共查询到18条相似文献,搜索用时 250 毫秒
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冷榨菜籽油的流变特性 总被引:2,自引:0,他引:2
以3种不同芥酸含量的油菜籽为原料,通过低温压榨获得冷榨菜籽油(cold-pressed rapeseed oils,CROs),分析其静态和动态流变特性以及特征指标,同时采用Bingham模型对其流体行为进行拟合。结果表明:在剪切速率为0.1~200s-1条件下,CROs呈剪切变稀的假塑性流体;当剪切速率大于5s-1时,CROs表现为牛顿流体行为;温度是影响CROs流变性质的重要因素,CROs的黏度、损耗模量(GO`)和塑性稠度系数(ηp)随着温度升高而降低,但是温度变化对CROs的贮能模量(GO`)影响较小;另外CROs的黏度和GO`随芥酸含量增加而提高,而且ηp值与芥酸含量成正相关。 相似文献
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以菜籽毛油为原料,分析了脱胶、脱酸、脱色和脱臭(四脱精炼)对菜籽油流变特性以及品质的影响。研究结果表明,四脱精炼对菜籽油的脂肪酸组成和折光指数无显著影响;在恒温下,随着剪切速率的增加,菜籽油的粘度先逐渐减小再趋于稳定,即菜籽油是由非牛顿流体逐渐向牛顿流体转化;同时在大范围的剪切速率下,剪切应力与剪切速率呈近线性关系,菜籽油为牛顿流体;精炼所导致的菜籽油粘度差别与微量成分相关,并且精炼可以降低菜籽油的屈服应力值;Herschel-Bulkley的简化方程τxy=τo+K(dVx/dY)或者Bingham方程相对适用于表征菜籽油在四脱精炼过程中的流变特性。 相似文献
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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。 相似文献
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为研制低密度聚乙烯(LDPE)纤维,确定合理的纺丝工艺参数,利用毛细管流变仪研究LDPE材料的流变性能.研究结果表明:LDPE剪切黏度随剪切速率的增大而降低,随温度的升高而降低,非牛顿指数n小于1,随温度的升高而变大;当LDPE纺丝在加工温度为205℃时,非牛顿指数n为0.498,最接近牛顿流体.在150~250℃温度范围内,LDPE的黏流活化能在10 ~13 J/mol之间,且黏流活化能随剪切速率增加而降低,稠度系数K随温度升高而降低,属于假塑性流体,在纺丝过程中可以通过调节温度和剪切速率来改变LDPE熔体的可纺性. 相似文献
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为探讨马铃薯淀粉糊在加热过程中的流变特性,利用DV-I型旋转式黏度计对马铃薯淀粉糊进行流变性测定,并对其流变特性进行分析.结果表明:在讨论的加热温度范围内马铃薯淀粉糊是假塑性非牛顿流体,其流变特性服从幂律指数模型,随着加热温度的升高其稠度系数k减小,流变指数n基本上没有变化,随着浓度的增大其稠度系数k增大,流变指数n减小. 相似文献
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The rheological behaviour of two different loquat juices was studied. Juices containing pectins and pulp exhibited non-Newtonian with yield stress behavior. Juices from which pectins and pulp were removed exhibited Newtonian behavior. The Bingham model described the relationship between shear stress and shear rate for the first type of juice and the Newtonian model described the second type. The effect of temperature on the Bingham plastic viscosity and the Newtonian viscosity was described by Arrhenius equation. The effect of soluble solids contents was described by power-law and exponential expressions. Finally, two equations that described the combined effect of temperature and concentration were developed. 相似文献
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ABSTRACT: Rheological behavior of a slurry consisting of 1- to 3-mm diced tomatoes suspended in tomato juice was evaluated by an in-line measurement method based upon ultrasonics. This technique permitted the measurements of yield stress, consistency index, and apparent wall slip. The suspension exhibited a yield stress at every flow rate studied, and its value was found to be 0.79 ±0.11 Pa. The shear viscosity at different shear rates was obtained in-line without assuming a specific constitutive equation. A comparison of Herschel-Bulkley, Power Law, Bingham Plastic, and Casson models showed that this suspension was best characterized with the Herschel-Bulkley model. The apparent wall slip region was successfully modeled as a Bingham fluid. This study shows the usefulness of this method for in-line characterization of particulate tomato products. 相似文献
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Masakuni Tako Yukihiro Tamaki Takeshi Teruya Teruko Konishi Kiyoshi Shibanuma Isao Hanashiro Yasuhito Takeda 《Starch - St?rke》2009,61(5):275-281
The non‐Newtonian behavior and dynamic viscoelasticity of Halberd wheat starch (23.0% amylose content) pastes were determined with a rheogoniometer. The flow curves, at 25°C, of Halberd starch pastes showed plastic behavior at concentrations of more than 4.0%. The shear viscosity of the starch pastes decreased gradually with an increase in temperature at concentrations less than 4.0%, but remained constant at a concentration of 5.0%. The storage modulus of the starch pastes increased with increasing concentration and remained high during increase in temperature up to 80°C. Almost the same storage modulus was observed upon addition of urea (4.0 M) to the paste at low temperature (0°C), and the modulus stayed at a large value with increase in temperature up to 