Creep/Recovery Behavior of Oil-Water Emulsions: Influence of Disperse Phase Concentration

The rheological (creep/compliance) behavior has been studied for a series of soya oil (soybean oil)-water emulsions with the disperse phase (oil) concentration ranging from 20% to 70%. The compliance response was due to three mechanisms: instantaneous elastic, retarded elastic and viscous flow. It was necessary to postulate the presence of two retardation processes to account for the Theological behavior. As the oil concentration was increased, the emulsions became more elastic, with the instantaneous elastic mechanism becoming more dominant. In the non-linear region, the viscous flow was more dominant, with the emulsions becoming less elastic with increasing shear stress. The results are rationalized in terms of the breaking and reforming of bonds in the network like coagulation structure.     

Effects of Constituent Concentration on Rheological Properties of Corn Oil-In-Water Emulsions

Rheological properties were studied with a tube viscometer. Emulsifying agents were soy lecithin and Tween 20. The volume concentration of dispersed phase, φ, ranged from 0.32-0.62. The emulsions behaved as pseudoplastic fluids. The flow behavior index, n, of the lecithin emulsions increased slightly with increasing φ and concentration of emulsifying agent, C_e. However, the n values of Tween 20 emulsions were nearly constant. Apparent viscosity of the emulsions increased with increase of φ and C_e. With φ constant the apparent viscosity was still strongly affected by C_e.     

Concentration and Temperature Dependence of Flow Behavior of Xanthan Gum Dispersions

Apparent viscosities of xanthan gum dispersions over shear rates of 0.5–3000s^?1 were studied at concentrations of 0.05–1.00% (w/w) and temperatures of 5–45°C. All dispersions were shear rate thinning non-Newtonian fluids described accurately by the power-law model. The logarithm of viscosity varied with the logarithm of concentration and the reciprocal of absolute temperature. A combined model was derived to describe the variation of viscosity with shear rate, concentration and temperature for aqueous dispersions of xanthan gum.     

Effect of Xanthan Gum Upon the Rheology and Stability of Oil-Water Emulsions

Soyabean oil-water emulsions were studied. In oil-water emulsions (up to 60% oil) xanthan is essential to prevent creaming. A yield stress arises primarily from the polysaccharide liquid crystalline structure. In concentrated systems where the oil droplets interact strongly there is a significant contribution to the yield stress arising from the need to modify individual droplet shapes when shear is applied to the system. Studies of droplet sizes suggest that the xanthan gum can also modify the equilibrium droplet size by lowering the oil-water interfacial tension.     

Rheological Characterisation of Dairy Emulsions For Cold Foam Applications

Dairy foams are complex aerated materials where the liquid matrix is an emulsion made by oil droplets dispersed in a water system. An innovative application of these systems leads to an interesting product derived from instant whipped creams that are stored and consumed at low temperatures (typically between??4 and??18°C) like an ice cream. This novel product requires a specific texture due to the particular conditions related to its consumption. In the present work, the effects of some relevant ingredients (emulsifiers, sugars, and fats) on rheological properties and freezing temperature of dairy emulsions were investigated. Samples were prepared on lab scale and it was found that structure extension is affected strongly by stabilizers (carrageenan and guar gum) and in a lower measure by fat content. As far as freezing point is concerned a significant effect only of sugars (type and amount) and fats was measured. A formulation having interesting properties for low temperature applications was obtained and it was prepared on a pilot plant scale to investigate the potential effects of the industrial production. These samples exhibited a relevant reduction in both viscosity and elasticity; it was speculated that this effect could be attributed to the whey protein thermal damage (induced by the UHT treatment) and to the homogenisation conditions, different from those adopted on lab scale.     

黄原胶体系的流变性及糖和盐对体系的影响

报道了对黄原胶水溶液以及以黄原胶水溶液为水相的２０％（Ｏ／Ｗ体积分数）乳状液在３０℃的流变学性质的研究。实验中通过振荡和蠕变测试考察了从０．０５％～０．５％系列质量分数的黄原胶溶液和乳状液的流变学性质以及０．５ｍｏｌ／ＬＮａＣｌ和质量分数１０％的蔗糖对这些体系的影响。发现，随着黄原胶质量分数的增加，体系逐渐表现固态的反应，这表明大分子交联或其它方式的缔合逐渐提高了体系结构化的程度。蔗糖的存在在一定程度上增强了大分子的这种功能作用，而ＮａＣｌ的引入则明显降低了大分子的这种影响，并且ＮａＣｌ的这种影响对黄原胶质量分数较高的体系更加明显。乳状液体系的测定结果与水相的情况一致。     

