Comparison of Different Mechanical Methods for the Modification of the Egg White Protein Ovomucin,Part A: Physical Effects

Egg white (EW) is required to be reduced in viscosity and particle size prior to chromatographic fractionation of single EW proteins. This study reports on an assessment of various shear devices for this purpose. Evaluation criteria for the head-to-head comparison of high-pressure homogenization, colloid mill, and toothed disc dispersing machine treatment were the achieved viscosity reduction as well as the network diminution, determined by particle size measurements. It was shown that each of the devices was able to decrease the viscosity by a reduction of fibril size. However, only the high-pressure homogenizer fulfills the requirement to disintegrate the fibrils sufficiently, so that they can be filtered through membranes with a pore size of 0.45 μm, which is indispensable for chromatographic fractionations. Generally, the achieved viscosities decreased with increasing energy input, independently of the specific shear forces resulting from the applied device. Otherwise, there was no direct correlation between the energy density and the extent of fibril destruction, indicating that the kind of energy depending on the respective device with its specific destruction mechanism was not decisive. To sum up, this study provides profound knowledge concerning the effects on the EW structure that result from different mechanical forces.     

热处理辅助木瓜蛋白酶改善蛋清蛋白的起泡特性

为获得起泡特性优良的蛋清蛋白制品,试验以新鲜鸡蛋蛋清为原料,采用热处理辅助木瓜蛋白酶有限酶解的方法来改性蛋清蛋白,通过单因素实验,分析了底物浓度、酶的添加量、酶解时间、酶解温度、酶解pH等因素对起泡能力、泡沫稳定性的影响,并在单因素实验的基础上,以起泡能力和泡沫稳定性为响应值,通过响应面分析和方差分析得出热处理辅助木瓜蛋白酶改性蛋清蛋白的最佳工艺条件:底物质量分数3%、热处理温度90℃、热处理时间10 min、酶的添加量3 500 u/g、酶解时间2.5 h、酶解温度55℃、酶解pH 7。在此条件下,蛋清蛋白的起泡力为1741.38%,泡沫稳定性为93.38%。与未改性的蛋清蛋白相比,起泡力提高了112.97%,泡沫稳定性提高了93.27%。泡沫流变学特性结果表明改性蛋白的泡沫储存模量G′是未改性蛋白的1.5倍,泡沫更加稳定。     

不同改性方法对蛋清粉致敏性与功能性的影响

本文研究了热处理、糖基化、超声、超声预处理结合糖基化复合改性以及复合改性后再模拟体外消化对蛋清粉致敏性和功能性的影响。结果表明:热处理和超声改性均会增加蛋清粉的致敏性,分别提高了12.77%和20.84%;糖基化改性和复合改性后其致敏性分别降低了29.08%和43.9%,复合改性再模拟体外消化后致敏性进一步降低,最高降低了52.76%。热处理不能有效改善蛋清粉的功能性,而超声可以增强其乳化性能;糖基化后,蛋清粉的溶解性、乳化性能、抗氧化活性等功能性均得到不同程度的改善;复合改性后功能性有了更大提升,并且经消化后抗氧化活性显著增强。这说明复合改性可以更全面显著的改良产品品质,且经人体消化后仍能保持甚至提升。     

不同处理方法对蛋清蛋白免疫原性及结构的影响

为研究降低蛋清蛋白免疫原性的有效方法,分别采用微波、酶解、微波协同酶解对蛋清蛋白进行处理,采用酶联免疫吸附试验测定蛋清蛋白的免疫原性,并利用十二烷基硫酸钠-聚丙烯酰胺凝胶电泳、傅里叶变换红外光谱、荧光光谱及紫外光谱等对蛋清蛋白结构进行表征。结果表明,微波700 W/20 s处理和碱性蛋白酶水解后蛋清蛋白免疫原性分别降低了50.81%和55.83%,而微波协同酶解后免疫原性进一步降低,最高降低了67.48%。经不同方法处理后十二烷基硫酸钠-聚丙烯酰胺凝胶电泳条带均发生变化;荧光光谱分析结果表明,3种方法处理使氨基酸微环境发生改变;利用傅里叶变换红外光谱进一步分析发现,不同方法处理的蛋清蛋白二级结构向无序方向转变,蛋白的二、三级结构均发生改变;此外,蛋清蛋白的表面疏水性均有所升高。说明蛋清蛋白免疫原性降低与不同方法处理改变蛋白质原有的结构特性相关。综上,微波协同酶解更有效地降低了蛋清蛋白致敏性,蛋清蛋白结构的变化与其免疫原性有关。     

