Effect of formulation on protein breakdown, in vitro digestibility, rheological properties and acceptability of tarhana, a traditional Turkish cereal food

Three formulations of tarhana, a traditional Turkish fermented yogurt-wheat mixture used in soups, were prepared in the laboratory. The effects of white or wholemeal wheat flours and amount of yogurt on the protein breakdown, rheology and acceptability of the samples were measured and the samples were compared with single samples of homemade and commercial tarhana from Turkey.
Replacement of white wheat flour with wholemeal flour and increasing the yogurt had little effect on protein breakdown, but the true- to crude-protein ratio fell slightly during fermentation. Tarhana soups behaved as pseudoplastics (ñ < 1) at 80°C, and those with ñ values (>0.8) closer to Newtonian flow (ñ= 1) were most liked in mouth feel; however high apparent viscosity and samples with less liked mouth feel were not less liked in overall acceptability than the commercial sample. In vitro digestibility of commercial tarhana was lower than the laboratory prepared tarhana.     

Rheological behavior of syrups containing sugar substitutes

The rheological properties of syrups prepared using bulk sweeteners such as sorbitol and bulking agents like maltodextrin and polydextrose along with aspartame were studied. The apparent viscosity, consistency index, yield stress, and flow behavior index were determined from the shear stress versus shear rate data. The Herschel–Bulkley model was found to adequately describe the flow behavior of the syrups. The activation energy for all the syrups at different concentrations was determined from the Arrhenius equation. The yield stress, flow behavior index, and consistency index were dependent on the temperature and concentration of the syrups. The apparent viscosity increased from 8.8 to 129 mPa·s for sugar and sorbitol syrups, respectively, over the concentration range from 35 to 65%. In general, the rheological characteristic of sorbitol syrup was similar to that of sugar syrup, while syrups made with polydextrose and its mixture with maltodextrin were significantly different from those of sugar syrup.     

Effect of processing and storage on rheological properties of fortified milk and curd systems

Fortified milk systems were prepared by blending pasteurized standardized milk with skim milk powder, peanut flour or peanut protein isolate to 15, 18, 20, and 23% total solids followed by processing at 60°C and 80°C for 30min and storage at 4°C for 24h. Curds were prepared by the lactic fermentation of the processed milk systems. The rheological properties showed that all the systems exhibited pseudoplastic flow. The flow became less Newtonian with increasing total solids, heat treatment, and storage. Curd obtained from the fortified milk processed at 80°C showed increased yield stress and curd strength with the increasing concentration. Degree of heat treatment, total solids content and storage were shown to have a pronounced effect on the apparent viscosity, consistency index, and yield stress of the fortified milk systems.     

糖对蚝油流变性影响

采用哈克流变仪研究了蔗糖对蚝油体系的流变学性质,所用的糖浓度依次为5%、10%、15%和20%,温度分别为10、20、30、40、50℃。结果表明:蚝油中糖浓度5%、10%和15%的蚝油为假塑性流体,20%的蚝油为非宾汉塑性流体;随着温度的升高,蚝油的粘度逐渐下降,随着蚝油中糖浓度的增加,温度对粘度的影响减小;蚝油粘度与糖浓度的关系符合指数模型。     

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.     

Structural variation and rheological properties of water-extractable arabinoxylans from six Greek wheat cultivars

Aqueous extractions (at 25 °C) of flours from six Greek wheat cultivars that differed in their bread-making quality, followed by porcine pancreas α-amylase digestion to remove starch contaminants and precipitation with ammonium sulphate (saturation at 95%), yielded arabinoxylan isolates with notable differences in molecular weight, ranging from 146,500 to 397,000, and in arabinose-to-xylose ratios (Ara/Xyl, varying between 0.57 and 0.71). The arabinoxylan isolates contained only small amounts of proteins and were relatively free of other polysaccharide contaminants. Generally a very high ratio of trans to cis-ferulic acid content was detected for all samples. The genotype also had an impact on the molecular characteristics of these polysaccharides. ¹H NMR spectroscopy revealed variations in the un-substituted (61.1–67.9%) and di- (19.4–28.1%) and mono-substituted xylose residues (10.0–16.6%). Using 2D NMR spectroscopy, it was feasible to identify the spin sequence of individual monosaccharide residues and elucidate their structure, despite the extensive overlapping of ¹H and ¹³C resonances. Differences in the physicochemical properties of the arabinoxylans, such as the critical concentration values (c∗ and c∗∗), viscosity, shear-thinning behaviour, as well as the gelling ability, could not be fully explained by differences in molecular size and structure of the isolated polysaccharides.     

