Gelation Properties of Ovalbumin as Affected by Fatty Acid Salts

The physicochemical properties of heat-induced ovalbumin (OVA) gels containing fatty acid salts (FAS) were investigated. Water-holding ability and transparency markedly increased in the presence of sodium caprate or sodium laurate. At 9% of the protein concentration transparent and hard gels formed; at 7%, transparent and soft gels formed. Scanning electron microscopy showed that the transparent gels had a more homogeneous structure than turbid gels without FAS. Differential scanning calorimetry indicated that denaturation temperature of OVA was decreased and the peaks became broader after addition of FAS.     

hCG受体的结合特性及卵清蛋白的抑制作用

本文采用Ｉｏｄｏｇｅｎ固相氧化法制备高活性１２５Ｉ—ｈＣＧ，建立了大鼠睾丸细胞膜制齐ｈＣＧ受体－放射配基结合分析法．１２５Ｉ—ＨＣＧ与受体的结合具有可饱和性、可逆性和特异性等基本特征．在所用１２５Ｉ—ｈＣＧ浓度范围内，Ｓｃａｔｃｈａｒｄ分析为直线，Ｈｉｌｌ系数接近玉，属简单单位点系统．卵清蛋白糖肽可抑制１２５ｈＣＧ与受体的结合，其ＫＩ为３５．１±７．１ｎｍ，ＩＣ５０为５９．５±１１．９ｕｍ，经ＬＩＧＡＮＤ软看数据处理表明，这种抑制作用亦属简单单位点系统，提示ｈＣＧ—Ａｓｎ—连接的寡糖链并非与膜上凝集素样成分结合，而是直接参与ｈＣＧ与受体分子的相互作用，卵清蛋白糖肽Ａｓｎ—连接的糖链可干扰ｈＣＧ糖链与受体的结合．     

鸡卵清蛋白食物过敏大鼠中药口服治疗的实验研究

目的：建立鸡卵清蛋白（OVA）食物过敏大鼠模型,利用中药复方 Formula-3对食物过敏大鼠进行治疗,探讨其治疗效果及其机制。方法将24只 BN 大鼠按随机数字表法分为 PBS 对照组、OVA 模型组及中药复方 For-mula-3治疗组,每组8只。OVA 模型组与中药复方 Formula-3治疗组在前6周和第7、9、11、13周分别予 OVA（1 mg·mL－1）灌胃致敏,每天1次;于第13周末以 OVA（100 mg·mL－1）进行激发,建立大鼠 OVA 食物过敏模型。其中中药复方 Formula-3治疗组于第7周开始同时给予1 mL 中药复方 Formula-3（150 mg·mL－1）灌胃治疗,每天1次;OVA 模型组则以1 mL 的0．1 mmol· L－1 PBS 灌胃治疗。PBS 对照组致敏、激发和治疗均予以浓度为0．1 mmol·L－1的 PBS 1 mL 灌胃。激发24 h 后处死大鼠,测定3组大鼠血清中 OVA 特异性 IgE 水平、计算肥大细胞脱颗粒的百分比、观察肠道组织超微结构病理变化等,对治疗效果进行评价。结果 OVA 模型组血清中OVA 特异性 IgE 抗体显著高于 PBS 对照组、脱颗粒肥大细胞数量显著多于 PBS 对照组（均 P ＜0．01）;中药复方Formula-3治疗组血清中 OVA 特异性 IgE 水平显著低于 OVA 模型组、肥大细胞脱颗粒显著少于 OVA 模型组（均P ＜0．01）。OVA 模型组肠黏膜微绒毛变形,细胞内细胞器损伤,细胞间连接破坏,炎性细胞浸润增多;中药复方Formula-3治疗组微绒毛均匀整齐,细胞器基本正常,细胞间连接紧密,与 OVA 模型组相比病变明显轻微。结论中药复方 Formula-3能有效地降低食物过敏大鼠血清中 OVA 特异性 IgE,减少肥大细胞脱颗粒并减轻肠道的病理改变,对食物过敏有良好的治疗效果。     

Immunochemical detection of ovalbumin in dairy-based foods

Commercially available antibodies were used for the detection and quantitation of ovalbumin in ice cream and cheese. Electrophoretic separation of protein components, followed by blotting and immunochemical recognition of ovalbumin allowed the detection of the addition of 50 g kg^-1 egg white to processed cheese and allowed detection of egg in ice cream. For quantitative purposes a competitive ELISA method was set up. Calibration curves for ovalbumin in various products were obtained. A marked matrix effect was evident in ice cream, cheese and yoghurt. Different types of cheese gave nearly identical matrix effects. Analytical application of the method should therefore be possible, at least within a given class of products. A study on the influence of thermal treatments on the ELISA response showed that melting of cheese at various temperatures modifies only slightly the ELISA response for ovalbumin.     

