A new method for determination of antithrombotic activity of egg white protein hydrolysate by microplate reader

A new method for the determination of antithrombotic activity of egg white protein hydrolysate （EWPH） was developed using a microplate reader. Reaction was carried out at 37℃and pH 7.2 with fibrinogen concentration 0.1%. Microplate reading was conducted at 405 nm. Inhibition rate of EWPH on thrombin activity showed linearity （R2 = 0.9971）, when the inhibition rate was in the range of 10-90%. The lower limit of detection （LLD, at 99.7% probability） and the biological limit of detection （BLD, at 99.7% probability） of the method were 10.643 and 40 mg/mL, respectively. The repeatability standard deviation （R.S.D.） was 1.08%. The standard deviation of the method was ±0.027 AT-U.

Regulation of Microstructure of Calcium Carbonate Crystals by Egg White Protein

Crystal growth of calcium carbonate in biological simulation was investigated via egg white protein with different volume fractions,during which calcium carbonate was synthesized by calcium chloride and sodium carbonate.The morphology,thermal properties and microstructure of the calcium carbonate micro-to-nanoscale crystals were characterized by scanning electron microscopy（SEM）,transmission electron microscopy（TEM）,Fourier transform infrared spectroscopy（FTIR）,thermogravimetric analysis（TG） and X-ray diffraction（XRD） analysis.The results show that the volume fraction of egg white protein has great influence on the shape,size and morphology of calcium carbonate crystals.The calcium carbonate crystals were the mixtures of calcite-vaterite-like crystals including spherical and rough surface,which are different from that formed in pure water.With the increase of egg white protein concentration,the diameter of calcium carbonate crystals changed,the amount of formed spherical calcium carbonate particles decreased and that of vaterite increased.These results indicate that the coordination and electrostatic interaction between egg white protein and Ca2＋ significantly affect the calcium carbonate crystalization.

Phase Transformation of Amorphous Calcium Carbonate to Single-Crystalline Aragonite with Macroscopic Layered Structure in the Presence of Egg White Protein and Zinc Ion

Highly oriented calcium carbonate lamellas are exquisite structure produced by biomineralization. Strategies mimicking nature have been developed to synthesize inorganic materials with excellent structures and optimal properties. In our strategy, egg white protein and zinc ion were employed in the solution to induce the crystallization of calcium carbonate, resulting in the macroscopic aragonite laminate with an average length of 1.5 mm, which was comprised of single-crystalline tablets. During the crystallization at initial stage, it was found that the particles displayed the characteristics of amorphous calcium carbonate, which was then transformed into the sophisticated structured aragonite through a multistage assembly process. The rebuilt nacre structure in vitro was achieved owing to the synergistic effects of egg white protein and zinc ion.

Interaction mechanism of egg white-derived ACE inhibitory peptide TNGIIR with ACE and its effect on the expression of ACE and AT1 receptor

The egg white-derived hexapeptide TNGIIR inhibits angiotensin-converting enzyme(ACE)activity in vitro.In this work,molecular docking revealed that TNGIIR established hydrogen bonds with the S1(Ala 354),S2(Gln 281,His 513,Tyr 520 and Lys 511)and S1(Glu 162)pockets of ACE.In addition,the potential antihypertensive effect of the oral administration of TNGIIR in spontaneously hypertensive rats(SHR)was investigated,as was the effect of this peptide on the mRNA expression of ACE and angiotensin type 1(AT1)and type 2(AT2)receptors in renal tissue.The oral administration of TNGIIR(2,10 and 50 mg/kg)for up to four weeks did not reduce the blood pressure of SHR,in contrast to captopril(10 mg/kg,orally),but attenuated the mRNA expression of ACE and AT1 receptor(as did captopril).In contrast,both TNGIIR and captopril enhanced the expression of AT2 receptor mRNA.There was no change in the circulating concentration of angiotensin I,but a slight decrease(about 10%)was seen in the concentration of circulating angiotensin II with TNGIIR and captopril.

