大豆蛋白/蛋清蛋白复合凝胶性能的影响因素

蛋清蛋白可作为大豆蛋白热致凝胶形成过程中游离巯基的供体,赋予凝胶良好的质构。该研究考察在不同影响因素(还原剂、离子强度、热处理及多糖)下大豆蛋白+蛋清蛋白复合凝胶的成胶特性、持水性及微观性质,揭示诱导凝胶二硫键形成复合凝胶网络结构的最优条件。结果表明,蛋清蛋白的加入可以增加大豆蛋白凝胶的二硫键含量,显著改善其硬度及持水性。低浓度的NaCl、NaHSO₃和结冷胶有助于凝胶形成更多二硫键,保持更好的质构强度和持水性。随着热处理时间延长,蛋白有更多机会及充足时间打开原有二硫键并生成更多的二硫键,复合体系形成的凝胶的强度和持水性也随之提高。由NaCl、NaHSO₃和结冷胶共同作用的多条件复合凝胶能够拥有最优的凝胶强度及持水性能。     

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。     

黄原胶和魔芋胶抑制碱诱导鸭蛋清凝胶的高温液化

本研究分别将黄原胶和魔芋胶添加至鸭蛋清中制备碱诱导凝胶,以探究亲水胶体对凝胶高温液化的抑制作用,结果表明:与对照组相比,添加亲水胶后的蛋清凝胶黏度、储能模量和损耗模量增大明显(p<0.05),褐变强度增加了7.99%和33.21%;当黄原胶和魔芋胶的浓度由0.50%增加至1.50%,凝胶硬度值提高49.60%和119.56%,穿刺强度提高20.59%和78.42%,持水性提高1.02%和9.47%,且添加黄原胶的蛋清凝胶硬度、穿刺强度和持水性均显著大于魔芋胶(p<0.05)。两种胶的浓度均为1.00%时,蛋清凝胶的感官评分最高。两种亲水胶的加入会改变蛋白质的二级结构及凝胶内部的分子间作用力:黄原胶量的增加显著降低了离子相互作用(p<0.05),无规则卷曲减少了41.23%,α-螺旋增加了81.29%;魔芋胶量的增加显著降低了疏水相互作用(p<0.05),β-折叠减少了34.97%,无规则卷曲和α-螺旋分别增加了68.97%和70.37%;氢键和二硫键均随两种胶浓度的增加而增强。综上所述,添加黄原胶和魔芋胶均能抑制碱诱导蛋清凝胶在高温处理过程中的液化现象,且加入黄原胶所形成的凝胶质构特性和持水性优于魔芋胶,而魔芋胶对于凝胶褐变强度的影响大于黄原胶。     

亚麻粕分离蛋白对鱼糜制品品质特性的影响

以大豆蛋白(SPI)、谷朊粉(WG)为对照品,研究亚麻粕分离蛋白(FPI)对鱼糜制品凝胶特性、色泽特性和持水性的影响,应用响应面法探索亚麻粕分离蛋白(FPI)、亚麻胶(FG)、卡拉胶(KCG)复合应用于鱼糜制品的最优添加配比。结果表明:向鱼糜制品中单独添加FPI可提高鱼糜的凝胶强度、持水性;响应面分析得到添加FPI 11.01%、FG 0.34%、KCG 0.30%,鱼糜的凝胶强度为4 935.03 g·mm,是对照组的1.57倍。     

热诱导大豆分离蛋白对肌原纤维蛋白凝胶特性的影响

大豆分离蛋白(soybean protein isolate,SPI)经60、80和95℃热处理,分别与鱼肌原纤维蛋白(myofibrillar protein,MP)按质量比1∶3(总蛋白质量浓度45 g/L)热诱导得到混合蛋白凝胶。结果表明,从流变特性来看,与天然大豆分离蛋白复合凝胶(MP-N-SPI)相比,MP-SPI(80℃)的储能模量值(G')(P 0. 05)显著上升,而MPSPI(60℃和95℃)却低于MP-N-SPI。在MP中加入SPI后,复合凝胶的持水性均高于单纯MP,适宜的热诱导温度SPI(80℃),可以明显改善复合凝胶的持水力(water holding capacity,WHC)(P 0. 05)。从质构特性看出,MP-SPI(95℃)的硬度显著提升。电泳图谱显示,MP-N-SPI凝胶条带与单纯MP无明显差异,MP-SPI(80℃和95℃)条带比MP-N-SPI和MP-SPI(60℃)浅,说明预热SPI(80℃或95℃)容易与MP相互作用。化学力测定显示,预热大豆蛋白与MP的凝胶网络形成主要是疏水作用的结果,而氢键和二硫键不是复合凝胶形成的主要化学力。由此可见,适宜的热诱导大豆分离蛋白,可以明显改善复合凝胶的特性。     

