Some remarks on rheological properties of concentrated solutions of galactomannans

Rheological properties of concentrated solutions of galactomannans, locust bean gum (lb-gum) and guar gum (g-gum), were compared between samples from different manufacturers to examine the effects of prescreening for polysaccharides. The angular frequency dependence curves of the storage and loss moduli were similar in shape between lb-gum samples but were different quantitatively. This results in different values of the molecular weight between entanglements in the molten state (M_e,melt) for the lb-gums, although M_e,melt is a material constant. On the other hand, M_e,melt for g-gum samples agreed with each other. It was demonstrated that the quantitative difference in the rheological properties of lb-gum solutions was attributed to the effective lb-gum concentration in the solutions and that M_e,melt is surely a material constant even for these galactomannans. This study confirms that prescreening of samples is very important for polysaccharides to estimate M_e,melt.     

Sensory and rheological properties of Polish commercial mayonnaise

Sensory and rheological analyses were performed to compare seven commercial mayonnaises having various fat contents and containing, or not, thickening and stabilizing agents. It was found that mayonnaise samples differed in their sensory and rheological properties. The samples with a higher fat content scored higher in sensory analysis than the low-fat ones. The mayonnaises studied showed non-Newtonian, pseudoplastic flow with yield stress and thixotropy. All mayonnaises, although to a different degree, exhibited a decrease in the apparent viscosity at constant shear. The mayonnaise samples which contained thickeners and stabilizers had a greater rheological stability.     

核壳型聚氨酯-聚丙烯酸酯复合乳液的合成及流变性能研究

以水性聚氨酯(PU)乳液为种子,甲基丙烯酸甲酯(MMA)、苯乙烯(St)、丙烯酸丁酯(BA)、丙烯酸(AA)等为核层单体,采用半连续种子乳液聚合工艺,合成了具有核壳结构的水性聚氨酯-聚丙烯酸酯(PUA)复合乳液.通过透射电镜(TEM)、差示扫描量热分析(DSC)、傅里叶红外光谱(FTIR)、粒径分析等方法对乳液及其所成乳胶膜的结构和性能进行了测定.另外,还对PUA复合乳液及以其作为粘合剂所制成的数码喷墨印花墨水(乳液墨水)进行了流变性能研究,结果表明:PUA复合乳液在高速率剪切条件下呈现牛顿流体的特性,粘性在乳液体系中占主导地位;乳液墨水也表现出相似的流变学性能,乳液粒子与颜料粒子之间存在一定的相互作用.     

Gelation behaviour and rheological properties of acid-induced soy protein-stabilized emulsion gels

The protein concentration dependence on the rheological properties of acid-induced gels formed with unheated and heated soy protein-stabilized emulsions (UHSPE and HSPE) was investigated at different acidification temperatures. Pre-heat treatment on soy protein solutions resulted in a higher storage modulus (G′) and a shorter gelation time (t_gel) of acid-induced emulsion gels. A maximum in tan δ was observed in the UHSPE gels but no maximum was detected in the HSPE gels. Increasing the acidification temperature decreased the G′ and t_gel. The dependence of the G′ on the protein concentration (c) can be scaled with a power law: G′ ∼ c^A. The exponent (A) increased with pre-heat treatment and acidification temperature. The experimental data.fitted the fractal scaling model (G′ ∼ φ^A) and the simple time- scaling model above very well for the acid-induced soy protein-stabilized HSPE gels with varying oil volume fraction. The large deformation and fracture properties were significantly affected by soy protein concentration, pre-heat treatment, acidification temperature and volume fraction of oil droplets (p < 0.05).     

薯类淀粉对兔肉肉糜流变性质和凝胶特性的影响

探讨木薯淀粉、甘薯淀粉和马铃薯淀粉对兔肉肉糜流变性质和凝胶特性的影响,研究了不同淀粉添加量时,兔肉肉糜弹性模量G'、质构特性、凝胶强度、保水性和色泽的变化规律。结果表明:升温过程中,兔肉肉糜的弹性模量G'经历了3个阶段的变化。首先在40~50℃,G'缓慢上升,接着在50~57℃,G'急剧下降,然后在57~80℃,G'快速上升,之后趋于稳定。降温过程中,G'逐渐升高。淀粉对兔肉肉糜在升温和降温过程中弹性模量的变化影响显著。添加淀粉能增加兔肉肉糜凝胶的硬度、胶着性和咀嚼性,降低其内聚性,而弹性则呈现先上升后下降的趋势。添加淀粉能增加兔肉肉糜的凝胶强度、持水性,同时降低压力失水率,同一添加量时,马铃薯淀粉对改善兔肉肉糜凝胶的品质、增加肉糜凝胶保水性的效果最好。添加淀粉能增加肉糜凝胶的亮度值和白度值,降低肉糜凝胶的黄度值,但淀粉的种类和添加量对兔肉肉糜凝胶的色泽影响不显著。3种薯类淀粉中,马铃薯淀粉的应用效果最好。     

