Fractionation and characterisation for antioxidant activity of hydrolysed whey protein

Whey protein isolate (WPI) was hydrolysed for 1 h using Alcalase, Protamex and Flavourzyme. Native WPI, hydrolysed WPI and two commercial WPI hydrolysates were subjected to fractionation by size exclusion chromatography. Antioxidant activity of WPI fractions was measured with a liposome‐oxidising system (50 µM FeCl₃/0.1 µM ascorbate, pH 7.0). Lipid oxidation was measured as thiobarbituric acid‐reactive substances (TBARS). Gel electrophoresis and amino acid analysis were run to identify the peptide composition. The influence of amino acid composition on antioxidant activity was evaluated using multivariate analysis methods (correlation analysis, principal component analysis, multiple linear regression and discriminant analysis). TBARS assays indicated the presence of antioxidant activity in all protein fractions, including non‐hydrolysed WPI. For native and hydrolysed WPI samples the first fraction (> 45 kDa) showed a higher TBARS inhibition effect (24–27%) when compared with lower‐molecular‐weight fractions and hydrolysate mixtures. In contrast, for commercial WPI hydrolysates a higher inhibitory effect was found in most of the lower‐molecular‐weight fractions (30–55%). The ability of WPI fractions to delay lipid oxidation was found to be related to the prevalence of histidine and hydrophobic amino acids. Copyright © 2004 Society of Chemical Industry     

甲基丙烯酸缩水甘油酯对大豆蛋白塑料改性作用研究

用模压的方法制备了甲基丙烯酸缩水甘油酯(GMA)改性大豆分离蛋白质(SPI)塑料。表征了GMA改性SPI塑料的力学性能、耐水性,并分析了GMA与SPI之间的相互作用。结果表明GMA在模压过程中,环氧基与蛋白质分子间发生接枝和交联反应,同时自聚,在GMA含量较低时可以同时对SPI塑料起到增强和增塑作用,但是随着GMA含量增加,交联作用增强,塑料的断裂伸长率下降。     

大豆分离蛋白改性的研究(二)

用海藻酸钠对大豆分离蛋白进行了改性,对一些环境因素如温度、ｐＨ值、离子浓度等对反应的影响作了研究。研究表明,海藻酸钠能显著提高大豆分离蛋白的粘度,在０．５％海藻酸钠和０．０１ｍｏｌ／Ｌ氯化钙作用下,大豆分离蛋白的粘度能提高１０００多倍。确定了海藻酸钠与大豆蛋白的最佳浓度比,其数学模型为ｙ＝７．３４１０－４．４０２１ｘ。     

高速U盘病毒隔离器的设计与实现

U盘的普及使U盘病毒繁衍迅速,针对信息系统安全保护的需要,设计出一种U盘病毒隔离器。该隔离器具有隔离Autorun病毒、防止PC的数据通过U盘泄密、防止PC中的病毒感染U盘的功能。隔离器能够快速捕获到U盘与主机之间所有底层数据,在此基础上,隔离器中的微控制器(MCU)通过分析、审计和过滤流过隔离器中的底层数据来实现上述功能。经实际检测,该设计能够实现上述功能。     

大豆分离蛋白/壳聚糖共混膜热力学性能

采用差示扫描量热法(DSC)研究了成膜基质比例、增塑剂丙三醇体积分数和pH值对大豆分离蛋白(SPI)/壳聚糖(CS)共混膜热力学性能的影响。结果表明:共混膜较相同条件下SPI和CS单纯膜的结构更加稳定,成膜基质比例SPI∶CS=1∶1时共混膜交联度最高,热稳定性最好;增塑剂丙三醇体积分数的提高可降低共混膜放热峰的高度,增加放热峰的宽度,但是玻璃化转化温度和熔融温度随之降低;当pH值在1～3时,共混膜的玻璃化转化温度、熔融温度和结晶度值均较低,pH值在4～6时,各值升高,共混膜的热稳定性较好。     

Characterization of Fractionated Soy Proteins Produced by a New Simplified Procedure