不同热处理条件制备的大豆分离蛋白凝胶性质研究

为了改善大豆分离蛋白(SPI)的凝胶性能,研究了SPI制备过程中采用不同热处理对产品凝胶性质的影响。结果显示,碱溶酸沉中的不同阶段加热可以显著提高SPI的凝胶强度和凝胶持水性,并可降低SPI的凝胶温度。热处理条件最佳组合为碱溶阶段60℃,酸沉阶段40℃,中和阶段超高温瞬时处理(130℃,4 s)。热处理后SPI130产品凝胶温度从80℃降低为62.7℃;其凝胶强度为54 g,比未经热处理低变性SPI样品的凝胶强度(9.9 g)提高了4.5倍,比商业SPI的凝胶强度(19 g)提高了1.8倍;其凝胶持水性比未经热处理低变性SPI样品的凝胶持水性(27%)提高了58.3%。     

酶解大豆蛋白/乳蛋白基质复合凝胶的制备与功能性质研究

为改善蛋白基质凝胶的功能性和多样性,6%大豆蛋白经4%的酶(酶与蛋白质量比)在pH 8.0,37℃水解10~180 min,分别与6%乳清蛋白和6%酪蛋白混合均匀,分别调节pH至6.5和8.0,90℃水浴加热30 min,冰浴至室温成胶。对所得复合凝胶的质构特性、溶胀性、持水性、蛋白浸出率以及胶体内分子间的作用力等进行表征,结果表明,胰蛋白酶处理大豆蛋白2 h,水解度达到最大(35%)并基本保持不变;乳蛋白与大豆蛋白复合能提高复合凝胶的质构特性,然而大豆蛋白水解则降低复合凝胶的这种性质,并显著提高复合凝胶的溶胀率,降低复合凝胶持水性和蛋白质浸出率,其值随着浸出时间的增加而显著增加,达90%左右。化学作用力分析显示,水解主要降低分子间的氢键作用,提高二硫键作用。感官分析表明,加入高水解度的大豆蛋白可显著提高复合凝胶的黄度,降低其透明性。适当水解大豆蛋白,是大豆蛋白-乳蛋白复合凝胶功能改造的一种方法。     

大豆分离蛋白热变性程度对肌纤维蛋白凝胶性质的影响

研究大豆分离蛋白(SPI)热变性程度对肌肉纤维蛋白(MPI)凝胶性质的影响.将SPI在80,90,100℃分别热处理0,15,30,60,100,180 min,得到一系列不同热变性程度的SPI,将其与MPI按1:3(V:W,总蛋白浓度为4%)的比例混合,热诱导得到混合蛋白凝胶.分别研究这些混合蛋白的流变学性质、凝胶性质以及凝胶持水性.结果表明:热变性的SPI有利于混合凝胶的性质提高,经过100℃热处理180 min的SPI与MPI形成的混合蛋白的弹性模量G'值最大,凝胶强度和弹性也最接近纯MP凝胶性质,持水性甚至好于纯MP凝胶性质.     

氯化钙诱导大豆分离蛋白冷凝胶相图与流变性质研究

主要研究了Ca Cl2诱导大豆分离蛋白冷凝胶在不同预加热温度、蛋白质含量和盐浓度下的相图、持水性与流变性质。结果表明:随着预加热温度的升高(75~95℃),诱导大豆分离蛋白冷凝胶形成所需要的Ca Cl2浓度降低,且相同条件下,蛋白质含量越高,冷凝胶越易形成;冷凝胶持水性与蛋白质含量成正比,与Ca Cl2浓度成反比,而在85℃预加热温度下冷凝胶持水性最高,75℃预加热温度条件下冷凝胶持水性最低;随着蛋白质含量、预加热温度和Ca Cl2浓度增加,冷凝胶的凝胶强度和屈服应力逐渐增加;冷凝胶的线性黏弹性区域(LVE)在15 mmol/L Ca Cl2浓度下随蛋白质含量增加而增加,但在10 mmol/L Ca Cl2浓度下呈现出相反的变化趋势;15 mmol/L Ca Cl2诱导冷凝胶在一定应变下会发生流动现象,而10 mmol/L Ca Cl2诱导冷凝胶没有流动现象,表明两种Ca Cl2浓度下形成的冷凝胶结构有很大差异。     