Desalted duck egg white nanogels as Pickering stabilizers for food-grade oil-in-water emulsion

Achieving the reuse of traditional egg by-products,salted duck egg whites(SEW),is an urgent problem to be solved.In this current work,we constructed a heat-induced gel-assisted desalination method for SEW.Subsequently,a top-down way was utilized to prepare desalted duck egg protein nanogels(DEPN)with uniformly distributed diameters and their application in the oil/water(O/W)interface system was explored.The results revealed that the increase of DEPN concentration could lower the droplet size,however,the size was negatively correlated with the oil phase fraction.Moreover,the effect of pH,ionic strength,and temperature on the emulsion stability demonstrated that the DEPN-stabilized emulsion displayed superior physical stability under different conditions.The addition of NaCl resulted in the significant decrease in droplet size of the emulsion,while further increasing the NaCl concentration,the droplet size did not decrease accordingly.Besides,heat-treatment and cold-treatment had little negative effect on the stability of the emulsion.Even if the droplet size of the emulsion increased at 80℃for 3 h,the morphology of the emulsion remained unchanged.Our study demonstrated DEPN had great potential as a stabilizer for food-grade Pickering emulsions.

Efficient Protein Refolding Using Surfactants at High Final Protein Concentration

The refolding of denatured hen egg white lysozyme (HEWL) was examined by surfactants at a high final refolded HEWL concentration (1 mg/mL). Hexadecyltrimethylammonium bromide (CTAB) and sucrose fatty acid monoester (DK-SS) were used to dissolve denatured HEWL without denaturants such as guanidine hydrochloride (GuHCl) and urea. When denatured HEWL was perfectly dissolved in buffer solutions containing surfactants and dithiothreitol (DTT), the concentration of CTAB was about one-twentieth times less than that of DK-SS. The concentration of CTAB strongly affected the refolding yield, and the maximum refolding yield was obtained at 0.88 mM CTAB, which is around the critical micelle concentration of CTAB. The refolding yield was influenced by the molar ratio of oxidized glutathione (GSSG) to DTT, and the maximum refolding yield was obtained when [GSSG]/[DTT] was 1.5. The refolding yield was markedly dependent upon the solution pH of HEWL, and exhibited 80% at pH 5.2.

超高压协同TG酶改性蛋清蛋白热诱导凝胶机理

为提高蛋清蛋白凝胶性,本研究以蛋清蛋白(Egg white protein,EWP)为研究对象,通过分析质构、持水率、分子作用力、傅里叶红外色谱、圆二色谱、粒径、电位、巯基含量、表面疏水力及扫描电镜的变化,探究超高压处理(Ultra-high pressure,UHP)、谷氨酰胺转胺酶处理(Transglutaminase,TG)及超高压协同TG酶处理(Ultra-high pressure synergistic Transglutaminase,UTG)的蛋清蛋白热诱导凝胶机理及结构的变化。结果表明:UHP-EWP、TG-EWP、UTG-EWP的硬度、弹性和持水性均有所提高,疏水相互作用力是维持凝胶的主要作用力;UHP-EWP、TG-EWP、UTG-EWP的α-螺旋含量均不同程度下降、β-折叠含量均上升;UHP-EWP的平均粒径值下降、电位绝对值下降,TG-EWP、UTG-EWP的变化与之相反;UHP-EWP、TG-EWP、UTG-EWP的游离巯基含量上升、总巯基含量下降、表面疏水性升高;凝胶结构更加致密光滑,平整度提高。本研究为蛋清蛋白热诱导凝胶改性提供了理论基础及研究思路。

蛋清蛋白微粒基低脂沙拉酱流变学特征及品质优化

本实验以蛋清蛋白微粒(egg white protein microparticles,EWPM)为代脂基质,研究EWPM/黄原胶(xanthan gum,XG)共混质量分数、pH值、氯化钠含量、糖含量、均质条件等对超低脂沙拉酱产品流变学特性的影响规律。研究发现,XG对EWPM基超低脂沙拉酱具有显著的增稠效果,然而含量过高会导致低脂沙拉酱恢复性下降。基础调味组分对超低脂沙拉酱品质的影响存在较大差异,pH值和盐对体系黏度影响较大,糖添加量对黏度的影响相对较小。适度的胶体磨均质转速和均质时间可以减小产品的粒径,增加其内部均一性,显著提高产品的整体黏度。本实验以沙拉酱流变学行为调控为重点,为低脂沙拉酱的研究提供一个更加明确的工艺优化方向。

