Selected Rheological Properties of pH-Adjusted or Succinylated Egg Albumen

Apparent viscosities of pH-adjusted or succinylated raw egg albumen were measured at 10, 20, and 30°C using a Haake rotary viscometer. Viscosities decreased with increasing temperature. Rheological power law model parameters indicated that as pH approached 5–6 and 11, albumen became more Newtonian. Control albumen (pH 9.0) and succinylated albumen were pseudoplastic. Intrinsic viscosities of DH 9.0, 10.0, and 11.0 albumens were 0.083, 0.092, and 0.102 dl/g, respectively, and that of succinylated albumend (0, 0.1, 0.2, and 0.4% w/w) were 0.052, 0.147, 0.149, and 0.184 dl/g, respectively. Apparent viscosities of coagulated albumen, measured by capillary extrusion, increased with pH but did not change with succinylation. Yield forces and rigidity moduli of these gels increased with pH but not with succinylation level.     

Changes in Heat-Induced Rheological Properties During Cold Storage of Egg Albumen

Two groups of eggs were stored at 15°C for 0, 5 and 10 days. One group was stored, with the shell removed, in sterile Whirl-Pak bags. A second group was stored as intact whole eggs. Viscosity index, apparent elasticity, and initial penetration force were determined for heat-induced (80°C, 80 min) gels of the thick, thin and mixed albumens from each group. The rheological parameters increased with storage time, with the greater increase exhibited by the gels of the albumens that were stored as shell eggs. Solution pH was a major factor controlling these rheological properties of heated egg albumen.     

Structural and Rheological Properties of Aerated High Sugar Systems Containing Egg Albumen

ABSTRACT: Structural and rheological properties have been investigated for an aerated system containing a high content of invert sugar and 2 to 10 wt% egg albumen. The specific gravity and the overrun were found to be influenced by the protein concentration and the whipping time. The systems exhibited rheopexy and shear-thinning at high shear rate, with flow data fitted to a power-law model. At small deformations, viscous character was found to dominate over elastic character over the frequency range 10⁻² to 10 Hz. Images taken from confocal microscopy indicated that mean bubble size and concentration varied systematically with protein concentration and whipping time, and that more protein accumulated on the bubble surfaces as whipping proceeded. The study of this model system illustrates how the texture of a high sugar content aerated food depends on protein content and whipping conditions.     

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.     

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。     

Mechanical and Barrier Properties of Egg Albumen Films

Films were cast and dried from heated, alkaline aqueous egg albumen solutions containing glycerin (GLY) at 30, 40, or 50% w/w of protein, polyethylene glycol (PEG) at 50 or 60%, or sorbitol (S) at 50 or 60% as plasticizers. PEG-plasticized (60%) films also were prepared by substituting 10, 30, 50, or 70% of albumen with yolk solids. Film tensile strength (TS), elongation at break (E), water vapor permeability (WVP), and Hunter color values were measured. At a plasticizer content of 50%, films with S had the lowest WVP while films with PEG had the greatest E. S- and PEG-plasticized films had greater TS than GLY-plasticized films. Yolk solids decreased film TS, E, and WVP while increasing film yellowness.     

不同冷却温度添加氯化镁和谷氨酰胺转氨酶对大豆全粉凝胶流变性质的影响

以超微粉碎技术处理的大豆全粉为原料,利用氯化镁和谷氨酰胺转氨酶(glutamine transaminase,TG)制备大豆全粉凝胶,并探究温度、氯化镁添加量及TG对大豆全粉凝胶的质构特性、流变特性和微观结构的影响规律.结果 表明:全豆豆乳分别冷却至25、15、5℃添加氯化镁和TG时,随着冷却温度的降低凝胶强度逐渐变大...     

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.     

Rheological Properties of Two Heat-Induced Protein Gels

Rheological properties of heat-induced gels from egg albumen and bovine plasma proteins were measured using a mechanical loading device. Each protein was tested at 8% protein concentration and heated for 0–120 min at 80°C in an agitating water bath. After heating, the viscosity index, apparent elasticity and initial penetration force of the gels were evaluated. Bovine plasma protein dispersions exhibited a substantially higher viscosity index, apparent elasticity and initial penetration force than egg albumen gels. Bovine plasma proteins produced a gel structure which was strong and elastic. By comparison, heat-induced gels of egg albumen proteins were fragile and somewhat brittle.     

Rheological Properties of Concentrated Wheat Starch Gels

The rheological properties of concentrated wheat starch gels were measured with shear stress relaxation experiments in cone-plate geometry. The water content of the investigated gels were 80, 60, 50 and 30% (w/w), respectively, and the relaxation modulus (G) and half relaxation time (T1/2) were studied after heating to different temperatures. For the gels with 50% and 60% (w/w) of water, a maximum value of G was obtained when the temperature interval for gelatinization was passed. When these gels were heated to higher temperatures, G decreased, and T1/2 increased, whereas gels with 30 and 80% (w/w) of water behaved differently. The influence of particle size distribution on the rheological properties of concentrated starch gels, was also investigated. It was found that G and T1/2 increased with a greater fraction of small starch granules.     