干燥方式对蛋清蛋白理化性质和功能特性的影响

为探究干燥方式对蛋清蛋白（egg white protein,EWP）功能特性的影响及其内在机理,分别通过喷雾干燥与真空冷冻干燥制备蛋清蛋白粉,并对其蛋白结构、理化性质与功能特性进行研究。结果表明,与蛋清液（EWP-C）相比,喷雾干燥使蛋清蛋白（EWP-P）的内源性荧光强度降低,表面疏水性和表面游离巯基含量增大。傅里叶变换红外光谱分析显示,EWP-P的α-螺旋、β-折叠和β-转角分别为16.30%、25.72%和40.23%,冷冻干燥蛋清蛋白（EWP-D）分别为20.43%、24.32%和35.69%。不同pH下,EWP-D的溶解度均高于EWP-P,表面张力小于EWP-P。此外,EWP-P的接触角为99.62°,高于EWP-D（接触角为65.97°）,表明喷雾干燥能显著提高蛋白的疏水性（P<0.05）。EWP-D在不同pH下的乳化性、乳化稳定性以及起泡性均大于EWP-P,但起泡稳定性更小,这与EWP-D较高的溶解性与较低的表明疏水性有关。荧光倒置显微镜及激光共聚焦扫描显微镜分析表明EWP-D乳液的微粒更小,分布更均匀,其稳定性高于EWP-P。综上,喷雾干燥蛋清蛋白的β-折叠结构较多,表面游离巯基含量和表面疏水性较高,具有较好的凝胶性;冷冻干燥蛋清蛋白的表面疏水性较小,且表面张力小、溶解度大,具有更好的乳化能力与起泡性。     

茶多酚改性对蛋清蛋白凝胶特性的影响及机理

研究不同添加量的茶多酚改性对蛋清蛋白凝胶特性的影响,并对其影响机理进行探讨。结果表明：蛋清蛋白的凝胶强度和持水性随茶多酚添加量的增加而逐渐增大,茶多酚添加量为0.8%时蛋清蛋白的凝胶强度提高了130.2%,失水率从29.41%降至19.29%。经茶多酚改性后蛋清蛋白的凝胶网络结构更加有序,凝胶表面更加平滑均匀,蛋白的表面疏水性和表面巯基含量增加,而总巯基含量下降。差示扫描量热分析和傅里叶变换红外光谱进一步分析表明,茶多酚改性作用增加了蛋清蛋白的热稳定性,且蛋白的二级结构发生改变,表现为蛋白结构由有序变为无序,α-螺旋相对含量下降,β-折叠相对含量则明显上升。     

提高鸭蛋蛋清蛋白凝胶强度的酰化改性工艺优化

以鸭蛋蛋清蛋白为原料,通过琥珀酸酐酰基化改性以提高鸭蛋蛋清蛋白的凝胶强度。在单因素试验的基础上,选择琥珀酸酐与蛋清蛋白质的添加比例、反应温度、反应时间、反应pH值4个因素为自变量,以蛋白凝胶强度为响应值,进行中心组合试验,建立鸭蛋蛋清蛋白的凝胶强度的二次回归方程,并通过响应面(Box-Behnken)分析,得到优化组合条件。结果表明：经过修正最优工艺为琥珀酸酐与蛋清蛋白质的添加比0.118:1、反应时间35.24min、反应温度22.91℃、反应pH8.09,在此条件下鸭蛋蛋清蛋白的凝胶强度预测值为324.66N,与验证值319.56N接近,优化结果可靠。     

