鸡蛋清卵白蛋白酶解工艺优化及其结构性质

研究鸡蛋清卵白蛋白的酶解工艺及其结构性质,以水解度为指标,确定最佳酶源为碱性蛋白酶,其水解度为26.55%,显著优于其他蛋白酶（P＜0.05）。以碱性蛋白酶酶解鸡蛋清卵白蛋白,采用单因素和五元二次正交旋转试验研究酶解工艺;针对酶解前后卵白蛋白的功能特性进行分析,并采用紫外扫描、傅里叶红外变换光谱、差示扫描量热针对卵白蛋白及其酶解产物进行结构表征。结果发现,碱性蛋白酶酶解鸡蛋清卵白蛋白最佳工艺条件为反应温度52.5 ℃、反应时间5 h、pH 8.25、酶用量5 500 U/g、底物添加量5%,此条件下水解度为27.88%。酶解后产物表面巯基含量降低了3.6 mol/（L·g）,溶解度大幅度提高,起泡性降低了18.18%,泡沫稳定性降低了20.24%,乳化活性指数升高了13.56 m2/g,乳化稳定性提高了10.46%。同时,酶解后的卵白蛋白肽链发生了裂解,有序的二级结构被破坏,暴露出更多氨基酸残基,α-螺旋略有减少,β-转角相应增加,亲水基团也相应的增加。     

燕麦麸皮球蛋白的糖基化结构修饰及功能性变化

在氨基葡萄糖存在的条件下,利用转谷氨酰胺酶(transglutaminase,TG)对燕麦麸皮球蛋白糖基化结构修饰,进而探讨糖基化蛋白功能性质与结构之间的关系。结果表明,糖基化交联球蛋白的溶解性、乳化稳定性、起泡性及泡沫稳定性相比于未修饰的球蛋白都有明显的改善,但表面疏水性明显下降;另外,酶促糖基化球蛋白的变性温度和焓变值都有所下降,其二级结构变化为:α-螺旋结构相对含量呈增加趋势,β-折叠和β-转角结构相对含量呈下降趋势,无规卷曲结构相对含量几乎没变。经糖基化处理的球蛋白酪氨酸分子主要呈现"暴露态",色氨酸相对拉曼强度更趋近于"包埋态"。酶促糖基化球蛋白二硫键振动模式为t-g-t。通过对球蛋白、修饰球蛋白的功能特性与空间构象的比较分析,明确TG催化葡萄糖结合在燕麦麸球蛋白上,进一步明晰修饰蛋白功能特性与空间构象之间的构效关系。结果可为延长杂粮产业链提供良好的理论依据,同时可以为今后制备燕麦蛋白特定产品进行分子设计和重组提供基础数据。     

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.     

动态超高压均质对蛋清蛋白溶液的粒度和流变性影响

本实验以10%的蛋清蛋白溶液为研究对象,采用动态超高压均质处理,研究蛋清蛋白溶液平均粒度和流变性的变化。研究表明,10%的蛋清蛋白溶液的平均粒度随着压力的增加而出现明显减小的现象,其经过超高压均质后,由非牛顿流体的胀塑性流体转变为假塑性流体,均质后的蛋清蛋白溶液的表观黏度明显升高。     

燕麦β-葡聚糖流变特性的测定

以燕麦麸皮为原料提取β-葡聚糖，并通过ARl000流变仪和毛细管粘度计对其流变特性进行了研究。实验结果表明：β-葡聚糖溶液是一种非触变的假塑性流体体系，且假塑性随着浓度的升高而增强。一定条件下溶液同时表现出粘弹性质，但无屈服应力的存在。较之于其它几种常用的食品胶体，β-葡聚糖能产生更大的粘度及良好的口感。此外β-葡聚糖还具有较好的热稳定性，这些性质决定了它在用作食品增稠剂和稳定剂等方面有着巨大的前景。     

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.     

