小米蛋白的分子组成及结构特性

利用十二烷基硫酸钠-聚丙烯酰胺凝胶电泳、扫描电子显微镜、差示扫描量热法以及傅里叶红外光谱（Fourier transform infrared spectrometer,FTIR）对小米中4 种蛋白组分进行结构特性分析。研究表明,醇溶蛋白是由低分子质量亚基（11～25 kDa）构成,而清蛋白、球蛋白和谷蛋白亚基分布较广（11～180 kDa）,其中清蛋白所含亚基数目最多,醇溶蛋白、清蛋白以及球蛋白分子之间连接紧密,以聚集状态存在,而谷蛋白分子连接松散,表面光滑。球蛋白在71.33 ℃条件下发生变性;醇溶蛋白的变性温度最高,达到110.67 ℃。FTIR研究表明,醇溶蛋白、谷蛋白和球蛋白的二级结构主要由β-折叠构成,其含量分别为37.72%、43.39%、42.23%;β-转角以及β-反平行折叠结构含量最丰富的是醇溶蛋白,分别为16.64%和12.73%。4 种蛋白组分结构含量差异显著（P＜0.05）。     

米渣谷蛋白的纯化及功能性质研究

按照Osborne蛋白分级提取渣蛋白,分别得到了清蛋白、球蛋白、醇溶蛋白和谷蛋白,然后采用α-淀粉酶对谷蛋白进行纯化,提纯的谷蛋白纯度可达到90%以上,进而研究食品体系中pH、盐离子和多糖等因素对米渣谷蛋白溶解性、乳化性和乳化稳定性的影响。pH在远离等电点时,有利于谷蛋白的溶解,并提高了乳化性和乳化稳定性;在0.5%NaCl溶液中,谷蛋白的溶解性和乳化性最大,而NaCl浓度为1.0%时,乳化稳定性最低;卡拉胶的添加能显著提高谷蛋白的溶解性、乳化性和乳化稳定性,但过量的卡拉胶会破坏谷蛋白的乳化稳定性。     

不同莲子蛋白氨基酸结构与热特性研究

目的：研究不同莲子蛋白(分离蛋白、清蛋白、球蛋白、醇溶蛋白、谷蛋白)的氨基酸组成结构与热特性的差异。结果：谷氨酸含量均占比最高，且含有较多带负电荷的极性氨基酸基团。莲子蛋白的E/T、E/N比值与FAO/WHO提出氨基酸比值接近，说明莲子蛋白氨基酸组成与含量均衡。电子能谱中硫元素谱图显示，清蛋白具有更高的吸收峰值，表明其他蛋白中可能含有较多的二硫键，而巯基含量较少。热特性分析表明，莲子蛋白在90℃时逐渐变性，200℃后发生玻璃化转变，内部有序结构向无序转变。其中分离蛋白、醇溶蛋白、谷蛋白的热变性温度高，可能是因为分子内部二硫键含量较高，结构紧密，且在热特性变化中重量损失更大，功能性基团改变。结论：分析不同莲子蛋白氨基酸组成、含量以及热特性的差异性，可为莲子蛋白更深入的基础性研究提供科学依据。     

米胚蛋白组分的提取及功能性质研究

采用Osborne的方法,从米胚中提取清蛋白、球蛋白、醇溶蛋白和谷蛋白,4种蛋白中谷蛋白的含量最高,占72.69%,其余3种蛋白的含量相差不大;考察4种蛋白的溶解性得出,在pH5下4种蛋白的溶解性最低,随着pH的增大或减小,溶解性逐渐增加,且清蛋白和球蛋白的溶解性较醇溶蛋白和谷蛋白高;在pH11、0.1mol/L NaCl浓度、1mg/mL蛋白浓度下,加入3mL大豆油,4种蛋白的乳化活性及乳化稳定性均达到最大值。     

挤压处理对薏米蛋白组分结构及功能性质的影响

以脱脂薏米粉为原料进行挤压,采用Osborne分级法提取清蛋白、球蛋白、醇溶蛋白与谷蛋白,探讨挤压处理对4种蛋白组分结构与功能性质的影响。结果表明,挤压后4种蛋白组分的粒径均呈下降趋势（低至3 nm）。挤压导致清蛋白、球蛋白与谷蛋白发生不同程度的聚集融合,游离巯基含量分别降低了72.37%,40.64%和51.71%,蛋白的最大荧光吸收波长蓝移,电泳图谱中高分子质量区域分布的条带逐渐消失,亚基种类减少,而醇溶蛋白无明显变化。除球蛋白外,挤压后清蛋白、醇溶蛋白与谷蛋白中有序结构,即α-螺旋与β-折叠结构的含量明显下降（P <0.05）,分别减小了1.58%,22.88%和7.75%。此外,挤压后清蛋白、球蛋白与谷蛋白的持水性分别提高了1.74,3.18倍和4.89倍,持油性分别增长了2.00,2.23倍和1.67倍。结论：挤压处理诱导清蛋白、球蛋白与谷蛋白的结构性质发生明显改变,而醇溶蛋白具有较高的结构稳定性与抗热剪切能力。研究结果为薏米蛋白组分的工业化制备及在多种食品配方中的应用提供参考。     

甜荞蛋白质组分的物化特性研究

研究甜荞不同蛋白组分的物化特性.采用分步提取法分离收集甜荞清蛋白、球蛋白、醇溶蛋白和谷蛋白.结果表明甜荞清蛋白、球蛋白、醇溶蛋白和谷蛋白的含量分别占总蛋白的21.91%、19.36%、2.26%和19.95%,等电点分别为pH4.40、5.00、4.80和4.60,变性温度分别为79.39℃、70.36℃、80.04℃和83.09℃,前三种蛋白白色略偏黄,而谷蛋白偏红色.甜荞清蛋白、球蛋白和谷蛋白的必需氨基酸含量丰富.甜荞清蛋白含铁量高,醇溶蛋白含锌量高,球蛋白含镁量高,而铅、锡、砷在各蛋白质组分中的含量均很低.     

