碱性蛋白酶控制酶解诱导大豆分离蛋白纳米颗粒的形成机制

以大豆分离蛋白（soy protein isolate,SPI）为原料,利用碱性蛋白酶对其进行酶解处理（0～24 h）,探究SPI的结构变化规律,发现碱性蛋白酶控制酶解可诱导SPI自组装形成系列分布均匀（多相分散系数＜0.3）、粒径可控（90～200 nm）且具有不同表面特性的大豆蛋白纳米颗粒（soy protein nanoparticles,SPNs）,其中水解度（degree of hydrolysis,DH）及亚基解离/降解是影响SPNs形成的关键性因素。酶解初期（10～30 min,DH约3%）,SPI中β-伴大豆球蛋白（7S）组分α与α’亚基的部分降解有利于两亲性结构的释放,提高蛋白表面疏水性,降低临界聚集浓度,形成包含相对完整的7S及大豆球蛋白（11S）亚基的I类纳米颗粒（SPNs-DH 3%）。随着酶解时间的延长（1～2 h）,α与α’亚基的进一步降解促进了疏水性β亚基与B亚基的暴露,增强的疏水相互作用导致体系浊度增加,其中可溶性聚集体向不溶性疏水聚集的转化使得蛋白表面疏水性急剧下降,形成以A亚基及部分β亚基为主导的II类亲水型纳米颗粒（SPNs-DH 5%）。酶解后期（4～24 h）,A亚基的进一步降解则产生更多亲水性多肽,不利于纳米颗粒的形成。进而探究SPNs的形成机制,圆二色光谱结构表明,SPNs的形成与蛋白α-螺旋和无规卷曲结构向β-折叠转化有关。两类SPNs的整体结构均由疏水相互作用维持,而氢键和二硫键分别参与颗粒表面与内部结构的形成。与SPNs-DH 3%相比,SPNs-DH 5%中形成了更多由二硫键与氢键稳定的折叠结构。此外,由于酶解过程中不断释放抗氧化肽段,其所形成SPNs的抗氧化性较原始SPI均有所提升。     

基于配位作用的铁-大豆蛋白纳米复合物制备及性质

为拓宽铁强化剂在食品工业生产中的应用，本研究以大豆分离蛋白(soy protein isolate,SPI)为原料对其进行碱热预处理(pH 12,85℃，30 min)后，与FeSO₄反应制备纳米复合物。结果表明，预热处理后大豆分离蛋白(alkali-heat-treated soybean protein isolate,HSPI)可与适当浓度的FeSO₄反应形成稳定分散的纳米复合物(Fe-HSPI)，该过程受反应pH值影响。随着反应pH值的升高，Fe-HSPI的尺度改变，颜色逐渐加深；不同pH值下制备的Fe-HSPI均具有较好的消化稳定性，经模拟胃肠消化后仍保持蛋白与Fe²⁺的结合，有利于避免游离铁对胃肠道的刺激。其中，pH7下制备的纳米复合物(Fe-HSPI_pH7)均一性较好(多分散系数<0.2)，且消化后的可溶性铁含量超过80%，具有良好的吸收利用潜力。Fe-HSPI_pH7中，Fe²⁺与HSPI的结合会引起HSPI肽链折叠并形成二硫键维持稳定...     

EGCG对大豆蛋白结构的调控机理

采用添加量不同的表没食子儿茶素没食子酸酯（epigallocatechin gallate,EGCG）与大豆分离蛋白（soy protein isolate,SPI）相互作用形成复合体系,运用多种检测手段探究EGCG对SPI结构的调控机理,以及热处理条件下SPI-EGCG复合体系相互作用的改变。EGCG对SPI的作用机制为静态猝灭,且通过非共价疏水相互作用结合。傅里叶红外光谱和拉曼光谱结果显示,热处理前后EGCG与SPI的复合使SPI的α-螺旋结构相对含量升高,β-折叠结构相对含量降低,而β-转角及无规卷曲结构含量变化不明显。荧光光谱与紫外-可见光光谱表明二者相互作用使SPI的最大发射波长发生红移,且热处理增强了复合体系的红移程度。本实验综合研究SPI与EGCG的营养价值,为开发功能型大豆蛋白产品提供理论基础。     

