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。     

Dielectric properties of egg whites and whole eggs as influenced by thermal treatments

Effects of cooking on dielectric properties of liquid whole eggs and liquid egg whites were studied in connection with radio frequency and microwave heating processes to preserve shelf-stable products. Dielectric measurements were made using an open-ended coaxial probe method over a temperature range of 20 and 120 °C at radio frequencies 27 and 40 MHz, and microwave frequencies 915 and 1800 MHz. Thermal denaturation of liquid egg whites and whole eggs influenced the dielectric constants and dipole loss component of eggs, as reflected by changes in loss factors above 60 °C. In addition, loss factor of liquid whole eggs was generally smaller than that of egg whites and larger than the loss factor of egg yolk. Ionic conductivity was a dominant factor determining the dielectric loss behavior of egg products at radio frequencies, whereas dipole water molecules played an increasing role with an increase in microwave frequencies.     

Effect of Drying on Rheological,Thermal, and Structural Properties of Desert Truffles (Terfezia Claveryi) Powder Dispersions

The effect of drying methods (freeze-drying and tray-drying) on the rheological, thermal and functional properties of truffle flour dispersion was studied. Sieve analysis showed the number of finest particles in the freeze-drying samples were significantly higher than the tray-drying samples whereas no significant difference was observed in the particle size distribution through laser diffraction measurement. The freeze-drying sample had significantly higher water holding capacity, sediment volume fractions, and superior instrumental color values than the tray-drying sample. Upon thermal scanning, two distinct starch-lipid complex melting transitions for the freeze-drying and one for the tray-drying sample were detected. Contrary to differential scanning calorimetric measurement, the oscillatory shear measurement successfully detected a distinct gelatinization temperature for the freeze-drying sample between 64 and 67.6°C. The mechanical rigidity of the dispersion was significantly influenced by the drying method and the freeze-drying sample exhibited the higher mechanical strength over the tray-drying sample throughout the frequency range (0.1 to 10 Hz). Viscoelasticity of the dispersion was estimated by a power-type relationship correlating the elastic modulus and frequency. Various shapes of truffle particles including rod, round, oval, and irregular were observed through the scanning electron microscope. This study provided in-depth knowledge on structural/rheological properties of truffle powder produced by two drying processes.     

糖基化卵清蛋白的凝胶性与凝胶稳定性

以卵清蛋白为对照,以糖基化卵清蛋白为研究对象,研究二者所成凝胶在贮藏期间质构、持水性以及微观结构的变化。结果表明:糖基化卵清蛋白的凝胶硬度、弹性、凝聚性与持水性比卵清蛋白高146%、7%、24%和61%。4℃条件下贮藏180d时,糖基化卵清蛋白的凝胶硬度与凝聚性均降低2%,凝胶弹性与持水性增加1.3%、0.6%,卵清蛋白的凝胶硬度降低9%,凝胶弹性、凝聚性与持水性增加0.6%、3%和5.2%。在500倍扫描电子显微镜(SEM)下观察,糖基化卵清蛋白所成凝胶的结构较紧密、均匀,且随贮藏时间的延长无明显变化,而卵清蛋白所成凝胶的间隙较大,随贮藏时间的延长其空间结构变得更加疏松。研究结果证明,糖基化可以明显提高卵清蛋白的凝胶性与凝胶稳定性。     

Influence of pH and Salts on Egg White Gelation

ABSTRACT: Egg white is used in food products for various functional properties. These are strongly influenced by pH, ionic strength, type and concentration of salts. Through an experimental design strategy, the aim of this study was to quantify the influence of pH, cations, and anions naturally present in egg white, and of citrate on egg white gelation. Results showed that pH and Fe³⁺ modified the coagulation temperature of egg white and consequently, the gel characteristics. High concentrations of NaCl decreased the water-holding capacity and the microstructure of egg white gels. At pH 7, viscoelastic properties and microstructure of egg white gels were altered by Ca²⁺ and Mg²⁺ addition.     

