银耳多糖-壳寡糖纳米复合体系构建及其对BSA释放特性的影响

功能性蛋白质因其在疾病预防与健康改善方面的功效突出,从而受到广泛关注,但其生物利用率较低,使用范围被极大限制。研究银耳多糖（Tremella fuciformis polysaccharide,TFP）和壳寡糖（chitooligosaccharides,COS）通过聚电解质络合法构建制备负载牛血清蛋白（bovine serum protein,BSA）的COS-TFP纳米复合体系,并以复合物粒径、多分散指数、电位为指标,探究复合物稳定性,以牛血清蛋白（bovine serum protein,BSA）为模型,研究COS-TFP复合物的载药与释药特性。结果表明：当COS与TFP总浓度为2mg/mL、COS与TFP浓度比为1∶5～1∶3、NaCl浓度为20mmol/L～50 mmol/L、pH值为4.0时,纳米粒具有良好的稳定性;当COS-TFP∶BSA浓度比为1∶0.6时,包埋率达到91%;同时,BSA在pH值为4.0（饱食胃液环境）时释药量低且速率缓慢,pH值为7.0（肠道环境）时释药迅速,可作为潜在的蛋白质类控释运载体系。     

明胶与海藻酸钠的静电复合机制及热动力学分析

为探明明胶（gelatin，GEL）与海藻酸钠（sodium alginate，AG）静电作用机制及影响因素，对不同GEL和AG质量比（r）、不同pH值的液体体系进行常温浊度滴定、Zeta电位测定及亚甲基蓝吸收光谱实验等，研究复合物形成的影响因素，并利用等温滴定微量热技术对GEL与AG结合过程进行热动力学分析。结果表明，常温下GEL与AG结合是以强烈的静电相互作用为主的焓驱动放热过程；NaCl通过静电屏蔽作用，在低浓度（＜0.02?mol/L）时促进GEL与AG的结合，高浓度时抑制其结合。环境pH值通过调整GEL与AG所带的净电荷从而影响其静电作用，低pH值时形成不溶性复合物，高pH值时形成可溶性复合物；提高r或者提高GEL和AG总浓度可以促进其相互作用，r=7∶3时，可以在较高pH值下形成稳定的复合物悬浊液，pH值在2.5～3.5变化对悬浊液影响较小。本实验为GEL-AG基生物材料的开发及其在食品、医药领域应用提供理论依据。     

NaCl浓度对麦醇溶蛋白与槲皮素相互作用的影响

利用荧光光谱、紫外光谱、傅里叶变换红外光谱法,研究不同NaCl浓度下麦醇溶蛋白（gliadin,G）与槲皮素（quercetin,Q）的相互作用。荧光光谱分析结果表明：不同NaCl浓度下,Q导致G荧光猝灭现象的发生,且随NaCl浓度的增大,荧光强度伴随明显蓝移现象（10?nm左右）;当Q浓度为50?μmol/L时,荧光猝灭率为96%～98%,表明两者发生强相互作用;Q对G产生静态或动、静态结合的猝灭作用;50?mmol/L?NaCl浓度下,G与Q的结合常数（Ka）和结合位点数（n）数值最大,为4.87×107?L/mol和1.477?1,说明添加适量NaCl有利于相互作用的增强。热力学数据分析结果表明：50?mmol/L?NaCl浓度下,G与Q之间主要为疏水作用力,而其他NaCl浓度下,G与Q之间主要为氢键相互作用。同步光谱和紫外光谱分析结果表明：Q改变了G中芳香族氨基酸所处的微环境,使蛋白分子构象发生变化,且色氨酸残基对蛋白固有荧光的猝灭贡献更大。傅里叶变换红外光谱和拉曼光谱分析结果表明：在特定NaCl浓度下G与Q存在特定作用方式,氢键或疏水相互作用在复合物的形成中起重要作用,蛋白质的二级、三级结构及氨基酸侧链微环境发生改变。研究结果证明,NaCl浓度影响蛋白-多酚的相互作用,添加适量NaCl有利于G和Q的结合以及蛋白质的构象变化。本研究为Q作为一种天然食品添加剂应用于小麦制品提供了理论基础和科学依据。     

