Particle Size Distribution in Tomato Concentrate and Effects on Rheological Properties

The particle size distribution of a tomato concentrate was determined by wet sieving. Wet sieve fractions were then investigated by microscopy and a method based on laser diffraction. Both methods showed that the size of many particles was considerably larger (up to two to three times) than the diameter of the pores through which they have passed during wet sieving. This was explained by the deformability of the tomato cell wall. Effects of particle size distribution on rheological properties were studied by standardizing wet sieve fractions (dry matter, pH). Highest values for yield stress and apparent viscosity were found for the 90–125 and 125–180 μm wet sieve fractions.     

Effect of Egg Yolk and Egg Yolk + Salt on Rheological Properties and Particle Size Distribution of Model Oil-in- Water Salad Dressing Emulsions

The role of egg yolk and egg yolk + salt in stabilizing oil-in-water (o/w) salad dressing emulsions pre-stabilized with xanthan and propylene glycol alginate was studied using creep tests, steady shear, and particle size analysis. Results show that each combination significantly affects rheological stability of model o/w salad dressing emulsions. All emulsions exhibited viscoelasticity and wcrc characterized by three parameters: η₁, E₁ and η_N. Steady shear measurements showed that both egg yolk and salt increased viscosity radically. Particle size data showed significant changes with both addition of egg yolk and salt to the model system.     

Effect of Wheat Bran Particle Size on Dough Rheological Properties

Commercial hard red spring, hard red winter, soft white and durum wheat brans were used to investigate the effect of wheat bran particle size on the rheological properties of doughs. Wheat brans were first coarsely ground and passed through a bran finisher to remove additional endosperm and aleurone layers. These processes increased total dietary fibre content and decreased starch content of the wheat bran samples. Three particle size distributions, for each wheat bran class, were obtained by further grinding (not by sifting) of the bran samples by different experimental mills. Coarse bran can retain significantly more water than medium or fine bran as measured by a centrifuge method, but bran particle size had no significant effect on dough water absorption. Addition of wheat bran into bread dough systems increased dough water absorption rate, reduced mixing time and decreased dough mixing tolerance as measured by farinograph. Fine particle size wheat bran decreased dough mixing tolerance and reduced mixing time compared to coarse bran. Dough containing fine particle size bran exhibited more strength than dough containing coarse bran after a 180-min rest period as measured by the extensigraph. © 1997 SCI.     

Rheological Properties of Tomato Concentrates as Affected by Particle Size and Methods of Concentration

Shear rate-shear stress data were obtained on tomato concentrates made from juices that were produced using finisher screen openings (FSO): 0.020, 0.027, 0.033, and 0.045 in. In general, the apparent viscosity of the concentrates at a shear rate of 100 set^-1 increased with increase in FSO. However, concentrates made from juice using a 0.027 in FSO had the highest apparent viscosity. Magnitudes of yield stress of concentrates increased in direct proportion to FSO. Apparent viscosities of concentrates made by evaporating tomato juice were lower than those obtained either by evaporating the serum or by reverse osmosis concentration of the serum.     

Particle Size Distribution of Natural Peanut Butter and Its Dynamic Rheological Properties

This study compared the dynamic rheological properties of natural peanut butter with commercial peanut butter at 25°C. The natural peanut butter was produced using ultra-high speed grinding (?20,000 rpm) at different grinding times (2–5 min) from peanuts of China and India. Multimodal particle size distribution was observed for all the samples. The linear viscoelastic region obtained from stress sweep test of the peanut butter produced at 2–3 min fell within the linear viscoelastic region of commercial peanut butter of 0.1–11 Pa. Longer grinding time (3.5–5 min) produced a shorter and lower linear viscoelastic region of 0.03–3 Pa. The storage modulus, G′ is an increasing function of particle size distribution. All peanut butter samples exhibited elastic properties.     