体外消化对β-胡萝卜素大豆分离蛋白纳米颗粒黏液层渗透及跨膜转运的影响机制

纳米载体体内吸收过程复杂，受生物吸收屏障影响，纳米制剂在促进活性分子吸收利用度方面受到质疑。本实验采用大豆分离蛋白（soy protein isolate,SPI）制备包埋β-胡萝卜素的植物基纳米颗粒（β-carotene loaded soy protein isolate nanoparticles,BC-SPIs），并通过体外模拟消化模型研究BC-SPIs在消化过程中的结构特性变化。同时，通过Caco2细胞转运模型考察消化条件对消化后BC-SPIs跨膜转运的影响机制。此外，利用含黏液层的Caco2-HT29共培养模型考察消化前后BC-SPIs的黏液层渗透性。研究发现，在消化前，BC-SPIs可以直接通过网格蛋白和小窝蛋白依赖的内吞作用被Caco2单层细胞吸收；而在经过体外模拟消化后，BC-SPIs粒径增大，可以通过网格蛋白依赖的内吞作用、小窝蛋白依赖的内吞作用以及巨胞饮3种内吞形式被细胞直接吸收。消化后的BC-SPIs带有更高的负电荷，跨越黏液层屏障的能力提高了0.48倍，同时β-胡萝卜素的跨膜转运量提高了0.56倍。本研究明确了BC-SPIs在消化前和消化后的不同吸收途径，揭示...     

酸热诱导大豆分离蛋白纳米颗粒形成及其荷载姜黄素的特性

以大豆分离蛋白(soy protein isolate,SPI)为原料,在特定pH值条件下(pH 7.0、5.9)静态加热处理(95℃、30 min)诱导SPI自组装形成纳米颗粒,分别记作HSPI及HSPI(pH 5.9)。进一步以姜黄素为模型疏水性活性物质,较系统地比较均质及超声处理对不同结构的蛋白颗粒荷载姜黄素的影响。荧光光谱结果表明,SPI、HSPI和HSPI(pH 5.9)均可与姜黄素发生疏水相互作用,使蛋白发生荧光猝灭并提高姜黄素的水分散性。热处理可显著提高蛋白颗粒的表面疏水性,其中HSPI(pH 5.9)的粒径分布更均一(多相分散系数0.2),且较SPI与姜黄素有更高的结合力。通过均质或超声处理,SPI、HSPI和HSPI(pH 5.9)可进一步通过疏水驱动作用荷载姜黄素形成富载姜黄素的纳米颗粒。与SPI及HSPI相比,HSPI(pH 5.9)的核-壳结构有利于蛋白与姜黄素在超声过程中发生共组装,形成形态均一且性质稳定的纳米颗粒,显著提高了姜黄素的水溶性及贮藏稳定性。     

金针菇多糖对大豆分离蛋白凝胶的增强作用及其结构表征

通过将金针菇多糖（Flammulina velutipes polysaccharide，FVP）添加到大豆分离蛋白（soy protein isolate，SPI）水凝胶中并进行热处理以提高SPI水凝胶强度、持水性和热稳定性。通过对二三级结构及分子间作用力的检测，进一步分析FVP-SPI水凝胶的稳定性。结果显示：热处理及添加FVP显著提高SPI水凝胶的持水能力，热变性焓ΔH提高了25.46%，水凝胶稳定性显著提高。疏水相互作用、二硫键和静电相互作用是形成热处理FVP-SPI水凝胶的主要作用力。FVP的加入提高了静电相互作用，使水凝胶中α-螺旋向β-折叠转变，SPI中色氨酸暴露于表面，疏水性增强。FVP对SPI水凝胶的增强作用为SPI水凝胶的开发应用提供一定参考。     

