定了番茄汁的剪切速率-剪应力数据。通过剪切速率-剪应力实验数据的关联发现,番茄汁液的流变行为可用Bingham模型表征。确定了不同温度和不同网目下番茄汁液的稠度指数和屈服应力。同时也建立了不同网目下番茄汁液的表观粘度与温度函数关系的关联式。     

THE EFFECT OF TEMPERATURE ON SOME RHEOLOGICAL PROPERTIES OF WHEAT FLOUR DOUGHS

Abstract. Doughs from three flours were sheared between a cone and plate at constant rates in the range 6 times 10^-4-2 times 10^-2 s^-1.
At temperatures between 25 and 40C, the apparent viscosity decreased with increasing temperature and with increasing rate of shear. The effects of the temperature and of the rate of shear were independent one of another, and can be described by an Arrhenius type equation and a power equation, respectively. At temperatures between 45 and 60C, the apparent viscosity increased rapidly with increasing temperature; this is ascribed to starch gelatinization. In this temperature range, the apparent viscosity decreased more rapidly with increasing rate of shear than at lower temperatures.
At temperatures between 25 and 45C, the shear modulus decreased with increasing temperature and slightly increased with increasing rate of shear. From the former fact it is concluded that the elasticity of dough has an origin different from rubber elasticity. In this temperature range, the shear modulus can be described by an equation similar to that for the apparent viscosity. At temperatures between 45 and 65C, the modulus increased with increasing temperature, though to a lesser extent than the apparent viscosity.
Changes in the rate of stress relaxation are in accordance with the effects of temperature and rate of shear on the apparent viscosity and the modulus.     

3 种发酵乳制品流变性质的比较与分析

用流变仪分析评价发酵乳制品的流变学特性。分别测定以牛乳和豆乳以及二者的混合乳为原料制备的3种发酵乳制品的流变学特性。结果表明：3种发酵乳制品均是正触变性流体,其滞后环面积之比为1:0.56:0.69。黏丝性指数之比为1:0.63:0.91;恒温恒速下表观黏度初始值之比分别为1:0.99:1.28,发酵豆乳表观黏度下降速率最慢;应变扫描中发现3种发酵乳制品的稳定性从高到低依次为：发酵豆乳、发酵混合乳和发酵牛乳;在温度扫描中发现发酵豆乳耐温度变化的能力最强,发酵混合乳的表观黏度值最高。通过比较三者的流变学特性说明发酵牛乳的稳定性较差,发酵豆乳的表观黏度值较低,但其稳定性较好。发酵混合乳不仅表观黏度值较高,而且其稳定性也高于发酵牛乳。     

驴乳的系统流变学性质研究

目的:研究不同温度对驴乳流变学性质的影响。方法:选取测试温度为4、20、36、50℃,测试其流动性、触变性、动态粘弹性,并采用流变学模型进行拟合分析。结果:驴乳为非牛顿流体,表现出剪切稀化行为;流动曲线服从Carreau模型,随温度升高,其黏度越小,触变测试中形成的滞后环面积变小;并且在粘弹性测试中4℃的储能模量G'表现出最大值,储能模量G'和损耗模量G″对温度的依赖性较大;4~50℃测量温度范围内驴乳黏度随温度增加逐渐减小。结论:驴乳的流变性对温度的依赖性较大。     

Time-independent and time-dependent rheological characterization of vegetable-based infant purees

Flow behavior of vegetable-based infant purees was analyzed at different temperatures (5–65 °C) giving particular attention to their time-dependent properties in a shear rate range (5–200 s⁻¹). Power law model parameters describing flow behavior of samples depended on kind of infant puree, its water content and measurement temperature. Arrhenius model was used to explain temperature effect on apparent viscosity at 50 s⁻¹. Infant purees exhibited thixotropic behavior for all temperatures tested. For the same temperature, differences in hysteresis loop magnitudes were observed among purees, being more noticeable at lower temperatures. Two models were used to describe the time-dependent behavior, namely Weltman model, and second-order structural kinetic model. For all infant purees, the initial shear stress and the extent of thixotropy increased and decreased significantly with increases in shear rate and temperature. The breakdown rate of puree associations also accelerated at higher shear rates, but no trend was observed with temperature.     

Flow properties of sweetened sesame paste (halawa tehineh)

Sweetened sesame paste, known as halawa tehineh, is a food product that consists of heat-treated sugar, citric acid and tehineh. Some natural flavor may be added, for instance vanilla and nuts. The steady and time-dependent flow properties of halawa tehineh were investigated in the temperature range between 25–45 °C. The flow behavior of halawa tehineh was observed to be pseudoplastic and thixotropic at all temperatures measured, and the apparent viscosity–shear rate data can be described by a power law model. Increasing the temperature increases the flow behavior index and significantly reduces the consistency coefficient. The temperature dependency of the consistency coefficient is given by an Arrhenius-type relationship. A second order structural kinetic model describes the thixotropic behavior of halawa tehineh well. An empirical equation was developed for predicting the rate of thixotropic structural breakdown as a function of shear rate and temperature.     