Chemical Modification of Egg White with 3, 3-Dimethylglutaric Anhydride

SUMMARY— Egg white, near its normal concentration, was reacted at 25°C, pH 9.0, with levels of 3,3-dimethylglutaric anhydride (DMGA) from 0 to 60 mol/mol egg white protein (EWP) (assuming egg white to have an average mol wt of 50,000). Analysis for amino acids and functional groups showed about 26% of the lysine residues reacted at 15 mol DMGA/mol EWP. Sulfhydryls are more resistant to reaction with 60% unreacted at 150 mol DMGA/mol EWP. Electrophoresis indicates significant changes in net charges on the protein, particularly on lysozyme which migrates anodically in six separate bands at higher DMGA levels. Ultracentrifugation sedimentation data suggest no hydrolysis or aggregation changes. Foam formation is not seriously altered, but the heat coagulation properties, as evidenced by angel cake failures, are changed. As measured by viscosity, light transmission and aerating ability, DMGA exerts a protective action against the effect of heat on these properties.     

不同方法处理724树脂对蛋清溶菌酶吸附作用的影响

以不同方法对724树脂进行再生处理,在同样的提取工艺条件下,分析了不同方法再生的树脂对蛋清溶菌酶提取活力及产量的影响。结果表明,724树脂经用45℃温水处理2h,3％HCI浸泡4h,3％NaOH浸泡6h,0.1mol/L pH6.5的磷酸缓冲液浸泡12h以上,再生出的724树脂提取蛋清溶菌酶的活力及产量最高,平均活力和产量分别为(3000±109.5)u/mg与2.24g/kg蛋清。在树脂与蛋清比例为1:6.25的情况下,每克湿树脂可吸附约43680个活性单位的溶菌酶。     

不同压力条件下蛋清蛋白结构和凝胶性的比较分析

针对传统蛋制品中卤蛋、咸蛋、皮蛋需要较长加工时间的问题,为提高加工效率和产品质量,本研究选择常压、高压、脉动压三种加工方式,在无盐和含盐的条件下对鸡蛋进行处理,对比分析蛋清含盐量、表面疏水性、一级和二级结构变化以及蛋清蛋白的凝胶特性。发现脉动压处理后蛋清的含盐量是未处理的2.10倍;压力、温度和盐的共同作用使表面疏水性增加,其中,脉动压处理后酰胺II带波长红移至1520 cm-1,α-螺旋和无规则卷曲含量减少,β-折叠含量增多;Na Cl会降低蛋清的凝胶性,与高压处理对比,脉动压能够相对改善Na Cl带来的不利影响;脉动压处理后的蛋清凝胶的弹性提高至1.02、T21弛豫时间降低至25.79 ms、微观结构得到较大改善。因此,脉动压可以提高蛋制品的加工效率和质量,为其投入生产应用提供一定的理论依据。     

不同改性方法对蛋白质溶解性的影响研究进展

溶解性是蛋白质主要的功能特性之一,更重要的是,溶解性是蛋白质生理功能特性及其他加工功能特性的前提和基础。通过对蛋白质溶解性的物理、生物酶及化学改性3大类改性方法进行了分类论述,分析了不同改性方法对蛋白质溶解性的影响。其中,物理方法介绍了微波、超声波及热处理等方法;生物酶方法介绍了木瓜、碱性及胰蛋白酶等处理方法;化学方法介绍了不同活性基团的改性方法。分别对各种改性过程中蛋白质的结构变化和蛋白质溶解性提高的机理进行了初步探讨。通过物理、生物酶和化学等方法等来引起分子结构的微变化,可使人们获得各种符合预期的性能优良的蛋白产品。     

不同打发状态蛋清泡沫及其凝胶特性的比较

蛋清具有良好的起泡性和凝胶性,其在充气食品中具有难以取代的地位。为研究不同状态蛋清泡沫凝胶的理化性质,该文在室温条件下以恒定搅拌速率（980 r/min）制备了不同打发状态（打发时间为0、50、70和90 s）的蛋清泡沫,并测定了蛋清泡沫的理化特性。随后将不同打发时间的蛋清泡沫加热固化,制备了蛋清泡沫凝胶,通过显微观察、色度、质构和流变分析考察了蛋清泡沫凝胶的特性。实验结果表明,在恒定的搅拌速率下蛋清泡沫的气泡状态会随打发时间的变化而变化。适当延长打发时间,有利于形成比重较低的（0.16～0.17）、具有高起泡性和泡沫稳定性的固态泡沫。打发70 s的蛋清泡沫（蛋清泡沫呈小弯钩状,比重为0.165）稳定性最佳,且经加热固化后,该蛋清泡沫凝胶的亮度（L*=90.28）显著升高,硬度（27.69 g）和弹性（0.78 mm）显著降低（P<0.05）,凝胶性质优良。结果揭示了蛋清泡沫的流变学性质能显著影响蛋清泡沫及其凝胶的性能,为蛋清泡沫在充气食品中的应用提供了理论参考。     