乳化剂、油浓度及油滴粒径对乳状液中油脂氧化稳定性的影响

以过氧化值(POV)为指标,研究了乳化剂类型、油浓度及油滴粒径对O/W乳状液中油脂氧化稳定性的影响.以用十二烷基硫酸钠(SDS)和Tween-80为乳化剂制备的含红花籽油的乳状液为研究对象,结果表明,乳化剂类型和油浓度对乳状液体系中油脂氧化有较显著的影响.用阴离子型表面活性剂SDS稳定的乳状液中的油脂氧化速率明显大于用非离子型Tween-80稳定的乳状液;随着油浓度下降,油脂氧化速率增大.油滴粒径和油脂氧化速率没有显著的相关性.     

Correlation of the Rheological Behavior of Egg Albumen to Temperature, pH, and NaCl Concentration

Rheological parameters of viscosity, gel strength, and elasticity were determined on heat-set egg albumen gels over various treatment combinations ranging from 65-90°C, pH 6.4-9.6, and NaCl concentrations of 0.0-0.1M added NaCl. Maximum viscosity was measured at a treatment combination of 77.5°C, pH 8.00, and 0.1M NaCl. Elasticity and gel strength were highest in gels with a treatment combination of 85.2°C, pH 9.0, and 0.08M NaCl. Temperature had the greatest effect on all three rheological parameters. Gels heated above 80°C were of unusual character, exhibiting syneresis and shrinkage.     

肉桂酸基油脂凝胶的制备及其流变特性和结晶特性分析

选择米糠油为溶剂体系,肉桂酸作为凝胶剂制备油脂凝胶,借助流变仪、X-射线衍射仪、荧光显微镜研究其流变特性及结晶特性。结果表明：米糠油凝胶的持油性和熔点随肉桂酸添加量的增加逐渐增加,当肉桂酸添加量超过10%,油脂凝胶的持油性和熔点增加不显著（P＞0.05）;米糠油凝胶的持油性随加热温度升高迅速上升,在85?℃时升高至93.62%,此时的凝胶熔点也相对较高;当冷却温度从0?℃升高至5?℃时,凝胶的持油性和熔点相对较高,当冷却温度进一步升高,凝胶的持油性和熔点显著下降至93%（P＜0.05）。通过对肉桂酸添加量10%、加热温度85?℃、冷却温度5?℃形成的油脂凝胶进行流变学特性分析,发现该油脂凝胶呈现假塑性流体状态,样品的表观黏度-剪切速率的关系符合幂律方程关系;并且在频率扫描范围内,油脂凝胶体系的储能模量（G’）明显大于损耗模量（G”）,样品形成较为紧密的凝胶结构;通过凝胶结晶特性分析发现,米糠油凝胶中的结晶结构细小,分布均匀,存在同质多晶现象,主要含有β和β′?2?种晶体类型。     

Rheological Behavior of Comminuted Meat Batters

Good agreement was observed between the shear stress-shear rate results obtained with a capillary extrusion viscometer and the yield stress as determined with a rotational viscometer. The frankfurter batter used in this study was pseudoplastic with a flow behavior index of 0.2–0.4, and a yield stress of approximately 840 Pa at 10°C. To compare the effects of batter composition, an apparent viscosity term was defined. Dilution of the batter resulted in reduced apparent viscosities, while increased fat led to increased apparent viscosities. Although chopping time significantly altered the stability of the batter and the visco-elastic properties of the cooked product, no significant difference in the apparent viscosity was detected. This observation was discussed in light of the apparent insensitivity of viscosity measurements to the degree of fat comminution.     

共混可润湿聚丙烯的流变性能研究

共混可润湿聚丙烯流体的流动特征与常规聚丙烯相似 ,为典型的假塑性流动 ,其非牛顿指数随剪切速率的增大而减小 ,表观粘度和粘流活化能随共混比的增大而减小     

Rheological Behavior of Hot-Air-Puffed Amaranth Seeds

Force-deformation and force-relaxation experiments were performed on amaranth seeds puffed at 290, 330 and 370°C. Less force and energy was required to cause a given deformation in seeds processed at 290°C than in those puffed at 330 and 370°C. It was also observed that the forces and energies required to produce a given deformation did not differ significantly (p ≤ 0.05) for seeds puffed at 330 and 370°C. The three-element generalized Maxwell model and Peleg model were applied for modeling force relaxation of puffed amaranth seeds. It was found that the generalized Maxwell model predicted the experimental data better than the Peleg model. The elastic parameters and asymptotic residual force of the generalized Maxwell model were significantly affected by puffing temperature, showing an increase with its rise. Relaxation times were not significantly affected by the puffing temperature. It was concluded that a higher puffing temperature resulted in a more rigid material and less viscous behavior.     

