Gelation of Egg White Proteins as Affected by Combined Heating and Freezing

Combined effects of preheating (60°C, 0 ～ 30 min) and freezing (– 10 or –20°C, 20 hr) on the gelation of dried egg white induced by reheating (80°C, 30 min) were examined in comparison with those of refrigerating (5°C, 20 hr). Refrigeration consistently induced harder gels, while freezing resulted in either harder or softer gels. Results of soluble protein content, turbidity, SDS-PAGE and gel filtration indicated that the unfolded and aggregated levels of ovotransferrin, caused by the cooperative effects of preheating and freezing or refrigerating, mainly determined the characteristics of gel properties.     

Effect of Various Types of Egg White on Characteristics and Gelation of Fish Myofibrillar Proteins

ABSTRACT:  Three types of egg white protein (regular dried egg white [REW], special dried egg white [SEW], and liquid egg white [LEW]) were compared for their effect in surimi (CON), containing no egg white (EW). They were characterized for enzyme inhibition and time of EW addition, either with cryoprotectants prior to freezing or during gel preparation, using Pacific whiting surimi. In addition, the setting (suwari) effect and fish protein–EW protein interactions (dynamic rheological properties, total sulfhydryl groups, and fracture gel analysis) were evaluated using Alaska pollock surimi. After 12 mo frozen storage, adding 2% and 3% SEW to Pacific whiting surimi during chopping significantly ( P  < 0.05) increased the force and deformation values compared to adding the respective EW before freezing. The highest ( P  < 0.05) force (175.2 g) and deformation (9.0 mm) values after 12 mo were obtained when 3% SEW was added during chopping. Enzyme autolysis showed that addition of 2% EW protein was effective at inhibiting enzyme activity. During setting, adding 2% SEW maintained force (1047.4 g) and deformation (17.9 mm) values similar ( P  > 0.05) to CON (1055.1 g; 19.3 mm) and significantly ( P  < 0.05) better than 2% REW (666.1 g; 15.6 mm). Texture results corresponded well to other data where 2% SEW showed the lowest total sulfhydryl groups (48.3 mole/10⁵ g), and higher elastic modulus (G'), which suggests improved protein interaction for gel formation. Overall, the addition of 2% to 3% SEW improved gel textural properties of Pacific whiting and Alaska pollock fish protein.     

Modeling Gelation of Egg Albumen and Ovalbumin

The Flory gelation theory and a new protein gelation model were used to investigate the aggregation reactions of egg albumen and ovalbumin. Results showed that 178 to 267 ovalbumin monomers were required to establish the initial ovalbumin gel at the gel point temperature, 81°C. The gel point temperature for egg albumen was 72°C by the Instron and 60°C by protein solubility. The values of the activation energy rate constants for the formation of the different aggregates in the pre-gel stage suggested that the larger ovalbumin aggregates were more reactive than the smaller ones.     

Role of Reduced Ionic Strength and Low pH in Gelation of Chicken Breast Muscle Protein

ABSTRACT: Elastic gels with a high moisture content of 88% were prepared at an acidic pH and low ionic strength. The relationship among pH, ionic strength, water-holding capacity, and fold score of gels was investigated. A decrease of pH from 4.1 to 3.7 or below increased gel elasticity and significantly decreased water loss under pressure ( P < 0.05). In the presence of sodium chloride, gels made at pH 3.5 to 3.7 had decreased elasticity and increased water loss under pressure. Prior freezing increased the water loss of gels under pressure. Gels made with phosphoric acid and hydrochloric acid lost less water under pressure than those made with citric acid. The percentage loss of water from cylindrical gels was inversely related to the height of the cylinders, suggesting that surface effects were involved. These results suggest that net positive charges on the protein molecules at low pH produced electrostatic repulsion, which was a major driving force for water uptake in the low-salt gels.     

转谷氨酰胺酶提高蛋清粉凝胶性能的研究

为改善蛋清粉的加工品质,探讨了酶交联反应对提高蛋清粉凝胶性能的影响。通过研究转谷氨酰胺酶用量、反应温度及作用时间对蛋清粉凝胶强度的影响,采用Box-Benhnken设计对转谷氨酰胺酶交联蛋清粉的凝胶强度进行优化。以蛋清粉凝胶强度为响应值,进行响应面分析。结果表明,转谷氨酰胺酶交联蛋清粉的优化工艺条件为:酶用量6U/g蛋清粉,作用时间3.99h,温度35℃,在此条件下,蛋白粉的凝胶强度达到820g/cm2,与实测值基本一致,说明利用该试验建立的模型在实践中具有可行性。     

Heat-induced Egg White Gels as Affected by pH

The functional properties of heat-induced egg white gels were investigated at five pH values. Textural characteristics were determined using the Instron Universal Machine. Hardness, elasticity, cohesiveness, chewiness, and fracturability were maximum at pH 11. Hunter L values were maximum at pH 5 and 7. Microstructure studied with electron microscopy was distinctly different at the five pH values. Alkaline gels showed a fine ordered network that might have contributed to excellent textural characteristics. Water-holding capacity (WHC) was high at alkaline pH, but decreased with addition of 2-mercaptoethanol, suggesting that disulfide bonds were important in egg white gels. Sodium dodecyl sulfate (SDS) improved WHC at pH 7 and 9. No significant correlation was observed between textural profiles and WHC.     