Correlation of the Rheological Behavior of Egg Albumen to Temperature, pH, and NaCl Concentration

Rheological parameters of viscosity, gel strength, and elasticity were determined on heat-set egg albumen gels over various treatment combinations ranging from 65-90°C, pH 6.4-9.6, and NaCl concentrations of 0.0-0.1M added NaCl. Maximum viscosity was measured at a treatment combination of 77.5°C, pH 8.00, and 0.1M NaCl. Elasticity and gel strength were highest in gels with a treatment combination of 85.2°C, pH 9.0, and 0.08M NaCl. Temperature had the greatest effect on all three rheological parameters. Gels heated above 80°C were of unusual character, exhibiting syneresis and shrinkage.     

CMC与CMC-Na 改性鸡蛋清蛋白溶胶- 凝胶性质研究

将一定质量分数的离子型多糖羧甲基纤维素(CMC)与羧甲基纤维素钠(CMC-Na)分别溶于蛋清中,冷冻干燥后,将得到的样品置于相对湿度为75% 的环境中干热反应一定时间后,通过质构分析、色度分析、SDS-PAGE、差示扫描量热分析、扫描电子显微镜研究鸡蛋清蛋白与CMC 及CMC-Na 交联改性后性质的变化。结果表明：反应温度60℃、反应时间2d 时,各样品的凝胶强度显著增大,凝胶的微观网络更为均匀致密,蛋清粉中的小分子质量蛋白质减少。证明适度的反应可增强蛋清粉的凝胶强度,但随时间延长,过度反应则会造成分子质量过大、溶解度下降,色泽显著加深。起泡性的分析表明：各反应2d 后样品的起泡性均明显增强,其中以60℃,添加0.25% 的CMC 和CMC-Na 的起泡力最强,分别增大了0.6 倍和0.5 倍,泡沫稳定性亦明显增强。证明在此反应条件下,可获得同时兼顾较高凝胶性和较高起泡性的新型蛋白粉。     

不同大豆分离蛋白凝胶的流变学性质

本文比较研究了三种不同大豆分离蛋白(分别为SG、ADM和ON)的凝胶性能。三种大豆分离蛋白的7S／11S比率和变性热焓类似，但表面疏水性和混浊度却明显不同。通过小变形振荡流变分析研究了三种大豆分离蛋白的热凝胶性能。在去离子水中，SG和ADM的凝胶浓度均是90mg／ml，且两者的凝胶强度接近；ON的凝胶浓度是110mg／ml。在1．0mol／L NaCl溶液中，ADM的凝胶强度高于SG。在NaSCN存在的情况下。ON的凝胶强度明显增加。尽管N-乙基马来酰亚胺(NEM)能够封闭巯基，但该试剂可增强三种大豆分离蛋白的凝胶强度。结果显示SG和ADM之间的凝胶性能的差别主要是由于表面疏水性不同，而造成ON凝胶性能较差的主要原因是大豆蛋白分子的聚集。     

Preparation of Heat-induced Transparent Gels from Egg White by the Control of pH and Ionic Strength of the Medium

Egg white was dialyzed against distilled water or diluted with water, and the precipitates formed were removed by centrifugation. The supernatant gave a transparent gel after being heated at an acidic pH (2–4). At other regions of pH, except for the highly alkaline region, the gel or suspension was turbid upon heating. Insufficient centrifugation of the dialyzed egg white or the addition of NaCl to the supernatant after centrifugation resulted in a turbid gel on heating at even acidic pH. The removal of the slight precipitate formed at low ionic strength and the maintenance of low ionic strength during heating were both necessary for production of a transparent gel.     

Rheological Properties of Gellan Gels Containing Filler Particles

ABSTRACT: Influences of rigid (glass) and deformable (gellan) particles dispersed in gellan gels were studied to better understand the effect of structure on the rheological properties of model composite foods. Composites with inclusions at 0%, 10%, 20%, and 30% volume fractions (VF) were tested under small deformation oscillatory shear. In gels containing rigid particles, the dynamic shear storage modulus (G') decreased initially, exhibited a minimum around 20% VF, then increased at 30% VF behavior that was attributed to physical interactions among particles. In gels containing deformable particles, the linear decrease in G' with increasing VF may be due to particle compliance under stress or to particle separation from the matrix, thereby causing gel weakening.     

