Effect of ionic strength on the heat-induced soy protein aggregation and the phase separation of soy protein aggregate/dextran mixtures

The effects of ionic strength on heat-induced aggregation of soy protein and phase separation of different soy protein aggregates with dextran were investigated. The increase of ionic strength accelerated protein aggregation as shown by an increase in turbidity, aggregate fraction and particle size of salt-induced aggregates (SA). Adding salt (NaCl) to the aggregates formed at the ionic strength of zero (non-salt aggregates, non-SA), the increase of aggregate size was also found. Zeta potential results evidenced the charge screening effects of NaCl. The results of phase diagrams indicated that the compatibility of mixtures at higher ionic strength was lower than those at lower ionic strength, and SA was more incompatible with dextran than non-SA. The effects of the increase of aggregate size on the phase separation outweighed the ionic strength, which indicated that the depletion interaction also played an important role in the phase separation of soy protein aggregates and dextran. CLSM (Confocal Laser Scanning Microscopy) and rheological observations provided additional information of the microstructures of the mixtures.     

几种大豆分离蛋白膜的特性及其在汤料包装上的应用

以大豆分离蛋白（SPI）为主要基质的成膜溶液加入其它成分（阿魏酸、淀粉、明胶、乙醇）后调pH、热处理后铺板干燥，揭膜，在相对湿度为65％的室温环境下平衡48h后测定膜的颜色，水蒸气透性（WVP）、抗拉强度（聪）、断裂伸长率（E）等；并研究这些膜用作方便面汤料包装时的应用特性。结果表明，乙醇对膜的以上特性都有显著影响，表现为黑度降低，透明度增加，WVP显著降低，断裂伸长率增加，但TS有所下降。成膜溶液pH为中性的加100mg阿魏酸的膜在沸水中的溶解情况最理想，1min完全溶解，用其包装汤料，煮或泡后该膜对汤的外观和口味均无不良影响。     

Effect of concentration,ionic strength and freeze-drying on the heat-induced aggregation of soy proteins

The effects of protein concentration, ionic strength, and lyophilization on heat-induced aggregation of soy proteins were analyzed by SDS-PAGE, SEC-HPLC and laser light scattering (LLS). SDS-PAGE profile suggested that the aggregates were formed via non-covalent forces and/or disulfide bonds. At ionic strength of zero, SEC-HPLC revealed that the samples were composed of three major fractions: aggregates, intermediate fractions and non-aggregated molecules. Furthermore, the relative proportion of the aggregate fraction increased as protein concentration increased. Similarly, LLS indicated that the average hydrodynamic radius (R_h) increased at higher protein concentration. In sample with an ionic strength of zero, the intermediate fraction decreased after freeze-drying with a concomitant increase of the aggregate fraction. When the sample was heated at elevated ionic strength, the SEC-HPLC and LLS profiles changed substantially, the intermediate fractions decreased, and lyophilization had effect on the fraction of aggregates. These experiments suggest novel strategies for producing soy protein aggregates with controlled properties.     

Influence of temperature,pH and ionic strength on the production of isoflavone-rich soy protein isolates

Soy protein isolates (SPI) may present different isoflavone profiles and contents, depending on processing conditions. In the present work, seven different SPI, resulting from changes in the processing steps, were obtained. The best parameters for obtaining isoflavone-richer SPI were: extraction at pH 9 and temperature of 55 °C, acid precipitation performed at pH 4.5, acid-washing of the precipitate and mild centrifugation conditions for the separation of acid-precipitated proteins. Isoflavones were soluble in aqueous solution in the pH range 2–10 (73–93% of the amount solubilized in 80% methanol). The profile of isoflavones was dependent on the temperature used for the aqueous extraction. Temperatures below 50 °C caused hydrolysis of β-glucosides with increase of aglucones, by endogenous β-glucosidase activity.     

Effects of soy protein isolate and egg white solids on the physicochemical properties of gluten-free bread

Gluten-free formulations are often supplemented with proteins to improve their quality. To determine the effects of alternative proteins on a hydroxypropyl methylcellulose (HPMC)-treated gluten-free dough system, soy protein isolate was added at 1%, 2% and 3% while egg white solids were investigated at 5%, 10% and 15%. The formulated doughs were analysed using thermoanalytic and rheological techniques to determine the role of water and subsequent flow behaviour upon hydrocolloid addition. The baked loaves were measured for specific loaf volume and tensile strength to determine bread quality. The addition of soy protein isolate and egg white solids (5% and 10%) reduced dough stability by suppressing HPMC functionality, reducing available water, weakening HPMC interactions with the starch matrix and reducing foam stability. At 15% addition, egg white solids became the primary protein scaffolding in the dough and overcame negative interactions with HPMC, improving the loaf volume. However, this formulation may need further optimisation to meet full consumer acceptability.     

