乳类食物中β-酪蛋白的结构及营养功能

综述了人类母乳(以下简称母乳)和牛乳蛋白质中乳清蛋白与酪蛋白比例、相应蛋白质种类、含量及其营养特点,并重点叙述了酪蛋白的亚型及结构,母乳中含量最多的酪蛋白组分β-酪蛋白的消化特性、营养价值和促进钙铁等矿物质吸收、免疫调节和肠道健康促进等生物学功能的最新研究进展。由于牛乳蛋白质在组分含量和比例与母乳的差异,乳基婴幼儿配方粉中蛋白质的调整,既要考虑乳清蛋白和酪蛋白的比例,还需要进一步精细调整蛋白质亚组分的含量和比例,是当前乃至今后婴幼儿配方食品配方创新和工艺技术研发的重要方向。     

日本香川地区荷斯坦牛乳与娟姗牛乳营养成分的比较

目的比较日本香川地区荷斯坦和娟姗牛乳中乳清蛋白的总蛋白质含量,乳过氧化物酶(LPO)和乳铁蛋白的一些基本性质。方法以荷斯坦和娟姗牛乳为对象,经酸沉淀除酪蛋白后,通过离心,SP-Sepharose离子交换层析分离纯化得到乳过氧化物酶和乳铁蛋白,利用考马斯亮蓝定量、SDS-PAGE定性、ABTS检测乳过氧化物酶活性、最后通过基质辅助激光解吸电离飞行时间质谱(MALDI-TOF-MS)确认分子量。结果娟姗牛乳中乳清蛋白的总蛋白质和乳过氧化物酶含量均高于荷斯坦中乳清蛋白中的总蛋白质和乳过氧化物酶含量。娟姗乳清蛋白中的乳过氧化物酶活性(0.870 5 U/ml)高于荷斯坦乳清蛋白中的乳过氧化物酶活性(0.758 9 U/ml)。娟姗乳清蛋白中的乳过氧化物酶和乳铁蛋白分子量分别为786 48.154和831 23.538 k Da,荷斯坦乳清蛋白中的乳过氧化物酶和乳铁蛋白分子量分别为777 64.841和827 65.494 k Da。结论对于乳酪行业,当考虑养殖奶牛品种生产乳酪同时又想最大限度利用需要处理的乳清蛋白和乳铁蛋白的时候,相比于荷斯坦奶牛,娟姗奶牛是更好的选择。     

新型食品乳化剂—乳蛋白质及其应用

牛乳中的蛋白质是最有营养价值的成份。它是由酪蛋白、乳清蛋白、乳球蛋白和其它的血清蛋白质所组成。荷兰DMV公司生产的乳蛋白质制品分为: (1) 酪蛋白——无机酸酪蛋白和乳酸酪蛋白。 (2) 酪朊酸盐——可溶性(Na+K和NH_4)可分散(Ca+Mg) (3) 乳清蛋白——乳清蛋白,乳球蛋白和次等乳清蛋白质成份。 (4) 复合乳蛋白质——及其沉淀物。在营养上,酪蛋白含有全部人体必需氨     

美国乳清蛋白的应用研究和最新进展

牛乳中的蛋白质包括两个主要组成部分──酪蛋白（80％）和乳清蛋白（20％）。在干酪生产中酪蛋白从牛乳中被分离出来，剩余部分称为乳清，乳清蛋白就存在于乳清中。乳清蛋白在很多方面与酪蛋白不同，它们是一些更小的、紧密的球状蛋白质。它们独特的氨基酸序列和三维结构赋予它们广泛的功能特性，这些性质对亚洲和中国的食品加工者来说是十分有益的。新技术产生的新产品随着现代科学技术的发展，具有多种功能特性的，满足许多企业不同需要的乳清蛋白产品不断增加。乳清蛋白的加工能产生多种不同的最终产品。在过去的十年中，随着膜技术和离…     

牛乳中乳清蛋白质的功能活性研究进展

近年来,牛乳的营养功能备受关注,牛乳乳清中的活性蛋白在其中发挥重要的作用。随着对其研究的深入,乳品加工技术的升级与创新,对牛乳乳清中的活性蛋白认知逐渐明晰。本文重点介绍牛乳乳清中α-乳白蛋白、β-乳球蛋白、乳铁蛋白、免疫球蛋白的功能活性的研究进展,阐述牛乳加工灭菌过程对上述牛乳乳清蛋白活性的影响,旨在为我国牛乳乳清蛋白的功能活性基础研究以及乳功能基料的产业化提出新思路,为乳品行业技术创新指明方向。     