NaCl对γ-聚谷氨酸-大豆分离蛋白复合凝胶特性的影响

为提升γ-聚谷氨酸-大豆分离蛋白复合凝胶特性，在复合凝胶体系中加入氯化钠，采用激光共聚焦、质构仪和流变仪测定复合凝胶的微观结构、质构特性和流变特性。结果表明，蛋白浓度为12%的复合凝胶网络结构更加致密且耐盐性更强；当加入0.1 mol/L的NaCl时，复合凝胶内部形成了众多尺寸较小且大小均一的球状空隙，复合凝胶的持水性增加，硬度增加，弹性、内聚性和胶黏性也均增大，而0.5 mol/L NaCl的加入削弱了凝胶网络结构的形成。由此显示，低浓度NaCl有助于复合凝胶形成较好的凝胶体系，提高复合凝胶的强度。     

Co-precipitation of whey and pea protein – indication of interactions

The aim was to optimise the yield of co-precipitation of whey protein isolate (WPI) and pea protein isolate (PPI) and compare co-precipitates and protein blends with respect to solubility. The yield of co-precipitates was tested with different protein ratios of WPI and PPI in combination with different temperatures and acid precipitation (pH 4.6). The highest precipitation yield was obtained at protein ratios WPI < PPI, high temperature and alkaline protein solvation. The solubility was measured by an instability index and absorption spectroscopy of re-suspended precipitated proteins at pH 3, 7 and 11.5. Co-precipitates had significantly lower solubility than protein blends. Protein ratios WPI > PPI, low precipitation temperature and high pH showed the highest solubility. Differences in protein composition between co-precipitates and protein blends were observed with SDS-PAGE and matrix-assisted laser desorption ionisation time-of-flight, and indicated different protein–protein interaction in samples, which needs further investigations.     

大豆蛋白溶解性研究

该文概述大豆蛋白溶解特性及其与一般物质溶解差异,介绍提高大豆蛋白溶解性改性方法及研究现状,对比不同改性增溶方法优、缺点,并提出今后大豆蛋白改性研究方向。     

细菌中蛋白质样品制备方法研究进展

细菌在生长繁殖时,细菌蛋白的表达受到环境影响而存在较大差异,使得细菌蛋白表达具有复杂性.在食品生产加工过程中可能会受到致病菌污染,细菌产生的内毒素和外毒素均会对人体健康构成威胁,因此需要高灵敏度和高特异性的检测方法来定量分析和鉴定食品中的细菌毒素.蛋白组学方法可以揭示细菌蛋白组成及其潜在的生物学功能,感染过程中菌体蛋白...     

Physicochemical and Functional Properties of Soy Protein Substrates Modified by Low Levels of Protease Hydrolysis

ABSTRACT: Endo-protease treatments achieving low degrees of hydrolysis (DH 2% and 4%) were used to improve functional properties of hexane-extracted soy flour (HESF), extruded-expelled partially defatted soy flour (EESF), ethanol-washed soy protein concentrate (SPC), and soy protein isolate (SPI). These substrates had protein dispersibility indices ranging from 11% to 89%. Functional properties, including solubility profile (pH 3 to 7), emul-sification capacity and stability, foaming capacity and stability, and apparent viscosity were determined and related to surface hydrophobicity and peptide profiles of the hydrolysates. Protein solubilities of all substrates increased as DH increased. Emulsification capacity and hydrophobicity values of the enzyme-modified HESF and EESF decreased after hydrolysis, whereas these values increased for SPC and SPI. Emulsion stability was improved for all 4% DH hydrolysates. Hydrolyzed SPC had lower foaming capacity and stability. For substrates other than SPC, foaming properties were different depending on DH. Hydrolysis significantly decreased the apparent viscosities regardless of substrate. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) indicated differences in the molecular weight profiles of the hydrolysates. HESF and EESF, which had high proportions of native-state proteins, showed minor changes in the peptide profile due to hydrolysis compared with SPC and SPI.     