大豆分离蛋白与寡糖静电相互作用及复合物乳化性的分析

以大豆分离蛋白（soybean protein isolate,SPI）和寡糖（棉子糖和水苏糖）为原料制备复合溶液,通过调节pH值（3.0～10.0）研究SPI-寡糖形成复合体系的相行为、微观结构,确定形成可溶性静电复合物的条件及其对蛋白质溶解性、乳化性的影响。Zeta电位、激光共聚焦显微镜观测和浊度测定的结果显示,在酸性条件下,SPI与寡糖通过静电相互作用形成复合物,且等电点与SPI相比向酸性偏移;内源荧光光谱扫描发现SPI-寡糖复合物的荧光强度低于SPI,且静电相互作用越强荧光强度降低越明显。当pH?6.0时,SPI-寡糖较大程度形成可溶性静电复合物,此时复合物的功能性质较SPI有所改善,SPI-水苏糖和SPI-棉子糖的乳化性与SPI相比分别提高了50.66%和39.69%。     

CaCl2和NaCl诱导对大豆分离蛋白纳米纤维冷凝胶的影响

蛋白质自组装形成的纳米纤维因独特的功能和生物学特性而引起人们的关注。本文通过加入CaCl2和NaCl诱导大豆分离蛋白（SPI）纤维溶液制得冷凝胶,研究不同蛋白浓度及离子浓度对凝胶性质的影响。流变学测量结合Percolation模型拟合结果表明：冷凝胶的临界渗滤浓度（cp）比纤维热凝胶方法低,CaCl2和NaCl浓度分别为30 mmol/L和150 mmol/L时cp最小。形成的冷凝胶表现为各向同性渗流和均匀的网络。SPI浓度越大,冷凝胶储存模量G′、凝胶硬度越大,凝胶持水性越好,形成凝胶所需的盐浓度越低。在低离子强度下（CaCl2浓度<50 mmol/L,NaCl浓度<150 mmol/L）,离子强度越大,G′、凝胶硬度和持水性越大。盐浓度进一步增加时,G′、凝胶硬度和持水性下降。在冷固性凝胶中,同等离子强度的条件下,NaCl诱导凝胶的cp值均高于加入CaCl2的cp,说明多价阳离子形成盐桥是形成凝胶网络的主要驱动力。     

L-赖氨酸对鲢肌球蛋白热聚集行为的影响

研究外加L-赖氨酸（L-Lys）对鲢肌球蛋白热聚集行为的影响。将浓度为1、5、10、20?mmol/L的L-Lys添加到肌球蛋白中,分别进行未加热（25?℃稳定30?min）、预加热（40?℃加热60?min）和二段式加热（40?℃加热60?min的基础上90?℃加热30?min）,测定其pH值、浊度、流变特性及凝胶强度的变化。结果表明：肌球蛋白溶液的pH值随L-Lys浓度的增加而增加;20?mmol/L的L-Lys能够显著降低肌球蛋白溶液在未加热状态下的浊度,1～20?mmol/L的L-Lys能够显著降低肌球蛋白溶液在加热过程中的浊度,尤其是二段式加热后的浊度;添加L-Lys后的肌球蛋白更偏向于黏性流体,成胶能力更弱,形成的凝胶强度更小。L-Lys作为一种常见的可溶性小分子添加剂,且为人体必须氨基酸之一,能够通过静电相互作用及改变肌球蛋白溶液的pH值抑制鲢肌球蛋白的热聚集行为,对其开发利用还有待进一步研究。     

微生物谷氨酰胺转移酶对大豆分离蛋白凝胶性能的影响

研究了底物浓度pH、酶浓度、温度、时间、离子浓度和二巯基苏糖醇（DTT）的添加对微生物谷氨酰胺转移酶（MTGaSe）诱导的大豆分离蛋白（sPI）凝胶强度的影响。结果表明，在SPI溶液中加入MTGaSe，可以使体系在低温下形成凝胶；SPI低于8％不能形成凝胶；pH7.0，酶量为30U／g．pro，50℃水浴加热1h，NaCl为O，6N时，均可获得最高的凝胶强度；添加DTT，对体系无影响。     

