胡芦巴胶溶液的流动性模型拟合和动态粘弹性分析

在特定温度(25℃)下,通过对葫芦巴胶(FG)溶液进行稳定剪切和小振幅振荡处理后,测定其触变性及粘弹性,以及通过Carreau和Herschel-Bulkey模型对FG溶液流动性进行评估。结果表明:FG溶液刚开始表现出剪切增稠特性,当超过临界剪切速率时表现为剪切变稀行为,表现出非牛顿流体特性。Herschel-Bulkey和Carreau模型对流动曲线的拟合表明实验结果更符合流变学的Carreau模型。触变测试表明FG溶液具有一定的触变性,FG溶液质量浓度越高,触变性越强,当FG溶液质量浓度小于0.35 g/d L时,触变环面积为负值,表明样品结构破坏且不能恢复。动态粘弹性测试表明FG溶液的储能模量和损耗模量随角频率和FG质量浓度的增大而增大,随着温度的升高而降低,并表现出类似于固体的弹性行为。     

黄原胶流变学特性及其协效性研究

研究了不同浓度的黄原胶溶液的黏度变化以及剪切速率和时间对其流变学特性的影响,此外还对黄原胶与瓜尔豆胶、CMC、果胶的协效性进行了研究.研究结果表明,黄原胶溶液的黏度值随浓度的增加而逐渐增大,对其进行线性回归得方程y=157.8x-182.07,其相关系数达到0.9838.触变性的测定发现,在升速过程中黄原胶的表观黏度随剪切速率的增加而逐渐降低,而在降速过程中,表观黏度有一定的回升,具有很明显的假塑性,并且能够形成触变环,不同浓度黄原胶溶液的黏度值都是随剪切速率的增加而逐渐减小,这些现象表明,黄原胶溶液是一种正触变性流体.此外还发现,黄原胶和瓜尔豆胶具有一定的协效性,当黄原胶同瓜尔豆胶的比例为9 ∶ 1时,表观黏度值达到最大,为768.2mPa.s.黄原胶与CMC、果胶无协效性.     

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。     

两种糖对食品胶—马铃薯淀粉物理特性的影响

利用快速黏度分析法、质构分析法、离心法、冻融循环等方法研究蔗糖和葡萄糖对5种食品胶—马铃薯淀粉混合物糊化、凝胶、膨润、冻融稳定性等物理特性的影响.结果表明:添加糖类后,食品胶—马铃薯淀粉混合物的糊化温度、溶解度、冻融稳定性均显著升高,膨胀势显著降低,持水力则基本不变.亚麻多糖、卡拉胶、黄原胶与马铃薯淀粉混合物的峰值黏度、末值黏度随糖的添加而显著升高.与不加糖的对照样品相比,添加糖的亚麻多糖—马铃薯淀粉混合物的凝胶硬度显著升高,黄原胶—马铃薯淀粉混合物的凝胶硬度则显著降低.添加蔗糖基本不影响食品胶—马铃薯淀粉混合物的衰减值,但添加葡萄糖则导致食品胶—马铃薯淀粉混合物的衰减值显著升高.     

海藻酸丙二醇酯流变学特性的研究

重点对海藻酸丙二醇酯(PGA)的流变学特性进行了研究。分析比较了不同温度、质量分数、pH、蔗糖浓度下PGA溶液的流变性和不同质量分数下的触变性,以及不同温度、质量分数、pH下的动态黏弹性。结果表明:PGA溶液是假塑性非牛顿流体,具有一定的触变性,且随PGA浓度的升高而增大;其黏度随着PGA质量分数和蔗糖添加量的增加而增大;随着剪切速率、温度和pH的升高而减小。PGA溶液在测定频率范围内均表现为黏性,G′′和G′均随着质量分数的增加而增大,随着温度、pH的升高而减小。     