大豆分离蛋白-甜菊糖苷复合稳定剂制备纳米乳液

为适应食品工业对食品配料天然绿色、营养健康的追求,采用大豆分离蛋白（soy protein isolate,SPI）-甜菊糖苷（steviol glycosides,STE）复合体系作为稳定剂制备纳米乳液,研究稳定剂组成、微射流参数、油相质量分数等对纳米乳液形成的影响,并对乳液稳定性及微结构进行表征。结果表明：油相质量分数为10%时,单独SPI（1%）制备的乳液粒度较大（d43为0.548 μm）,稳定性差。添加0.25%～1% STE时,乳液粒度分布更均匀,粒度变小;当STE质量分数为0.5%和1%时,乳液粒度小于200 nm,且具备较好的贮存稳定性（30 d）。添加2% STE会导致乳滴表面蛋白被完全取代,从而弱化乳液的长期稳定性。微射流压力、均质次数及STE质量分数的增加均可降低乳液粒度,但油相质量分数的增加可增加乳液粒度。进一步将纳米乳液进行冷冻干燥处理,可制得结构化良好且高油含量的油粉;相对于单独SPI稳定的结构化乳液,SPI-STE纳米乳液制得的油粉结构更为完整,表面黏性小。     

预热处理大豆蛋白对鲤鱼肌原纤维蛋白凝胶和流变学特性的影响

以鲤鱼肌原纤维蛋白（myofibrillar protein isolate,MPI）为研究对象,研究经过预热处理的大豆分离蛋白（soy protein isolate,SPI）对MPI凝胶和流变学特性的影响。SPI在90 ℃热处理0（天然SPI）、30 min和180 min,分别与MPI以不同的比例（0∶1、1∶1、1∶2、1∶3、1∶4）混合,所有溶液总蛋白质量浓度均为40 mg/mL。结果表明,经过预热处理的SPI与MPI混合后其凝胶硬度、弹性、白度和持水性显著高于天然SPI与MPI混合所形成的蛋白凝胶（P＜0.05）,且预热处理时间越长的大豆蛋白（180 min）与短时间处理（30 min）相比增加得更为明显（P＜0.05）。此外,随着SPI-MPI复配1∶1～1∶4,混合蛋白凝胶硬度、弹性、白度和持水性显著增大（P＜0.05）。流变学研究表明,SPI添加到MPI溶液中能增加蛋白变性温度,而经过预热处理SPI能够显著地提高储能模量（G’）。热稳定性结果表明,MPI中添加天然SPI能够显著降低Tmax3（P＜0.05）而对Tmax1和Tmax2无影响（P＞0.05）;当SPI经过热处理后添加到MPI中能够显著降低Tmax1（P＜0.05）而提高Tmax3（P＜0.05）。总之,与未经预热处理的SPI相比,经过预热处理后的SPI添加到MPI中能够改善蛋白凝胶特性和流变学特性。     

无籽刺梨纳米纤维特性及其对大豆分离蛋白膜性能的影响

该文以无籽刺梨果渣为原料，采用硫酸水解法制备无籽刺梨纳米纤维(Rosa sterilis cellulose-nanocrystalline cellulose, RSC-NCC),利用扫描电镜(scanning electron microscopy, SEM)、透射电镜(transmission electron microscopy, TEM)、X-射线衍射(X-ray diffraction, XRD)、傅里叶变换红外光谱(Fourier transform infrared spectroscopy, FTIR)及差示扫描量热仪(differential scanning calorimetry, DSC)等技术研究RSC-NCC性质。同时，以大豆分离蛋白(soybean protein isolate, SPI)为成膜基材，研究了RSC-NCC对SPI膜性能的影响，并结合SEM、DSC、FTIR、XRD分析了RSC-NCC/SPI膜的微结构。结果表明，RSC-NCC直径约10 nm,长约500 nm,保留了纤维素的基本化学结构，结晶度较高，熔融温度100℃。RSC-NCC使...     

竹笋不溶性膳食纤维对大豆蛋白凝胶性质的影响

为考察竹笋不溶性膳食纤维(bamboo shoots insoluble dietary fiber,BSIDF)对大豆蛋白凝胶的流变及质构特性的影响,以大豆分离蛋白(soy isolate protein,SPI)为原料,加入不同比例的BSIDF制备大豆蛋白-竹笋不溶性膳食纤维复合凝胶(SPI-BSIDF),研究SPI-BSIDF的流变、质构及微观结构的变化。结果表明,BSIDF的添加使大豆蛋白凝胶网络结构形成的时间延后,凝胶网络结构形成减少,凝胶强度下降;随着BSIDF添加量的增加,SPI-BSIDF的硬度、内聚性、咀嚼性和黏着性均下降,而粘力则呈现出先增强后减弱的趋势,当BSIDF添加量为0.5%时,混合凝胶体系的粘力最强。同时从微观结构可以看出,BSIDF的添加使蛋白质凝胶体系组织结构的褶皱明显增多,大豆蛋白聚集体和凝胶孔均增大。     