母乳、牛乳与主要小品种乳蛋白质组成及乳清蛋白二级结构比较

目的 对比母乳、牛乳、山羊乳、绵羊乳、驼乳和驴乳的蛋白质组成及乳清蛋白二级结构,厘清主要加工乳种与母乳的蛋白质差异。方法 通过十二烷基硫酸钠-聚丙烯酰胺凝胶电泳（sodium dodecyl sulfate-polyacrylamide gel electrophoresis, SDS-PAGE）和傅里叶变换红外光谱法（Fourier transform infrared spectroscopy, FTIR）对比各乳种的蛋白质组成和乳清蛋白二级结构。结果 绵羊乳中蛋白质、乳糖、脂肪含量均显著高于母乳、牛乳、山羊乳、驼乳和驴乳（P<0.05）,母乳中蛋白质、乳糖、矿物质与驴乳各对应指标均无显著性差异（P>0.05）;酪蛋白﹕乳清蛋白（C:W）是衡量动物蛋白质量的指标,检测结果为母乳C:W为38.58﹕61.42,牛乳C:W为81.43﹕18.57,山羊乳C:W为61.14﹕38.86,绵羊乳C:W为68.42﹕31.58,驼乳C:W为56.16﹕43.84,驴乳C:W为8.91﹕91.09;母乳与驼乳均含有较高的乳铁蛋白与血清白蛋白,且几乎不含β-乳球蛋白;驼乳与母乳乳清蛋白的α?螺旋结构占比较高。结论 母乳与主要加工乳种蛋白质组成与乳清蛋白二级结构不尽相同,该研究为各种乳源高值化利用和纯度鉴别提供了参考依据。     

牛乳、羊乳和人乳中的蛋白质组成及消化特性研究

在分析牛乳、羊乳和人乳蛋白质组成的基础上,通过模拟胃肠消化环境,研究牛乳、羊乳和人乳中蛋白质的消化特性。结果表明:牛乳中的蛋白质主要由αs1-酪蛋白、β-酪蛋白和β-乳球蛋白组成,羊乳中的蛋白质主要由αs2-酪蛋白、β-酪蛋白和β-乳球蛋白组成,人乳中的蛋白质主要由β-酪蛋白和α-乳白蛋白组成。牛乳、羊乳和人乳中酪蛋白与乳清蛋白的比例分别为4.45±0.03,3.65±0.07,0.51±0.03。牛乳、羊乳和人乳中的蛋白质主要在肠液中消化,其中酪蛋白在胃液中消化120 min时的消化率分别为88.6%、89.7%、98.1%,在肠液中消化30 min时的消化率分别为97.6%、98.4%、98.9%,在胃肠液中消化30 min后,酪蛋白几乎完全消化。3种乳相比较,人乳中的蛋白质在胃肠中最易消化,而羊乳中的蛋白质比牛乳更易消化。     

牛乳中不同部分蛋白质的组成及功能分析

本研究通过SDS-PAGE电泳将牛乳中不同蛋白质组成部分进行分离鉴定发现,乳脂肪球膜中存在201种蛋白,乳清中存在96种蛋白,酪蛋白中存在21种蛋白,乳粒中存在43种蛋白,其中有27种相同表达的蛋白。通过GO功能注释分析发现,在生物过程中乳脂肪球膜蛋白发挥的作用大于乳清、乳粒蛋白,尤其是生物的调控作用;在分子功能上,牛乳蛋白的主要分子功能是结合作用,其中乳脂肪球膜蛋白的结合作用最强;而乳粒蛋白参与的转运活性分子功能大于乳脂肪球膜、乳清蛋白。在细胞组成上,与乳清、乳粒蛋白相比乳脂肪球膜蛋白参与的细胞组成均较多,而在细胞膜的组成上乳粒蛋白参与较多。通过京都基因与基因组百科全书(KEGG)代谢通路分析可知,乳脂肪球膜、乳清、乳粒中的蛋白均参与过氧化物酶体增殖物激活受体信号通路。对牛乳蛋白质组成进行研究,不仅能够增加牛乳的利用率,并且为日后以乳脂肪球膜、乳粒蛋白作为原料生产乳制品提供理论依据。     