影响蛋白质抗氧化活性的因素

以桃仁分离蛋白(PKPI)、大豆分离蛋白(SPI)、乳清分离蛋白(WPI)、酪蛋白(CA)为研究对象,以6-羟基-2,5,7,8-四甲基色烷-2-羧酸(Trolox)为对照,测定其DPPH自由基清除率,研究蛋白质浓度、温度、热处理时间、盐离子及其浓度、pH对蛋白质抗氧化活性影响。结果表明:蛋白质浓度0.05~2.00g/100mL,4种蛋白质抗氧化活性随其浓度的增大而增强。温度对蛋白质抗氧化能力有不同程度影响,且当温度为40,40,30,70℃时,PKPI、WPI、CA、SPI分别达到最大抗氧化活性。热处理时间对SPI、CA、PKPI抗氧化活性影响较小,但WPI抗氧化活性随热处理时间的延长而增大。NaCl、CaCl_2浓度0~10 mmol/L时,其对SPI、CA抗氧化活性影响较小;PKPI抗氧化活性受NaCl影响较小,而CaCl_2浓度增大降低了PKPI抗氧化活性;WPI抗氧化活性随着NaCl和CaCl_2浓度的增大而减小,且CaCl_2对WPI抗氧化活性影响大于NaCl。4种蛋白质抗氧化活性都受pH影响,pH 2.0时,其抗氧化能力高于pH 8.0。     

草鱼皮胶原的体外自组装动力学研究

体外自组装是天然胶原的重要分子行为特征之一,并对胶原基产品性能产生显著影响。以草鱼皮酶溶性胶原蛋白为研究对象,重点开展胶原体外自组装动力学行为、影响因素、组装纤维的微观结构及其热稳定性能研究。浊度实验和自组装程度分析的结果表明,草鱼皮胶原蛋白具备体外自组装能力,其自组装进程受胶原质量浓度、pH值、离子强度、温度等因素的影响。在pH 7～8、胶原质量浓度3～5 mg/mL、体系温度25～30 ℃以及NaCl浓度0～200 mmol/L条件下胶原自组装进程较快、自组装程度较高;组装动力学分析的结果表明,在较高的离子强度（NaCl浓度300 mmol/L）和较低的组装温度（20 ℃）时,胶原组装进程表现为：成核、组装和平衡3 个阶段,而在较高组装温度（25～30 ℃）和较低离子强度时（NaCl浓度0～200 mmol/L）,胶原组装进程表现为：快速组装段、低速组装段和平衡段;胶原纤维形态学观察结果表明,草鱼皮胶原组装纤维具有典型的D周期特征但D周期长度值（64.6 nm）小于哺乳动物胶原纤维（约67 nm）;示差扫描量热法（differential scanning calorimetry,DSC）分析结果表明,经纤维重组后,草鱼皮胶原蛋白的热稳定性得到明显提升。     

影响精氨酸-还原糖模拟体系荧光性晚期糖基化终末产物形成的因素

目的：通过建立精氨酸-还原糖模拟体系,考察影响该体系荧光性晚期糖基化终末产物（advancedglycation end products,AGEs）形成的因素。方法：对建立的精氨酸-还原糖模拟体系,采用荧光光谱法（λex/λem =370 nm/440 nm）检测反应温度、还原糖浓度、pH值、金属离子和抑制剂染料木黄酮对AGEs形成的影响;并分析各个影响因素的作用效果。结果：在单个影响因素：反应温度（121 ℃）、还原糖及其浓度（3 mmol/L的核糖）、pH值（9.2）和金属离子（Fe3＋）作用下,产生荧光性AGEs作用效果最强,9 mmol/L抑制剂染料木黄酮对荧光性AGEs的形成有抑制作用。结论：反应时间、反应温度、还原糖种类及其浓度、pH值、金属离子和抑制剂染料木黄酮均对精氨酸-还原糖模拟体系荧光性AGEs的形成有影响,在该模拟体系中,反应时间是影响荧光性AGEs产生最主要的因素,其次为还原糖的种类。     