亚硫酸铵法焦糖色的流变性研究

目的研究亚硫酸铵法焦糖色的流变性质。方法用黏度计测定亚硫酸铵法焦糖色在不同剪切速率、温度、固形物含量下的黏度和剪切应力,研究其黏度随剪切速率和时间的变化,通过回归分析拟合出亚硫酸铵法焦糖色的流体方程、温度与黏度关系方程、固形物含量与黏度关系方程。结果不同剪切速率下亚硫酸铵法焦糖色的黏度有明显差异,但是不随时间而变化;Power Law模型的拟合效果优于Bingham模型;不同固形物含量亚硫酸铵法焦糖色的阿伦尼乌斯方程相关系数均有R~2 0.995;指数函数模型拟合亚硫酸铵法焦糖色固形物含量与黏度关系方程的效果优于幂函数模型。结论亚硫酸铵法焦糖色属于非牛顿流体中的时间独立性假塑性流体;流体方程中的Power Law模型τ=kγ~n能较好地表示亚硫酸铵法焦糖色剪切应力与剪切速率之间的关系;亚硫酸铵法焦糖色黏度与温度的关系符合阿伦尼乌斯方程η=Aexp(Ea/RT);指数函数模型η=a′exp(b′C)能较好地表示亚硫酸铵法焦糖色固形物含量与黏度的关系。     

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。     

塔拉胶流变学特性研究

应用哈克(Hakke)旋转流变仪和原子力显微镜等手段,研究了塔拉胶静态和动态流变学特性。结果表明:塔拉胶溶液具有无触变性和一定的粘弹性,体系在低频区域以黏性为主,在高频区域以弹性为主,其流动模型符合幂律模型;盐离子(NaCl、CaCl2)的加入导致塔拉胶溶液的表观黏度降低;蔗糖在低浓度时可减小塔拉胶溶液的表观黏度,但高浓度时可增大其黏度;塔拉胶溶液对温度具有一定依赖性,其表观黏度随温度的升高而降低,经高温灭菌锅处理后其黏度有所下降,但在不同酸碱环境和冻融条件下都表现出良好的稳定性。     

沙蒿籽胶的流变学性质研究

研究了沙蒿籽胶的静态流变学特性和动态流变学特性。静态流变学表明:沙蒿籽胶溶液是触变性流体,其表观粘度随质量分数的增加而增加,且随剪切速率变化的影响符合Herschel-Bulkey模型;温度、pH值等对沙蒿籽胶溶液的表观粘度影响较小;盐的加入能改变沙蒿籽胶溶液的粘度。动态流变学特性表明:沙蒿籽胶溶液显示弱凝胶特性。     

压力对不同特性黏度聚酯流变行为的影响

采用毛细管流变仪及其配套的反向压力腔组件控制毛细管出口压力,在平均压力为5~50 MPa下研究了3 种不同特性黏度的聚酯（PET）的流变行为。结果表明：PET的剪切黏度随着平均压力的增大都呈指数增加,符合Barus方程。压力系数随着特性黏度的增大而减小,当特性黏度由0.48增加至0.67 dl/g时,压力系数显著减小,且这种变化随着剪切速率的增大而衰减,当特性黏度≥0.67 dl/g时,压力系数随剪切速率的变化不大。压力系数随剪切速率的增大而减小,特性黏度为0.48 dl/g时变化显著,当特性黏度≥0.67 dl/g时,压力系数随剪切速率的变化不大。压力系数随着温度的升高而减小,且变化率随着温度的升高显著减小。不同特性黏度PET压力系数的变化表明,特性黏度较低时,自由体积较大,表现在玻璃化转变温度低,受压力的影响显著;当特性黏度为0.67和1.00 dl/g时,自由体积的减小不再明显,因此受压力的影响也不再明显。     

基于Z-score评价模型优化梨膏护色工艺

为优化鸭梨膏护色工艺,以褐变度、总酚、总黄酮含量和感官评价得分结果为基础建立Z-score(Z值)法综合评价模型,以Z值为评价指标,通过单因素试验和响应面试验确定鸭梨膏最佳护色参数,并采用电子鼻和电子舌对护色和未护色鸭梨膏的气味和滋味进行比较分析。结果表明：鸭梨膏最优护色工艺为抗坏血酸添加量0.02%(m/v)、柠檬酸添加量0.05%(m/v)、偏重亚硫酸钾添加量0.02%(m/v),在此条件下,鸭梨膏呈亮黄色半透明膏状,带有梨果特殊香味,酸甜感适中,感官得分为9.38,褐变度为0.201,总酚和总黄酮含量分别为59.80和80.10μg/mL,Z值法综合评价得分为5.14,与理论值5.03接近。电子鼻可以准确区分护色和未护色的梨膏。电子舌分析表明护色鸭梨膏具有明显的丰富度和酸味。     