蛋清蛋白对低脂凝固型酸奶品质的影响

该研究以蛋清蛋白作为品质改良剂制备低脂凝固型酸奶,探究乳蛋白与蛋清蛋白比例、总蛋白质含量和蔗糖含量对凝固型酸奶pH、硬度、流变学特性、水分状态及感官品质的影响。蛋清蛋白添加比例的升高使得酸奶pH、硬度、储能模量、表观黏度和持水性增加。总蛋白质量分数2.5%时无法形成凝固酸奶,总蛋白质量分数为3.5%和4.5%的酸奶能良好凝固。添加蔗糖能够改善酸奶的感官品质,结果显示添加蔗糖质量分数为6%的酸奶具有最高的感官评分。相关性分析表明,酸奶质地与其储能模量、pH呈正相关,与持水能力呈负相关。这些结果表明,蛋清蛋白能够改善低脂凝固型酸奶的品质。

鸡蛋清蛋白质糖肽的结构鉴定

鸡蛋清中主要蛋白质均为糖蛋白,经胃肠消化后将在消化道内产生大量糖肽,这些糖肽的结构需要被鉴定和明确。本研究采用胰蛋白酶将鸡蛋清消化,然后从水解物中通过亲水相互作用层析富集N-糖肽、以Retain AX层析结合AminoLink树脂吸附富集O-糖肽,运用液相色谱-质谱联用技术对糖肽结构进行解析,并借助生物信息学分析探究蛋清糖蛋白对肠道的潜在作用。经质谱解析,共鉴定到来自于49种N-糖蛋白的1720个N-糖肽结构,以及来自29种O-糖蛋白的565个O-糖肽结构。其中,卵黏蛋白糖肽结构最为多样,共有490个N-糖肽结构和216个O-糖肽结构。京都基因与基因组百科全书通路富集分析发现,含唾液酸修饰的N-糖蛋白主要涉及白细胞介素-17信号通路和铁死亡,而含唾液酸修饰的O-糖蛋白主要涉及胆固醇代谢、维生素消化吸收、低氧诱导因子-1信号通路和肾素-血管紧张素系统。本研究系统解析了鸡蛋清蛋白质的糖肽结构,为后续探究蛋清糖肽对肠道的潜在作用提供了重要的结构信息。

蛋清蛋白和魔芋胶对鹰爪虾虾糜凝胶制品消化和酵解特性的影响

通过构建体外消化及酵解模型,探究蛋清蛋白(eggwhiteprotein,EWP)和魔芋胶(konjac glucomannan,KGM)对鹰爪虾SSG(shrimp surimi gel,SSG)制品消化和酵解特性的影响。结果表明:SSG-EWP组的蛋白质消化率随EWP含量的增加先升高后降低,EWP也能提高SSG消化过程多肽的含量,其中SSG-EWP4%的体外消化率最高;而KGM对SSG的蛋白质消化率和多肽的释放无显著影响(P>0.05)。EWP和KGM均可以提高SSG消化产物中必需氨基酸的含量。抗氧化结果表明,EWP可以提高SSG制品消化产物的Fe2+螯合能力,但会降低1,1-二苯基-2-三硝基苯肼(1,1-diphenyl-2-picrylhydrazyl,DPPH)自由基清除能力,KGM可以同时提高消化产物的Fe2+螯合能力和DPPH自由基清除能力,从而增加消化产物的抗氧化活性。此外,微生物组学分析结果显示,EWP在维持肠道微生物多样性和调控有益菌方面发挥的积极作用优于KGM。蛋白相邻类的聚簇代谢结果表明,肠道微生物的代谢途径主要有24条,其中碳水化合物、氨基酸等物质的转运和代谢是主要的相关途径。本研究为制备高品质鹰爪虾虾糜制品提供了技术指导。