Rheological Properties of Tomato Paste: Influence of the Addition of Tomato Slurry

ABSTRACT: This article deals with the influence that the addition of tomato slurry into tomato juice exerts on the viscous flow and linear viscoelastic behavior of the final tomato paste. With this aim, 5 tomato paste samples, manufactured at industrial scale, have been studied. Three breaking temperatures and 2 different screen sizes were used to prepare 4 regular tomato paste samples. Moreover, a tomato paste sample with addition of "treated tomato slurry" was manufactured using a breaking temperature of 80 °C and a sieve screen size of 1.2 mm. The results obtained suggest that the addition of treated tomato slurry may be of great interest for tomato paste production.     

Rheological and Ultrastructural Properties and Particle Size Distribution of Soymilk as Affected by Processing Methods

Soymilk was prepared from boiled and unboiled comminuted suspensions of dehulled soybean and water using pressurized homogenization (one pass and two pass). Particle size showed significant differences between soymilks homogenized by one pass and two pass. Apparent viscosities and total solid contents showed significant differences between boiled and unboiled treatments. Soymilks exhibited pseudoplastic and thixotropic behavior and Arrhenius model was fitted to express temperature dependence of apparent viscosity. Microscopic images showed hydrated, separated, uniformly distributed, and homogeneous particles in boiled two-pass soymilk as they were disrupted easily and it was selected as the best treatment for processing soymilk containing all of the soybean solids.     

Rheological Properties and Conformation of Tomato Paste Pectins, Citrus and Apple Pectins

Rheological properties of dilute and concentrated solutions of water-soluble, alcohol-precipitated tomato pectins from hot break and cold break tomato paste as well as alcohol-precipitated commercially available apple and citrus pectins were studied. Superposition of rheological data was possible when n_sp was plotteds vs c[η] and when η/η_o was plotted vs τγ The slope of n_sp vs cMw plot and the limiting slope of η/η₀ vs (τγ suggested that citrus, apple and hot break tomato pectin had random coil conformation while cold break tomato pectin had a more rigid conformation. Tomato processing had significant influence on the chain length and rheological properties of tomato pectins.     

颗粒粒径对马铃薯淀粉糊黏弹性的影响

讨论了超细粉碎马铃薯淀粉颗粒粒径对淀粉糊黏度及弹性的影响.分析结果表明机械研磨作用能够明显地破坏淀粉分子的结晶结构,导致其结晶度降低,而无序化程度增加.淀粉糊的静态黏度随样品颗粒粒径的增大而增大,随球磨时间的增长而减小,静态弹性也同样随样品颗粒粒径的增大而增大,随球磨时间的增长而减小;当颗粒粒径为10～30μm,淀粉糊黏度呈现最小值,但是淀粉的弹性不变.     

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。     

高能球磨处理对赣南脐橙全果原浆粒径和流变特性的影响

为了开发柑橘全果产品,降低全果原浆粒径,改善其流变特性,对柑橘全果粗浆进行球磨处理。以赣南脐橙为原料,经粗粉碎后球磨处理不同时间（0、30、60、90、120、150、180 min）,得到不同粒径的全果原浆,研究经球磨处理后赣南脐橙全果原浆的粒径和流变特性的变化。结果表明,球磨处理能有效降低全果原浆的粒径,球磨处理180 min后果浆平均粒径由110.00 μm下降到56.53 μm,整体下降了49%。随着球磨处理时间的延长,全果原浆越来越均匀细腻,且无团聚现象。球磨处理的赣南脐橙全果原浆体系随剪切速率的上升,剪切应力增大,而表观黏稠度下降,出现剪切稀化现象,是一种典型的假塑性流体,具有较好的黏弹性。与未经球磨处理的原浆相比,球磨处理60 min得到的赣南脐橙全果原浆黏稠度最高,凝胶状态最为稳定,适合加工为果酱类黏稠度较高的产品;而球磨处理30 min得到的原浆体系黏稠度最低,但流动性最佳,适合加工为果汁类流动性较好的产品。本实验为柑橘全果产品加工提供了参考依据。     

