不同提取方法下米渣蛋白理化性质和聚集态的研究

实验采用碱提酸沉和稀碱脱脂除杂的方法,分别得到两种米渣蛋白(碱提蛋白、除杂蛋白)。测定两种蛋白的功能性(溶解度、乳化性),实验显示,在p H 2.0~p H 11.0范围内,两种蛋白的溶解性和乳化性均呈现先降低后升高的趋势,碱提蛋白相比除杂蛋白,具有更好的溶解性和乳化性。为了更好地分析两种蛋白性质差异性,实验通过测定蛋白的表面疏水性、粒度、分子量和表面微观形态,表征两种蛋白的聚集态变化。碱提蛋白具有高的表面的疏水性和更小的粒度,通过扫描电镜观察发现,碱提蛋白呈现表面粗糙的颗粒堆积,而除杂蛋白表面较平滑,蛋白颗粒呈现相互团聚交联的状态。实验表明,两种提取方法得到的蛋白形成了不同的聚集态,与除杂蛋白相比,碱提蛋白具有更小的聚集体颗粒,同时暴露出更多的疏水性基团,使其表面疏水性高于除杂蛋白,从而表现出更高的溶解度和乳化性。     

Functional properties of plant proteins. Part 8. Effect of succinylation on some functional properties of the main globulin fraction from rapeseed (Brassica napus L.)

The changes of some functional properties - solubility, emulsifying and foaming properties, heat-induced aggregation - of a native rapeseed globulin preparation after succinylation has been studied. In correspondence with the results obtained with the purified rapeseed 12 S globulin and other globulin preparations from plant seeds, a total blocking of the amino groups of the rapeseed globulin could not be attained. The highest degree of modification reached was 83%. The unmodified protein has high foam capacity and stability. Succinylation until 61% did not change these properties. The emulsifying activity and emulsion stability were slightly improved after a modification at a low or moderate level. The heat-coagulation of the native protein is depressed by increasing succinylation.     

NaCl对大菱鲆肌原纤维蛋白特性的影响

以大菱鲆肌原纤维蛋白为对象,考察不同NaCl浓度（0.1、0.2、0.3、0.4、0.5、0.6?mol/L）下肌原纤维蛋白的溶解度、乳化性、化学作用力（离子键、氢键、疏水相互作用）、巯基的变化,并对其二级结构以及流变学特性进行测定。结果表明,随着NaCl浓度的增加,大菱鲆肌原纤维蛋白的溶解度、乳化活性、乳化稳定性、总巯基和活性巯基含量均不断增加;离子键、氢键呈先增加后下降趋势,疏水性相互作用呈先下降后增加的趋势;蛋白质二级结构呈现由螺旋向折叠转化的趋势,其他二级结构无明显变化;肌原纤维蛋白储能模量（G’）不断增加,其中以NaCl浓度0.6?mol/L的实验组储能模量最大。综上所述,NaCl浓度为0.6?mol/L时,大菱鲆肌原纤维蛋白的各项指标良好。     

Foaming and emulsifying properties of pea albumin fractions and partial characterisation of surface‐active components

Whole albumin of pea seed (Palb) was extracted from pea flour (var Frilene) by solubilisation at pH 4.9 and dialysis against water. Palb was fractionated by differential solubilisation in 60% methanol, yielding a soluble (S60) and an insoluble (IS60) fraction. The composition of the fractions was determined by SDS‐PAGE and RP‐HPLC. Albumins exhibited a wide variability of surface hydrophobicity. Albumin PA2 was present as a major component in Palb and IS60. Low‐MW hydrophobic albumins were concentrated in S60. Foaming and emulsifying properties of the three extracts were determined in model conditions. Functionality of albumins was highest at acid pH, but the fractions differed in their properties. The presence of PA2 albumin resulted in the best foaming and emulsifying properties. This protein was shown to adsorb preferentially at air/water and oil/water interfaces, whereas low‐MW hydrophilic albumins did not. Low‐MW hydrophobic albumins were also adsorbed at interfaces, as shown by the behaviour of the S60 fraction, but they formed more fragile films than did PA2. This was related to the structure of the polypeptide chains. © 2000 Society of Chemical Industry     