牛乳中活性蛋白生物学功能研究进展

牛乳以及牛初乳被认为是天然活性成分最重要的来源,具有很高的营养价值。牛乳中活性蛋白的多功能特性已经得到广泛的表征,其生物学特性越来越受关注。酪蛋白和乳清蛋白是牛乳中两个主要的蛋白组,其完整的分子结构及众多的生物活性肽在幼龄动物及人体内发挥着不同的生理功能。本文对牛乳中主要活性蛋白的生物学功能进行了综述。     

牛乳清蛋白的性质及其在食品工业中的应用

乳清蛋白的蛋白质生物价比许多高品质的膳食蛋白(如鸡蛋白、牛肉蛋白及大豆蛋白)高。目前,乳清蛋白产品除有乳清浓缩蛋白和乳清分离蛋白外,一些具有功能特性的蛋白组分被分离出来,如α-乳白蛋白、b-乳球蛋白、乳铁蛋白、免疫球蛋白。 乳清浓缩蛋白(WPC)和乳清分离蛋白(WPI)WPC是乳清经超滤、双重过滤和浓缩等一系列步骤,将乳糖脱去加工而成的,蛋白质含量为35％～80％。WPI还要经     

乳铁蛋白的抗病毒活性

和很多金属结合蛋白一样,乳铁蛋白是一种结合铁离子的糖蛋白,这种糖蛋白发现在人和牛乳中,由中性粒细胞和几种粘膜细胞分泌。已经发现乳铁蛋白有很多功能,属于非特异性免疫系统,具有与众不同的抗病毒活性。本文将就目前有关乳铁蛋白抗不同病毒的活性和抗病毒模式进行综述。乳铁蛋白表现出抗人免疫缺陷病毒(HIV)、抗RNA和DNA病毒、包括呼吸道合胞体病毒和疱疹病毒等。乳铁蛋白最主要的抗病毒机理就是作用于病毒侵染的早期,防止病毒对宿主细胞的识别和入侵。这种钝化病毒侵染能力的机制是通过切断病毒对受体的接触和识别或直接结合到病毒粒子上使其失去侵染能力。这显然是一种全新的不同于以前的细胞因子,如干扰素的抗病毒机制。     

母乳和牛乳中乳脂肪球膜蛋白质的差异分析

为比较乳脂肪球膜（milk fat globule membrane,MFGM）蛋白在母乳和牛乳中的差异,采用有机试剂提取法,从母乳和牛乳中提取分离出MFGM蛋白,经皮尔斯TM去垢小柱去除十二烷基硫酸钠后,通过液相色谱-质谱联用技术检测分析,检测结果根据特异性肽段匹配数不小于1筛选后,在母乳和牛乳中分别检测到863 种和454 种蛋白,其中二者共有175 种,分别独有688 种和279 种。将母乳中差异表达的688 种蛋白质按PANTHER数据库进行蛋白质的Gene Ontology（GO）功能注释,这些蛋白主要是细胞部分、细胞器、细胞膜等组分,参与的生物途径有新陈代谢过程、生物调节、刺激性反应、免疫系统过程、再生作用等,具有催化、黏合、转运、酶调节等多种分子功能。另外,母乳中的这些差异蛋白参与氨酰tRNA生物合成、致病性大肠杆菌感染、脂肪酸代谢、丙酸代谢、甾体合成、酸降解等都是牛乳中的乳脂肪球膜蛋白不具有的功能。通过分析得出母乳和牛乳中的MFGM蛋白具有明显差异,虽然有部分组成和功能的重叠,但在丰度和代谢路径上,牛乳MFGM蛋白不能替代母乳MFGM蛋白。     

不同等电点沉淀法和超速离心法提取牛奶乳清蛋白的双向电泳分析

为探索牛奶乳清蛋白提取的最适方法,以生鲜荷斯坦牛奶为对象,采用不同等电点（pH 4.6和pH 4.8）沉淀法和超速离心法提取牛奶乳清蛋白样品,并对提取效果进行双向凝胶电泳（two-dimensional electrophoresis,2-DE）图谱分析。依据凝胶图谱上蛋白斑点比较图谱质量,采用PDQuest 8.0凝胶图像分析软件进行凝胶图谱分析。结果显示：2 种方法均能有效提取牛奶乳清蛋白,且获得的2-DE凝胶图谱背景清晰、蛋白点个体独立、无明显的拖尾现象,且重复性强,但都存在一定的酪蛋白残留。与超速离心法相比,pH 4.6沉淀法和pH 4.8沉淀法提取乳清蛋白的2-DE凝胶图谱可检测到较多的蛋白质斑点。pH 4.6沉淀法提取乳清蛋白制备的2-DE凝胶图谱中蛋白点的表达丰度略高于pH 4.8沉淀法。研究表明：pH 4.6沉淀法提取乳清蛋白制备2-DE凝胶图谱略优于pH 4.8沉淀法和超速离心法。但2 种等电点沉淀法和超速离心法都可有效去除牛奶中的高丰度酪蛋白,提高低丰度蛋白的检出敏感性。     