Complex coacervation of soybean protein isolate and chitosan

The formation of coacervates between soybean protein isolate (SPI) and chitosan was investigated by turbidimetric analysis and coacervate yield determination as a function of pH, temperature, time, ionic strength, total biopolymer concentration (TB(conc)) and protein to polysaccharide ratio (R(SPI/Chitosan)). The interaction between SPI and chitosan yielded a sponge-like coacervate phase and the optimum conditions for their coacervation were pH 6.0-6.5, a temperature of 25 °C, and a R(SPI/Chitosan) ratio of four independently of TB(conc). NaCl inhibited the complexation between the two biopolymers. Fourier transform infrared spectroscopy (FTIR) revealed that the coacervates were formed through the electrostatic interaction between the carboxyl groups of SPI (-COO(-)) and the amine groups of chitosan (-NH(3)(+)), however hydrogen bonding was also involved in the coacervation. Differential scanning calorimetry (DSC) thermograms indicated raised denaturation temperature and network thermal stability of SPI in the coacervates due to SPI-chitosan interactions. Scanning electron microscopy (SEM) micrographs revealed that the coacervates had a porous network structure interspaced by heterogeneously sized vacuoles.     

Soy protein-polysaccharide complex coacervate under physical treatment: Effects of pH,ionic strength and polysaccharide type

The objective of this paper is to explore the effects of pH, ionic strength and polysaccharide type on the aqueous phase behaviors and rheological properties of soy protein isolate-chitosan (SPI-CS) and soy protein isolate-carboxymethyl cellulose (SPI-CMC) coacervates treated by vortex fluidic device (VFD) and shear homogenization. Characterization in terms of phase behavior and microstructures depicted that the VFD and shear homogenization treatments affected only the SPI-CS complex. According to the ζ-potential values at tested pHs (3.0–8.0), both physical processing had insignificant effect on charge stabilization of protein-polysaccharide complex. Both the SPI-CS coacervates (at pH 7.0) and SPI-CMC coacervates (at pH 3.0) showed gel-type rheological behaviors (G′ > 1000 Pa), suggesting that the SPI and polysaccharides did not form complex coacervate (liquid in nature) but interpolymeric complex (solid in nature). In the absence of salt ions, independent on the type of coacervate, VFD slightly decreased the modulus (G′ < 1000 Pa) while homogenization significantly decreased the modulus (G′ < 20 Pa). Alternatively, the addition of salt ions produced an electrostatic shielding and weakened the protein-polysaccharide electrostatic interaction, resulting in a decrease of coacervate modulus. Interestingly, under certain condition, VFD treatment probably promoted the interaction between protein molecules in protein-polysaccharide coacervate, resulting in another increase in the elastic modulus of the complex coacervate.     

Complex coacervates obtained from lactoferrin and gum arabic: Formation and characterization

Proteins and polysaccharides are the most frequently used hydrocolloids in the food industry, and their interaction can provide products such as complexes coacervates, which can be used as ingredients and biomaterials or in microencapsulation systems. In the present work, the interaction between lactoferrin (0.1, 0.2, 0.3, 0.5 and 1% w/w) and gum arabic (0.1% w/w) with various concentrations of NaCl (0, 0.01, 0.25, 0.3 and 0.5 mol/L) and at various pH values (from 1.0 to 12.0) was studied. The pH for the formation (higher turbidity) of the insoluble complex coacervates (pH_Ø1) varied according to the amount of NaCl used in the system (pH 3.5 to 5.3); these values are below the isoelectric point of lactoferrin (8.0), at which the protein is more positively charged, generating electrostatic binding. At a pH of approximately 2.0, this bond weakens, leading to the solubilization of precipitates, resulting in a sudden decrease in the turbidity (pH_Ø2). Samples containing a lower concentration of lactoferrin (0.1, 0.2 and 0.3% w/w) showed greater turbidity and consequently a higher formation of precipitates or aggregates. Even these samples, which contained a salt concentration of 0.3 mol/L, showed higher turbidity and displacement points of pH_Ø1 and pH_Ø2. The zeta potential and particle size values were used to study the influence of the pH, ionic strength and temperature on the interaction between the biopolymers. It was observed that the formation of macromolecules occurred between the isoelectric point of the protein (8.0) and the pKa of the polysaccharide (2.0), and a certain salt concentration (0.25 mol/L) led to larger particle sizes. It was observed that, at pH 7.0, a concentration of 0.1% gum arabic was able to stabilize the denaturation of the protein in solutions containing 0.1% lactoferrin, resulting in a constant particle size at all temperatures studied.     