Effect of dextran glycation on nanofibril assembly of soya β‐conglycinin at pH 2.0 and the pH stability of nanofibrils

In this study, we investigated the effects of dextran glycation on soya β‐conglycinin self‐assembly into nanofibrils at 85 °C and pH 2.0, as well as their stability at pH 2.0–10.0. Although the hydrolysis rate of β‐conglycinin decreased, glycation significantly increased the structural change rate in the initial stage of nanofibril formation and the growth of nanofibril. It is suggested that the glycation of three subunits (α′, α, β) in β‐conglycinin may promote fibril assembly because the extension regions of α′ and α subunits play an important role in affecting the rate of structural changes in fibril formation. At neutral pH, conjugate nanofibrils are highly dispersible and transparent and remained greater structural stability compared with mixture. The improvement stability of conjugate nanofibrils may be contributed to dextran which provides some steric hindrance to prevent the aggregation of nanofibrils; this would also facilitate the application of soya β‐conglycinin nanofibrils in food industry.     

不同方法制备的大豆分离蛋白功能性质的比较研究

采用普通的碱溶酸沉方法、Samoto法、钙离子沉淀法制备出几种大豆分离蛋白,并对其产率、总脂含量及溶解性、乳化性等物化性质和功能性质进行系统比较。结果表明：钙离子沉淀法制备的大豆分离蛋白(Less-LP SPI)的产率是碱溶酸沉大豆分离蛋白(APP)产率的65%,但高于由Samoto法提取的7S与11S两种大豆分离蛋白产率之和;Less-LP SPI的总脂含量比APP降低了45%,由Samoto法提取的亲脂性蛋白(LP)中总脂含量达到7.48%,而7S与11S蛋白中脂含量分别为1.45%、2.36%。在功能性质上,LP的溶解性、乳化活性均比较差,7S、11S质量比1:2混合蛋白的溶解性最好,而Less-LP SPI在pH≤10时溶解性低于APP;乳化性方面,Less-LP SPI的乳化活性稍低于7S、11S质量比1:2的混合蛋白及APP,但乳化稳定性远高于后者。总体上,Less-LP SPI脂含量少、乳化稳定性好,方法简单,且可提高其货架期。     

Impact of whey protein isolates and concentrates on the formation of protein nanoparticles‐stabilised Pickering emulsions

Whey protein nanoparticles (NPs) were prepared by heat‐induced method. The influences of whey protein isolates (WPIs) and concentrates (WPCs) on the formation of NPs were first investigated. Then Pickering emulsions were produced by protein NPs and their properties were evaluated. After heat treatment, WPC NPs showed larger particle size, higher stability against NaCl, lower negative charge and contact angle between air and water. Dispersions of WPC NPs appeared as higher turbidity and viscosity than those of WPI NPs. The interfacial tension of WPC NPs (~7.9 mN/m at 3 wt% NPs) was greatly lower than that of WPI NPs (~12.1 mN/m at 3 wt% NPs). WPC NPs‐stabilised emulsions had smaller particle size and were more homogeneous than WPI NPs‐stabilised emulsions. WPC NPs‐stabilised emulsions had higher stability against NaCl, pH and coalescence during storage.     