蛋清蛋白絮凝处理脱除玉米秸秆水解液中的木质素衍生物

为了提升玉米秸秆水解液(corn stalks hydrolysate,CSH)的可生化降解性,研究了蛋清蛋白(egg white protein,EWP)絮凝处理对CSH中木质素衍生物去除的影响,并与氯化铁、阳离子聚丙烯酰胺等常规絮凝剂的效果进行对比。结果表明,在初始CODCr浓度为40 g/L的CSH中使用EWP进行热絮凝处理(100℃下加热5 min),CSH中大分子木质素(以浊度计算)去除率达(76.87±3.00)%,显著优于氯化铁、阳离子聚丙烯酰胺的处理结果 (P <0.05)。同时,EWP热絮凝处理未造成糖、呋喃及弱酸等化合物明显损失。这是由于EWP通过疏水反应与木质素衍生物结合,进一步通过巯基-二硫键交联形成大分子化合物,促进了木质素衍生物从CSH中去除。

蛋清蛋白/黄油复合凝胶的特性研究

以蛋清蛋白(egg white protein,EWP)和黄油为原料,按照不同比例(1∶1、1∶2、1∶3、1∶4、1∶5,质量比)进行复配,经热诱导制备EWP/黄油复合凝胶,并分析其质构特性、持水性、乳化性、乳化稳定性、流变特性、扫描电镜及激光共聚焦的变化规律。结果表明,质构特性中的硬度及胶黏性随着黄油添加量的增加而增加,而弹性及内聚性则在EWP/黄油为1∶3(质量比)时达到最高(P<0.05);复合凝胶的持水性随着黄油添加量的增加而增加,在1∶4及1∶5(质量比)时差异不显著(P>0.05);当二者质量比为1∶3时,乳化性及乳化稳定性显著高于其他组(P<0.05);流变结果显示当二者质量比为1∶3时,复合凝胶具有较大的储能模量(G′)及较低的损耗因子tanδ,说明此比例下的黄油提高了复合凝胶的黏弹性;扫描电镜结果表明二者质量比为1∶3时促使复合凝胶形成了更致密紧凑的网络结构,而未添加黄油的蛋清蛋白凝胶则呈现孔洞较大且大小不均匀的结构特征;激光共聚焦结果显示EWP/黄油1∶3(质量比)时网络结构相对均匀,且无析水无孔隙。综上所述,EWP和黄油的质量比为1∶3时可以改善蛋清蛋白的乳化特性及凝胶特性,为后续替代食品中部分乳化盐,以降低食品中钠含量,制备相关低钠食品提供了数据支撑。

蛋清热凝胶透明机制研究进展

蛋白基凝胶由于其光学透明属性在食品和医药领域具有独特优势而倍受关注,透明凝胶有望成为类似于燕窝的高端蛋白基凝胶食品或其加工辅基(料),探明蛋清热凝胶光学性质的差异机制有望成为攻克蛋清凝胶高质化利用的关键。文章对蛋清凝胶透明度的形成机制及其影响因素进行综述。深入分析了蛋清热凝胶的形成机理,探讨了蛋白质的改性方法,并对蛋清透明热凝胶未来的研究发展方向进行了展望。

蛋清蛋白/黄油复合凝胶对减钠再制干酪品质特性的影响

针对减钠再制干酪存在的质地、风味变差,组织状态缺陷等问题,通过利用蛋清蛋白/黄油复合凝胶替代部分乳化盐制备减钠再制干酪,检测其质构特性、色差、融化性、油析性、感官评价及钠含量等品质特性,并阐明复合凝胶对减钠再制干酪品质特性的影响。结果表明,复合凝胶替代30%乳化盐所制备的再制干酪质地均匀、表面光滑细腻,提高了其整体可接受度;也赋予了产品更好的质构特性;融化性及油析性得到改善同时,钠含量得到降低。复合凝胶能够有效替代乳化盐进行减钠再制干酪的制备,为减钠再制干酪的实际生产提供数据支撑。