Partial Lipid Extraction of Egg Yolk Powder: Effects on Emulsifying Properties and Soluble Protein Fraction

Egg yolk powder was partly defatted using hexane, 95% ethanol, isopropanol, chloroform-methanol (2:1, v:v) hexane-isopropanol (77:23, w:w) and hexane-ethanol (77:23, w:w). Hexane-isopropanol was most efficient, extracting more than 50% of the lipid. Protein solubility and emulsifying activity of the extracted powder decreased after extraction. Hexane-isopropanol reduced emulsifying activity about 14% and protein solubility to 13.8% from 15.7%. Extraction with other solvents resulted in up to 41% loss of emulsifying activity; protein solubility decreased to as low as 3%. Ovalbumin in the water-soluble fraction of extracted egg yolk powder reduced its emulsifying effectiveness.     

Emulsifying properties of proteins extracted from Australian canola meal

Canola protein albumin fraction, globulin fraction, and canola protein isolate (CPI) were compared to commercial soy protein isolate (SPI) in terms of their emulsifying properties at various pH values. The globulin fraction had higher emulsifying capacity (EC), higher emulsifying activity index (EAI), and the droplet size of emulsions it stabilized was consistently smaller irrespective of pH compared to albumin fraction or CPI. In comparison to SPI, globulin fractions also had higher EC at all pH values tested, higher EAI at acidic pH, and smaller or comparable average emulsion droplet size at both pH 4 and 7. The stability of canola protein based emulsions were comparable to those of SPI based emulsions at most pH values (except the emulsion stabilized by the CPI at pH 4), with no significant (p > 0.05) changes in droplet size during storage for up to 7 days at room temperature. These emulsions, however, experienced separation into the emulsion and serum phases after 24 h storage at room temperature with the exception of CPI- and SPI-stabilized emulsions at pH 9. This study demonstrates the comparable emulsifying properties (forming or stabilizing) of some canola proteins to commercially available SPI, suggesting the potential use of canola proteins in food applications.     

Physicochemical properties of hydrophobic and hydrophilic peptides from oyster protein

The physicochemical properties of the hydrophilic peptides (HIPs) and the hydrophobic peptides (HOPs) from the oyster protein hydrolysates (OPHs) were analysed. The technology of high-performance liquid chromatography and dynamic light scattering was used to determine the molecular weights and the particle sizes of HIP and HOP. About 60–70% of them had a molecular weight below 500 Da and the particle size was all about 100 nm, which were smaller than OPH. Furthermore, compared with OPH and HIP, HOPs have obvious advantages in surface hydrophobic and emulsifying properties because they have more hydrophobic groups on the surface. The emulsifying activity and emulsion stability of HOP can be significantly improved from 3.80 to 42.88 m² g⁻¹ and 131.17–163.70 min, respectively, because of its high surface hydrophobicity. Thus, our results suggest that HOPs have a great potential to be developed as an emulsifier.     

Functional Properties of a Peptide of 23 Residues Purified from the Peptic Hydrolyzate of asl-CASEIN: Changes in the Emulsifying Activity During Purification of the Peptide

The pH 4.6-soluble fraction of the peptic hydrolyzate of as 1-casein contained the 23 N-terminal residues, αsl-CN(fl-23), as a major pep-tide. Reversed-phase HPLC indicated that small amounts of other peptides such as αsl-CN(f154-199) were also contained in this fraction. By removing of these peptides, the emulsifying activity (EA) of the αsl-CN(fl-23) fraction was markedly decreased. However, when the removed peptide fraction was added to the purified αsl-CN(fl-23), the EA was increased. Some synergistic effect in the emulsification seemed to exist between αsl-CN(fl-23) and the other peptides. Although the purified αsl-CN(fl-23) had low EA values at neutral pH levels, it showed high emulsifying and surface activities in the acidic pH region.     