动态超高压均质对蛋清蛋白溶液的粒度和流变性影响

本实验以10%的蛋清蛋白溶液为研究对象,采用动态超高压均质处理,研究蛋清蛋白溶液平均粒度和流变性的变化。研究表明,10%的蛋清蛋白溶液的平均粒度随着压力的增加而出现明显减小的现象,其经过超高压均质后,由非牛顿流体的胀塑性流体转变为假塑性流体,均质后的蛋清蛋白溶液的表观黏度明显升高。     

Effect of Ultra-high-pressure Homogenization on Structure and on Rheological Properties of Soy Protein-stabilized Emulsions

ABSTRACT: An ultra high-pressure homogenizer (20 to 350 MPa) was used to realize fine food emulsions stabilized by soy proteins. The first aim of the work was to understand how dynamic high-pressure processing affects soybean globulin conformation. Then, the effect of homogenizing pressure on the emulsions structure and rheology was investigated. High-pressure homogenization caused denaturation of proteins due to strong mechanical forces and high temperatures encountered in the valve. Droplet sizes of emulsions were greatly reduced with high-pressure homogenization and Newtonian liquid emulsions were converted into shear-thinning emulsion gels by homogenization at pressures above 250 MPa. Hydrophobic interactions between proteins were supposed to cause the gel-like network structure of emulsions.     

板栗糊饮料流变学特性研究

在保留板栗全营养成分的基础上,研究板栗糊体系的贮藏稳定性。本文利用流变仪考察加入黄原胶、卡拉胶、CMC及复合稳定剂的板栗糊流变学特性与贮藏稳定性的关系。设定剪切速率在2.0~200 s^-1之间,角频率范围在0.1~100 Hz之间,测定其在4℃冷藏和25℃常温条件下静态与动态流变特性。研究表明:在贮藏50 d内,加入复合稳定剂的板栗糊品质最佳,其黏度变化范围为0.2~6.6 Pa·s,剪切应力范围为4~12 Pa。当温度从4℃升至40℃时,板栗糊表观黏度从1.1 Pa·s降到0.45 Pa·s,说明板栗糊具有良好的贮藏稳定性。     

阴米淀粉糊的流变特性

考察两优培九、荆糯六号大米以及阴米淀粉糊在不同质量浓度和温度下的流变特性,结果表明：这两种大米和阴米淀粉糊都是典型的非牛顿型和剪切变稀流体,黏度随剪切速率的增加而降低;同时用幂律函数描述淀粉糊的流变特性,拟合精度较高。淀粉糊的动态流变行为表现为：在升温初期,储能模量(G′)和耗能模量(G″)的值先显著下降,进而平缓下降,在90℃时出现不同程度的升高,随后又下降。损耗因子(tanδ)随温度的升高呈现先下降后上升的趋势。原米淀粉糊的黏性大弹性小,而阴米淀粉糊的弹性大黏性小。     

番茄浆料的流变特性

对不同浓度的番茄浆料在30～60℃时的流变学性质进行了研究.结果显示,番茄浆料为假塑体系,屈服应力值的范围比较宽(40～140Pa).通过回归分析得到数学模型K=K0exp(Ea/RT)和K=Aexp(BC).可以分别用来描述温度和浓度对番茄浆料稠度系数的影响.利用这些方程,可以预测实际加工过程中不同温度和不同浓度条件下番茄浆料的粘度.     