Effect of high-pressure treatment on denaturation of bovine lactoferrin and lactoperoxidase

Lactoferrin and lactoperoxidase are whey proteins with biological properties that may provide health benefits to consumers. These properties are vulnerable to potentially denaturing conditions during processing. High-pressure treatment is an appealing alternative to the traditional heat processing of foods because it exerts an antimicrobial effect without changing the sensory and nutritional quality of foods. In this work, the effect of high-pressure treatment on the denaturation of lactoferrin and lactoperoxidase present in skim milk and whey, and as isolated proteins in buffer, was studied over a pressure range of 450 to 700 MPa at 20°C. Denaturation of lactoferrin was measured by the loss of reactivity with their specific antibodies using a sandwich ELISA. Denaturation of lactoperoxidase was determined by measuring the loss of enzymatic activity using a spectrophotometric technique. No substantial inactivation of lactoperoxidase was observed in any treatment assayed. The concentration of the residual immunoreactive lactoferrin after each pressure treatment was determined, and the data were subjected to kinetic analysis to obtain D and Z values. Denaturation of lactoferrin increased with pressure and holding time, and D values were lower when lactoferrin was treated in whey than in milk, and lower in both whey and milk than in phosphate buffer. Thus, protein is denatured more slowly in buffer and in milk than in whey. Denaturation of lactoferrin in the 3 media was found to follow a reaction order of n=1.5. Volumes of activation of about -34.77, -24.35, and -24.09 mL/mol were obtained for lactoferrin treated in skim milk, whey, and buffer, respectively, indicating a decrease in protein volume under pressure.     

The effect of bovine milk lactoferrin on human breast cancer cell lines

The evidence that biologically active food components are key environmental factors affecting the incidence of many chronic diseases is overwhelming. However, the full extent of such components in our diet is unknown, as is our understanding of their mechanisms of action. Beyond the interaction of these food components with the gut and intestinal immune functions, whey proteins such as lactoferrin are being tested as anticancer agents. Lactoferrin is an iron-binding protein that has been reported to inhibit several types of cancer. In the present work, the effects of bovine milk lactoferrin on human breast cancer HS578T and T47D cells were studied. The cells were either untreated or treated with lactoferrin concentrations ranging from 0.125 to 125 μM. Lactoferrin decreased the cell viability of HS578T and T47D by 47 and 54%, respectively, and increased apoptosis about 2-fold for both cell lines. Proliferation rates decreased by 40.3 and 63.9% for HS578T and T47D, respectively. For the T47D line, cell migration decreased in the presence of the protein. Although the mechanisms of action are not fully known, the results gathered in this work suggest that lactoferrin interferes with some of the most important steps involved in cancer development.     

Lactoferrin research,technology and applications

Lactoferrin is an iron-binding glycoprotein present in milk as well as other exocrine secretions and neutrophil granules in mammals. Lactoferrin is considered to be an important host defense molecule and has a diverse range of physiological functions such as antimicrobial/antiviral activities, immunomodulatory activity, and antioxidant activity. During the past decade, it has become evident that oral administration of lactoferrin exerts several beneficial effects on the health of humans and animals, including anti-infective, anticancer, and anti-inflammatory effects. This has enlarged the application potential of lactoferrin as a food additive. The technology of producing bovine lactoferrin on a factory scale was established over 20 years ago. Bovine lactoferrin is purified by cation-exchange chromatography from bovine skim milk or whey, and is commercially available from several suppliers. Recombinant human lactoferrin is produced by Aspergillus niger, transgenic cows, and rice, and its efficacy is being evaluated. In this article, we review basic research and technological aspects of the application of lactoferrin.     