超声波处理对全蛋液流变特性的影响

采用不同超声声能密度(0.4,0.8,1.2,1.6,2.0 W/g)及超声作用时间(0,5,10,15,20 min)对全蛋液进行处理,再用流变仪测其流变特性。试验结果表明,全蛋液是一种假塑性非牛顿流体,具有剪切稀化现象,其流变曲线在温度为0～40℃时服从Herschel-Bulkley模型。随着超声作用时间及声能密度的增大,全蛋液的流变特性指数增大,屈服应力及黏稠系数减小,流动性增加,全蛋液的非牛顿流体特性减弱,牛顿流体特性增强。动态流变试验结果表明,随着超声作用时间及声能密度的增大,全蛋液的损耗模量G"和贮能模量G'均减小,说明全蛋液的黏性特征和弹性特征均减弱,流动性增强,与静态流变试验结果一致。     

卡拉胶凝胶特性及其在巧克力牛奶中的应用

针对卡拉胶水凝胶的两个主要指标凝胶强度和胶体黏度,研究了卡拉胶含量、钾离子浓度和pH值三个主要因素对卡拉胶水凝胶特性的影响,结果表明:凝胶强度随胶体含量的增加线性增大后渐趋平稳、受钾离子的影响出现峰值、在pH值8.0和10处出现两个拐点;胶液黏度随卡拉胶含量增加迅速增大、随钾离子浓度提高而减小、中性时的黏度最大.通过正交实验确定了影响卡拉胶凝胶因素的主次顺序为卡拉胶浓度、钾离子浓度和溶液的pH值,最佳条件组合为卡拉胶浓度1.2%,钾离子浓度1.2%,pH值9.0;通过考察单独使用卡拉胶以及卡拉胶与魔芋胶、刺槐豆胶及结冷胶等几种食品胶在巧克力牛奶中形成凝胶时的结构状态,判定卡拉胶与刺槐豆胶的协同作用效果最佳.     

酪蛋白酸钠流变特性的研究

研究了酪蛋白酸钠溶液的流变特性.酪蛋白酸钠属于假塑性流体,粘度与浓度成对数相关性,其流变特性受温度、pH、盐种类及盐浓度等因素的影响.     

壳聚糖溶液的流变学性质及应用研究

对壳聚糖稀溶液的流变学性质进行了研究,探讨了分子量和脱乙酰度结构参数以及温度、浓度、剪切速率、pH、离子强度等环境因素对壳聚糖稀溶液流变性质的影响。结果表明:壳聚糖溶液的黏度随分子量的增大而增大;随着脱乙酰度的增大和pH的增大,壳聚糖溶液的黏度先减小后增大,分别在脱乙酰度70.8%和pH4.9时黏度达到最小;离子强度的增大导致壳聚糖溶液的黏度降低。壳聚糖溶液是剪切变稀的假塑性流体,其黏度随浓度的增加逐渐增加,随温度的升高而减小,在0~80℃范围内,温度对壳聚糖溶液的黏度的影响符合Arrhenius模型,活化能为32.60kJ/mol。因此当作为食品增稠剂时,应该选用高分子量、高脱乙酰度的壳聚糖,添加到酸性低盐食品体系中。     

不同分子量降解壳聚糖和降解卡拉胶复合凝胶体系及其流变性质

以降解壳聚糖与降解卡拉胶为主要原料,将不同分子量级别的降解多糖在一定条件下共混制得不同凝胶体系,通过选取3个代表性的体系考察分子量对凝胶体系流变特性的影响。在特定条件下,降解壳聚糖和降解卡拉胶复配可形成凝胶。通过流变测试可见,G'、G'随着分子量的不同有差异,通过考察凝胶触变环可得到复合凝胶体系受力后恢复能力也随分子量的不同有差异,可见分子量对复合凝胶性能有显著影响;通过幂律模型表征该凝胶体系剪切速率随黏度变化趋势,表明该复合凝胶体系为假塑性流体。     