60°C, which was estimated to be a transition temperature; then it decreased rapidly with further temperature increase. A transition temperature of 60°C was also observed in the dynamic viscosity. A very large storage modulus and dynamic viscosity were observed in alkaline solution (0.05 M NaOH) at low temperature (0°C), both quantities decreased slightly with increase in temperature up to 25°C, which was estimated to be a transition temperature, then decreased rapidly with further increase in temperature. A possible intermolecular hydrogen bonding between amylose and amylopectin molecules is proposed. 相似文献
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ASHRAF M. SHAROBA MOHAMED FAWZY RAMADAN 《Journal of Food Processing and Preservation》2011,35(2):201-219
Goldenberry (Physalis peruviana) juice was prepared and enzymatically treated with two dosages (300 and 600 ppm) of Pectinex Ultra SP‐L, then, the juice was concentrated to 30 and 40°Brix. Rheological properties of juices were studied at a wide range of temperatures (5 to 100C) and shear rate range from 0.3 to 100/s using Brookfield Digital Viscometer. The Herschel–Bulkley, Casson and Bingham rheological models were applied to describe the rheological properties of different juices. These properties are key parameters required to solve food industry problems in numerous areas such as quality control, evaluation of consumer acceptance and texture. The results indicated that juice concentrates behave as non‐Newtonian fluids (pseudoplastic) and have a definite yield stress. The Bingham and Casson, plastic viscosity, yield stress, consistency index and flow index decreased with increasing enzyme dosage and temperature. The effect of temperature on the viscosity described by means of an Arrhenius‐type equation. The activation energy for viscous flow depends on the total soluble solids. Moreover, sensory evaluation for juices was carried out. In consideration of industrial utilization, detailed knowledge on the rheological and physicochemical characteristics of cape gooseberry juice is of major importance. 相似文献
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Effects of temperature,shear rate and constituents on rheological properties of tahin (sesame paste)
In this paper, rheological properties of tahin are reported at temperatures from 20 to 70 °C and shear rates in the range 0.13–500 s?1. Temporary hysteresis loops were observed in the first cycle of the flow curves. The steady shear behaviour of tahin was pseudoplastic and described by a power law model. The consistency coefficient exhibited strong temperature dependence for which the activation energy of flow was 21.6 kJ mol?1. The flow behaviour index of tahin tended to increase whereas the consistency coefficient tended to decrease during storage at room temperature. Tahin oil exhibited Newtonian behaviour with a strong dependence of viscosity on temperature. The activation energy of flow for tahin oil was 35.7 kJ mol?1. While reconstituted suspensions containing up to 20% solids exhibited Newtonian behaviour, those with more solids and the original tahin showed pseudoplastic behaviour. The Krieger–Dougherty model fitted the suspension viscosity data well. Below 20% solids level there was no effect of particle size on the viscosity of the reconstituted suspensions. It was shown that for the same amount of solids the viscosity of a ‘polydisperse’ suspension was lower than that of a ‘monodisperse’ suspension. Copyright © 2004 Society of Chemical Industry 相似文献
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研究了可溶性丝素蛋白的流变性质和胶凝性质。丝素蛋白溶液的黏度随质量浓度的增加而增加;随着温度的升高,丝素蛋白溶液的黏度不断的降低;在剪切速率为0~30S-1的范围内,丝素蛋白溶液是剪切变稀的假塑性流体,剪切速率大于30S-1时,丝素蛋白溶液是牛顿流体;动态流变性质的研究表明,丝素蛋白溶液是典型的粘性流体;随着丝素蛋白质量浓度的增大,凝胶强度增大;丝素蛋白溶液的质量浓度大于100g/L时,丝素蛋白溶液在加热后的冷却过程中会形成凝胶,丝素蛋白溶液的质量浓度越高,则其胶凝点也越高。 相似文献
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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 (ηa,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 (Ea) 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. 相似文献