大豆分离蛋白与麦芽糊精的Maillard反应性及产物乳化性质研究

以SDS-聚丙烯酰胺凝胶电泳和毛细管电泳研究了大豆分离蛋白-麦芽糊精的Maillard反应形成的共聚物。电泳分析表明:7S亚基与麦芽糊精的反应性较高,而且在文中所研究的蛋白质与多糖质量比的范围内,7S亚基都能与麦芽糊精发生定量的共聚合反应,形成分子特性高度一致的共聚物;而11S亚基与麦芽糊精间的反应性较低,共聚物的分子特性受蛋白质与多糖质量比的影响。共聚物在pH7.0和pH4.5时的乳化性能优于酪朊酸钠,尤其是在pH4.5时具有优良的乳化稳定性。但在较高NaCl浓度时的乳化活性与大豆分离蛋白相比没有明显的改善,其乳化稳定性则明显优于酪朊酸钠。     

Conditions Affecting Emulsifying Properties of Egg Yolk Phosvitin

The effects of protein concentration (0.1–2.0%), oil volume fraction (0.17–0.67), mixing speed (10,000–22,000 rpm) and mixing time (0.5–8 min) on the emulsifying properties of phosvitin and bovine serum albumin (BSA) were compared. Emulsifying activity and emulsion stability increased with protein concentration, oil volume fraction and mixing. Effects of these variables were assessed quantitatively using an empirical equation. Mixing speed had the greatest influence and protein concentration had the least influence on emulsifying activity for both phosvitin and BSA. For emulsion stability, mixing speed had the greatest influence for phosvitin; oil volume fraction had the greatest influence for BSA. Phosvitin was a better emulsifier than BSA at pH7.     

高压微射流处理对大豆分离蛋白构象及功能特性的影响

通过测定溶解度、乳化性、疏水性和运用差示扫描量热仪分析(DSC)和圆二色光谱(CD)分析探讨不同压力微射流处理(HPM)对大豆分离蛋白(SPI)构象和功能特性的影响。HPM诱导不溶性蛋白聚合物解聚,增加SPI的溶解度、乳化活性指数和疏水性。DSC图谱结果表明,处理后的SPI变性温度基本维持不变,但变性焓值呈现下降趋势。CD光谱分析表明,HPM对SPI的二级、三级结构没有明显的影响。     

Structural characterization and functional properties of egg white protein treated by electron beam irradiation

This study investigated the functional properties and structural characteristics of egg white protein (EWP) powder treated by electron beam irradiation (EBI) at the doses of 5, 10, 20, 30, 50, 70 and 100 kGy. In comparison with the untreated sample (0 kGy), the EBI-induced EWP showed generally better solubility and higher antioxidant capacity by ABTS•⁺ radical scavenging assay. Furthermore, the emulsifying activity index of EBI-induced EWP increased with increased EBI dose, reaching the maximum value of 15.8 ± 0.4 m²/g at 100 kGy. The emulsifying stability index and ϛ-potential of EBI-induced EWP showed fluctuating tendencies. These functional property changes of protein were attributed to the conformational changes caused by EBI. SDS-PAGE patterns confirmed that high-dose EBI would result in protein depolymerization to low-mass molecules at 11 kDa, contributing to the increased solubility. Circular dichroism data demonstrated that EBI-induced EWP exhibited partial denaturation and a flexible structure, which was responsible for the improved emulsifying properties. Fluorescence spectra revealed that high EBI doses led to an increase in the polar environment around tryptophan, which could enhance the solubility and antioxidant activity of EWP. In addition, high EBI doses decreased the content of free and total sulphydryl groups, and changed the intermolecular forces of protein, including ionic bonds, hydrogen bonds, hydrophobic interactions, and disulfide bonds. These findings can provide solid support for practical applications of EBI technology in EWP food processing.     