Structural characteristics and rheological properties of locust bean galactomannans: a comparison of samples from different carob tree populations

Water‐soluble galactomannans were isolated from the seeds of 12 carob tree populations grown in different regions of southern Greece. Their structures, molecular weight distributions and rheological properties were examined. The intrinsic viscosity values and estimated average molecular weights varied in the ranges 8.15–13.02 dl g⁻¹ and (2.3–3.9) × 10⁶ respectively. Molecular sieve chromatography showed large variations in the molecular size distributions. The Manp/Galp ratio varied between 3.08 and 3.82, as determined by GC analysis of the alditol acetate derivatives of the monomeric constituents. There were also differences in the relative distribution of the free (Manp‐Manp), monosubstituted (Manp‐Manp(Galp)) and disubstituted (Manp(Galp)‐Manp(Galp)) dyads of β‐(1→4)‐mannose, as revealed by ¹³C NMR spectroscopy of the native polysaccharides. The pseudoplastic behaviour of galactomannan solutions (10–20 g l⁻¹) was confirmed by steady shear and dynamic rheological tests. Aqueous galactomannan (5 g l⁻¹)–xanthan gum (5 g l⁻¹) mixed systems gave gels on cooling (G′ ≫ G″). Galactomannans with high limiting viscosities, high Manp/Galp ratios and a low proportion of the Manp(Galp)‐Manp(Galp) dyad yielded the strongest mixed gel network structures with xanthan, implying that interchain associations between the two polymers occur via the unsubstituted segments (‘smooth regions’) of the carob galactomannan chains. © 2000 Society of Chemical Industry     

大豆多糖对乳清分离蛋白—乳状液稳定性与流变特性的影响

本文研究了大豆多糖（SSPS）与乳清分离蛋白（WPI）乳状液静电组装,形成乳状液聚集体,考察了不同浓度的SSPS对WPI-乳状液稳定性与流变特性的影响,以期提高体系的粘弹性,形成高流变特性的食品体系。将不同浓度的大豆多糖与2%乳清分离蛋白乳状液（油相为20%）静电组装,分析乳状液的粒径,Zeta-电位,稳定性指数,流变性质和微观结构。结合剪切流变与微流变技术,深入研究了SSPS对乳清分离蛋白（WPI）乳状液流体特性与结构的影响。结果表明:随着SSPS浓度的增加,WPI乳状液的粒径在添加0.25%SSPS时达到峰值（3350±0.35）nm,而后随着SSPS浓度的增加而降低;Zeta-电位绝对值呈递减的趋势,表明SSPS与WPI间产生静电吸附作用;SSPS静电吸附提高WPI乳状液的稳定性;剪切流变结果表明,SSPS浓度为0.5%时,其粘度最大,并在剪切速率为95.8 s-1处其粘度是WPI乳状液粘度的10倍以上;微流变结果表明,0.5%SSPS-WPI乳状液的MSD曲线出现平台区,表明其弹性指数（EI）与宏观粘度指数（MVI）均显著提高达到最大值。微观结构结果表明,0.5%SSPS-WPI乳状液形成均一的乳状液聚集体。本研究将有助于理解大豆多糖与蛋白质乳状液的相互作用,同时为低脂高流变特性的食品（如蛋黄酱、调味汁、巧克力和植脂奶油等）生产提供理论指导。      

魔芋胶溶液浓度对其流变学特性的影响研究

配制质量分数为0.1~1.0%的魔芋胶溶液,通过稳态流动、应变扫描、频率扫描以及动态粘弹性温度扫描、动态粘度温度扫描,观察不同溶液浓度对粘度特性随剪切速率及温度的变化情况,粘弹性随应变、频率及温度的变化,以及考察模量频率相交点、松驰时间等与结构特性相关的各因素。试验结果表明：在1%浓度范围内,魔芋胶溶液的零剪切粘度、粘度、剪切稀化指数、特征松驰时间及弹性模量、粘性模量、损耗正切与浓度之间存在高度的相关性。另外,浓度的改变影响频率扫描中G’=G’’时交点处频率、模量及松驰时间,亦影响动态粘弹性温度扫描中凝胶-溶胶转换时温度的高低与模量的大小。     