Relationship of Disulfide Bond Formation to Altered Rheological Properties of Oleic Acid Modified Egg White

Egg white modification with oleic acid (OEW) had no effect on disulfide bond formation during the thermal gelation process. Lower transition temperatures were seen for oleic acid treated egg white (70°C) relative to native egg white (EW) (74°C). Torsional failure testing showed increases of 60 and 100% for shear stress and strain at failure, respectively, of OEW over EW. Dialysis, pH-adjustment, and treatment with N-ethylmaleimide (NEM) lowered stress values while shear strain Was affected only by pH-adjustment. Scanning electron micrographs indicated a more dense structure for OEW than that of EW. No visible structural change was apparent due to treatment with NEM.     

Study of Thermal Properties of Oat Globulin by Differential Scanning Calorimetry

The thermal behavior of oat globulin was studied by differential scanning calorimetry (DSC). The effects of pH, salts, and of various structure perturbants upon thermal characteristics were determined. Raising or lowering pH from near neutrality reduced denaturation temperature. (T_d), enthalpy (ΔH) and cooperativity indicated by increase in width at half height (ΔT_1/2). The effect of salts on thermal stability was related to their position in the lyotrophic series and suggests involvement of hydrophobic interaction in the thermal stability of oat globulin. Increasing concentrations of urea progressively lowered T_d and ΔH and increased ΔT_1/2; sodium dodecyl sulfate (SDS) lowered ΔH without affecting T_d; ethylene glycol (EC) lowered T_d without changing ΔH. Dithiothreitol did not affect DSC characteristics suggesting that disulfide bonds do not contribute to the thermal response of oat globulin.     

传统高温炒制工艺对裸燕麦清蛋白和球蛋白特性的影响

通过扫描电子显微镜观察炒制裸燕麦清蛋白和球蛋白的形貌特征,并测定其理化特性及消化特性。结果表明：与未炒制裸燕麦清蛋白和球蛋白相比,炒制裸燕麦清蛋白和球蛋白颗粒变小,结构疏松;并且在弱碱性条件下,其黏度较高;传统高温炒制工艺导致裸燕麦清蛋白吸油性发生显著提高,球蛋白乳化性、乳化稳定性、吸油性及持水性均显著提高,但其对裸燕麦清蛋白和球蛋白消化特性均没有影响,也没有改变它们的非牛顿流体本质。     

燕麦β-葡聚糖溶液流体性能及其协同增稠效应研究

采用动态流变仪和乌氏粘度计测定动态粘度方法,系统研究燕麦β-葡聚糖流体力学性能和与 其它增稠剂协同增稠效应。     

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。     

Rheological Properties of Liquid Egg Products (LEPS)

Rheological properties were determined at 4°C (refrigerated temperature), 25°C (room temperature), 60°C (pasteurization temperature) for liquid whole egg (LWE) and liquid egg yolk (LEY) and 4, 25, 55.6°C for liquid egg white (LEW) by using concentric cylinder viscometer. The shear rate range was 8 to 53.7 s^?1 for LEW and LWE, and 1 to 34 s^?1 for LEY. Selected physical properties (e.g., density) of LEPs were studied at broad range of temperatures from 4°C to 60°C. All liquid egg products (LEPs) exhibited mildly shear thinning (pseudoplastic) behavior. Experimental data of LWE and LEW successfully fitted Herschel-Bulkley model, LEY data were well described by power law model. LEW and LWE showed thixotropy and time-dependency at their pasteurization temperatures (55.6°C for LEW, 60°C for LWE) and considered being time-independent below these temperatures. LEY exhibited time-dependent behavior at 4°C and 60°C. But its rheological behavior showed no thixotropy and time-dependency at room temperature. The density of all three products decreased with increasing temperature. Density data were correlated by polynomial models (r² > 0.99).     