4种花生粕蛋白的理化性质及功能特性研究

以花生粕为原料,采用分级提取工艺提取花生清蛋白、球蛋白、醇溶蛋白和谷蛋白,研究4种花生粕蛋白的理化性质和功能特性。扫描电镜观察,4种花生粕蛋白的形态结构各不相同。SDS-PAGE法测定分子量表明,清蛋白含有4种亚基,相对分子量分别为70kDa、40kDa、30kDa、25kDa和15kDa;醇溶蛋白含有2种亚基,分子量分别为25kDa和15kDa;球蛋白含有5种亚基,分子量分别为40kDa、38kDa、30kDa、25kDa和15kDa;谷蛋白含有4种亚基,分子量分别为40kDa、30kDa、25kDa和15kDa。花生清蛋白、醇溶蛋白、球蛋白、谷蛋白的等电点分别为pH3.6、pH5.2、pH4.6、pH5.0。功能性质研究表明,球蛋白的持水性最好,为1.52mL/g,其次为谷蛋白1.10mL/g,清蛋白和醇溶蛋白的持水性较低分别为0.49mL/g、0.14mL/g;清蛋白的持油量相对较高为8.21mL/g,其次为球蛋白为7.16mL/g,谷蛋白和醇溶蛋白的持油量相对较低,分别为3.82mL/g和5.49mL/g;清蛋白的乳化性和乳化稳定性相对较高,乳化能力EC值和乳化稳定性ES值分别为71.4% 和83.33%,谷蛋白次之,EC和ES值分别为66.7% 和82.86%,醇溶蛋白和球蛋白相对较低,EC值分别为64.0% 和62.2%,ES值分别为82.35% 和76.67%。综上,花生粕清蛋白的持油性、乳化性和乳化稳定性相对较好。     

不同酸碱体系中绿豆蛋白功能及构象

探讨了不同酸碱体系中绿豆分离蛋白、清蛋白和球蛋白的构象和溶解度、乳化性、乳化稳定性。结果表明:绿豆分离蛋白、清蛋白和球蛋白在酸性体系中溶解度、乳化性和乳化稳定性较低,随着pH的升高其功能特性随之升高;绿豆分离蛋白的α-螺旋结构在接近等电点时较低,随着pH的升高,α-螺旋结构升高,β-折叠结构和无规则卷曲结构含量随pH的增大而降低;绿豆球蛋白在碱性体系中,β-折叠结构和无规则卷曲结构的含量呈现先降低后升高的趋势,β-转角结构的含量呈现先升高后降低的趋势;绿豆清蛋白在酸性条件下的α-螺旋结构含量、β-转角结构和无规则卷曲结构较高,随着pH值的升高,β-转角结构逐渐向的α-螺旋、β-折叠、无规则卷曲等结构变化;在不同酸碱体系中绿豆蛋白的空间构象不同,造成各条件下所暴露的基团不同,进而影响绿豆蛋白的功能特性。这为绿豆蛋白加工利用过程中功能特性变化规律研究提供可靠的理论依据。     

非洲山毛豆蛋白质组成及其功能特性研究

以山毛豆种子为原料,研究其蛋白质组成及其功能特性。结果表明,脱脂山毛豆粉的总蛋白质量分数为47.11%,其中清蛋白、球蛋白、醇溶蛋白和谷蛋白的质量分数分别为64.04%、8.83%、11.06%和14.50%,另有1.57%的难溶复合蛋白。清蛋白和谷蛋白在pH4和球蛋白和醇溶蛋白在pH5溶解性、起泡性、乳化性均差,而泡沫稳定性和乳化稳定性较好。各蛋白组分的持水持油性均较好。在pH5或pH4的条件下,清蛋白和球蛋白的溶解性、起泡性和乳化性较好,其余蛋白组分相对较差。与大豆蛋白相比,山毛豆主要蛋白清蛋白有较好的溶解度、持水持油性、起泡性、泡沫稳定性、乳化性及乳化稳定性。     

小米中四种蛋白的分级提取及结构表征

利用扫描电子显微镜、十二烷基硫酸钠-聚丙烯酰胺凝胶电泳、粒径和Zeta电位、傅里叶红外光谱、紫外光谱、荧光光谱以及表面疏水性对小米四种蛋白组分进行结构表征。结果表明：微观状态下的清蛋白和球蛋白存在簇状结构,有聚集成块的趋势,醇溶蛋白和谷蛋白形状完好,没有融合,但堆积程度高,醇溶蛋白亚基带分布明显清晰,亚基分子质量小且不杂乱,清蛋白、球蛋白和谷蛋白亚基带分布广泛,球蛋白的粒径分布区间小,强度高,谷蛋白的Zeta-电位高,其稳定性最好。二级结构表明四种蛋白在各个结构都有分布,但醇溶蛋白的有序结构相比其他三种蛋白最少。三级结构发现四种蛋白在紫外光的照射下均出现不同波长下的特征吸收峰,清蛋白的表面疏水性最低,溶解特性更好,醇溶蛋白疏水性高,溶解性低。     

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。