Effect of Soluble Solids Concentration and Temperature on Thermo-Physical and Rheological Properties of Mango Puree

Thermo-physical and rheological properties of mango pulp were evaluated at different temperatures (20, 40, 60, and 80°C) and total soluble solids concentrations (15, 20, 32, and 40°Brix). Thermal properties were primarily dependent on the moisture content of the sample, and increased with temperature and decreased with soluble solids concentrations. Density showed a reverse trend. Glass transition temperatures increased with an increase in soluble solids concentrations indicating better stability. Empirical models developed for each thermal property as a function of temperature and soluble solids concentrations (R² > 0.90) generally showed better predictions than published models. Mango puree exhibited pseudo-plastic behavior during steady shear measurements, and the power law model well described their flow behavior. Consistency coefficient increased with soluble solids concentrations and decreased with temperature. The flow behavior index ranged between 0.27 and 0.38 but did not show a clear trend either with soluble solids concentrations or temperature. Small amplitude oscillatory shear measurements revealed that mango puree behaved like a weak gel and demonstrated visco-elastic properties.     

Rheological Properties of Chymosin-Induced Skim Milk Gels as Affected by Milk Storage Time and Temperature

Fundamental dynamic rheological tests were used to measure the rigidity (|G*|) and viscoelasticity (tan δ) of gels made from skim milk samples that were (1) never cooled, (2) stored at 4°C, or 3) stored at 4°C and then rewarmed to 25°C. Milk cooled and held at 4°C prior to gel formation produced gels with lower |G*| and higher tan(δ) than fresh milk gels. Chilled milk samples that were rewarmed to 25°C for 16h prior to gel formation produced gels with rheological properties similar to fresh milk gels. The solubilization of β-casein during cold storage was hypothesized to be the cause of observed differences in gel rheology.     

燕麦β-葡聚糖流变特性的测定

以燕麦麸皮为原料提取β-葡聚糖，并通过ARl000流变仪和毛细管粘度计对其流变特性进行了研究。实验结果表明：β-葡聚糖溶液是一种非触变的假塑性流体体系，且假塑性随着浓度的升高而增强。一定条件下溶液同时表现出粘弹性质，但无屈服应力的存在。较之于其它几种常用的食品胶体，β-葡聚糖能产生更大的粘度及良好的口感。此外β-葡聚糖还具有较好的热稳定性，这些性质决定了它在用作食品增稠剂和稳定剂等方面有着巨大的前景。     

Effect of Temperature on Rheological Properties of Different Jams

The rheological behavior of selected jams was analyzed at different temperatures, from 20 to 40°C in a rotational viscosimeter (HAAKE VT550). The rheograms were fitted with Power-Law, Carreau, Herschel-Bulkley, and Cross models. It was observed that the jams presented a pseudoplastic behavior, and the suspended solids influenced the consistency index.     

燕麦β-葡聚糖溶液流体性能及其协同增稠效应研究

采用动态流变仪和乌氏粘度计测定动态粘度方法,系统研究燕麦β-葡聚糖流体力学性能和与 其它增稠剂协同增稠效应。     

Rheological Properties of Extruded Milk Powders

Whey protein concentrate, whey protein isolate, and nonfat dry milk may be processed through a twin-screw extruder to produce ingredients for protein-fortified food. The products ranged from rigid to flexible to soft, and small amplitude oscillatory shear measurements showed that these properties varied with extrusion temperature and moisture content. The whey proteins showed different effects than nonfat dry milk due to the type and amount of protein present. The characteristics of extruded milk powders can be manipulated through processing parameters to obtain texturized products with the desired rheological properties.     

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。     

超声处理对类PSE鸡肉分离蛋白结构和乳化特性的影响

碱溶酸沉法得到的类苍白松软渗水（pale, soft and exudative,PSE）鸡肉分离蛋白功能特性较差,研究不同超声功率（0、150、300、450 W）对类PSE鸡肉分离蛋白（以下简称类PSE分离蛋白）结构和乳化特性的影响及其相关性。结果表明：随着超声功率的增加,类PSE分离蛋白的粒径和ζ电位绝对值显著降低（P＜0.05）,粒径分布逐渐从双峰分布转变为单峰分布;十二烷基硫酸钠-聚丙烯酰胺凝胶电泳显示蛋白组成成分没有发生明显变化,而肌球蛋白重链和肌动蛋白的条带强度总体上增强;圆二色谱显示α-螺旋和无规卷曲相对含量增加,β-折叠和β-转角相对含量降低;自由巯基含量、表面疏水性和荧光强度明显增加;通过扫描电子显微镜进一步证实超声处理改变了分离蛋白的结构,并且减小分离蛋白尺寸;超声处理后,类PSE分离蛋白溶解性、乳化活性和乳化稳定性显著提高（P＜0.05）;同时,相关性分析和主成分分析结果表明,超声处理后类PSE分离蛋白乳化特性的提高与其结构的改变存在高度相关性。综上,超声处理能够改变类PSE分离蛋白的结构并提高其乳化特性,为类PSE鸡肉深加工提供一定的参考依据。     