蛋清肽的抗氧化稳定性与功能特性

选用胃蛋白酶水解冻干蛋清制得蛋清肽,测定蛋清肽的抗氧化稳定性及功能特性。研究温度和pH值对蛋清肽抗氧化稳定性的影响以及蛋清肽的乳化性、吸水能力和吸油能力。结果表明：随着蛋清肽质量浓度的增加其清除羟自由基( ·OH)、超氧阴离子自由基(O2－ ·)及DPPH自由基的能力均随之增加;温度与pH值对蛋清肽的抗氧化活性影响较大,在pH12.0条件下存放4h后其抗氧化活性消失;蛋清肽具有较好的乳化能力、乳化稳定性、吸油和吸水能力,这些均有利于其在食品和化妆品行业中的应用。     

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.     

鸡蛋清蛋白水解物的抗氧化性研究

本试验研究了利用Alcalase酶解鸡蛋清蛋白制取水解度为5～15％的酶解物并对其DPPH自由基清除能力、羟自由基清除能力、还原力进行了测定,同时对不同水解度的水解物的溶解度、表面疏水性和总游离巯基含量进行了测定.结果表明,酶解产物具有较低的表面疏水性和总游离巯基含量,同时DPPH自由基清除能力在最大蛋白浓度1.0 m...     

Composition and Gel-forming Properties of Vacuum-evaporated Liquid Egg White

Liquid egg-white was evaporated under vacuum (4.7 kPa) in a water-jacketed vessel to produce a concentrated, liquid egg white product. Three water-jacket temperatures (40, 50 and 60°C) and four processing times (0, 30, 45 and 60 min) were used. For the 60°C, 60-min treatment, solids content increased (p≤0.05) from 11.5% to 21.8%. Concentration did not affect (≥0.05) true gel strain but gel shear stress increased (p≤0.05) with increased solids concentration.     

Antioxidative Activity and Gelling Rheological Properties of Dried Egg White Glycated with a Rare Keto-hexose through the Maillard Reaction

ABSTRACT: The functional properties of egg white (EW) glycated with a rare D-psicose and 2 alimentary sugars (D-fructose and D-glucose) were investigated. Glycation led not only to the formation of cross-links but also to the formation of antioxidative substances to EW, the extent of which depended on the sugar used, modification, and incubation time. The temporal development of browning and fluorescence of psicose-EW was relatively faster than those of fructose-EW and glucose-EW. The psicose-EW showed the greater 2,3-bis (2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5carboxanilide (XTT) reducibility, 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid radical scavenging activity, and gelling rheological properties. These results indicated that psicose-EW as a food ingredient might have the ability to improve gelling behavior and decrease oxidation reactions during food processing and storage.     

液体咸蛋清的流变性质及其在工程设计中的应用

用旋转粘度计研究了液体咸蛋清在温度５～４５℃范围内，剪切速率在１７３～２７７０ｓ－１范围内的流变行为。推导出相应剪切应力作为剪切速率函数的幂律模型，并导出流变参数Ｋ和ｎ．参数Ｋ和ｎ是温度的函数。     

Effect of Concentration and Temperature on the Rheological Properties of Oat Milk

The rheological behavior of oat milk (Avena sativa L.) at different concentration (5, 10, 15, and 20 °Brix) was studied in the temperature range of 10, 20, 30, and 40 °C using a controlled stress rheometer. Power law model adequately described the flow behavior of oat milk (0.881–0.987). The value of flow behavior index (n) was less than unity (0.19–0.68) at all temperature and concentration range indicating the shear-thinning (pseudoplastic) nature of oat milk. Consistency index (k) increased with soluble solids concentrations and decreased with temperature. The Arrhenius equation adequately described the effect of temperature on the viscosity. The activation energies for flow of oat milk quantified using Arrhenius equation increased with solid concentration and ranged from 7.43 to 303.64 kJ/mol. The effect of concentration on the viscosity followed the exponential model. The empirical model obtained from the study could well-describe the combined effect of temperature and concentration within the range of the study. It was concluded that temperature and concentration had a significant effect on the rheology of the oat milk.