阿拉伯木聚糖与壳聚糖复凝聚物的制备及表征

研究了不同因素对壳聚糖-阿拉伯木聚糖复凝聚的影响,通过测定平衡相的浊度和复凝聚相收率确定玉米阿拉伯木聚糖（CAX）和壳聚糖（CS）间复合物形成的条件。采用红外光谱、热重分析、扫描电子显微镜和流变学特性对复凝聚物进行表征。研究结果表明,在CAX/CS配比为9:1,体系pH值为4.0,总固形物浓度为3%（m/m）,室温下反应10 min,最大复凝聚相产率达76.04%。红外光谱和热重分析结果表明,CAX/CS复凝聚物是通过CS中的-NH3+和CAX中-COO-之间的相互吸引形成的。用SEM扫描成像显示复凝聚物具有规则且分布均匀的多孔网络结构。CAX/CS复凝聚物粘弹特性取决于发生复凝聚的pH值。在pH值3.5和4.0时,复凝聚物为液体粘弹行为;在pH值5.0时,复凝聚物为固体粘弹性行为。pH值5.0下形成的复凝聚物的G’最高,说明除静电作用外,其他因素也可能对CAX/CS复凝聚物粘弹特性起重要作用。CAX/CS复凝聚物可以作为包封营养素和功能性因子的微囊化壁材。     

Complex coacervation of pea protein isolate and tragacanth gum: Comparative study with commercial polysaccharides

The ability of pea protein isolates (PPI) to form complex coacervates with tragacanth gum was investigated. The coacervate formation was structurally compared to three other PPI-polysaccharide interaction models: arabic gum and sodium alginate (known to form coacervates with PPI) and tara gum, a galactomannan. The effects of the pH and protein/polysaccharide ratio were mainly investigated using turbidity and zeta potential measurements. Regarding the pH of soluble complex formation, the pH of complex coacervates increased with the increase in protein-anionic polysaccharide mixture ratio. SEM images revealed the ability of the spray-drying process to form spherical particles of pea protein-polysaccharide complexes. The specificity of the microparticle surface was protein-dependent. FTIR analyses of coacervates showed the electrostatic interaction between the PPI and the polysaccharides. The results showed that tragacanth gum could be used as an alternative to gum arabic to form complex coacervates with PPI based on zeta potential measurements and coacervation yield studies.     

酱油渣中蛋白的乳化特性研究

对比分析了酱油渣中蛋白(SRP)、糖基化大豆分离蛋白(GSP)和大豆分离蛋白(SPI)的ξ-电位、疏水性以及乳化活性和乳化稳定性。发现SRP的总糖和蛋白含量比为1∶1.4,其中含有大量的糖蛋白;SRP疏水性是SPI的2.5倍。SRP等电点接近pH=3.5,在酸性环境下溶解性较好。在酸性、高盐环境下SRP乳化能力高于GSP和SPI,在pH=5时,SRP的乳化活性(EAI)是SPI的8.1倍,在NaCl浓度为0.3mol/L时,SRP的EAI是SPI的1.77倍。     

The effect of ionic strength on the rheology of pH-induced bovine serum albumin/κ-carrageenan coacervates