羧甲基纤维素的添加对蛋清蛋白功能特性的协同效应的影响

为了提高蛋清蛋白的功能性质,分别向蛋清蛋白溶液中加入0.2‰、0.4‰、0.6‰、0.8‰、1.0‰的羧甲基纤维素(CMC),研究蛋白-多糖混合体系的流变、质构、起泡性和差示热量扫描分析的变化。结果表明:羧甲基纤维素添加到蛋清蛋白溶液提高了起泡性,0.8‰CMC-蛋清蛋白泡沫稳定性最优。对于其回复性、咀嚼性、硬度、凝聚力和弹性也呈增强趋势,0.8‰CMC-蛋清蛋白的硬度和咀嚼性最优,其他性能均与1.0‰CMC-蛋清蛋白差别不大。热性能和流变性能表明CMC的加入提高了共混体系的热稳定性,0.8‰CMC-蛋清蛋白的溶胶转变温度达到最大值。

Effects of freeze-drying and spray drying processes on functional properties of phosphorylation of egg white protein

Egg white protein(EWP)was phosphorylated with Sodium Tripolyphosphate(STP)at pH 4.5.Freeze drying and spray drying were used for drying purpose and the effects of these drying methods on the functional properties were investigated.The functional properties of native and modified proteins were also determined.The results demonstrated that phosphorylation of EWP markedly improved its functional properties,and that it was more effective for the food industry.The freeze-dried STP-EWP powders were superior in terms of solubility,emulsion stability,water holding capacity,oil and water absorption capacity and heat gel strength than spray-dried STP-EWP powders.The results in viscosity showed no significant differences between freeze-dried and spray dried.The spray-dried powders were better in terms of foaming ability and foam stability than freeze-dried powders.However,the spray drying required the longest time to produce.Freeze drying was found to be the best method in terms of production of modified EWP powders with superior functional properties.

Fast separation of hen egg white protein with a phosphorylcholine type zwitterionic ion chromatography stationary phase

In this work, a kind of preparation method of zwitterionic ion chromatography （ZIC） stationary phase modified with phosphorylcholine （PC） was obtained by hydrolyzing after bonding phosphorylcholine dichloride to diol-silica to better explore the characteristics of the PC groups as ZIC stationary phase ligand in simultaneous separation of acidic proteins and basic proteins. The results showed that tv^o kinds of acidic proteins and three kinds of basic proteins can be separated completely, meanwhile, hen egg white was separated and purified and three kinds of egg white components ovalbumin, G2 ovoglobulin and ovotransfemin proteins were separated completely by one single step on PC-ZIC column, the purity of all proteins reached above 95%. PC-ZIC stationary phase was successfully improved with better separation capacity and selectivity than previously reported in this paper.

Aspergillus oryzae reduces IgE binding ability of allergenic egg white proteins

Egg white proteins are one of the major allergens. The objective of this study was to investigate the effect of Aspergillus oryzae cultivation on IgE binding ability of egg white proteins. Effect of A. oryzae on egg white proteins was determined using ninhydrin method,SDS-PAGE, ELISA, fluorescence FITC labeling, MALDITOF-MS and LC-MS/MS analysis. Adding mycelium of A. oryzae ATCC 1011 and 16868 substantially reduced the IgE binding ability of acidified egg white after 24 h incubation. The binding capacity of egg white proteins to IgE in plasma from four egg allergy patients was almost completely lost after incubation with mycelium of ATCC16868. Results from SDS-PAGE, free amino acid analysis,MALDI-TOF-MS and LC-MS/MS indicated that there was no substantial protein degradation during incubation.Therefore, the reduction of IgE binding ability of egg white proteins during A. oryzae treatment was probably due to a loss of ～1700 Da mass including a fragment of the ovomucoid N terminus.

鸡蛋清中抑菌活性蛋白作用机制的研究进展

鸡蛋清中富含多种具有抑菌功能的生物活性成分。随着鸡蛋贮存时间延长,蛋清中的浓蛋白会发生稀化现象,从而导致抑菌效果降低,微生物繁殖加快,鸡蛋品质下降。本文对鸡蛋贮藏过程中的卵黏蛋白、溶菌酶及其复合物的相互作用形式、抑菌机制等进行探讨,以期为优化鸡蛋加工过程中的消毒杀菌工序、改良鸡蛋贮藏方法、延长鸡蛋保质期提供参考。