It was possible to fractionate soy protein into two soy protein isolate fractions (>90% protein) enriched in either glycinin or β-conglycinin by using a new simplified procedure (referred to as the Deak procedure) employing CaCl₂ and NaHSO₃. The Deak procedure produced fractions with higher yields of solids, protein, and isoflavones, and similar protein purities as well as improved functional properties compared to fractions recovered by established, more complex soy protein fractionation procedures. The Deak glycinin-rich fraction comprised 15.5% of the solids, 24.4% of the protein, and 20.5% of the isoflavones in the starting soy flour, whereas the glycinin-rich fraction of the established procedure (Wu procedure) comprised only 11.6% of the solids, 22.3% of the protein, and 9.6% of the isoflavones. The Deak β-conglycinin-rich fraction comprised 23.1% of the solids, 37.1% of the protein, and 37.5% of the isoflavones in the starting soy flour, whereas the Wu β-conglycinin-rich fraction comprised only 11.5% of the solids, 18.5% of the protein, and 3.3% of the isoflavones. Protein purities were >80% for both fractions when using both procedures. The Wu procedure produced protein fractions with slightly higher solubilities and similar surface hydrophobicities; whereas, the fractions produced by the Deak procedure had superior emulsification and foaming properties and similar dynamic viscosity behaviors.     

一种WWW数据自动应急恢复系统的设计

在分析了将通用网络数据备份与恢复系统应用于WWW数据的应急恢复所带来问题的基础上，提出了一种专用的物理隔离型WWW数据备份与应急恢复系统，给出了系统的设计目标、主要功能、工作原理和系统的主要特点。     

蛋清蛋白、大豆分离蛋白及其美拉德反应产物膜包裹对核桃仁脂质过氧化作用的比较研究

本文通过测定核桃油酸价、过氧化值、丙二醛含量、碘值和DPPH自由基清除率五个指标的变化研究比较蛋清蛋白膜、大豆分离蛋白膜及其与木糖美拉德反应产物膜包裹对核桃仁脂质过氧化的影响。结果表明,随着反应时间（0⁸d）的增加,核桃仁酸价、过氧化值和丙二醛含量均呈现上升趋势,DPPH自由基清除率均呈现下降趋势,而碘值则变化不明显。加热第8d时,四种膜包裹核桃仁的酸价、过氧化值和丙二醛含量均小于未包膜的核桃仁,DPPH自由基清除率高于未包膜的核桃仁。四种膜包裹核桃仁的酸价无显著性差异（p>0.05）;而过氧化值中以蛋清蛋白膜组较高,且其余三组的无显著性差异（p>0.05）;四种膜包裹核桃仁的丙二醛含量均明显低于未包膜组,延缓丙二醛含量上升的效果依次为:大豆分离蛋白-木糖膜>蛋清蛋白-木糖膜>大豆分离蛋白膜>蛋清蛋白膜;大豆分离蛋白-木糖膜包裹核桃仁保留的DPPH自由基清除率明显高于其它三种膜。综上所述,两种蛋白及其美拉德反应产物膜包裹均可延缓核桃仁脂质过氧化,综合各项指标其效果依次为:大豆分离蛋白-木糖膜>蛋清蛋白-木糖膜>大豆分离蛋白膜>蛋清蛋白膜。      

大豆分离蛋白/可溶性大豆多糖作为生物活性物质包埋载体的研究进展

目前大豆分离蛋白(soy protein isolate,SPI)和可溶性大豆多糖(soluble soy polysaccharide,SSPS)均已实现工业化生产,在食品领域中得到了广泛的应用.作为生物大分子物质,以SPI和SSPS为壁材来包埋疏水性小分子生物活性物质受到众多学者的关注.以姜黄素为代表的疏水性小分子...     

糖基化改性提高大豆分离蛋白凝胶特性的研究

研究蛋白-葡萄糖质量比（4∶1、2∶1、1∶1、1∶2）、反应温度（70、80、90℃）和反应时间（0、1、2、3、4、5、6 h）对大豆分离蛋白糖基化产物蛋白凝胶特性的影响。结果表明:反应体系的颜色随加热时间延长逐渐加深,p H逐渐降低;在适当的糖基化改性条件下,大豆分离蛋白（SPI）凝胶质构特性呈现先升高后下降的趋势,在蛋白与葡萄糖质量比为1∶1时,70℃下反应6 h所得产物的硬度最大值达383.21 g,是未改性SPI硬度的7.51倍;相同比例底物在70℃反应4 h所得产物的弹性最大,达到0.981,比天然SPI的弹性提高了8.16%;不同底物比例的各温度反应体系产物的色差值随着加热时间的增加均逐渐变大;SPI在SDS-PAGE图谱中主要显示了6条带,不同比例反应底物在70、80、90℃反应1⁶ h的糖基化产物均在大于200 k D分子量处出现新的条带。因此,对大豆分离蛋白进行适当的糖基化改性能够有效地提高其凝胶特性。