Effect of Temperature of Milk Acidification on Rennet Gel Properties

Changes in mineral solubilization and rennet reaction rate were investigated after decreasing milk pH to 6.3 by lactic acid addition at a temperature of acidification (TAC) of 25 or 35 °C with a short period of equilibration. With increasing TAC, casein micelles retained higher amounts of Ca and P, and at a given temperature of coagulation, rennet clotting time was increased, and dG'/dt decreased. This effect was confirmed by the microstructure of casein micelles during the first stage of the enzymic coagulation indicating that the aggregation of para-k-casein was observed later at higher TAC. The effect of TAC on rennet milk gel formation could be attributed to the nature of the micellar mineral content and the conformational state of casein micelles before rennet action.     

超声处理改善羊乳理化性质及其酶凝胶流变学特性

在超声频率20 kHz,超声功率800 W,超声时间15、20、25、30 min的条件下处理生羊乳,分析超声处理对羊乳粒径、Zeta-电位、表面疏水性和二级结构的影响,并通过流变学分析和扫描电子显微镜观察进一步研究添加凝乳酶对羊乳酶凝胶的流变学特性和微观结构的影响.结果表明,超声处理降低了羊乳样品的粒径,使蛋白质的二...     

Rheological and Structural Properties of Egg White/Oat Globulin Co-Gels

Co-gels of egg white (EW) and oat globulin (native and deamidated) were prepared by heating mixtures of the two proteins at different ratios. Rheological properties of the co-gels were assessed by small amplitude oscillatory tests. Storage (G′) and loss (G″) moduli of the co-gels increased with increases in EW content in the mixtures. At comparable EW/non-EW ratios, EW formed much stronger co-gels with deamidated oat globulin (DOG) than with native globulin (OG) or several other non-EW proteins. Microscopic examination of mixed gels revealed structural differences between EW/OG and EW/DOG co-gels. The former exhibited a two gel system with OG distributed discontinuously throughout the supporting EW matrix. DOG and EW formed a homogenous gel network, demonstrating compatibility between the two proteins.     

原味燕麦乳的研制及其理化性质

以燕麦粒为原料,感官评分为指标,采用单因素、响应面优化原味燕麦乳加工工艺条件。在此基础上,对比研究加入耐高温淀粉酶和糖化酶的原味燕麦乳与不加酶原味燕麦乳的稳定性。结果表明：燕麦粒∶水=1 ∶20（g/mL）,液化条件为耐高温淀粉酶添加量0.20‰,酶解时间90 min,酶解温度90 ℃,糖化条件为糖化酶添加量0.2‰,酶解时间60 min,酶解温度60 ℃,在此工艺下原味燕麦乳总固形物含量6.39%,蛋白质含量0.54%,还原糖含量3.23%,微生物指标符合要求（菌落总数＜10 CFU/g,大肠杆菌未检出）,且加入耐高温淀粉酶和糖化酶的原味燕麦乳稳定性比不加酶的原味燕麦乳稳定性好。在此工艺下得到的原味燕麦乳组织状态均匀、稳定性较好、具有燕麦的清香。     

热处理和蛋白浓度对肌原纤维蛋白乳液的稳定性和流变特性的影响

为了获得稳定的肌原纤维蛋白乳液,本文以冷冻白鲢鱼糜为原料提取肌原纤维蛋白,研究热处理(85℃10 min)和蛋白浓度(5、10、15、20、25 mg/mL)对肌原纤维蛋白溶液聚集比例、粒径、电位和微观结构等及对大豆油-肌原纤维蛋白乳液结构、表观粘度和色度的影响。结果表明：热处理使肌原纤维蛋白溶液中的蛋白发生聚集,使乳液粒径增大,表观粘度减小,乳液的L^*和b^*增加,疏水性减弱。随蛋白浓度的增加,未热处理组和热处理组的肌原纤维蛋白溶液的表观粘度逐渐增大,电位值波动上升,且分别在蛋白浓度为10和25 mg/mL时平均粒径最小。随蛋白浓度增加,肌原纤维蛋白乳液中参与乳化的油滴数量增多,油滴粒径减小,聚结程度减小。因此,在油相比为0.6,蛋白浓度为10～20 mg/mL时,热处理组的肌原纤维蛋白乳液液滴小而分散,表观粘度低,乳液稳定性高。本研究对开发稳定的肌原纤维蛋白乳液具有重要意义。     