Pasting and rheological properties of quinoa‐oat composites

Quinoa (Chenopodium, quinoa) flour, known for its essential amino acids, was composited with oat products containing β‐glucan known for lowering blood cholesterol and preventing heart disease. Quinoa–oat composites were developed and evaluated for their pasting and rheological properties by a Rapid Visco Analyzer (RVA) and an advanced rheometer. All quinoa–oat composites showed increased pasting viscosities with increases in oat contents. The elastic modulus G′ and viscous modulus G″ for all quinoa–oat composites were higher than quinoa, suggesting that oat products increased the viscous properties of composites. Shear‐thinning properties were observed for all the composites. Improved water‐holding capacities (WHC) were found for the composites containing quinoa with nutrim or oat bran concentrate compared to quinoa alone. All the WHC of quinoa–oat composites were increased with the higher amounts of oat components. These quinoa–oat composites have improved nutritional value and texture qualities suitable for functional food applications.     

带果肉芹菜汁的流变特性研究

研究了带果肉芹菜汁的流变特性,发现带果肉芹菜汁的表观粘度随浓度的增大而增大;随温度的升高而减小;在72～314μm的范围内,随果肉颗粒粒度的减小而减小。     

藻酸丙二醇酯的流变学特性研究

利用MCR101流变仪研究了质量分数、pH、蔗糖、NaCl、温度对藻酸丙二醇酯（PGA）流变学特性的影响。结果表明:藻酸丙二醇酯溶液是假塑性流体,其流动特性符合Power-law模型,其粘度随PGA质量分数和蔗糖浓度的增加而升高;随剪切速率、pH、温度的增加而降低;在较低NaCl浓度下（0.01和0.1mol/L）,PGA溶液粘度降低,NaCl浓度在1mol/L时,溶液粘度增加。PGA溶液具有一定的触变性和粘弹性,在低频率区域体系以粘性为主,高频率区域体系以弹性为主,G′和G″的交点受PGA浓度、pH和温度的影响。      

Effects of different milk substitutes on pasting, rheological and textural properties of puddings

Commercial pudding powders are usually composed of starch, hydrocolloids, sugars, colorings and aromas, and are intended to be dissolved in milk. However, the use of milk substitutes is mandatory for people suffering from lactose intolerance and milk allergies, but these ingredients have an effect on pudding structure and rheological behavior that has been little studied. This work investigates the pasting, rheological and textural behavior of two commercial pudding powders dissolved in rice drink, light soy drink, partially skimmed milk (reference sample), and water (model system). The eight different puddings were evaluated both during preparation (heating and cooling phases) and a 3 day refrigerated storage period, by means of viscoamylographic tests, rotational and oscillatory measurements, and penetration tests. The two pudding powders, apparently similar in formulation, resulted in final products with large structural differences, that could be ascribed to different types and quantity of starch and carrageenans present in the formulation. Soy and rice drinks can not be indifferently used for pudding production, as the optimal texture of the final product is not always achieved. Generally, the properties of soy drink-based puddings were similar to those of the reference samples, while the characteristics of rice drink-based products were comparable to those of the water systems.     

马铃薯果胶流变特性的研究

以马铃薯果胶(potato pectin extracted by chelating agent,PPCH)为研究对象,研究果胶溶液质量分数、剪切速率、温度、pH、金属离子等因素对马铃薯果胶流变学特性的影响.研究表明,PPCH溶液的黏度随溶液质量分数上升而增加.随着剪切速率的增大,PPCH溶液黏度下降,剪切变稀现象随...     

啤特果果汁流变学特性研究

为掌握啤特果果汁的流变学特性,试验对啤特果果汁的流体类型、模量以及温度和可溶性固形物对黏度的影响进行了研究.结果表明,在25、35、45、55、65℃条件下,啤特果果汁的流变曲线方程拟合参数n值<1,属于假塑性流体,其储能模量G′大于损耗模量G″;Arrhenius方程 η=Ke-Ea/RT对温度与黏度的拟合参数R2>...     

凝胶多糖发酵液流变学特性及提取条件的初步研究

初步研究了凝胶多糖发酵液的流变学特性并应用正交实验对其提取条件进行了研究,通过极差和方差分析可知,碱液浓度对多糖得率有显著影响(P<0.05),碱液浓度和pH对多糖含量有显著影响(P<0.05),在a=0.05的条件下,各因素对含氮量的影响在统计学意义上不是很显著。通过评价多糖得率、多糖含量及含氮量三个指标,确定了其提取的最佳工艺条件为0.6moL/LNaOH,碱溶时间2h,pH8.0,以及添加乙醇倍数为1.5倍。