Collaborative Tests of ELISA Methods for the Determination of Egg White Protein and Caseins Used as Fining Agents in Red and White Wines

Methods are needed for detecting allergenic proteins in wine after fining processes, both for legal requirements and to estimate any risk for allergic individuals. Two of the critical allergens in this case are the protein fraction from egg white and caseins. Requirements for methods were set up both by the International Organisation of Vine and Wine (OIV) and the European Commission and included collaborative tests to determine repeatability, reproducibility, limit of detection (LOD), and recovery. Two collaborative tests with 18 participants from all over the world were conducted using commercial enzyme-linked immunosorbent assay kits to quantify egg white protein and casein. For each analyte, nine red and white wines (RW and WW, respectively) with different analyte concentrations were prepared and sent to the participants. Resulting sets of data were analyzed according to the AOAC by eliminating outliers and calculating the performance statistics for each assay. For wines with no or very low analyte concentrations, the values were extrapolated from the calibration curve and the resulting LODs are in accordance with the performance criteria set by the OIV method OIV-MA-AS315-23: R2012. For casein in WW and egg white protein in RW, all Horwitz ratio values for samples with concentrations above the required limit of quantification (0.5 mg/L) were below 2. While the recovery of egg white protein from RW is 90 % or more, the recovery of casein from WW is between 73 and 76 %, which is attributable to the instability/solubility of casein in wine.     

涤纶表面接枝蛋清蛋白改性及其服用性能研究

涤纶是合成纤维中服用性能最突出的纤维,蛋清蛋白具有良好的生物相容性,将蛋清蛋白接枝到涤纶织物上可以开发出服用性能好、生物相容性又好的复合面料。以聚乙烯醇缩水甘油醚(PVAGE)为交联剂,研究了在涤纶织物表面接枝蛋清蛋白的工艺及接枝率对服用性能的影响。采用单因素法得出接枝的最佳工艺条件为:PVAGE浓度1.89%,接枝温度100℃,时间30 min。接枝后涤纶的回潮率有大幅增加,抗静电性能大幅提高,折皱弹性回复性略有下降。     

酶解蛋清蛋白制备ACE抑制肽的工艺研究

为获取酶解蛋清蛋白制备血管紧张素转化酶(ACE)抑制肽的工艺参数,研究4种蛋白酶酶解蛋清蛋白所得产物对ACE的抑制活性,筛选出胰蛋白酶作为制备蛋清蛋白ACE抑制肽的适宜用酶。运用响应曲面法研究酶解时间、底物浓度([S])和酶与底物质量比([E]/[S])对制备ACE抑制肽工艺的影响,建立以上3因素与ACE抑制率关系的数学模型。结果确定胰蛋白酶酶解蛋清蛋白制备ACE抑制肽的适宜酶解条件为酶解时间4.87h、[S]3.06%、[E]/[S]2.91%、酶解温度45℃、pH7.4,此条件下制备的蛋清蛋白酶解产物ACE抑制率达到50.73%。     

不同孵化时期鸡蛋蛋清小分子多肽的鉴定及功能分析

通过聚丙烯酰胺凝胶电泳(SDS-PAGE)和基质辅助激光解吸电离飞行时间串联质谱(MALDI-TOF MS/MS)技术,比较不同孵化时期鸡胚蛋蛋清中产生的小分子多肽,研究肽段与鸡胚发育之间的联系。结果显示在孵化第0、6、14、16 d分别得到837、879、872和842条肽段(共3430条)。除丛生蛋白肽段外,大部分被鉴定到的肽段来源于蛋清中低丰度蛋白。其中926条肽段来源于与鸡胚先天免疫有关的9种蛋白质,如防御素、白细胞介素6等;256条肽段来源于与鸡胚呼吸系统发育相关的3种蛋白质,cx9C基序蛋白、sprouty蛋白和碳酸酐酶。结果表明由蛋清蛋白质内源性酶降解形成的小分子多肽可能对鸡胚发育时形成的呼吸和免疫系统等发挥重要作用。     