Protein/polysaccharide coacervates are frequently applied to food products to control the rheology. This study investigated the effect of ionic strength (I) on the rheology of pH-induced protein/polysaccharide coacervates. Bovine serum albumin (BSA) and κ-carrageenan were used as a model protein and a polysaccharide, respectively. As the formation of BSA/κ-carrageenan coacervates increased the turbidity of an aqueous mixture, pH_c, pH_?, and pH_max values were identified corresponding to the pH of the formation of soluble coacervates, insoluble coacervates, and large insoluble coacervates respectively. Based on pH_c, pH_?, and pH_max, a state diagram of BSA/κ-carrageenan coacervation versus pH and I was constructed. Involvement of salt in coacervation screened out the electrostatic interaction between BSA and κ-carrageenan coacervation, resulting in the shift of pH_c, pH_?, and pH_max to lower pH. The shift was linearly changed to 1/I^1/2 that corresponded to the Debye length. BSA/κ-carrageenan coacervates were more elastic than viscous. The transition from insoluble coacervates to large insoluble coacervates contributed to enhancement of the rheology, especially in elasticity. An increase in the I of a BSA/κ-carrageenan mixture reduced the degree of coacervation and the elasticity, and the viscosity of BSA/κ-carrageenan coacervates.     

Simplified optimization for microcapsule preparation by complex coacervation based on the correlation between coacervates and the corresponding microcapsule

A close correlation between coacervates and the corresponding microcapsule was established using gelatin and gum arabic as a model system. Through turbidimetric titration and zeta-potential measurement, the optimum coacervates were obtained at pH 4.1 with the mixing ratio of 1:1 (w/w). Comparisons on morphology, yield and internal characteristic of heat-resistance were performed to testify the correlation between coacervates and the corresponding microcapsule. A simplified method for optimization of microcapsule preparation by complex coacervation was then proposed, in which the zeta-potential measurement helps to establish the approximate mixing ratios of wall materials; the turbidity analysis facilitates the finding of suitable pH corresponded to the highest turbidity to make the perfect microcapsule. Then, gelatin and sodium carboxymethyl cellulose was provided as a new combination of wall materials for the verification.     

Complex coacervates obtained from interaction egg yolk lipoprotein and polysaccharides

Protein–polysaccharide coacervates formation was evaluated under influence of pH (3.0, 4.0, 6.5, 8.5 and 10.0), temperature (10, 20, 30, 40 and 50 °C) and polysaccharide mass (0.025, 0.033 and 0.050 g). It was possible to observe that solutions with lower turbidity values were found in pH band 3.0 to 4.0. Statistical analysis of turbidity data have shown that for all polymers pH was meaningful in coacervate formation, although for some, besides pH, temperature and polymer concentration could also influence significantly (p < 0,05) in coacervate formation. Encapsulates morphology made by coacervation was directly linked to the kind of polymer used and its interactional degree. Dehydrated coacervates have presented heterogeneous morphology, different from their original structures.     

玉米醇溶蛋白/阿拉伯胶负载槲皮素纳米颗粒制备

以玉米醇溶蛋白为载体,阿拉伯胶为稳定剂,反溶剂法制备负载槲皮素的玉米醇溶蛋白-阿拉伯胶纳米颗粒。考察阿拉伯胶浓度、槲皮素与玉米醇溶蛋白/阿拉伯胶质量比、p H、盐离子强度等因素对纳米颗粒稳定性的影响。结果表明,阿拉伯胶质量浓度50 g/L,制得粒径201.5 nm,多分散指数0.35,电位-31.5 mV的稳定玉米醇溶蛋白/阿拉伯胶载体;槲皮素/玉米醇溶蛋白-阿拉伯胶质量比1︰10时,粒径、颗粒分散性、ζ-电位均在稳定范围内,且包封率和负载率能达到84.3%和13.96%以上;盐离子浓度高于30 mmol/L时,玉米醇溶蛋白与阿拉伯胶之间的静电作用减弱,纳米颗粒体系不稳定,发生聚集;纳米颗粒能经历广泛pH变化,不发生聚集,大幅提高了包埋对象的生物利用度。