不饱和脂肪酸对猪肉蛋白质乳化特性的影响

研究不同饱和程度且不同添加量的脂肪酸对全肉盐溶性蛋白乳化特性、流变特性以及Zeta电位等影响。结果显示：脂肪酸添加量越大,乳化液的乳化活性越强,而乳化液的分层现象越严重;添加油酸和亚油酸可以明显增加乳化液的表面活性巯基;各乳化液粒度分布曲线均呈现“单峰”型,且较空白组的分布均向粒径较小的范围偏移;此外,随着剪切速率的增大,各乳化液黏度均逐渐减小,最后趋于平缓,在同一剪切速率下,添加量越大,乳化液剪切应力越大;Zeta电位值显示,荷电粒子不稳定。总之,C18的脂肪酸饱和程度越大,添加量越多,猪肉盐溶性蛋白质乳化的效果越好,在脂肪酸液滴表面形成蛋白膜的能力就会越强,使得乳化液的乳化特性越好。     

葛根淀粉糊流变学特性的研究

以葛根淀粉糊的动态及稳态流变特性为研究对象,以储存模量(G')、损耗模量(G")和表现黏度(η)为主要试验指标,利用旋转流变仪,研究淀粉浓度、氯化钠、蔗糖以及麦芽糊精对淀粉糊流变学特性的影响,旨在探究淀粉糊的弹性、黏性、表观黏度的变化,为葛根食品的工业生产提供一定理论依据。研究结果表明:葛根淀粉糊是典型的剪切变稀的非牛顿流体,其G'、G"及η均受这4种因素的影响。1)动态流变特性的研究结果显示,G'、G"与淀粉浓度呈正相关;随特定添加范围内的氯化钠、蔗糖以及麦芽糊精的添加量增加,G'、G"均有先升后降的趋势。2)稳态流变特性的研究结果显示,同一剪切速率下,η与淀粉浓度呈正相关,与麦芽糊精的添加量呈负相关;在特定添加范围内,氯化钠、蔗糖的添加量增加,η有先升后降的趋势。在工业生产中,葛根淀粉糊剪切稀化的行为有利于流动的淀粉糊充模成型,节省能耗。添加麦芽糊精会降低淀粉糊的弹性和黏性,而添加适量的氯化钠和蔗糖一定程度提高淀粉糊的弹性和黏性。     

荸荠淀粉糊流变性质的研究

为有效开发利用荸荠淀粉,研究不同浓度的淀粉、食盐、蔗糖、黄原胶、卡拉胶以及瓜尔豆胶对荸荠淀粉糊动态及静态流变特性的影响,结果表明:荸荠淀粉糊是典型的剪切稀化的非牛顿型流体,荸荠淀粉浓度的改变以及食盐、蔗糖、黄原胶、卡拉胶和瓜尔豆胶的添加都对此性质不产生影响。表观黏度与剪切速率呈负相关。淀粉浓度越高,体系的储存模量(G′)、损耗模量(G″)越大,但损耗角正切值(tanδ)越小;食盐可提高体系的G′、G″和tanδ;高浓度的蔗糖使体系的G′、G″增大,但蔗糖的加入却使体系的tanδ降低;高浓度的黄原胶、卡拉胶和瓜尔豆胶3种亲水性胶体可提高体系的G′、G″和tanδ。     

Effect of Different Extrusion Treatments and Particle Size Distribution on the Physicochemical Properties of Rice Flour

Rice flour is an interesting alternative for developing gluten free products, but its features do not always meet the process requirements. The objective of this study was to modify the functional properties of rice flour by combining extrusion and size fractionation. Different extrusion conditions (barrel temperature, feed moisture content and feed rate) were applied to vary the severity of the treatment on the flour constituents. Extrusion and mechanical fractionation of the rice flours modified their behavior affecting hydration, thermal and pasting features, besides their susceptibility to enzymatic hydrolysis. Specifically, onset and peak temperature increased and gelatinization enthalpy decreased when increasing barrel temperature of the extrusion. Fine flours with stronger extrusion (high temperature barrel) showed the highest susceptibility to enzymatic hydrolysis. Overall, the combination of both physical treatments maybe an attractive alternative for obtaining clean label rice flours with modified features.