Solubility of Proteins from Quail (Coturnix coturnix japonica) Egg White as Affected by Agitation Time,pH, and Salt Concentration

The solubility of proteins from quail egg white subjected to different agitation times, pH, and NaCl at 25°C was evaluated in this study. The greatest solubility achieved was obtained in the 0.05 mol/L of NaCl, pH 10.0, and under agitation for 1 h. The lowest solubility was found in the NaCl 1.0 mol/L, pH 3.0, and agitated for 2 h. Under the test conditions, aqueous solutions of NaCl 1.0 mol/L, pH 3.0, and agitated for 2 h may provide the greatest extraction index of proteins from quail egg white because these conditions promoted the protein precipitation in a large extension.     

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.     

Failure Deformation and Stress Relaxation of Heated Egg White Gels

Stress-strain relationships were determined for heated egg white gels. Compressive strain at failure was independent of protein concentration, while stress at failure increased with protein concentration. Between the length ratios of 1.6 and 2.4 before and after compression, the heated egg white gels followed the Mooney Rivlin model. In stress relaxation, the asymptotic hypothetical equilibrium modulus increased with protein concentration.     

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。     

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。     

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 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.     

球磨处理对鸡蛋清蛋白结构、性质及起泡性的影响

蛋清因具有优良的起泡性而在焙烤等食品加工领域中被广泛应用,因此,提升蛋清蛋白的起泡性有重要意义。本实验对鸡蛋清蛋白进行球磨处理,通过测定球磨处理后蛋清蛋白的游离巯基含量、表面疏水性、水解度、Zeta-电位和粒径,并分析其热力学性质、二级结构、起泡特性和微观结构,以研究球磨处理对蛋清蛋白结构性质及其起泡性的影响。结果表明：球磨处理后的蛋清蛋白粉随处理时间的延长起泡性无明显变化,泡沫稳定性呈现先升高后降低的趋势,且在球磨处理40 min时达到最大值（33.5 s）,比对照组提高近3 倍;此外,球磨处理可显著降低蛋清蛋白表面疏水性和热变性焓（ΔH）（P＜0.05）,显著提高水解度和降低Zeta-电位绝对值（P＜0.05）,并增大粒径,但对游离巯基含量和变性温度无显著影响（P＞0.05）;随着球磨时间的延长,蛋清蛋白β-折叠结构相对含量显著升高（P＜0.05）,α-螺旋结构相对含量先降低后升高,而β-转角结构相对含量先升高后降低;扫描电子显微镜结果显示球磨处理使蛋清蛋白呈现出零散碎片化和絮状。综上,适度球磨处理可以改变蛋清蛋白分子结构,进而提升其泡沫稳定性。     

高场强超声对蛋清液起泡特性的影响

为改善蛋清液的起泡性,采用不同超声功率(120,240 W)和超声时间(1,5,10,20,30 min)的高场强超声(20 kHz)对蛋清蛋白进行改性.结果表明,在功率120 W下超声处理20 min,蛋清蛋白的起泡性最佳(266.7％),是未处理蛋清的6.9倍.超声处理显著降低了蛋清液的表观黏度、表面张力和粒径大小...     

超声波加工对蛋清蛋白质结构和凝胶特性的影响

为研究超声波加工对蛋清蛋白质结构和凝胶特性的影响,以蛋清为原料进行超声处理,通过对超声前后蛋清蛋白质的空间结构、分子分布和流变学性能进行分析,同时对超声后蛋清凝胶的保水性、质构特性等进行测定。结果表明,在200 W和400 W的超声处理下,蛋清蛋白发生了折叠和聚集,也有小部分发生了降解。在600 W的超声处理下,蛋清蛋白发生了部分降解,同时还有小部分蛋白发生了聚集。因此,超声使部分蛋白质分子粒径变大,部分蛋白质分子粒径变小,整体分子粒径分布变窄。200 W、10 min 和600 W、30 min 的超声处理下,蛋清溶液偏向于液体的流变性。在200、400 W和600 W 3 种功率的超声处理下,蛋清凝胶的保水性增强。200 W和400 W的超声处理有利于增强蛋清的凝胶强度,使凝胶更加坚固和致密。600 W、30 min的超声处理会使蛋清的凝胶强度显著降低,从而使凝胶的稳定性降低。研究结果可为改善蛋清的凝胶性能提供一定的参考。     