大豆蛋白生产与应用现状

该文综述大豆蛋白制品—大豆蛋白粉、大豆分离蛋白、大豆浓缩蛋白、大豆组织蛋白生产现状、存在问题及大豆蛋白在面制品、肉制品、乳制品、饮料制品等中应用现状。     

Effects of silage protein degradability and fermentation acids on metabolizable protein concentration: A meta-analysis of dairy cow production experiments

A meta-analysis was conducted using data from dairy cow production studies to evaluate silage metabolizable protein (MP) concentrations. The data consisted of 397 treatment means in 130 comparisons, in which the effects of silage factors (e.g., date of harvest, wilting, silage additives) were investigated. Within a comparison, a fixed amount of the same concentrate was fed. A prerequisite of data to be included in the analysis was that silage dry matter (DM), crude protein (CP), ammonia N, lactic acid (LA), and total acid (TA) concentrations and digestibility were determined. A smaller data set (n = 248) comprised studies in which silage water-soluble N concentration was also analyzed. The supply of MP was estimated as amino acids absorbed from the small intestine using a model with constant values for ruminal effective protein degradability (EPD) and intestinal digestibility of rumen undegraded protein. Microbial protein was calculated on the basis of digestible carbohydrates and rumen degradable protein (RDP). Alternative models were used to estimate microbial protein formation, assuming the energy values of RDP and TA to be equivalent to 1.00, 0.75, 0.50, 0.25, and 0 times that of digestible carbohydrates. Because EPD values are seldom determined in production trials, they were derived using empirical models that estimate them from other feed components. The goodness of fit of models was compared on the basis of root mean squared error (RMSE) of milk protein yield (MPY) predicted from MP supply (adjusted for random study effect) and Akaike's information criterion. Metabolizable protein supply calculated from basal assumptions predicted MPY precisely within a study (RMSE = 16.2 g/d). Variable contribution of RDP to the energy supply for microbial synthesis influenced the precision of MPY prediction very little, but RMSE for MPY increased markedly when the energy supply of rumen microbes was corrected for TA concentration. Using predicted rather than constant EPD values also increased RMSE of MPY prediction. These observations do not mean that the supply of MP from undegraded feed protein is constant. However, it suggests that our current methods overestimate the range in EPD values and that the techniques have so many inherent technical problems that they can mask the true differences between the feeds. Including new elements in feed protein evaluation models may not improve the precision of production response predictions unless the consequent effects on the supply of other nutrients are taken into account.     

The structures and functions of ice crystal-controlling proteins from bacteria

Many organisms have evolved into unique mechanisms which minimize freezing injury due to extracellular ice formation. Specifically, certain bacteria have produced a few proteins each with different functions. For example, the ice nucleation protein acts as a template for ice formation, which is responsible for imparting ice nucleating activity. The anti-nucleating protein inhibits the fluctuation of ice nucleus formation by a foreign particle in the water drop. Also, the antifreeze proteins depress the freezing temperature, modify or suppress ice crystal growth, inhibit ice recrystallization, and protect the cell membrane from cold-induced damage. In this article, a review on the current knowledge of the structure and the function of these three types of proteins, which are capable of interacting with ice itself or its nuclei from bacteria.     

Effect of amidation on the foaming and physico-chemical properties of bovine serum albumin

Amidation of bovine serum albumin (BSA) was achieved by a water-soluble carbo-diimide, ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC)-mediated reaction using ammonium chloride as the nucleophile. Partial and substantial amidation of 0.5% (w/v) BSA in 5.5 m ammonium chloride solution with 1 times 10-²mmol EDC over 120 min and 1 times 10^-1mmol EDC over 10 min respectively was achieved on a large scale using diafiltration for rapid termination of the reaction and purification. Residual ammonium chloride otherwise enhanced foaming properties. The amidated proteins were characterized by isoelectric focusing, electrophoresis and hydrophobicity and disulphide- and sulphydryl-group measurements. Compared with native BSA, partially amidated BSA (PA-BSA) produced enhanced foam expansion and foam stability values. This was attributed to minimal denaturation and to the presence of both acidic and basic components (pI range 5.25–7.50) within the single protein. In contrast, substantially amidated BSA (SA-BSA) (pI range 7–9.1) had similar foaming properties to those of the ultrafiltered BSA control which were slightly lower than those of native BSA. However SA-BSA interacted synergistically with native BSA producing enhanced foaming properties particularly at the 1:1 ratio through electrostatic interactions, conformational changes and increased hydrophobicity.     

大豆分离蛋白改性对其功能性质影响

大豆分离蛋白是大豆蛋白最为精制形式,广泛应用于食品工业,并在不同产品中表现出不同功能。该文综述近年来大豆分离蛋白物理、化学、酶法及基因工程改性对其功能性质影响,经不同方式改性可产生合适功能性质,从而拓宽大豆分离蛋白在食品工业中应用。     

芝麻蛋白研究概况

简述芝麻蛋白的结构及氨基酸组成、蛋白质性质和应用,并展望进一步研究芝麻蛋白的 前景。