Rheological properties and gel characteristics of polysaccharides from fruit-bodies of Sparassis crispa

Rheological properties and gel characteristics of Sparassis crispa polysaccharides (SCPs) were investigated under various concentrations, temperature, pH, salt concentrations, and sucrose concentrations. SCP solutions behaved as shear thinning pseudoplastic fluids; apparent viscosity increased with concentrations but decreased with extreme conditions and was highest for 1% SCPs at 80 ℃ under neutral conditions; 5% SCPs solutions formed a hysteresis loop and exhibited thixotropic properties. By oscillatory measurements, SCPs were viscoelastic materials. 0.5% and 1% SCPs solutions exhibited viscous behavior at low frequency and enhanced elastic property with the oscillation frequency increased. With the concentration increased to 3% and 5%, the elastic property was predominant in solutions and exhibited gel-like behavior. SCPs gel textural properties and water holding capacity increased with concentration (to 20%) and decreased with salinity, extreme sucrose, and pH. 10% SCPs gels were optimized at 10% sucrose in neutral conditions. Thus, these results implied SCPs had the potential utilization as a new hydrocolloid source in food industries.     

COLD-SLURRY VISCOSITY OF PROCESSED RICE FLOUR

Viscosities of dispersions of raw and various processed rice flours in water were examined with a coaxial cylinder viscometer. The measured viscosity increased with increasing degree of processing and with a reduced level of apparent starch reassociation in the processed rice. Measurement of the apparent viscosity of cold slurries could thus be a simple practical test of processed, including parboiled, rice and of the degree of processing. The system showed time-dependent thinning and a typical loop in the shear rate-viscosity curve, showing that it was thixotropic in nature. The viscosities were proportional to the hydration power and slurry-sedimentation behaviour of the samples.     

添加褐藻酸钠的冰淇淋乳浊液流变学性质的研究

<正> 添加褐藻酸钠冰淇淋乳浊液的流变性质,其分散体系呈塑性流动,屈服应力为4.21帕;剪切应力与剪切速率的关系遵从Herschel-Bulkley’s方程;当剪切速率从零增至119.4秒~(-1),然后再返回至零时,上升和下降曲线间呈现滞后环,表示了乳浊液试样剪切速率的触变性。 试样粘度随剪切时间的变化率,遵从Tiu′s方程,粘度开始变化迅速,20分钟后达到常     

Rheological and microstructural characterization of WPI-stabilized O/W emulsions exhibiting time-dependent flow behavior

The rheological behavior of oil-in-water (O/W) emulsions stabilized by whey protein isolate (WPI) and its relationship with the microstructural changes caused by shearing was studied. O/W emulsions (50, 55, and 60 g oil/100 g) were made using ultrasound and their rheological properties were determined by: flow curve test, constant shear rate test, and hysteresis loop test. Microstructural changes were evaluated in terms of droplet size and droplet size distribution. Emulsions containing 50 and 55 g oil/100 g showed a Newtonian behavior, whereas those with 60 g oil/100 g exhibited shear-thinning behavior. Under constant deformation, the apparent viscosity of the emulsions decreased with time. The hysteresis loop test revealed that increasing oil content increased the degree of thixotropy of the emulsions. Moreover, before and after the constant deformation test droplet size distributions did not show differences, indicating that the decrease in the apparent viscosity may be promoted by breakdown and further deformation and/or reorganization of oil droplets flocs. In turn, experimental data obtained from the constant shear rate test was fitted to a structural kinetic model. The rate constant values showed no particular trend with oil content and shear rate, implying that probably wall slip occurred at high shear rates and high oil contents.     

刺槐豆胶与黄原胶复配体系的流变性

研究刺槐豆胶/黄原胶复配体系的流变性,并采用流变学的Cross模型进行拟合分析。结果表明:刺槐豆胶与黄原胶复配可以产生协同作用,当刺槐豆胶与黄原胶的复配体积比为4∶6时,复配体系的黏度最大,触变测试中形成的滞后环面积最大,并且在黏弹性测试中储能模量G’表现出最大值。因此,刺槐豆胶与黄原胶的最佳复配比例为体积比4∶6。对最佳比例复配体系进行不同温度处理后测试可知,最佳复配体系的最适处理温度为80℃,得到的复配体系黏度最大;复配体系的p H值在6.0~10.0之间时,其黏度变化较小,保持相对稳定。