破碎温度对番茄浆流变性质与果胶分子结构的影响

对在不同破碎温度下所得番茄浆的动态流变性质以及果胶物质相对分子质量的分布和大小进行了研究.结果表明随着破碎温度的增加,番茄浆中果胶物质的平均相对分子质量增加.但当破碎温度为90℃时,果胶物质的平均相对分子质量却有所下降.在80℃和85℃破碎时,番茄浆具有相当大的贮能模量,而在75℃和90℃破碎时,贮能模量值较小.贮能模量值对振荡频率具有一定的依赖性,故番茄浆表现出弱凝胶特性.贮能模量G′和损耗模量G″交汇点的位置随着破碎温度的升高向低频区移动.这说明破碎温度越高,大分子物质被保留得愈多,体系呈较强的弹性;破碎温度越低,体系中大分子物质被保留得越少,体系呈较强的粘性.     

Effect of Break Temperature on Rheological Properties and Microstructure of Tomato Juices and Pastes

The rheological properties and microstructure of canned juices and pastes made from four tomato cultivars at three breaking temperatures of 85°, 96° and 107°C were studied. The apparent viscosities of tomato juices and pastes at a constant shear rate vary with cultivars and processing conditions. The hot break process produced a high viscosity product. The microstructure of tomato pastes and juices were related to their rheology. The microstructure of tomato juice and paste also vary with processing conditions.     

Effect of Soymilk Substitution on the Rheological and Sensory Properties of Salep (Traditional Turkish Milk Beverage)

Soymilk mixed at a proportion of 0%, 25%, 50%, and 75% (g/100 g total milk) with cow's milk to make a salep, a beverage prepared from the dried tubers of Orchis mascula. The values of the flow behaviour index, n, of salep samples decreased as the soymilk content in the beverage increased. All salep beverages exhibited a pseudoplastic behaviour. Among the samples, salep beverage containing 25% soymilk was scored the highest in terms of overall acceptance by sensory panellists. Statistically significant (p < 0.05) differences were determined for colour, odour, taste, mouthfeel, and overall acceptance as the concentration of soymilk increased in salep beverage. This study produced a beverage from cow's milk and soymilk to offer a promising nutritious and healthy alternative to the consumers with a reasonable acceptance. The rheological parameters of the cow's milk-soymilk salep blends obtained in this study may have useful implications for design and processing.     

Rheological Properties of Renneted Reconstituted Milk Gels by Piezoelectric Viscoprocess: Effects of Temperature and Calcium Phosphate

Scanning electron microscopy (SEM) and rheology and permeability were used to evaluate effects of clotting temperature and calcium phosphate on reneted reconstituted milk gels, especially microstructure and permeability. Dynamic measurements with a piezoelectric Viscoprocess determined rheological properties of curd after various times of renneting. An increase in clotting temperature accelerated specific rennet action and gel formation; maximum stiffness was reached faster but its value was weaker. Addition of calcium phosphate increased rate of gel formation. Maximum stiffness was reached faster but its value was not changed. Gel microstructure was not very different but its permeability coefficient decreased.     

Lactobacillus casei HS4胞外多糖对发酵乳组织结构和流变特性的影响

研究干酪乳杆菌（Lactobacillus casei）HS4所产乳酸菌胞外多糖（exopolysaccharide,EPS）及其对发酵乳微观结构和流变性的影响。通过Sephadex G-50柱纯化得到两种类型的EPS,分别命名为HS4-1-EPS和HS4-2-EPS。HS4-1-EPS主要由葡萄糖组成,峰面积为0.940。HS4-2-EPS主要由葡萄糖和甘露糖组成,峰面积比为0.3830.364。红外光谱结果显示,HS4-1-EPS和HS4-2-EPS均为杂多糖。分别采用干酪乳杆菌HS4、嗜热链球菌-保加利亚乳杆菌（11）复合菌株以及复合菌株添加纯化EPS制成的不同发酵乳作为样品,通过测定流变特性及微观结构观察,研究补充纯化EPS和原位EPS对发酵乳流变特性及微观结构的影响。结果显示,其在4 ℃贮存期间显示出不同的流变特性及微观结构。基于扫描电镜下样品的微观结构,可以推知,EPS的类型和空间阻挡效应与发酵乳的流变性质相关。