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。     

鸡蛋清中主要过敏原的研究进展

鸡蛋是引起食物过敏最常见的过敏原食物之一。本文重点介绍了鸡蛋清中主要过敏原卵类粘蛋白、卵白蛋白、卵转铁蛋白和溶菌酶的研究进展。     

蛋清肽及肽钙配合物的制备

为获得高生物效价的补钙制剂及提高蛋清蛋白的附加值,首先对鸡蛋清进行酶法改性,筛选实验用酶,采用正交试验,分别对酶解条件及肽钙反应条件进行优化,并采用红外光谱法比较反应前后图谱的变化。结果表明：选择先碱性蛋白酶后中性蛋白酶进行双酶酶解,酶解条件为底物质量分数6%、碱性酶酶底比1:100、pH8.0、酶解时间3h;中性酶酶底比1:25、pH7.0、酶解时间3h。制备肽钙配合物最优反应条件为肽钙(CaCl2)质量比2.5:1、pH9.5、底物质量分数4%、温度55℃,在此条件下,可溶性钙含量为21.15mg/L,水解度为8.66%。制备蛋清肽时,使用双酶的水解效果优于单酶,蛋清肽与钙形成了双单齿配合物,其钙质量分数为8.75%。     

糖基化反应对蛋清蛋白质凝胶性的影响

为研究糖基化反应提高蛋清蛋白质凝胶性的机理,利用氨基酸分析仪、苯酚硫酸法、奥氏黏度计、静态激光散射仪对糖基化蛋清蛋白质氨基酸组成、总糖含量、特性黏度、粒径分布进行测定与分析。结果显示：糖基化反应可使蛋清蛋白质的凝胶强度和持水性分别提高91.7%和35.2%,且二者均在反应4d后达到最高值;糖基化处理5d后,蛋清蛋白质的赖氨酸含量相对降低28.42%,总糖含量增至2.18%;特性黏度随反应时间的延长增幅较小;糖基化蛋白粒径分布在0.1～50.0μm之间,糖基化2d内,粒径分布由小粒径峰向大粒径峰转变;糖基化2d后,粒径分布变化不明显。     

蛋清中溶菌酶的提取

研究了从新鲜蛋清中提取溶菌酶的方法。通过控制温度，调酸和加盐，可以使溶菌酶得到分离和纯化。采用超滤的方法将溶菌酶提取液浓缩及脱盐并进一步纯化。最后采用喷雾干燥的方法制成产品。产品活力可达１１０００ｕ／ｍｇ．     

Effect of Sucrose Addition and Heat Treatment on Egg Albumen Protein Gelation

ABSTRACT: Studies were conducted to evaluate the effect of sucrose (0% to 60% w/w) on the heat denaturation and gelation of egg albumen solutions (pH 7.0) by thermal analysis and rheological measurements. Temperature and frequency sweeps were carried out under small deformations to determine the temperature at which structure development began (T_s) and the storage modulus plateau (G₀), respectively. The latter was used to estimate the molecular weight of the internal chains between cross-links (M_c) using the rubber elasticity theory. Gels were prepared under several heat intensities (70, 80, and 90°C/30 min), and the mechanical properties were determined under small (stress relaxation) and large (stress and strain at fracture) deformations. It was observed that increments in sucrose concentration could act in the stabilization of the proteins, promoting a significant increase in the onset values and temperature of denaturation. The gelling process showed aT_s increase with higher sucrose concentration. Gelation and the gel mechanical properties and network density showed a strong dependence on sucrose concentration and heat treatment temperature. In a general way, the sucrose promoted an improvement in the gel network up to a determined value of sugar concentration. At higher sugar concentrations, the values for the rheological properties decreased, which could be related to an incomplete unfolding of the oval-bumin under these conditions.     