Isolation and investigation of emulsifying properties of surface-active substances from rice bran

Surface-active substances were isolated from defatted rice bran. They were 70:30 w/w ethanol/water soluble and could be further divided into n-hexane soluble fraction (fraction A) and n-hexane insoluble fraction (fraction B). For both the fractions emulsifying properties (i.e., interfacial tension, emulsion droplet diameter, emulsifying activity, and emulsion stability), were investigated and compared to those of a commercial emulsifier Atmos 150 or Tween 20. It was found that fraction A produced lower interfacial tension data and smaller droplet sizes than those of fraction B and showed, at concentrations ⩾0.7 wt%, similar emulsifying properties to those of Atmos 150. Fraction B, however, was found to have inferior emulsifying properties to those of the fraction A and Tween 20. The main substances in fraction A responsible for the emulsifying properties and mechanisms involved need to be studied.     

Lipophilization of β-lactoglobulin: Effect on Hydrophobicity, Conformation and Surface Functional Properties

β-Lactoglobulin was chemically modified by attaching different levels of stearic acid, and the effect on hydrophobicity, emulsifying and foaming properties was investigated. Incorporation of the hydrophobic ligands led to increased hydrophobic interactions, resulting in a decreasing solubility with extent of incorporation. Surface hydrophobicity measurements showed that the two fluorescence probes 8-anilinonaphthalene-1-sulfonate (ANS) and cis-parinaric acid (CPA) used were not equivalent. Some improvement of emulsifying and foaming properties was observed at low and medium levels of incorporation which decreased as the extent of fatty acid attachment further increased. High solubility and ANS surface hydrophobicity were both needed for the best emulsifying properties.     

Changes in the physicochemical,structural and emulsifying properties of chicken myofibrillar protein via microfluidization

Microfluidization is a novel and effective technology to improve the properties of myofibrillar protein. The effects of microfluidization with varying pressures (0–120 MPa) on the physicochemical, structural and emulsifying properties of chicken myofibrillar protein (CMP) were studied. Microfluidization treatment remarkably increased the absolute ζ-potential, contact angle, solubility, emulsifying ability and emulsifying stability of CMP. Simultaneously, the turbidity of CMP decreased. After microfluidization treatment, more α-helix structures were transformed into disordered structures, more hydrophobic and negatively charged groups were exposed, leading to improvements in CMP properties. After 90 MPa treatment, the absolute ζ-potential, storage modulus, loss modulus and dynamic apparent viscosity of CMP-camellia oil emulsion reached the maximum values. The hydrophobic interaction between CMP and camellia oil induced CMP to expose more hydrophobic and negatively charged groups, leading to the improved emulsifying properties of CMP. Our results demonstrate that microfluidization treatment has great potential to improve the product qualities of emulsion-type meat products.     

罗非鱼头蛋白质的提取及性质研究

以罗非鱼头为原料,采用加热浸提、酶法水解、酸/碱溶解-等电点沉淀法提取鱼蛋白,冷冻干燥得到4种鱼蛋白粉,分别记为热提鱼蛋白(HFP)、酶解鱼蛋白(EFP)、酸溶鱼蛋白(AFP)和碱溶鱼蛋白(ALFP),并探讨了4种鱼蛋白的营养特性、溶解性和乳化性。结果表明:ALFP和AFP的蛋白含量分别为89.97%和85.87%,必需氨基酸占总氨基酸的比例达到49.72%和48.63%,而脂肪和灰分含量以及白度值均低于HFP和EFP,且差异显著(P<0.05)。溶解性和乳化性的研究显示,EFP和HFP在pH 2.0～10.0内溶解度均高于93%,但体系的乳化活性和稳定性较差;而AFP和ALFP的溶解度随pH值的变化非常明显,在pH 4.0～6.0内,体系的溶解性和乳化性极差,而在pH值低于4.0或高于6.0时,溶解度大大增强,乳化活性和乳化稳定性随之提高,且乳化活性和稳定性明显高于HFP和EFP。酸/碱溶解-等电点沉淀法可用于制备营养价值高,乳化特性相对较好的鱼分离蛋白。     