碳酸钙与外源蛋白复配物对含有MTGase的鱼糜凝胶特性的促进作用

目的研究钙盐、外源蛋白及其复配物对含微生物产转谷氨酰胺酶(MTG)的鲢鱼糜凝胶品质的影响。方法将碳酸钙、乳酸钙、卵清蛋白、大豆分离蛋白及其复配物添加到含MTG(2 U/gg_(鱼蛋白))的鲢鱼糜中并制成凝胶,测定鱼糜凝胶的持水性、质构特性(破断强度、凹陷深度、硬度、内聚性、咀嚼性)、白度和聚丙烯酰胺凝胶电泳图谱。结果添加碳酸钙、乳酸钙、卵清蛋白、大豆分离蛋白及其复配物均可不同程度地改善含MTG的鱼糜凝胶的凝胶特性,且添加其复配物优于单独添加碳酸钙、乳酸钙、卵清蛋白、大豆分离蛋白。经试验优化,将8μmol/U_(MTG)碳酸钙、4 mg/U_(MTG)卵清蛋白、4 mg/U_(MTG)大豆分离蛋白添加到含有2 U/g_(鱼蛋白)MTG的鲢鱼糜中可获得最佳凝胶品质,鱼糜凝胶的破断力、凹陷深度最高,硬度、咀嚼性、白度均显著高于单独添加MTG(P0.05),也明显高于添加2 U/g_(鱼蛋白)其他品牌商品MTG的(P0.05)。结论 CaCO_3与外源蛋白复配物对含有MTG的鱼糜凝胶特性具有显著促进作用,将碳酸钙、卵清蛋白、大豆分离蛋白与MTG按比例混合可制成鱼糜制品专用的复配酶制剂。     

双抗体夹心酶联免疫吸附法检测鱼糜制品中鸡蛋卵白蛋白

目的 建立鸡蛋卵白蛋白（ovalbumin, OVA）的双抗体夹心酶联免疫吸附（sandwich enzyme linked immunosorbent assay, sELISA）检测方法,组装定量检测鱼糜制品中OVA含量的ELISA检测试剂盒。方法 确定各步骤反应时间,使用棋盘法确定捕获抗体和检测抗体的最佳工作浓度,建立检测方法并对其性能进行评价。结果 设置各步骤时间为抗原孵育20 min,检测抗体孵育20 min,酶促反应显色10 min。兔抗OVA抗体为捕获抗体,工作质量浓度为1 μg/mL,辣根过氧化物酶(horseradish peroxidase, HRP)HRP标记兔抗OVA抗体为检测抗体,1:5000（V/V）稀释。采用四参数逻辑曲线拟合标准曲线,所建立sELISA方法的检测范围为8.5~200.0 ng/mL,最低检出限为3.5 ng/mL,定量限为8.5 ng/mL。批次内和批次间的变异系数分别为2.31%~4.58%和6.06%~12.23%;测得28种常见食物样品中4种样品的交叉反应率小于0.002%;鱼糜基质中的回收率在80%~130%;试剂盒在37℃储存7 d后检测标准品OD值下降率小于30%;试剂盒在4℃保存6个月期间,标准品检测结果的变异系数在4.29%~18.91%。结论 建立的方法快速、灵敏、准确、稳定性好,可用于鱼糜制品中鸡蛋OVA的定量检测。     

Influence of sodium chloride and glucose on the aggregation behavior of heat-denatured ovalbumin investigated with a multiangle laser light scattering technique