超声处理对蛋清蛋白结构性质及蛋清液起泡性的影响

研究脉冲式超声处理对蛋清液拉曼光谱、内源性荧光光谱、静态流变学性质、粒径和理化结构的影响,结合起泡性的变化进行相关性分析。研究发现,超声处理能够改变蛋清蛋白二硫键构象,降低蛋清液黏度,减少总巯基含量,对无规卷曲、β-转角含量和酪氨酸残基峰强比（I850/I830）影响较小,蛋清液依旧为假塑性流体。在超声处理15 min内,蛋清蛋白质粒径、表面巯基含量、热变性焓（ΔH）、α-螺旋和β-折叠含量逐渐减少,内源性荧光强度和表面疏水性逐渐增强,色氨酸残基趋向于“暴露的”展开形式;起泡性得到改善,且泡沫体积小,呈均匀紧密的排列,泡沫稳定性小幅降低。随着超声时间的延长,β-折叠含量继续降低,粒径、表面巯基含量、ΔH、α-螺旋含量、色氨酸残基峰强比（I1 363/I1 338）、内源性荧光强度和表面疏水性呈现不同的变化趋势,起泡性逐渐降低,但泡沫稳定性有所升高。相关性分析表明,起泡性与I1 363/I1 338、表面疏水性呈正相关,与ΔH、平均粒径、α-螺旋含量和表面巯基含量呈负相关,泡沫稳定性与表面疏水性呈负相关。     

鸡蛋清蛋白水解物的物化及功能性质的研究

蛋清蛋白质溶解性欠佳且容易起泡,使其应用受限。本文利用Alcalase酶解鸡蛋蛋清蛋白制取水解度为5~15%的酶解物并对酶解物的理化性质和功能性质进行了表征。测定性质包括乳化性、起泡性及稳定性以及溶解性、表面疏水性。所有酶解产物具有较低的表面疏水性,水解大大提高了溶解度,当水解度15%时最大值为89%,但乳化性有所降低,起泡性及稳定性也大约下降了40%。     

Denaturation Time and Temperature Effects on Solubility, Tensile Properties, and Oxygen Permeability of Whey Protein Edible Films

ABSTRACT Whey protein film solubility decreased as film-forming solution heating time and temperature increased. No differences were observed in solubility between films soaked in water at 25 °C for 24 h and 100 °C for 4 min. However, the degree of swelling was significantly larger for films soaked at 100 °C. Films became stiffer, stronger and more stretchable as film-forming solution time and temperature were increased. Oxygen permeability (OP) was lower for films made from heat-denatured whey protein than for films made from native whey protein. Results suggest that an increase in covalent cross-linking, as heat denaturation of the whey protein increases, is accountable for film water insolubility, higher tensile properties and lower OP.     

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.     

Effect of moisture content on selected physicochemical properties of two commercial hen egg white powders

After short-term storage at 23 °C, selected physicochemical properties of two hen egg white powders (with and without hydrolysis) were studied. Overall, the effect of moisture content on physicochemical properties of Hydrolysed Egg White powder (HEW) was more severe than those of Dried Egg White powder (DEW). The denaturation temperature (T_d) and its enthalpy change (ΔH_d) of ovalbumin in DEW followed an exponential model, as well as the T_d of HEW. The Gordon-Taylor equation modelled well the glass transition temperatures (T_g) of HEW and DEW. The Guggenheim-Anderson-de Boer (GAB) model fitted well to the type II moisture sorption isotherm. At the critical moisture content (12.0%, dry basis), compared with DEW, the colour of HEW began to darken dramatically and its hardness started to change significantly. These changes were closely related to the inherent characteristics of the two products. The mechanisms relevant to these physicochemical changes were discussed.