Time-dependent flow properties of starch–milk–sugar pastes

The time-dependent flow properties of starch–milk–sugar (SMS) pastes have been studied. The flow properties were assessed from the measurement of the shear stress versus time of shearing at constant shear rate. Corn and wheat starches were used in this study, while the sugars were glucose, sucrose, and fructose. The Weltman model was used to evaluate the flow properties of SMS pastes prepared under different conditions. SMS pastes heated at 95 and 85 °C exhibited a thixotropic behavior, while pastes heated at 75 °C behaved like a rheopectic fluid. It was noted that the thixotropy occurred at high shear stress (above 50 Pa), and the rheopexy occurred at low shear stress (below 45 Pa). The degree of thixotropy, as assessed by the Weltman model parameters, increased significantly with starch concentration, and with less pronounced effect with sugar concentration. The effect of sugar type on the degree of thixotropy of SMS pastes heated at 95 °C decreased in the following order: fructose>sucrose>glucose. The type of starch played a role in the time-dependent flow properties of the SMS paste, with a general conclusion that wheat starch had a greater degree of thixotropy than corn starch.     

基于双螺杆挤压技术的淀粉阿魏酸酯流变特性研究

利用双螺杆挤压技术制备淀粉阿魏酸酯,研究其流变性、剪切稀化及触变性变化规律,并建立流变模型。结果表明,淀粉阿魏酸酯糊化后,流体符合幂函数Ostwald-de Waele模型,呈假塑性流体特征;表观黏度增加,流动性降低,具有剪切稀化现象;触变性随样品浓度的增加而增大。     

Physicochemical and Organoleptic Properties of Yogurt with Cornelian Cherry Paste

Stirred-type fruit-flavored yogurt was made by adding cornelian cherry paste and sugar at different ratios. The effects of the paste and sugar addition on the physicochemical and organoleptic properties of yogurt were examined. The titratable acidity, pH, viscosity, whey separation, and organoleptic properties of experimental yogurts were determined at weekly intervals for 21 days. Statistically significant differences were found between the control and fruit-flavored yogurts in terms of viscosity and whey separation. The addition of the fruit paste and sugar to yogurt resulted in an increase in the whey separation, and a decrease in the viscosity. During the storage, the values of the titratable acidity, viscosity and whey separations of experimental yogurts increased, while pH of the yogurts decreased significantly (P < 0.01). Yogurt with 10 kg/100 kg fruit paste and 10 kg/100 kg sugar was more acceptable and high scored with respect to overall acceptability value by panelists; however the result was not significant statistically.     

18 个品种授粉‘鸭梨’果实品质和香气成分分析与评价

研究不同品种授粉对‘鸭梨’果实品质和香气成分的影响,探究‘鸭梨’果实品质性状的花粉直感效应,为授粉品种筛选和‘鸭梨’果实品质改善提供依据。以30 a生‘鸭梨’为试材,分别以18 个不同品种特性花粉为‘鸭梨’进行人工授粉,其中以‘雪花梨’授粉果实为对照,测定果实单果质量、果点直径、果点密度、石细胞团含量、可溶性固形物、糖酸组分含量及香气组分相对含量等品质指标,利用主成分分析对不同品种的授粉效果进行综合评价。结果表明,不同品种授粉对‘鸭梨’果实外观品质、内在品质及香气成分均有影响,变幅在12.57%～96.10%之间;与‘雪花梨’授粉果实相比,‘南水’、‘丰水’和‘库尔勒香梨’授粉‘鸭梨’果实可溶性固形物、可溶性糖含量和固酸比均显著提高,分别提高了0.55%～0.76%、7.53～16.54 mg/g和1.96～4.54,改善‘鸭梨’果实营养品质;‘南水’、‘库尔勒香梨’、‘Crispel’、‘绿宝石’和‘翠玉’授粉‘鸭梨’果实酯类物质相对含量显著增加了7.77～17.85 倍,其中乙酸己酯相对含量显著提高了2.76～14.86 倍,同时检测出6 种特有酯类香气物质,分别为乙酸乙酯、己酸乙酯、丁酸乙酯、(E)-乙酸-2-己烯-1-醇酯、乙酸苯乙酯和反-2-顺-癸二烯酸乙酯,改善‘鸭梨’果实香味。与父本果实品质特性相比,授粉‘鸭梨’果实在石细胞团含量、果肉质地、可溶性固形物、可溶性糖及香气组分方面表现明显的花粉直感效应,而在单果质量、果点直径、果点密度及总酸含量方面无明显花粉直感效应;综合评价表明,‘南水’授粉效果最好,适宜为‘鸭梨’授粉树。     