蛋清寡肽制备技术的研究

蛋清蛋白质是食物中最理想的优质蛋白质,但由于其受热易凝固、粘度大等性质,限制了它在食品加工中的广泛应用。利用Alcalase蛋白酶对蛋清蛋白进行水解制备蛋清寡肽,研究其工艺技术,并总结设计要点,为工业化生产提供依据。     

糖基化反应对鸡蛋清蛋白与低聚麦芽糖交联物活性和功能性的影响

本文以鸡蛋清蛋白与低聚麦芽糖为原料,进行糖基化修饰反应,以接枝度和褐变程度等指标分析糖基化程度,并研究糖基化修饰反应对接枝产物生物活性和功能特性的影响。结果表明,湿热法加热2 h的反应产物接枝度最高,褐变程度较小,即反应产物大多是初级阶段末期或中间阶段产物。糖基化修饰反应提高了鸡蛋清蛋白的金属还原力和清除DPPH自由基的能力,同时还可增强其螯合亚铁离子的能力。功能特性分析表明,糖基化修饰反应可提高鸡蛋清蛋白的溶解度和热稳定性,而不影响其乳化稳定性和乳化活性。同时,体外模拟消化实验表明,糖基化修饰反应降低了鸡蛋清蛋白的消化性,这可能与其在大肠中被肠道微生物降解有一定的关联。上述分析表明,糖基化反应可作为一种有效的修饰方法提高蛋白质的功能特性和生物活性。     

Volatiles and Sensory Characteristics of Cooked Egg Yolk, White and Their Combinations

Headspace volatiles were produced by heating fresh egg yolk, white and different ratios of yolk to white. Volatiles of the same treatments produced during steam distillation extraction were identified, compared, and related to sensory characteristics of fresh scrambled eggs. Overall impression, sulfur, and sweet notes were sensory characteristics identified to distinguish between samples with varying yolkwhite ratios. Volatile concentrations of compounds in the headspace, and steam distillation/ solvent extracts were used to distinguish between scrambled eggs with different yolk:white ratios. The concentration of both egg yolk and white had a significant effect on fresh scrambled egg sensory characteristics and flavor volatiles. The contribution of both must be considered when producing egg substitutes.     

蛋清利用研究进展

在食品行业中,蛋黄的需求量较大,而蛋清常常作为废弃物被丢弃,这既造成了环境污染,也浪费了宝贵的蛋白质资源,因此亟需开展蛋清的综合利用研究。目前国内外对蛋清研究的热点主要集中在溶菌酶的提取方法、蛋清的冷杀菌技术、蛋清的功能性质以及蛋清的酶水解物生物活性4 个方面,因此本文从这4 个方面综述了近年来对蛋清利用的研究进展。     

蛋白质量浓度对鸡蛋热诱导凝胶特性的影响

以蛋清、蛋黄和全蛋液为原料,研究蛋清、蛋黄和全蛋蛋白热诱导凝胶的形成能力以及蛋白质量浓度对蛋清、蛋黄和全蛋蛋白热诱导凝胶特性的影响。结果表明：蛋清、蛋黄和全蛋形成热诱导凝胶的最低蛋白质量浓度分别为50、55、50mg/mL;在50～135mg/mL范围内,随蛋白质量浓度的增加,蛋清、蛋黄和全蛋蛋白的凝胶强度和保水性不断增大,蒸煮损失整体呈下降趋势;蛋白质量浓度对蛋清、蛋黄和全蛋凝胶的弹性也有显著影响。     

鸡蛋清中溶菌酶的应用性研究

介绍了鸡蛋清中溶菌酶的生物化学特性,研究了它在食品、医学、生物工程、日化用品等工业上的应用性,提出其潜在的应用价值和发展前景。     

鸡蛋牛奶布丁在凝胶过程中的动态流变特性

为研究鸡蛋牛奶布丁在凝固过程中凝胶的形成及质量,对鸡蛋牛奶布丁在凝固过程中的动态流变特性进行研究。结果表明：在凝固温度分别为75、80、85 ℃时进行动态时间扫描,得出鸡蛋牛奶布丁的凝胶过程是一个连续一级反应;当凝固温度为75 ℃时,得到的鸡蛋牛奶布丁强度最好、质构最均匀。通过动态温度扫描得出鸡蛋牛奶布丁的凝固过程可以分为诱导阶段（65～71.5 ℃）、加速阶段（71.5～88 ℃）和稳定阶段（＞88 ℃）。     

Flavourzyme酶水解蛋清蛋白的工艺研究

以水解度和蛋白质残留量为指标,研究温度、pH、酶用量及蛋清浓度对Flavourzyme酶解蛋清蛋白的影响,并通过正交试验来确定其最佳工艺。结果是温度55℃、pH6.5、加酶量为质量分数6%、蛋清料液质量体积比1 g:5 m L为最佳工艺参数。在该条件下,6 h酶解物的蛋白质残留率为27.68%,水解度为38.75%,水解物的相对分子质量大部分集中在300以下,即主要以游离氨基酸及二肽形式存在。