Physicochemical and emulsifying properties of mung bean protein isolate as influenced by succinylation

The application of mung bean protein in foods is limited due to its poor functionality. Acylation with succinic anhydride could be used to improve the functionalities of protein. In this study, the influence of the weight ratio of succinic anhydride to protein (0–0.10) on the degree of N-acylation, physicochemical properties and protein functionalities including emulsifying properties of mung bean protein isolates (MPI) were investigated. The extent of N-acylation of MPI increased as the succinic anhydride:protein ratio increased, while the ζ-potential at neutral pH decreased. In addition, succinylation had an impact on the average particle size of MPI depending on the succinic anhydride:protein ratio. Succinylation had no impact on the total and exposed free sulfhydryl groups. Moreover, the isoelectric point (pI) of the succinylated proteins shifted from pH 5 to lower pH. Succinylation increased the emulsifying activity index (EAI), while the impact on the emulsion stability index depended on the succinic anhydride:protein ratio. Thus, succinylation at low succinic anhydride:protein ratio can alter mung bean protein charge and affect physicochemical and functional properties especially emulsifying properties that could be used to increase its utilization.     

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.     

3种天然酚类物质对大豆油脂体稳定性及体外消化性的影响

本研究旨在探讨儿茶素、白藜芦醇和没食子酸3种天然酚类物质对大豆油脂体理化稳定性及其消化特性的影响.结果表明,儿茶素和白藜芦醇可显著降低油脂体平均粒径(P＜0.05),而没食子酸对油脂体平均粒径影响较小;浓度为30 μmol/L的儿茶素和白藜芦醇可以使油脂体的平均粒径由未添加时的(15.29±0.28)μm分别下降至(0...     

酶解产物浓度和油相体积分数对甘薯蛋白酶解产物乳化特性的影响

本文研究了酶解产物浓度(0.10%、0.25%、0.50%、0.75%和1.00%,m/V)和油相体积分数(5%、15%、25%、35%和45%,V/V)对超高压下酶解制得甘薯蛋白酶解产物乳化液显微结构、乳化颗粒平均粒径(d4,3)、乳化活性指数(EAI)、乳化稳定性指数(ESI)和流变学性质的影响。当酶解产物浓度较低和油相体积分数较高时,乳化液的乳化颗粒均一细小。增加甘薯蛋白酶解产物浓度会使其乳化液的d4,3、EAI和ESI均逐渐降低;相反,增加油相体积分数会使乳化液的d4,3逐渐减小,EAI逐渐增大,而ESI则先降低后增加(p0.05)。在酶解产物浓度低和油相体积分数高时,乳化液的初始表观粘度较大,且在1~100 s-1的剪切速率范围内均表现出了剪切变稀现象。酶解产物浓度和油相体积分数与乳化液的d4,3、EAI、ESI和流变学性质密切相关,是影响甘薯蛋白酶解产物乳化特性的重要因素。     

Combined effects of limited enzymatic hydrolysis and high hydrostatic pressure on the structural and emulsifying properties of rice proteins

The combined effects of limited enzymatic hydrolysis and high hydrostatic pressure (HHP) treatment on the structural and emulsifying properties of rice proteins (RPs) were investigated. Alcalase exhibited higher hydrolysis efficiency than papain. Through alcalase-catalyzed hydrolysis and HHP treatment, emulsifying activity index (EAI) and emulsifying stability index (ESI) of RPs were improved from 14.58 m²/g and 22.54 min to 29.93 m²/g and 43.35 min, respectively. The content of random coil in RPs increased, while the content of α-helix decreased. HHP at 300 MPa led to the highest surface hydrophobicity (H₀) and fluorescence intensity. The enzymatic hydrolysis-HHP (300 MPa) modified RPs could form an oil-in-water emulsion with a d_4,3 of 0.347 nm, ζ-potential of −36.4 mV, and creaming index of 10.5% after 7 days storage. This work sheds light on employing limited enzymatic hydrolysis and HHP to modify RPs for better application in emulsion-based food products.     