FeCuCoY超细合金粉末胎体的烧结及其力学性能研究

采用共沉淀还原扩散法制备了不同Y含量的FeCuCoY超细合金粉,并采用真空热压机将之烧结为胎体试样块。重点研究了Y含量、烧结温度（700℃~900℃）对FeCuCoY胎体断口形貌、相对密度、硬度和抗弯强度的影响。实验结果表明：添加适量Y元素可明显改善FeCuCo超细合金粉胎体的硬度和抗弯强度,并能在一定程度上加快胎体烧结过程的进行。在不同的烧结温度下,FeCuCoY超细合金粉胎体的断口为沿晶断裂和穿晶断裂的混合型断口,且穿晶断裂所占比例随着温度的升高而增大;Y元素在合金中的最佳添加量为0.5wt.%,最佳烧结温度为800℃。此时,胎体的相对密度为98.0%,硬度为103.6HRB,抗弯强度为1531.41MPa。     

空气湿度对新闻纸裂断长的影响及补正系数的探讨

按行业检测标准,纸张物理指标的检测应在恒温(23±1)℃,恒湿(50±2)%条件下进行,但是对于规模较小的公司,特别是在生产现场,许多企业并不具备标准条件,所以物理指标的检测数据值(检测值)与报告值(近实际值)存在不相符的情况,特别是对于不施胶纸的裂断长指标,受空气湿度的影响很大.     

A comparison of the buttermilk solids functional properties to nonfat dried milk,soy protein isolate,dried egg white,and egg yolk powders

Physicochemical (i.e., sulfhydryl group, protein, and total solubility) as well as functional properties (i.e., water-holding and fat-absorption capacity, foaming and emulsification capacity, and stability) of commercial buttermilk solids (BMS) were compared to nonfat dried milk, soy protein isolate, and dried egg yolk and egg white powders on an equivalent protein basis. BMS showed limited functional properties in water-holding capacity (0.75 g water/g protein) and fat-absorption capacity (1.2 g of oil/g of protein), and foaming capacity (0.5 ml of foam/ml of solution) and stability. However, emulsifying capacity and stability of BMS was not significantly different from other dried protein powders. Results indicated that 0.9 g of protein (approximately 0.45%, wt/vol, concentration) from BMS was needed to emulsify a maximum oil concentration of 50% in water at temperatures up to 50 degrees C. Denaturation of protein, quantified by free sulfhydryl groups, was a critical factor affecting the functionality of BMS and all other protein powders tested. The milk fat globule membrane present in BMS did not enhance either emulsifying capacity or stability.     

Measurement of integrated absorption cross-section,oscillator strength and number density of caffeine in coffee beans by integrated absorption coefficient technique

Integrated absorption cross-section and oscillator strength of caffeine in water and dichloromethane were reported by UV–Vis spectrometer in the wave number regions of 20,000–39,062 cm⁻¹ at room temperature. The integrated absorption cross-section of caffeine in water and dichloromethane in these wave number regions were (4.44 ± 0.18) × 10⁷ and (4.32 ± 0.11) × 10⁷ L mol⁻¹ cm⁻², respectively. The corresponding calculated value for oscillator strength of caffeine in water and dichloromethane were 0.19 ± 0.01 and 0.18 ± 0.01, respectively. In addition number densities of caffeine in different coffee beans were reported using integrating absorption coefficient technique. The calculated number density of caffeine for different coffee varieties were varying from (3.53–4.76) × 10⁻⁵ mol L⁻¹. The new applied technique has an advantage over other techniques in that it provides additional information about the nature of the absorbing molecules and establishes accurate evaluation of the UV–Vis absorption intensity.     

醋蛋浸泡中蛋白质的变化及醋蛋粉的制备研究

醋蛋作为中国传统保健食品,因其取材方便、制作简易、服用安全、疗效显著受广大人民的欢迎,在国内外流传甚广。从醋蛋浸泡过程蛋白质水解度的变化着手,跟踪并测定了不同浸泡时间和不同醋蛋比浸泡下蛋白质的水解度。然后采用蛋醋比13∶的质量比浸泡4d,喷雾干燥得到醋蛋粉。经检测醋蛋粉中含水分5.83%、蛋白质11.4%、灰分7.68%、钙(Ca)2.53%、钾(Ka)0.257%。     

速溶芦笋粉营养成分分析及改善人体睡眠作用的研究

速溶芦笋粉是以芦笋（干或鲜）为原料,经水提、浓缩、喷雾干燥获得的固体饮料。本文测定了速溶芦笋粉中蛋白质、氨基酸、脂肪、总碳水化合物、维生素、矿物元素等营养成分及总皂苷含量,并通过志愿者试食实验观察了速溶芦笋粉对人体睡眠障碍的改善作用。结果表明,速溶芦笋粉含蛋白质24．5％,其中天门冬氨酸、谷氨酸、脯氨酸分别占氨基酸总含量的32．9％、25．0％、10．5％;含脂肪3．0％、总碳水化合物44．4％;含核黄素、硫胺素等6种维生素,钠、钙、钾、镁、铁、锌、铜、锰、硒等矿物元素;总皂苷含量为15．2％（以菝葜皂苷元计）。人体试食实验表明,速溶芦笋粉有改善睡眠质量作用     