Photo-oxidation of whey proteins: Molecular markers of modification

Oxidative damage significantly affects the food industry, with progressive modification of protein foods and ingredients altering structure, shelf-life, digestibility, nutritional value and function. A redox proteomic damage scoring system was applied to profile and track protein primary level photo-oxidative modification in UVB-irradiated bovine milk whey proteins, lactoferrin and β-lactoglobulin. Lactoferrin oxidation increased significantly after ultraviolet B (UVB) exposure, with the redox score increasing from 0.38 in the control to 1.00 in the irradiated sample. β-lactoglobulin oxidation also increased significantly, from a relatively high baseline redox score of 1.07 in the control to 1.67 in the irradiated sample. A potential marker peptides set for tracking photo-oxidation in milk whey proteins was characterised, with six lactoferrin and four β-lactoglobulin peptides identified. This is anticipated to be of significant utility in monitoring and tracking relative levels of modification, and therefore exposure to oxidative insult, in dairy products through processing, storage, and retail and consumer handling.     

Casein–whey protein interactions in heated milk: the influence of pH

Heat-treatment of milk causes denaturation of whey proteins, leading to a complex mixture of whey protein aggregates and whey protein coated casein micelles. In this paper we studied the effect of pH-adjustment of milk (6.9–6.35) prior to heat-treatment on the distribution of denatured whey proteins in aggregates and coating of casein micelles. Proteins were fractionated using an alternative fractionation technique based on renneting. Acid- and rennet-induced gelation of these milks were used to obtain more information on the characteristics of the milk. Acid-induced gelation appeared to be mainly influenced by the presence of whey protein aggregates. Rennet-induced gelation was determined by the whey protein coating of the casein micelles. Both the quantity of whey proteins present on the surface of the casein micelles and the homogeneity of the coating were determining the renneting properties. These results extend the current knowledge on pH dependent casein–whey protein interactions. In order to present a clear picture of the changes occuring during heat treatment of milk at various pH, the results are summarized in a model. In this model we propose that heating at a pH>6.6 lead to a partial coverage of the casein micelles and the formation of separate whey protein aggregates. Heating at a pH<6.6 lead to an attachment of all whey proteins to the casein micelles. At pH 6.55 the coverage is rather homogeneous but lowering the pH further lead to an inhomogeneus coverage of the casein micelles. Surprisingly small changes of the pH at which the milk was heated had considerable effects on the gelation behaviour both in renneting and in acid gelation.     

Acidification of lactoferrin-casein micelle complexes in skim milk

Lactoferrin electrostatically bound to the casein micelles when added to milk, which caused the absolute zeta potential to decrease and the micelle size to increase. On acidification, the lactoferrin progressively dissociated from the micelles, which, at pH below ∼5.0, caused the zeta potential of the casein micelles to be the same as those in milk without added lactoferrin. Acidification caused increased levels of casein to dissociate from the casein micelles at ∼pH 5.0 as the level of added lactoferrin in the milk increased. Lactoferrin decreased the pH at which the milk gelled and caused the G′ and yield stress of the set gels to increase at low levels of added lactoferrin, decrease at intermediate levels of added lactoferrin and increase again at high levels of added lactoferrin. This unusual effect of lactoferrin on gelation was hypothesised to be due to combined effects of dissociated casein and the lower gelation pH.     

羊乳乳清蛋白组成和功能及其与人乳、牛乳的对比分析

本研究将羊乳、牛乳、人乳中乳清蛋白进行分离并结合液质联用技术鉴定,在羊乳、牛乳、人乳乳清蛋白中分别鉴定出156、278、454种蛋白质。与牛乳与人乳乳清蛋白对比显示,羊乳含有99种特异性表达蛋白质,与牛乳和人乳分别有31种和15种相同表达蛋白质。通过分析基因本体(gene ontology,GO)功能注释发现,羊乳乳清蛋白在生物过程中主要发挥生物调节作用;在分子功能上,主要体现在结合作用方面;在细胞组成上,参与的细胞组成主要为细胞器区和胞外区。羊乳乳清蛋白在以上三种功能上与人乳有较大差距,但与牛乳相近。通过分析京都基因与基因组百科全书系统(Kyoto Encyclopedia of Genes and Genomes,KEGG)代谢通路可知,羊乳主要参与补体和凝血级联反应以及吞噬作用,对人体免疫能力有积极影响。对羊乳与人乳、牛乳乳清蛋白组成及功能区别的研究,为羊乳的进一步研究和开发提供一定的理论参考。