Emulsifying properties of sweet potato protein: Effect of protein concentration and oil volume fraction

The effect of protein concentrations (0.1, 0.25, 0.5, 1.0, 1.5 and 2.0% w/v) and oil volume fractions (5, 15, 25, 35 and 45% v/v) on properties of stabilized emulsions of sweet potato proteins (SPPs) were investigated by use of the emulsifying activity index (EAI), emulsifying stability index (ESI), droplet size, rheological properties, interfacial properties and optical microscopy measurements at neutral pH. The protein concentration or oil volume fraction significantly affected droplet size, interfacial protein concentration, emulsion apparent viscosity, EAI and ESI. Increasing of protein concentration greatly decreased droplet size, EAI and apparent viscosity of SPP emulsions; however, there was a pronounced increase in ESI and interfacial protein concentration (P < 0.05). In contrast, increasing of oil volume fraction greatly increased droplet size, EAI and emulsion apparent viscosity of SPP emulsions, but decreased ESI and interfacial protein concentration significantly (P < 0.05). The rheological curve suggested that SPP emulsions were shear-thinning non-Newtonian fluids. Optical microscopy clearly demonstrated that droplet aggregates were formed at a lower protein concentration of <0.5% (w/v) due to low interfacial protein concentration, while at higher oil volume fractions of >25% (v/v) there was obvious coalescence. In addition, the main components of adsorbed SPP at the oil–water interface were Sporamin A, Sporamin B and some high-molecular-weight aggregates formed by disulfide linkage.     

Effect of pH and NaCl/CaCl2 on the solubility and emulsifying properties of sweet potato protein

BACKGROUND: The effects of NaCl and CaCl₂ on the solubility and emulsifying properties, namely emulsifying activity index (EAI) and emulsion stability index (ESI) of sweet potato proteins (SPPs) at pH 1–10, were investigated. RESULTS: At lower NaCl (0.1 mol L^?1) and CaCl₂ (0.05 mol L^?1) concentrations, the solubility profiles of the SPPs were very similar to those in distilled water, and the lowest solubility occurred at pH 4. Increased NaCl and CaCl₂ concentration resulted in lower SPP solubility in most of the pH studied (P < 0.05). At pH < 3, NaCl improved the EAI of SPP while at pH > 7 it reduced the EAI of the SPP (P < 0.05). Moreover, addition of NaCl also resulted in reduction of ESI of the SPP in most of the pH studied (P < 0.05). On the other hand, the presence of 0.2 mol L^?1 CaCl₂ rendered the EAI and ESI of the SPPs independent of the influence of pH. CONCLUSION: The present studies show that pH and salts modified the emulsifying properties of the SPPs, and CaCl₂ at a certain concentration could be used to improve the emulsifying properties of the protein. Copyright © 2008 Society of Chemical Industry     

Relationship between physicochemical and functional properties of amaranth (Amaranthus hypochondriacus) protein isolates

Protein isolates from six amaranth lines/cultivars (APIs) were evaluated to study their physicochemical (hunter colour, protein content and zeta potential), structural (thermal and conformational) and functional (emulsification, foaming, water and fat absorption) properties. APIs had protein content, whiteness index and gel temperature in range of 79.4–85.4%, 41.17–54.26 and 87.8–91.8 °C, respectively. The Fourier‐transform infrared spectra of APIs revealed α‐helix, β‐sheets and random coil conformations in the secondary structure. APIs with higher relative proportion of β‐sheets had higher Differential Scanning Calorimeter denaturation temperature and gel temperature. Minimum protein solubility (PS) was observed at pH 5.0, indicating isoelectric point (pI) of amaranth proteins. The PS, emulsifying activity index (EAI), emulsifying stability index (ESI), foaming capacity (FC) and foam stability (FS) of APIs at neutral pH were related to their zeta potential (ζ). The emulsifying and foaming properties were also determined at different pHs (between 2.0 and 9.0). The EAI‐pH profile of APIs confirmed close relationship between the emulsifying ability and PS.     

The amino acid composition,solubility and emulsifying properties of sweet potato protein

A protein was purified from the high-protein type sweet potato variety 55-2 available in China. The amino acid composition, solubility and emulsifying properties of the sweet potato protein (SPP) were studied. The SPP was rich in aspartic acid (18.5%) and glutamic acid (9.30%) while essential acid amino acids made up approximately 40.7% of the SPP. The SPP was highly soluble in distilled water over a wide range of pH. However, solubility of the SPP in 1.0 M NaCl and 1.0 M CaCl₂ solutions was low especially at pH below the pI of the SPP. The SPP in CaCl₂ demonstrated emulsifying activity index (EAI) and emulsion stability index (ESI) many folds higher than those in distilled water and NaCl solution (P < 0.05).     