高温α-淀粉酶-挤压膨化耦合处理对全谷物糙米粉品质的影响

以普通糙米、红米和黑米为原料,分析了高温α-淀粉酶-挤压膨化耦合处理对全谷物糙米粉径向膨化率、水溶性指数、吸水性指数、分散时间、结块率、黏度、糊化度以及还原糖、总蛋白质含量和可溶性蛋白质含量的影响。结果表明:3种全谷物糙米经过高温α-淀粉酶-挤压膨化耦合处理后其径向膨化率和糊化度均显著降低(P<0.05);水溶性指数显著升高(P<0.05)了2.51倍、1.89倍和2.73倍,吸水性指数显著降低(P<0.05)了77.29%、33.41%和67.44%;分散时间和结块率均显著降低(P<0.05),分散时间分别减少了64.60%、60.66%和65.40%,结块率分别降低了75.57%、84.64%和75.24%;冲调黏度均显著下降(P<0.05),加酶处理的糙米粉在低剪切速率下具有较低黏度,其黏度曲线趋于平直;还原糖和可溶性蛋白质含量显著提高(P<0.05),总蛋白质含量提高不显著(P>0.05)。     

Changes in the volatile compounds and chemical and physical properties of Yali pear (Pyrus bertschneideri Reld) during storage

Volatiles from stored Yali pear (Pyrus bertschneideri Reld) were studied using high-resolution gas chromatography and the solid-phase microextraction (SPME) method of gas chromatography/mass spectrometry (GC/MS). The dominant components were ethyl butanoate, ethyl hexanoate, α-farnesene, hexanal, ethyl acetate, hexyl acetate, ethanol and so on. By using GC-olfactometry, it was demonstrated that the volatile compounds from SPME were responsible for the aroma of Yali pear. The levels of sugars, organic acids, and phenolic acids in Yali pear were investigated using high-performance liquid chromatography. Fructose was the dominant sugar, followed by glucose and sucrose. With increasing storage time, sucrose levels decreased, however fructose and glucose levels did not changed remarkably. There was a slight decrease in flesh firmness during storage. The general soluble solids concentration, slightly decreased after 5 months storage. Some aroma volatile components increased during storage, while others decreased, especially the esters. The organic acids and phenolic acids also changed. Yali pear flavor was affected by changes in the levels of volatile compounds, and chemical and physical properties.     

纳米微晶纤维素-玉米淀粉复合氧化过程参数对其复合成膜液流变特性的影响

用纳米微晶纤维素(cellulose nanocrystals,CNC)与吸水润胀的玉米淀粉进行插层复配形成"CNC-淀粉"复合材料,采用NaClO对复合材料进行了氧化,并利用氧化玉米淀粉与聚乙烯醇(polyvinyl alcohol,PVA)/甘油(glycerol,GL)组合制备复合成膜液,探究了玉米淀粉浓度(3.0%、5.0%、8.0%和10.0%)、氧化及成膜液组分( PVA浓度为30.0%、40.0%、50.0% 、60.0%、70.0%和80.0%)对复合成膜液流变特性的影响。结果表明:氧化可导致玉米淀粉糊的黏度降低,且最低值为0.08 Pa·s;增加氧化玉米淀粉浓度可提高氧化玉米淀粉糊和复合成膜液的黏度、剪切应力、触变性和黏弹性,但稳定性降低,其中浓度为5.0%时,黏度较高,稳定性最好;增加PVA用量可提高成膜液黏度、剪切应力和黏弹性,PVA浓度为60.0%时,成膜液的黏度达最大值为9.9 Pa·s,黏弹性最高。玉米淀粉糊和复合成膜液均属于剪切稀释型非牛顿流体,表现出正触变性,流变特性符合Ostwald-de-Waele流体模型。     

Semi‐dilute solutions of hydroxypropyl guar gum: Viscosity behaviour and thixotropic properties

Semi‐dilute solutions of hydroxypropyl guar gum (HPGG), the most widely used derivative of naturally occurring guar galactomannan, were investigated with respect to their viscosity, yield stress and thixotropy. It was found that the shear‐dependent viscosity behaviour under various HPGG concentrations, added salts and temperature could be well described by the Cross viscosity model. The zero‐shear‐rate viscosity was observed to change with HPGG concentration according to a power‐law function, and decease with the increase of temperature according to an Arrhenius‐type equation. The addition of salts (KCl and CaCl₂) lowered the zero‐shear‐rate viscosity. The HPGG solutions of high concentration showed a higher degree of thixotropy while the addition of salt lowered the thixotropic property. Copyright © 2007 Society of Chemical Industry