醇变性大豆7S球蛋白结构特征研究

利用不同体积分数乙醇溶液对大豆7S球蛋白进行变性。分别对醇变性大豆7S球蛋白溶解度、表面疏水性、二级结构和聚集形态进行分析。大豆7S球蛋白经醇溶液变性后,溶解度在乙醇体积分数为55%~65%时基本达到最低值;表面疏水性在乙醇体积分数为25%和65%时分别达到最大值和最小值。傅立叶红外光谱表明,在乙醇体积分数较低时,β-折叠结构能稳定存在;在乙醇体积分数较高时,β-折叠和α-螺旋之间结构发生转变,呈现较高螺旋态。凝胶电泳表明,7S球蛋白亚基间以非共价相互作用力为主;经醇变性后,导致聚集体产生,且7S球蛋白分子间非共价相互作用随乙醇体积分数增大呈有逐渐增大趋势。     

白酒对浙东白鹅肌原纤维蛋白结构的影响

以浙东大白鹅为原料,拉曼光谱技术为主要分析手段,研究白酒体积分数对浙东白鹅胸脯肉肌原纤维蛋白结构的影响。结果显示,随着白酒体积分数的增大,肌原纤维蛋白溶解度增大(p0.05),表面疏水性降低(p0.05)。在白酒体积分数较低时形成的凝胶特性较好,其微观结构很均匀,随着白酒体积分数的进一步增大,凝胶网络孔径变大,蛋白凝胶保水性显著降低(p0.05)。随着白酒体积分数的增大,二硫键的三种构象之间发生了转变;对照组中酰胺Ⅰ带的主峰出现在1655 cm-1,α-螺旋的含量为40.45%;而当体积分数为2%时,1668 cm-1成为主峰(无规卷曲),α-螺旋和β-折叠含量显著下降(p0.05),无规卷曲显著上升为31.58%(p0.05)。结果表明白酒能够影响肌原纤维蛋白的结构和凝胶特性。     

醇法菜籽浓缩蛋白提取工艺研究

以菜籽粕为原料,对乙醇法制取菜籽浓缩蛋白进行了研究.分别考察了浸提温度、浸提次数、乙醇体积分数和溶剂比对菜籽浓缩蛋白蛋白含量的影响.由单因素试验和正交试验得出醇法菜籽浓缩蛋白的最佳浸提条件为:浸提温度60℃,浸提次数6次,乙醇体积分数80%,溶剂比9:1,pH4.0.在此条件下所得菜籽浓缩蛋白的蛋白含量为65.96%,提取率为71.54%.     

射流空化对大豆11S球蛋白结构和功能特性的影响

以大豆11S球蛋白为研究对象,探究射流空化处理时间对不同质量浓度大豆11S球蛋白结构(荧光光谱、傅里叶变换红外光谱、表面疏水性以及羰基、巯基和二硫键含量)与功能特性(溶解度、乳化特性、起泡特性)的影响。结果显示:在射流空化处理下,2 g/100 mL与5 g/100 mL大豆11S球蛋白的荧光最大吸收波长(λ_(max))随处理时间的延长呈先红移后蓝移的趋势,荧光强度呈先升高后降低的趋势,且5 g/100 mL大豆11S球蛋白λ_(max)均大于2 g/100 mL;2 g/100 mL大豆11S球蛋白中α-螺旋与β-折叠转变为β-转角,在处理末期,β-转角向α-螺旋转变,无规卷曲结构相对含量在处理过程中变化不明显;5 g/100 mL大豆11S球蛋白中α-螺旋、β-折叠与β-转角转变为无规卷曲结构,在处理末期,无规卷曲和β-转角向α-螺旋和β-折叠转变;两种质量浓度的大豆11S球蛋白表面疏水性、羰基与游离巯基含量均随处理时间的延长呈先升高后下降的趋势,二硫键含量呈现先下降后升高的趋势;11S球蛋白的溶解度、乳化特性与起泡特性均得到明显改善,且5 g/100 mL大豆11S球蛋白与2 g/100 mL大豆11S球蛋白相比,结构和功能特性的变化更明显。结果表明:射流空化技术可改变大豆11S球蛋白的结构,进而改善其溶解、起泡和乳化特性,且5 g/100 mL大豆11S球蛋白的展开与聚集程度更明显,功能特性更佳。     