粉末触媒、石墨配比对合成金刚石质量的影响

将不同配比的Fe70Ni30粉末触媒与石墨混合压制成粉末触媒合成棒,在国产六面顶压机上进行金刚石高温高压合成实验,并对合成的金刚石单产、粒度分布、晶形、抗压强度值、TI、TTI值进行了对比测试与观察分析。结果表明,对Fe70Ni30粉末触媒合成棒而言,当合成棒中Fe70Ni30粉末触媒含量为30%时合成金刚石的单产达到最大值,金刚石的TI、TTI值较高且TI/TTI差值最小,热冲击韧性最好。     

葡萄糖添加量对发酵鲶鱼骨肉粉生物转化率的影响

利用植物乳杆菌发酵鲶鱼骨肉粉,研究了葡萄糖添加量对鲶鱼骨肉粉中矿物质和蛋白质溶出量的影响。结果表明,当葡萄糖的添加量为5%时,鲶鱼骨肉粉中蛋白质的转化率和溶出量最高,发酵液的pH值最低,乳酸度最高;当葡萄糖添加量为10%时,骨肉粉中总灰分、钙和磷的转化率及溶出量最高;当葡萄糖添加量为15%时,镁的转化率和溶出量最高,铁和锌的转化率及溶出量不随葡萄糖添加量的变化而变化。     

面料与针距密度对羊毛防寒服防钻毛性能的影响

针对长久以来普遍存在的影响羊毛防寒服保暖和美观性的钻毛现象,为了有效提升羊毛防寒服防钻毛性能,进行相关试验。试验过程参考GB/T 12705—2009《织物防钻绒性试验方法》中规定的织物防钻绒性试验方法与标准,并根据实际情况对试验参数进行调整,针对每种试样,制作了2个完全相同的试样袋分别投入左、右2个箱子中;同时在保证面料密度、针距密度以及填充量相同的条件下,对缝迹进行了黏封与不黏封的2种设计;在计数钻毛量时,分别计数了从面料和缝迹处针眼钻出的羊毛根数。对目前企业常用的羊毛防寒服面料和针距密度进行了相关试验,利用SPSS软件对试验数据进行分析与研究,得出面料及针距密度与羊毛防寒服钻毛量之间的关系。     

Changes in the volatile profile of skim milk powder prepared under different processing conditions and the effect on the volatile flavor profile of model white chocolate

The objective of this work is to determine the extent to which changes in the skim milk powder (SMP) manufacturing process alter the volatile profile of SMP, and whether these changes are carried through to a final product when the SMP is used as an ingredient and subjected to further processing. The manufacture of SMP is a multistage process involving a preliminary concentration step, heat treatment, and a drying stage. However, the methods and conditions used by the industry are not standardized, and the inherent variability in the production of SMP has consequences for the end-users, such as the confectionery industry, where the SMP is used as an ingredient during the production of milk chocolate, white chocolate, and caramel. This study investigates the effect of each stage of the manufacturing process on the concentration of reducing sugars and available amino groups (as precursors of the Maillard reaction) as well as on the volatile products of the Maillard reaction and lipid degradation. Eight types of SMP were produced using combinations of different processing conditions: concentration (by evaporation or reverse osmosis), heat treatment (low heat or high heat), and drying (spray-drying or freeze-drying). Maillard precursors were quantified after each processing stage and volatile compounds were extracted using solid-phase microextraction, and analyzed by gas chromatography-mass spectrometry. The resulting SMP were incorporated into a model white chocolate system, produced under varying conching conditions. We demonstrate not only that changes in the SMP manufacturing conditions affect the volatile profile of SMP, but also that these differences can be carried through to a final product when the SMP is used to prepare a model white chocolate. Understanding these differences is important to the industry for controlling the flavor of the end product.     

丙纶长丝土工布结构不匀与撕裂强度关系的研究

以用量极大的丙纶长丝机织物为研究对象,以人为强化织物结构不匀的方法试图探明该织物结构不匀与织物梯形撕裂强度的关系。经SPSS数据处理的结果表明:织物梯形撕裂强度与织物结构不匀的分布和程度均存在正相关关系。     

激光散射法测定非织造布纤维取向分布和面密度的研究

非织造布的光后向散射性质主要取决于纤维的物理性质、非织造布中纤维的取向分布以及非织造布面密度。通过对平行纤维束光散射特征的研究 ,本文给出了纤维取向分布与非织造布光散射强度分布之间的关系以及非织造布面密度与光后向散射强度之间的经验关系。自行开发研制了可自动显示的计算机程序控制激光散射测定系统 ,实验表明 ,非织造布的光后向散射强度及其分布与分析值之间具有较高的一致性。据此 ,非织造布的纤维取向分布和面密度能够根据实际测定的后向激光散射强度及其分布计算出来。