Improving Foaming Properties of Yolk-Contaminated Egg Albumen by Basic Soy Protein

ABSTRACT:  Yolk contamination of egg white is a common problem in the egg breaking industry. Foaming properties of egg white protein are affected by such contamination, but proteins of basic nature may restore the foaming properties of the yolk-contaminated egg white protein. The purpose of this study was to chemically modify a soy protein, that is, to esterify the acidic groups on the protein and to study the potential of such modified protein in improving foaming. We showed that the modification changed the isoelectric point of soy protein isolate (SPI) from 4.5 to about 10. Sonication was proven to be a very effective means to redisperse the methanol-denatured soy protein during reaction, as shown by the improved solubility profile. Such modified basic protein, that is, the sonicated-modified SPI (SMSPI), when added to the yolk-contaminated (at 0.4% level, as-is basis) egg white, gave significantly improved foaming properties. We have shown that the slight change in pH due to the addition of SMSPI was not the reason for improved foaming performance; instead, the modified protein itself was the main reason for such improvement. Addition of SMSPI increased the foaming performance of both pure egg white and yolk-contaminated egg white. SMSPI consistently performed better than the unmodified SPI for improving foaming. Addition of SMSPI (16%, based on dry egg white, and 1.6% based on liquid egg white) fully restored foam expansion and foam liquid stability of 0.4% yolk-contaminated egg white, and it even out-performed the foaming of pure white protein. Therefore, a feasible solution to restore the foaming properties of yolk-contaminated egg white has been identified. It is expected that such modified SPI can be used as an additive or ingredient in foaming formulation, especially when the egg white protein is suspected of lipid contamination.     

不同木薯淀粉对冻融魔芋葡甘聚糖凝胶特性的比较分析

为探究不同木薯淀粉对冻融魔芋葡甘聚糖凝胶的影响,采用木薯淀粉（cassava starch,CS）、木薯醋酸酯淀粉（starch acetate,SA）、木薯乙酰化二淀粉己二酸酯淀粉（acetylated di-starch adipate,ADA）、木薯乙酰化二淀粉磷酸酯淀粉（acetylated di-starch phosphate starch,ADP）四种市售淀粉代替37.5%魔芋葡甘聚糖（konjac glucomannan,KGM）,制备冻融脱乙酰KGM/淀粉复合凝胶。通过质构仪、傅里叶红外光谱仪、热重分析仪、冷场扫描电镜分析其凝胶特性的变化。结果表明,4种木薯淀粉可以改善冻融KGM凝胶的凝胶特性,但不同木薯淀粉间存在差异,KGM/ADP凝胶表现出最优的保水性和热稳定性,与KGM凝胶相比,其析水率从29.75%下降至8.71%,持水率从73.68%提高至87.42%,硬度从274.36 g下降至176.33 g,弹性、内聚性及回复性无显著差异;不同木薯淀粉均未影响葡甘聚糖的脱乙酰行为和结晶形态,但ADP可以改变冻融KGM凝胶微观形貌,提高其抗脱水收缩能力。综合分析,ADP代替部分魔芋葡甘聚糖改善冻融KGM凝胶特性效果最佳,为其在魔芋凝胶食品的应用提供指导。     

Simultaneous Isolation of Avidin and Lysozyme from Egg Albumen

A single column cation exchange method was developed which allowed simultaneous recovery of lysozyme and avidin from undiluted egg white. A unique application-elution sequence was developed, involving accumulation of avidin on the column through several cycles of egg white application and lysozyme elution. Lysozyme was recovered with higher yields than reported for the isoelectric precipitation methods often used in the industry (86% vs 60–80%). Lysozyme peaks appeared homogeneous on SDS-PAGE. Avidin recovery was also as good or better than that of previously reported ion exchange methods (74%–80%). The purity of the avidin fraction (up to 40.9%) was superior to that of other reported primary avidin fractions.     

Foaming Properties of Egg Albumen with a Bubbling Apparatus Compared with Whipping

Neither standard method nor instrument exists to accurately measure foaming properties in food. Usually, whipping methods are used but they are only moderately reproducible. We used an original apparatus in which foam was generated by bubbling and then analyzed by conductimetry (liquid in the foam) and a uniline camera (foam volume). The foaming properties of a series of egg-white powders were studied. Among parameters describing foam formation and destabilization, three were repeatable and discriminating. They were correlated with those obtained with whipping methods. Easy to use and rapid, the bubbling method is an alternative for controlling and measuring the foaming properties of egg-white.     

Factors Contributing to Antilisterial Effects of Raw Egg Albumen

Sensitivity of Listeria monocytogenes strain Scott A and Brie-1 to several factors in raw egg albumen was investigated. A concentration of ca 15% of albumen in trypticase soy broth was listeristatic after 24 hr at 35°C, and listericidal effects were observed at higher concentrations. Supplementation of albumen with iron or biotin did not reverse the inhibition. Preheating of albumen (50–80°C) caused progressive loss of antilisterial effects. Supplementation of broth with lysozyme (>1 mg/mL) produced antilisterial effects that were enhanced at pH 9; conalbumin (>6 mg/mL) suppressed cell growth, while ovomucoid (>2 mg/mL) was inhibitory only at pH 9. Results inferred that antilisterial effects of albumen were caused primarily by lysozyme and were enhanced by ovomucoid, conalbumin, and alkaline pH.