交联大豆分离蛋白的制备及流变学性质

利用二元酶系(辣根过氧化物酶、葡萄糖氧化酶)和葡萄糖,通过一步法或两步法对大豆分离蛋白进行交联处理.以修饰产物中相对二酪氨酸含量为指标,采用单因素实验确定一步法处理大豆分离蛋白的反应的适宜条件为:葡萄糖添加量1.8％、葡萄糖氧化酶添加量4.0U/g蛋白质、辣根过氧化物酶添加量200U/g蛋白质、反应时间3h.在一步法处理的反应条件下,一步法和二步法处理的大豆分离蛋白相对二酪氨酸含量分别为414和381.与大豆分离蛋白相比,交联蛋白分散液的表现黏度和黏弹性均有显著改变,同时其酸凝胶的胶凝时间缩短、胶凝温度降低.     

交联大豆分离蛋白的制备及流变学性质

利用二元酶系(辣根过氧化物酶、葡萄糖氧化酶)和葡萄糖,通过一步法或两步法对大豆分离蛋白进行交联处理。以修饰产物中相对二酪氨酸含量为指标,采用单因素实验确定一步法处理大豆分离蛋白的反应的适宜条件为:葡萄糖添加量1.8%、葡萄糖氧化酶添加量4.0U/g蛋白质、辣根过氧化物酶添加量200U/g蛋白质、反应时间3h。在一步法处理的反应条件下,一步法和二步法处理的大豆分离蛋白相对二酪氨酸含量分别为414和381。与大豆分离蛋白相比,交联蛋白分散液的表观黏度和黏弹性均有显著改变,同时其酸凝胶的胶凝时间缩短、胶凝温度降低。      

Effect of different starches on rheological and microstructural properties of (II) commercial processed cheese

A range of commercial processed cheese samples containing starch were prepared on a Rapid Visco Analyser (RVA) and on a pilot plant scale. This work clearly demonstrated that it was possible to manufacture processed cheese with part of the protein replaced with potato starch, while maintaining similar rheological attributes (firmness) to those of the control and an acceptable melt index. Sensory evaluation showed that, although the reduced‐protein cheese samples had a good, clean, fresh flavour that was comparable with that of the control, at high starch concentrations the starch‐containing processed cheese had a pasty texture and tended to stick to the wrapper.     

Chemical,sensory and rheological properties of some commercial German and Egyptian tomato ketchups

The rheological behaviour of eight tomato ketchups measured in the shear rate range from 0.1 to 100 1/s and with oscillatory tests was studied over a wide range of temperatures (0–50 °C) using a Physica UDS 200 rheometer. The results indicated that these tomato ketchups behave as non-Newtonian fluids semi-solid and have a definite yield stress. The relationship between _eff and temperature of all the tomato ketchup brands under investigation was examined. Significantly higher correlation was found between _eff and temperature. The _eff values decrease with an increase in temperature. Oscillatory test data revealed weak gel-like (dispersion structure) behaviour of the ketchup: the magnitudes of G were higher than those of G, and both increased with oscillatory frequency. The effect of temperature on the viscosity can be described by means of an Arrhenius-type equation. The flow activation energy for viscous flow depends on the chemical composition; the flow activation energy increases with the total solids contents. Chemical, physical and sensory tests for tomato ketchups were made.     

琼脂的流变特性对饮用型酸奶稳定性的影响

本文以琼脂为研究对象,采用频率扫描-粘弹性曲线来研究其流变特性,及其对饮用型酸奶稳定性的影响。结果表明:添加琼脂使样品的粘弹性模量增大,琼脂添加量0.08%的样品弹性特征区域最宽（0¹0 Hz）,其他添加量0.04%、0.12%和0.16%样品的弹性特征区域较窄（0² Hz）,体系的粘弹性模量随琼脂添加量的增加而呈现增大趋势,在低频范围内,粘弹性模量由大到小依次为:0.16%>0.12%>0.08%>0.04%>0.00%。样品的保温结果与离心沉淀率结果一致,随着琼脂添加量的增大,样品的离心沉淀率逐步降低,样品状态越趋于稳定,在0.08%的琼脂用量下离心沉淀率达到最低,样品状态达到最佳;继续增加琼脂用量,离心沉淀率呈快速上升趋势,样品状态越趋于不稳定,体系失稳。表明:琼脂添加量只在最适值时,才能使酸奶体系的稳定性达到最佳,高于或低于最适值,体系均不稳定。      