Interaction between soy protein isolate and surfactant at the interface of antibacterial nanoemulsions loaded with riboflavin tetra butyrate

Riboflavin tetra butyrate (RTB) is an effective antimicrobial photosensitiser that poses a challenge for long-term preservation and application due to its hydrophobicity and instability. To overcome this problem, a series of nanoemulsions loaded with photosensitiser RTB was prepared in this study by using soy protein isolate (SPI) as an emulsifier and small molecule surfactant (X) as co-emulsifier. The interaction mechanism of SPI+X co-emulsifier and its influence on the stability of emulsion and photosensitiser were explored, and the photodynamic bactericidal effect of the prepared RTB emulsion on S. aureus was studied. SPI and four types of surfactants were present in the form of synergistic (Tween 80, T80) or competition (Span 80, S80 and lecithin, LEC) adsorption or formation of Pickering emulsion (Sodium dodecyl sulphate, SDS) at the oil–water interface. The experimental results revealed that the stable encapsulation ability of RTB emulsions for photosensitisers and their preservation ability can be drastically improved. This work verified that all RTB emulsions could inactive S. aureus under blue light, with an antibacterial ratio of more than 70%. Therefore, the emulsion-based delivery system effectively improved the water dispersibility and chemical stability of RTB. These results demonstrate that RTB emulsion has the potential to be used as a food-grade antibacterial emulsion.     

Immobilization of selenite on Fe3O4 and Fe/Fe3C ultrasmall particles

The sorption of selenite ions onto Fe3O4 and Fe/Fe3C nanoparticles (NPs) was studied in aqueous solutions under anoxic conditions using gamma spectrometry and X-ray absorption spectrometry (XAS) techniques. This is the first study related to the remedial applications of Fe/Fe3C NPs. FesO4 NPs have been prepared by conventional coprecipitation of Fe(II) and Fe(III) in basic solutions. Stable Fe/Fe3C NPs have been prepared by Fe(CO)5 sonicating in diphenylmethane solutions and subsequently annealing the as-prepared product. Kinetic study demonstrated that Se(IV) sorption is extremely rapid: the equilibrium is reached in approximately 10 and 30 min for Fe3O4 and Fe/Fe3C NPs, respectively, at pH = 4.9-5.1 in solutions of 0.1 M NaCl. The distribution coefficients are also very high for both kinds of NPs (Kd > 3000). Increasing the pH to 10.3 or adsorption of organic ligands, like L-lysine or dodecanoate, at the surface of NPs causes the decrease in Kd values. However, even in these cases Kd values exceed 150. Magnetic NPs loaded with selenium can be easily and completely removed from solution with a 0.4 T permanent magnet. XAS study revealed the absence of Se(IV) reduction during the sorption onto Fe3O4 NPs in the pH range of 4.8-8.0. By contrast, the removal of Se(IV) with Fe/Fe3C NPs in anaerobic conditions occurs via Se(IV) reduction to Se(-II) and subsequent formation of iron selenide at the particle surface. Thus, the Fe/Fe3C NPs are superior to Fe3O4 NPs due to their ability to immobilize rapidly and irreversibly Se(IV) via reductive mechanism. Presumably these particles could be also effective for the removal of other contaminants such as hexavalent chromium, actinides, technetium, and toxic organic compounds.     

氧化对大豆蛋白结构、乳液稳定性及消化特性的影响

以大豆分离蛋白为原料,以脂质过氧化产物丙二醛（malondialdehyde,MDA）为氧化引发剂,逐级研究氧化对大豆蛋白结构、乳液稳定性及乳液消化特性的影响。结果发现：随着MDA浓度的升高,蛋白羰基及席夫碱含量明显升高而巯基含量显著降低。同时,MDA可促进蛋白聚集并诱导β-伴大豆球蛋白（7S）组分形成二硫键和非二硫键诱导的共价交联。进一步制备O/W型乳液,发现不同浓度MDA处理蛋白对乳液的形成影响较小,但可以显著改变界面蛋白组成。其中经中高浓度（2.5～10 mmol/L）MDA氧化后,更多7S组分以聚集状态参与界面组成。体外模拟胃肠道消化实验进一步表明,乳液消化主要在肠道进行,氧化诱导的蛋白交联/聚集可延缓或降低胆盐在界面的替代,进而减缓乳液消化并降低脂质释放率。     

Effect of Various Soy Protein Products on Retention of Nonheme Iron from a Casein Test Meal or from Soy-Based Test Meals

The influence of soy product processing on whole-body ⁵⁹Fe retention by the rat was examined. Some, but not all, soy protein products present in the diet previous to a casein-based radiolabeled test meal lowered iron retention relative to that by rats fed the casein diet. A soy fiber preparation in the diet did not adversely affect ⁵⁹Fe retention. When various radiolabeled test meals were fed in either acid or neutralized form, neutralization of soy protein isolate (SPI), but not of casein, led to less ⁵⁹Fe retention (PC 0.01) from the test meal. After appropriate heat treatment, ⁵⁹Fe retention from acid and neutralized SPI was not distinguishable.     