ABSTRACT:  The molecular characteristics of ovalbumin aggregates formed by heating with NaCl and glucose were investigated with a multi-angle laser light scattering system. The presence of NaCl and glucose affected the formation and molecular structure of the aggregates. Specifically, glucose increased the denaturation temperature of ovalbumin due to thermal stabilization of the native state of ovalbumin, regardless of the content of added NaCl. The surface hydrophobicity of the aggregates was increased by the addition of NaCl, which induced the denaturation of ovalbumin at a lower temperature. Aggregates with a larger weight-average molar mass ( M_w ) and root mean square radius ( R_g ) formed from heat-denatured ovalbumin with NaCl and glucose. The presence of NaCl during heat denaturation caused the formation of aggregates with a larger M_w (1.9 × 10⁵ and 3.5 × 10⁶ g/mol for 0 and 10 mM NaCl, respectively) and R_g (14.8 and 80.4 nm for 0 and 10 mM NaCl, respectively). Over a certain amount of NaCl, the addition of more glucose resulted in the formation of more aggregates with greater M_w and R_g values. In sum, the thermostability of ovalbumin was affected primarily by glucose, but the molecular characteristics of the soluble aggregates formed by heat denaturation varied primarily with NaCl content.     

Influence of sodium chloride and glucose on acid-induced gelation of heat-denatured ovalbumin

ABSTRACT:  We examined the effects of NaCl and glucose on cold-set ovalbumin gelation. Cold-set gels were prepared by adding glucono-δ-lactone (GDL) to a 2% heated ovalbumin solution. For the gel prepared from ovalbumin heat-denatured with NaCl and glucose, the gel with 10 mM NaCl was most transparent and had high gel strength. Its maximum complex shear modulus ( G *) and turbidity were 2.5 times greater and 3 times lower, respectively, than those of the gel without NaCl. The turbidity of the gel with the higher NaCl content increased steeply after the addition of GDL and did not change during the experimental period. The maximum G * of the gel exhibited positive correlations with the molar mass, radius, and surface hydrophobicity of soluble aggregates and the NaCl content, but the turbidity exhibited negative correlations with these factors. The presence of glucose did not significantly affect the turbidity or rheological properties of the gel. For the gel prepared by adding NaCl and glucose with GDL, the presence of glucose did not affect the turbidity, but the maximum G * decreased in inverse proportion to the glucose content. The turbidity of the gel with higher NaCl content (≥ 50 mM) was the greatest among all samples, and the increased turbidity was maintained throughout the measurements. The gels with 50 and 100 mM NaCl exhibited thixotropy during shearing at a constant shear rate. Therefore, the presence of NaCl and glucose during cold gelation could facilitate the preparation of cold-set gels having various properties for food applications.     

卵白蛋白提取及其可食性膜制备

提取鸡蛋清中的卵白蛋白,制备卵白蛋白粉。采用考马斯亮蓝标准曲线法和凯氏定氮法分析蛋白含量,SDS-PAGE电泳测定纯度。用甘油塑化卵白蛋白,制备可食性蛋白膜。     

Ferulic acid and EGCG alter the structural characteristics of ovalbumin and its application in mineral loading

This study aims to fabricate mineral-loading nanocarriers using natural materials. The interaction patterns between ovalbumin (OVA) and four water-soluble polyphenols, namely ferulic acid (FA), (-)-Epigallo-catechin 3-gallate (EGCG), gallic acid (GA) and epicatechin (EC), were investigated. Results showed that the optimised conditions for preparing stable OVA–polyphenol complexes are at the OVA–polyphenol ratio of 4:1 at pH 6, under which OVA–FA and OVA–EGCG showed the highest stability and mineral-loading capacity among four OVA–polyphenol complexes. The fluorescence results indicated that the addition of EGCG and FA induced a significant fluorescence quenching to OVA. The interaction between OVA and polyphenols involved hydrogen bonding, hydrophobic interaction and electrostatic interaction. Fourier transform infrared spectroscopy (FTIR) analysis suggested that both FA and EGCG enhanced the stability and orderliness of the structure of OVA. The transmission electron microscopy images also exhibited the spherical structure of OVA after the addition of FA and EGCG. Furthermore, scanning electron microscope–energy dispersive X-ray spectrum results suggested that OVA–FA and OVA–EGCG complexes were better mineral carriers than OVA–GA and OVA–EC. This study may serve as the theoretical support for the promising application of OVA in the fabrication of mineral-loading nanocarriers in functional food and pharmaceutic.