Emulsifying and structural properties of pectin enzymatically extracted from pumpkin

The present study investigated the emulsifying and structural properties of pectin enzymatically extracted from pumpkin. Pumpkin pectin fraction A was obtained from raw pumpkin with an enzymatic preparation of cellulase and α-amylase. Pumpkin pectin fraction B was achieved by treating the fraction A solution with pronase to reduce protein content. According to the findings (on protein content, galacturonic acid content, neutral sugar composition, and molecular weight distribution), the pronase treatment could remove protein from the fraction A without considerably influencing any other chemical and molecular properties. Moreover, the fraction A exhibited emulsifying properties in water and oil mixture, whereas the removal of protein in the fraction B resulted in the loss of emulsifying properties. The FT-IR and 1D NMR analysis revealed that the backbone of pumpkin pectin is mainly composed of α-1,4-d-galacturonic acid in which a considerable portion of galacturonic acid residues is present as methyl esters, and some l-rhamnose are involved in the linear region of the backbone through α-1,2-linkages.     

Emulsifying Property of Whey Peptide Fractions as a Function of pH and ionic Strength

Solubility and emulsifying properties of whey protein concentrate (WPC), heat-treated WPC (90°C, pH 2.5, 10 min), and their tryptic or chymotryptic peptide fractions obtained by ultrafiltration were measured from pH 3 to 9 at two ionic strengths (uμ=0 and 0.6). There was no correlation between solubility and emulsifying capacity (EC). Heat treatment induced some conformational changes in WPC, resulting in better EC. Some peptide fractions had better EC than proteins at pH 7 and 9. Treatments resulting in more hydrophobic peptides or a higheT content of larger peptides produced fractions with better emulsifying properties. pH and ionic strength affected conformation and emulsifying properties of proteins and peptides.     

花生球/伴球蛋白富集组分的制备及其物化与功能特性研究

本文以低温脱脂花生粉为原料,采用冷沉法分离制备了花生球蛋白和伴球蛋白富集组分,并研究了两种组分的物化和功能特性。通过冷沉法所制备花生球/伴球蛋白富集组分的蛋白含量分别为91.27%和84.87%,蛋白的纯度分别为93.1%和71.4%。研究结果表明,该法制备的花生球蛋白富集组分相比伴花生球蛋白富集组分和花生分离蛋白,具有更低的热变性程度和更高的热稳定性。而伴花生球蛋白富集组分和花生分离蛋白相比花生球蛋白富集组分具有更加松散的三级构象和更高的表面疏水性。花生球蛋白富集组分展示了更高的溶解性（pH 6.0处除外）。乳化活性和稳定性按从高到低的排序为花生球蛋白富集组分、伴花生球蛋白富集组分和花生分离蛋白。伴花生球蛋白富集组分的溶解性在pH值3.0~6.0的范围内变化最为敏感并表现出在中性条件下最佳的凝胶特性。     

Application of ultrasound treatment for modulating the structural,functional and rheological properties of black bean protein isolates

The modulating effect of ultrasound treatments at varying powers and times on the structural and functional properties of black bean protein isolate (BBPI) was investigated. Compared with native BBPI, low-power (150 W) and medium-power (300 W) ultrasound treatments increased the solubility, foaming and emulsifying properties of BBPI, especially at 300 W, 24 min. This effect arises predominantly due to increased exposure of hydrophobic groups, which serve to increase the interactions between the protein and water molecules. Additionally, an increase in the protein surface activity improved the absorption of protein molecules at the oil–water and air–water interfaces. Rheology data showed that increased hydrophobic and hydrogen-bonding interactions improved the water-holding capacity of BBPI gels following ultrasound treatment. However, high-power (450 W) ultrasound treatment weakened the functional properties of BBPI, and this was likely due to the formation of macromolecular BBPI aggregates. Overall, this study indicates that ultrasound treatment could be a promising approach for modulating other plant protein resources as well as expanding the application of black bean protein.