草鱼肌原纤维蛋白-葡萄糖糖基化产物的理化特性及乳化特性研究

选取葡萄糖作为糖基供体对草鱼肌原纤维蛋白进行糖基化修饰,探讨糖基化产物理化性质及其乳化性能。草鱼肌原纤维蛋白与葡萄糖按质量比1:2混合,在相对湿度为44%、50 ℃条件下进行糖基化反应,测定产物的糠氨酸含量、荧光强度、游离氨基含量、蛋白质二级结构以及乳化性和乳化稳定性。结果表明:随着加热时间的延长,糠氨酸含量和荧光强度呈现先增大后降低的趋势,游离氨基含量和褐变强度ΔE持续增加(p<0.05),其中在反应48 h时,糠氨酸含量达到最大值((4.09±0.07) mg/100 mg样品);二级结构分析表明,糖基化对草鱼肌原纤维蛋白的二级结构影响较小。此外,糖基化修饰显著提高了草鱼肌原纤维蛋白的乳化性能(p<0.05),且经过48 h制备的糖基化产物的乳化活性及乳化稳定性最高,分别为未反应草鱼肌原纤维蛋白的1.32倍(p<0.05)和1.53倍(p<0.05)。进一步通过相关性分析发现,草鱼肌原纤维蛋白的乳化性受糖基化反应程度的影响。     

Effects of high hydrostatic pressure on the physicochemical and emulsifying properties of sweet potato protein

The influence of high hydrostatic pressure (HHP) treatment on the physicochemical and emulsifying properties of sweet potato protein (SPP) at various concentrations, e.g. 2%, 4% and 6% (w/v, SPP‐2, SPP‐4 and SPP‐6), was investigated. Significant differences in hydrophobicity, enthalpy of denaturation and solubility were observed (P < 0.05). Emulsifying activity indexes (EAI) of SPP‐2 and SPP‐6 increased at 400 MPa, whereas EAI of all SPP significantly decreased at 600 MPa (P < 0.05). Emulsion stability (ESI) was significantly decreased for SPP‐2 and SPP‐6, while increase in ESI was observed for SPP‐4 above 200 MPa (P < 0.05). SPP‐2 emulsions showed sharp decrease in apparent viscosity with pressure increase, while pseudo plastic flow behaviour was not changed for all of emulsions. Sporamins A and B were well‐adsorbed in pressurised emulsion without displacement. These results suggest that HHP treatment could be used to modify the physicochemical and emulsifying properties of SPP.     

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.     

温度对不同油料作物油脂体理化稳定性的影响

以大豆、花生和葵花籽油脂体为研究对象,分析不同油料作物种子和油脂体组成之间的差异,通过考 察不同温度处理后油脂体ζ-电位和平均粒径、乳化特性以及氧化稳定性的变化,研究温度对不同油料作物油脂 体理化稳定性的影响。结果表明：从不同油料作物中提取的油脂体基本组成成分及提取率之间均存在较大差 异;大豆油脂体的ζ-电位显著高于葵花籽和花生油脂体（P＜0.05）,平均粒径显著低于葵花籽和花生油脂体 （P＜0.05）;随着温度的升高,大豆和花生油脂体平均粒径变化趋势平稳;温度由30 ℃升至80 ℃过程中,大豆和 花生油脂体乳化活性分别由（61.32±1.19）、（57.50±0.30）m2/g降低至（51.99±0.90）、（40.13±1.51）m2/g, 而葵花籽油脂体乳化活性在50～70 ℃时显著高于30～40 ℃和80～90 ℃（P＜0.05）;大豆、花生和葵花籽油脂 体在4 ℃和25 ℃贮存条件下具有良好的氧化稳定性,但花生油脂体氧化程度显著高于大豆油脂体和葵花籽油脂体 （P＜0.05）。研究表明,油脂体具有良好的热稳定性,不同油料作物来源的油脂体在不同温度条件下的理化性质 存在差异。     