黑小米与黄小米Mixolab流变学特性差异研究及其产品应用

通过对黑小米和黄小米进行营养组分差异分析,并采用Mixolab对黑小米和黄小米的流变学特性进行测定,研究比较了两者的蛋白质和淀粉等方面的功能特性,并采用3种不同工艺制作了小米锅巴。实验结果表明,黑小米较普通黄小米具有较高的营养价值,尤其在蛋白质、油脂和矿物盐类等方面都优于普通黄小米。Mixolab实验结果表明,黑小米具有较好的蛋白质稳定性、淀粉热黏度稳定性和加工特性。     

不同浓度阴离子瓜尔胶溶液的流变特性研究

采用AR-G2流变仪,通过稳态流动、应变扫描、频率扫描及动态黏弹性温度扫描等实验详细研究了瓜尔胶溶液浓度对其流变特性的影响,并从微观结构上进行解析。实验得到的各个流变特性参数与浓度之间存在高度相关性,通过数理统计分析,对上述相关性进行拟合并得到一系列方程。     

不同品种莲藕淀粉的颗粒形态及流变特性研究

利用扫描电子显微镜和流变仪等对四种莲藕(鄂莲五号,鄂莲一号,武植二号,3537)淀粉的颗粒形态和流变特性进行了研究。结果表明:四种莲藕淀粉大部分呈长棒状及不规则的片状。鄂莲五号莲藕淀粉粒径最大且大颗粒的淀粉粒占较大的比例,武植二号淀粉粒径最小,小颗粒和不规则片状的淀粉粒占较大比例。不同品种莲藕淀粉在升温和降温模量变化差异显著。在升温和降温过程中鄂莲五号淀粉具有最高的储能模量G’、耗能模量G″和低的损失因子tanδ,而四种淀粉中武植二号淀粉的G’和G″均最小且具有最大的tanδ。不同浓度(4%～8%)的莲藕淀粉糊随浓度的增加稠变系数也增加,且均为假塑性流体,表观黏度随剪切速率增加而降低,表现为剪切变稀。     

Relating the effect of saliva-induced emulsion flocculation on rheological properties and retention on the tongue surface with sensory perception

Perception of food emulsions can often not be directly related to the structure of the products before consumption. Taking into account the changing product structure upon oral processing might increase understanding of the relation between perception and product properties.     

蛋白质量浓度对玉米胚芽蛋白Pickering乳液凝胶流变学性质的影响

研究了不同质量浓度(10、20、30 mg/m L)的玉米胚芽蛋白Pickering乳液的表观黏度及动态流变性的变化,同时采用流变学分析的方法考察由葡萄糖酸内酯、谷氨酰胺转氨酶诱导的乳液凝胶的凝胶时间、凝胶强度及凝胶持水性的变化。结果表明:玉米胚芽蛋白质量浓度为10~30 mg/m L时,在剪切速率0.1~100 s~(-1)的范围内表观黏度随着剪切速率的增加逐渐下降,乳液呈剪切稀释,且随着蛋白质量浓度的增加,乳液表观黏度增大;动态流变学分析结果表明,不同蛋白质量浓度的乳液在频率0.1~50 Hz时,G'无明显变化,随后乳液的G'随着频率的增加而增加,且质量浓度为30 mg/m L的乳液增加得最显著;随着蛋白质量浓质的增加,由葡萄糖酸内酯和谷氨酰胺转氨酶诱导的玉米胚芽蛋白Pickering乳液所形成的凝胶时间缩短,凝胶强度增大,持水性增大。     

四种添加剂的流变性能研究

论文主要对四种添加剂进行了流变性能的研究,四种添加剂中,黄原胶、瓜尔豆胶其胶体溶液流变性有更多的相似性,它们浓度在0.3%以上时,均为非牛顿型流体,CMC浓度在0.5%以上时为非牛顿型流体,且为非触变性流体.海藻酸钠胶体溶液为牛顿型流体.四种添加剂胶体溶液的粘度,瓜尔豆胶＞黄原胶＞CMC＞海藻酸钠.但在搅动环境下,当剪切力大于一定的屈服应力时,剪切稀化效应将导致粘度的下降,下降幅度为瓜尔豆胶＞黄原胶＞CMC.黄原胶更具有独特的流变性、优良的热稳定性、酸稳定性,其次为瓜尔豆胶.CMC、海藻酸钠的热稳定性并不是很好,在高酸性的环境条件下,海藻酸钠的粘度反而增加.