酰化对大豆蛋白分子结构影响的研究

目的:研究化学改性对大豆分离蛋白(SPI)分子结构的影响;方法:采用SDS-PAGE电泳、DSC热分析手段探讨酰化对蛋白分子结构特征的影响;结果:DSC图谱显示,SPI经过琥珀酰化处理后热稳定性得到显著改善,乙酰化处理对大豆蛋白的热稳定性影响不大。SDS-PAGE电泳结果显示,改性后蛋白的11S酸性亚基和7S含量大大减少,说明SPI经酰化处理后亚基发生了降解。随着酸酐添加量的增大,11S球蛋白分子逐步分解为亚基。琥珀酰化的电泳图谱预示着可能存在一个琥珀酰化的临界点,在这一点上,解离的蛋白亚基突然展开。结论:实验结果有助于阐明SPI酰化后功能性质发生变化的内在结构因素。     

Nanocomplexation of soy protein isolate with curcumin: Influence of ultrasonic treatment

Soy protein isolate (SPI) can act as effective nanocarriers for water-insoluble curcumin, however, the maximal capacity of this protein to load curcumin and molecular mechanism for the formation of the nanocomplexes are still little known. This work investigated the formation and properties of SPI-curcumin nanocomplexes formed at a low concentration of 0.05% (w/v), as well as the influence of a high intensity ultrasonic treatment on the nanocomplexation. Most of the particles in non- or ultrasonic-treated SPIs were present in nanoparticle form with z-average sizes of about 50–52 nm. The load amount (LA) of curcumin in the non-treated nanocomplexes reached 103.9 μg/mg SPI. The ultrasonic treatment of the protein solution further significantly increased the LA, while the LA was considerably decreased by the treatment after the nanocomplexation. The complexation with curcumin significantly increased the particle size and ζ-potential of both non- and ultrasonic-treated SPIs, but led to a considerable reduction in surface hydrophobicity, with the greater changes observed for ultrasonic-treated SPI. The nanocomplexation with SPIs remarkably improved the storage stability of curcumin, with much better improvement observed for the ultrasonic-treated SPI. Both the number and nature of hydrophobic sites are important for the nanoparticles in SPI to exhibit high capacity to load curcumin molecules. This study confirmed that SPI exhibited a high capacity to load water-insoluble curcumin, and an ultrasonic pretreatment could further improve its encapsulation efficiency and stability of curcumin.     

超声改性大豆分离蛋白与大豆可溶性多糖复合乳化体系的冻融稳定性研究

本实验针对不同超声功率改性的大豆分离蛋白与大豆可溶性多糖形成的复合乳液的冻融稳定性进行研究, 揭示乳液冻融稳定机理与形成乳液复合物结构特性之间的构效关系。对2 次冻融循环处理前后乳液油滴进行共聚焦 观察,研究等温结晶固脂含量、油脂被乳化量的变化和作为乳化剂的大豆分离蛋白不同超声处理（0、200、300、 400、500 W）下二级结构的变化,进而分析其与乳液冻融稳定性的关系。结果表明：乳液经2 次冻融循环处理后 随着超声功率的增加聚结程度降低,400 W超声处理的大豆分离蛋白与大豆可溶性多糖复合乳液最为稳定;等温 结晶条件下不同乳液固脂含量增加速率不同,但最终平衡时总含量相同;油脂被乳化量发生不同程度的变化;不 同超声处理改变了大豆分离蛋白的二级结构,400 W超声处理的大豆分离蛋白无规卷曲结构含量最高。说明不同 超声改性的大豆分离蛋白与大豆可溶性多糖会形成不同结构的复合物,影响了乳液的冻融稳定性,初步明确了 适当的超声处理能够改善大豆分离蛋白的空间结构,促进其与大豆可溶性多糖分子的键合,进而影响大豆分离蛋 白-多糖界面结构特性和乳化体系的冻融稳定性。