不同解冻方法对冰蛋黄功能特性、理化特性及蛋白质结构的影响

为缓解冻融对蛋黄品质的劣变影响,本研究以鲜蛋黄为对照组,以经室温自然解冻、静水浴解冻、超声波解冻及微波解冻处理的冰蛋黄为实验组,对其主要功能特性（蛋白质溶解性、乳化特性和凝胶特性等）、理化特性（质构特性、粒径和巯基与二硫键含量等）进行表征与对比分析,同时结合拉曼光谱探究各解冻方法下蛋白质结构的变化。结果表明：冰蛋黄在室温下自然解冻后的浊度最大,拉曼光谱显示脂蛋白烷基链C＝C伸缩振动强度最小,蛋白质二级结构中β-折叠相对含量最高,该解冻方法下蛋白质的交联聚集程度最高;静水浴解冻后蛋黄的蛋白质溶解性、乳化活性及乳化稳定性均显著低于超声波解冻（P＜0.05）,表面疏水性最强;微波解冻下蛋黄的二硫键含量显著高于超声波解冻（P＜0.05）,脂肪族氨基酸非对称C—H弯曲振动强度最大,蛋白质α-螺旋结构相对含量最低,解冻后有凝胶微粒形成;超声波解冻下蛋黄的乳化活性与乳化稳定性均较高,粒径最小且分布最为集中,硬度、内聚性及黏性等质构特性均较小且与鲜蛋黄无显著性差异（P＞0.05）。综上,本研究证明超声波解冻是冰蛋黄较为适用的解冻方法。     

Protein Denaturation,Rheology, and Gelation Characteristics of Radio-Frequency Heated Egg White Dispersions

Gel properties of radio frequency (RF) heated egg white dispersions at 27.12 MHz were studied as function of concentration (2.5–2.5 kg/100 kg sample), pH (3–11) and heating time (60–180 s). Egg white dispersions demonstrated a gradual liquid-solid transformation as they denatured and gelled during RF treatment. The critical concentration and heating period for egg white protein denaturation and gelation were found to be 7.5% (w/w) and 150 seconds. The elastic modulus (G′) of RF-heated samples increased with concentration and heating period (temperature), whereas complex viscosity (η*) increased exponentially with concentration. In an alkaline condition, the egg white dispersion did not produce a gel; however, in acidic condition it resulted in a strong gel with significantly (P?<?0.05) higher G′. This could be attributed to the high dielectric constant (ε′) and loss factor (ε″) values of acidified samples as compared to the alkaline and control egg white dispersion. Effect of heating rate (1, 5, 10, and 20°C/min) in situ on rheometer plate significantly affected gel rigidity; the RF treated sample rigidity was comparable to samples heated at the rate of 5 and 10°C/min. Differential scanning calorimetry, dielectric measurement, and sodium dodecyl sulfate (SDS) PAGE electrophoresis results were used to confirm gelation behavior during both conventional and RF heating conditions.     

Isostrength Comparison of Large-Strain (Fracture) Rheological Properties of Egg White and Whey Protein Gels

The effects of protein concentration and heating conditions on the physical properties of whey protein isolate (WPI) (in 50 mM NaCl, pH 7) and egg white (pH 9) gels were examined. Egg white and WPI gels had similar values for shear stress at fracture (i.e., isostrength), while trends for shear strain at fracture were protein-type specific. The rigidity ratio (R_0.3), ratio of the rigidity at fracture (G_f) to the rigidity at 30% of fracture strain, measured departure from the stress-strain relationship of an ideal Hookean solid. All gels fit master curves of G_f vs R_0.3, which were described by a power law model of R_0.3=A(G_f)-°19, where "A" showed protein type-specific characteristics.