鲤鱼鱼肉蛋白酶水解物抗氧化性及功能特性

采用碱性蛋白酶对鲤鱼鱼肉蛋白进行酶解,制备不同水解度的水解物。测定水解物的抗氧化活性以及不同pH值条件下水解物的功能特性。结果表明:随着水解度的逐渐升高,水解物的抑制脂质氧化能力、D PP H自由基清除能力、还原能力以及金属离子(Cu2+和Fe2+)螯合能力逐渐增加(P<0.05);同时,水解物的溶解性、乳化性和起泡性都在pH值为4.0(等电点)时达到最低,而后溶解性和乳化性随着pH值升高而增大(P<0.05),而起泡性随着pH值的升高先上升后又下降。因此,鲤鱼鱼肉蛋白碱性蛋白酶水解物可以提高蛋白质的抗氧化活性和溶解性,但是较高的水解度会在一定程度上降低其乳化性和起泡性。     

Characterization of emulsions prepared by egg yolk phosvitin with pectin,glycerol and trehalose

Effect of pectin (34–40% esterification), glycerol and trehalose at two concentrations (0.1% and 0.5%, wt./wt%) on physicochemical and emulsifying properties of phosvitin (Pv) was investigated under the mild conditions (oil volume fraction, 0.25; protein concentration, 5 mg/mL; 10 mM sodium phosphate buffer, pH 7.0). Pv showed better emulsifying properties than sodium caseinate (Sc). Glycerol (0.5%) significantly increased the emulsifying activity index (EAI) of Pv from 19.8 to 20.9 and the emulsion stability index (ESI) from 67.6 to 75.1. The higher ESI of Pv was also obtained by 0.1% pectin and 0.5% trehalose. The results obtained from circular dichroism (CD) spectra indicated that all the tested additives displayed slight effect on the unfolded structure of Pv. Furthermore, fluorescence pattern demonstrated that glycerol and trehalose increased the hydrophobicity of Pv, while pectin displayed an opposite effect. All emulsions exhibited a shear-thinning behavior and the flow behavior was fitted to the power law model. Frequency sweeps of the emulsions illustrated that they behaved like a viscous liquid.     

A comparative study of physicochemical and conformational properties in three vicilins from Phaseolus legumes: Implications for the structure–function relationship

The polypeptide constituents, physicochemical and conformational properties of three vicilins from kidney, red and mung beans, fractionated using combined acid extraction and ion-exchange chromatographic techniques, were characterized and compared. The tested physicochemical and conformational properties included amino acid composition, surface charge and hydrophobicity, protein solubility (PS; as a function of pH), emulsifying activity index (EAI) and emulsion stability index (ESI), as well as secondary, tertiary and/or quaternary conformations. The amino acid composition (especially relative acidic/basic charged amino acid ratio, and the percentage of polar uncharged amino acids) was an intrinsic physicochemical parameter that largely determined other physicochemical and conformational properties. The PS and EAI (and ESI) of these vicilins at various pH values were associated with each other, and both were closely related to their surface charge and/or hydrophobicity. Far-UV CD spectral analyses indicated that these vicilins exhibited similar secondary structure compositions at pH deviating from the isoelectric point (about pH 4.5). However, their tertiary and/or quaternary conformations, as determined by differential scanning calorimetry, intrinsic fluorescence and near-UV CD spectroscopy, remarkably varied. At pH 7.0 or 9.0, there were close relationships between the EAI and the flexibility in quaternary conformation, and between the ESI and the flexibility in tertiary conformation. This is the first observation to elucidate the importance of tertiary and/or quaternary conformations for the emulsifying properties of legume vicilins. Additionally, an underlying mechanism of the emulsification process for the vicilins (trimeric form) with excellent emulsifying properties was proposed.     

Properties of beta-lactoglobulin/alginate mixtures as a function of component ratio,pH and applied shear

The objective of this research was to establish effects of selected process parameters (component ratio, pH, shear) on the properties of alginate (Alg)/beta lactoglobulin (βlg) mixtures. Effects were assessed by measuring apparent viscosity, particle size, ζ-potential, hydrophobicity and conformational changes (FTIR). Intrinsic viscosity and critical concentrations were also investigated. Intrinsic viscosity of individual Alg and βlg solutions increased with pH. Shearing of Alg/βlg mixtures resulted in greater apparent viscosity at pH 3 which declined proportional to increase in pH. Particle size and surface hydrophobicity were higher at pH 3 and directly related to Alg concentration. Shear induced changes were observed in the secondary structure of βlg in the βlg/Alg mixtures associated with β-sheet conformations shifting from 1635.64 to 1633.71/cm and occurred only at pH 5. Under certain conditions, application of shear could manipulate and create different structures from these two biopolymers.     