Effects of Sucrose Esters on Isothermal Crystallization and Rheological Behavior of Blends of Milk-fat Fraction Sunflower Oil

ABSTRACT: Crystallization kinetics and rhelogical behavior of blends of high-melting milk-fat fraction (HMF) and sunflower oil (SFO) with and without addition of the sucrose esters P-170, S-170, and P-1670 were investigated. Addition of sucrose esters delayed crystallization, as was evidenced by the longer induction times of crystallization (t) and the lower maximum solid fat content (Smax). Values of penetration force and time corresponding to the 1st peak of curves force compared with time also diminished with addition of SFO. When sucrose esters were added, a solid fat content greater than 10% at the 1st crystallization temperature was necessary to give a stronger structure that could be noticed as higher yield point.     

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。     

中国大鲵油脂肪酸组成、抗氧化及流变性研究

分析中国大鲵油的脂肪酸组成,并研究大鲵油抗氧化和流变学行为,提供大鲵油开发利用的基础理论.通过气相色谱/质谱联用技术分析大鲵油的脂肪酸组成;Schaal烘箱法(63±1)℃研究大鲵油的抗氧化特性;流变仪测定大鲵油和花生油不同配比(100:0,75:25,50:50,25:75,0:100)的黏度和剪切应力随剪切速率的变化情况.GC-MS分析结果表明:大鲵油主要含13种脂肪酸(24.2%C18:1,15.4%C16:0,13.7%C16:1,8.2%C18:2,6.7%C20:5,4.5%C18:3,4.3%C22:6,3.0%C14:1,2.8%C18:0,2.6%C22:5,2.2%C20:4,2.0%C17:0,1.9%C17:1),饱和脂肪酸(SFA)为20.2%,单不饱和脂肪酸(MUFA)为42.8%,多不饱和脂肪酸(PUFA)为28.5%,ω-6型PUFA为13.0%,ω-3型PUFA为15.5%.Schaal烘箱法研究结果表明:抗氧化剂二丁基对甲苯酚(BHT)、没食子酸丙酯(PG)、特丁基对苯二酚(TBHQ)对大鲵油均有抗氧化作用,其中特丁基对苯二酚抗氧化效果较佳.流变性分析结果表明:大鲵油及其与花生油75:25、25:75配比的黏度随剪切速率的增加变化不大,二者50:50的配比黏度显著降低,大鲵油及其和花生油不同配比呈牛顿流体特性.     

Rheological Behavior of High-Concentration Sodium Caseinate Dispersions

ABSTRACT: Apparent viscosity and frequency sweep (G′, G″) data for sodium caseinate dispersions with concentrations of approximately 18% to 40% w/w were obtained at 20 °C; colloidal glass behavior was exhibited by dispersions with concentration ≥23% w/w. The high concentrations were obtained by mixing frozen powdered buffer with sodium caseinate in boiling liquid nitrogen, and allowing the mixtures to thaw and hydrate at 4 °C. The low-temperature G′−G″ crossover seen in temperature scans between 60 and 5 °C was thought to indicate gelation. Temperature scans from 5 to 90 °C revealed gradual decrease in G′ followed by plateau values. In contrast, G″ decreased gradually and did not reach plateau values. Increase in hydrophobicity of the sodium caseinate or a decrease in the effective volume fraction of its aggregates may have contributed to these phenomena. The gelation and end of softening temperatures of the dispersions increased with the concentration of sodium caseinate. From an Eldridge–Ferry plot, the enthalpy of softening was estimated to be 29.6 kJ mol⁻¹. Practical Application: The results of this study should be useful for creating new products with high concentrations of sodium caseinate.     

含有改性纳米CaCO3的纸张涂料的流变行为

以阳离子表面活性剂、偶联剂及脂肪酸为表面改性剂获得表面性能不同的3种纳米CaCO3改性产品。用透射电镜桨相关化学分析方法表征了改性纳米CaCO3的界面行为。将改性纳米CaCO3加入纸张涂料体系中,制得不同配方的纸张涂料,并对涂料的静态流动性能和动态黏弹性进行了研究。结果表明,与加入普通CaCO3的传统涂料相比,含纳米CaCO3的纸张涂料具有较高的表观黏度、动态弹性模量和黏性模量,相位角则较低。表面亲油疏水的纳米CaCO3能够很好地与胶乳、增稠剂等聚合物胶体结合,弹性模量较大;而表面亲水的纳米CaCO3所制得的纸张涂料动态黏弹性较小。