不同低水解度的大米蛋白溶解性与结构变化的关系

为了研究不同水解度的大米蛋白溶解性与其结构变化之间的关系,本文采用碱性蛋白酶处理大米蛋白,得到不同低水解度的大米蛋白(0%、1%、3%、5%),并表征了不同水解度蛋白的溶解性、二硫键含量、表面疏水性、微观结构和分子量。结果表明,在p H2.0~11.0范围内,各蛋白样品的溶解度均呈现先降低后升高的趋势,且在同一p H下,溶解度随水解度的增大而增大。尤其是在水解度为5%时,蛋白溶解度达到最高为65.93%。随着水解度的增大,蛋白样品的分子量、二硫键含量及表面疏水值发生了显著降低(p≤0.05)。这些变化可能是因为蛋白分子内部结构的变化,导致蛋白质的结构发生去折叠或者解聚现象,促使大米蛋白内部亲水基团暴露,从而提高蛋白质的溶解度。扫描电镜显示原料蛋白颗粒不均一,质地坚硬,而酶解后的蛋白颗粒大小相对均一,表面有较多孔洞且较蓬松。随着水解度的增大,蛋白样品的结构和性质发生更加显著的变化。这些结构变化可能导致大米蛋白溶解性提高。     

热处理对大豆11S球蛋白表面疏水性的影响及拉曼光谱分析

研究热处理对大豆11S球蛋白表面疏水性（H0）的影响,并对蛋白质拉曼光谱进行分析。随着热处理时间的延长,在80?℃热处理下,大豆11S球蛋白的H0增加,二级结构中α-螺旋结构转变为β-转角和无规卷曲结构。在90?℃和100?℃热处理下,H0先增加后稍有降低,且100?℃热处理下H0变化地更快,且变化程度更大,α-螺旋和β-折叠结构转变为β-转角和无规卷曲结构。此外,热处理会使蛋白分子中的酪氨酸和色氨酸残基趋于“暴露”态,同时改变11S球蛋白分子间二硫键的振动模式,使二硫键由g-g-g构型转变为t-g-t构型,这可能会导致蛋白质H0的升高。     

醇法大豆浓缩蛋白浸提工艺研究

主要介绍了乙醇浸提法生产大豆浓缩蛋白的浸提工艺。探讨了主要工艺参数:乙醇浓度、浸提时间、浸提温度对整个浸提工艺的影响。通过正交试验确定了醇法生产大豆浓缩蛋白的最佳浸提工艺条件为:乙醇浓度70%,浸提时间90 m in,浸提温度50℃,在此条件下生产的大豆浓缩蛋白其蛋白含量可达到75.48%。     

亚油酸氧化诱导大豆分离蛋白氧化对其结构的影响

利用脂肪氧合酶催化不同底物浓度亚油酸氧化大豆分离蛋白,通过测定氧化后大豆分离蛋白的羰基值、巯基、表面疏水性、内源荧光以及凝胶电泳等指标,对氧化修饰后大豆分离蛋白的结构进行分析,并通过分析氧化后大豆分离蛋白在不同溶剂中溶解性能表征其分子间相互作用力。结果表明,随体系中亚油酸浓度的增加,大豆分离蛋白羰基含量增加56.3%,总巯基和游离巯基含量降低,表面疏水性呈先增大后减小趋势,内源荧光强度降低,发生先红移后蓝移现象,大豆分离蛋白粒径先减小后增大,主要分布于5~40 nm之间,蛋白质氧化过程发生去折叠和重聚集,蛋白质交联中存在非二硫键共价键生成。     

热榨芝麻饼生产浓缩蛋白工艺条件的研究

以热榨芝麻饼为原料,利用正己烷-50%乙醇混合溶剂浸提生产芝麻浓缩蛋白。以混合溶剂中乙醇体积分数、醇洗时间、固液比和浸提温度为考察因素,进行单因素实验和正交实验,研究热榨芝麻饼生产浓缩蛋白的最佳工艺。结果表明,芝麻浓缩蛋白最佳生产工艺条件为:混合溶剂中乙醇体积分数55%,浸提温度55℃,固液比1∶6,醇洗时间85 min。在最佳条件下所得芝麻浓缩蛋白的粗蛋白质含量为66.89%,粗脂肪含量为0.53%,氮溶解指数为2.56%。     

使用圆二色性光谱分析二级结构对大豆分离蛋白表面疏水性的影响

旨在采用圆二色性光谱手段研究二级结构对我国六种经常使用的大豆品种制备而成的分离蛋白的表面疏水性的影响。实验先是对六个品种的大豆进行分离蛋白的提取,并对其性质进行测定,包括溶解度和表面疏水性;再对六种大豆分离蛋白的二级结构进行测定和分析;通过SPSS软件对六种大豆分离蛋白的表面疏水性和二级结构的数值进行线性相关性分析,探究二者之间的构效关系。研究中发现六个品种的大豆分离蛋白的二级结构、溶解性、表面疏水性都差异显著(p0.05),表面疏水性的大小随着α-螺旋含量升高而减小,随着无规则卷曲和β-折叠含量增大而提高,因β-转角含量变化的影响不明显。SPSS线性相关性分析表明品种间的表面疏水性与β-转角含量线性关系不显著,与无规则卷曲、β-折叠含量呈正向相关,与α-螺旋含量呈负向相关。     

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。