Stability of flocculated particles in concentrated and high hydrophilic solid layer-by-layer (LBL) emulsions formed using whey proteins and gum Arabic

The objective of the present study was to investigate flocculation in layer-by-layer (LBL) emulsion systems with high total solids content and deflocculation at various pH conditions, and the effects of whey protein isolate (WPI) concentration and total solids content on the stability of LBL emulsions. WPI (1.96% (1WPI) or 10.71% (10WPI), w/w in water) was prepared in water and high-pressure homogenized with sunflower oil (10%, w/w, of total emulsion). Gum Arabic (0.15%, w/w, in total emulsion) was added to assemble electrostatically on WPI at oil particle interfaces at pH 3.5 using aqueous citric acid (10% w/w) forming LBL emulsion. The ζ-potential measurements showed charge reversal upon addition of gum Arabic solution into single layer (SL) emulsion confirming the formation of LBL interface. Trehalose:maltodextrin mixture (1:1, w/w, total emulsion, 28.57% (28) or 57.14% (57), w/w, in water) was used in the continuous phase. The high total solids content of the system results in depletion flocculation of the particles leading to bridging flocculation without coalescence as deflocculation into individual particles occurred with increasing pH from pH 3.5 to pH 6.5 in 10WPI systems. Deflocculation was evident in 10WPI-28 and 10WPI-57 as found from a decreased ζ-average diameter and visually under microscope. Coalescence was observed in 1WPI systems. Viscosity of the systems was significantly (P < 0.05) increased with higher total solids content. Accelerated destabilization test showed that systems at higher WPI and total solids contents exhibited the highest stability against creaming. Deflocculation in LBL systems can be controlled by pH while high solids in the aqueous phase provide stability against creaming.     

Characterization of Moringa oleifera leaf and seed protein extract functionality in emulsion model system

This study provides a comparative overview of Moringa oleifera leaf and seed protein extract (LPE and SPE, respectively) functionality in emulsions. Raw seed cake (RS) had more protein (45.8%) than raw leaf (RL) (27.4%). RL comprised higher polyphenol and flavonoid content than RS, Granny Smith apples, and Goji berries. Protein functionality data revealed that LPE had excellent solubility, and emulsifying properties than SPE at pH 7.0. In contrast, SPE had relatively strong surface hydrophobicity. At pH 7.0, leaf extract emulsions (LEE) possessed relatively small particle size distribution, strong negative charge, excellent stability, and minimum sedimentation velocity. On contrary, at pH 3.5, particle size, and velocity increased, contributing to monodisperse sedimentation. Seed extract emulsions (SEE) had an overall large particle size and demonstrated fast and extensive creaming and sedimentation at both pH conditions. Our findings indicate that M. oleifera leaf protein extracts have considerable potential for use in emulsion-based foods.     

Formation and characterisation of food protein–polysaccharide thermal complex particles: effects of pH,temperature and polysaccharide type

The objective of this study was to prepare and characterise the thermal complex particles (TCPs) based on heating food grade protein–polysaccharide electrostatic complexes. The soybean protein isolate (SPI), cationic polysaccharide (chitosan, CS) and anionic polysaccharide (carboxymethyl cellulose, CMC) were used. Turbidity, particle size, ζ-potential and morphology of TCPs were measured. The results showed that SPI-CS and SPI-CMC soluble complexes were obtained at specific pHs and kept at high electrostatic repulsive force. The particle size and polydispersity index of stable SPI-CS (pH 4.55/80 °C) and SPI-CMC (pH 6.15/95 °C) TCPs were 286.6 nm/0.282 and 171.5 nm/0.298, respectively. We inferred that the re-assembly of SPI after thermal denaturation resulted in the formation of TCPs. The pH and ionic strength sensitivity tests indicated that the TCPs with different properties can be controlled by pH, temperature and polysaccharide type during heating. These TCPs could be used to encapsulate food functional components which were thermal insensitive.