大豆7S蛋白热聚集体的形成及其性质研究

发布时间：2018-04-18 03:03

本文选题：大豆7S蛋白 + 热聚集行为　；参考：《华南理工大学》2015年博士论文

【摘要】：大豆蛋白来源丰富,营养价值高,在食品工业中广泛应用。经过适当修饰重组或改性可赋予大豆蛋白更好的功能特性从而拓展大豆蛋白的应用前景。通过控制蛋白质热聚集行为可以得到不同类型的蛋白聚集体,用于营养成分和风味物质的输送。目前,蛋白质聚集行为控制及其应用已被广泛研究,但关于不同类型蛋白聚集体对食品结构产生的差异性影响还鲜见报道。本文以大豆7S蛋白为原料,制备了两种不同类型的聚集体:无定型聚集体和纤维化聚集体,系统比较了不同类型蛋白聚集体的结构特性和消化特性,重点研究了以不同类型聚集体制备凝胶和泡沫性质的差异,为拓展大豆蛋白聚集在食品领域的应用提供信息和理论基础。本文主要结论如下:(1)在中性(p H 7.0)和酸性(p H 2.0)条件下通过加热分别制备大豆7S蛋白无定型聚集体和纤维化聚集体,对聚集体进行表征。采用还原电泳(SDS-PAGE)、天然电泳(Native-PAGE)、硫磺素-T荧光(Th T)、体积排阻色谱(SEC)和原子力显微镜(AFM)系统比较了天然大豆7S蛋白、7S无定型聚集体及7S纤维化聚集体在模拟胃液消化过程中组成和结构的变化。结果表明天然大豆7S蛋白的α和α’亚基会被优先水解,最终产物富集为α、α’亚基的核心区,分子量大小约为47 k Da,β亚基则不能被胃蛋白酶消化。7S无定型聚集体由于经过热处理,蛋白结构展开,大量酶切位点的暴露使其在5 min内迅速被酶解。7S纤维化聚集体在胃蛋白酶的作用下,首先水解成小的聚集体或者多肽,部分聚集体/多肽会通过疏水相互作用和静电相互作用重新聚集生成短粗状的纤维化聚集体。在蛋白分子的解离和重聚的过程中,溶液粘度明显增加。(2)系统比较了大豆7S蛋白和11S蛋白在p H 2.0时的热聚集行为,结果表明蛋白浓度越高,纤维化聚集程度越大,7S比11S更容易形成纤维化聚集体。以纤维化聚集体为原料,两步法制备了大豆蛋白纤维化凝胶。在酸性条件下,由于纤维化聚集体表面带有大量的电荷,分子之间互相排斥,尽管在凝胶形成的过程中加入盐离子屏蔽部分静电作用,但流变学和质构分析结果表明由大豆蛋白纤维化聚集体制备而成的凝胶强度较弱。在相同的预处理浓度下,11S纤维化凝胶的硬度较7S纤维化凝胶强,但7S较11S有更好的粘性和回弹性。(3)制备了天然大豆7S蛋白、7S无定型聚集体(7SA)、7S纤维化聚集体(7SF)与低酯果胶(LMP)复合凝胶,系统比较了三种复合凝胶的流变学特性、质构性质和形貌学特征。与7S-LMP和7SA-LMP的复合凝胶相比,7SF-LMP复合凝胶具有较高的弹性模量(G’)和粘性模量(G’’),并且具有较高的硬度、脆性和粘性。7S-LMP复合凝胶是以蛋白为连续相的凝胶网络结构,LMP以非连续相形式分布于凝胶孔隙中;7SA-LMP复合凝胶是以蛋白相和多糖相穿插分布,两相共同构成复合凝胶的基本结构;7SF-LMP复合凝胶是以LMP为连续相,7SF以填充物形式附着于LMP凝胶网络。(4)系统比较了天然大豆7S蛋白、7S无定型聚集体和7S纤维化聚集体的气-水界面性质和泡沫性质。与天然7S蛋白和7S无定型聚集体相比,7S纤维化聚集体具有更高的起泡能力和泡沫稳定性。蛋白的界面特性受蛋白分子结构的影响。纤维化聚集体在形成过程中生成的小分子肽能迅速吸附到气-水界面并铺展,具有较强降低表面张力的能力。随着界面压(π)的增大,7S纤维化聚集体动态膨胀粘弹模量(E)上升最快,说明蛋白分子能在界面形成紧密稳定的蛋白质膜,揭示了纤维化聚集体具有良好泡沫性能的原因。胃蛋白酶修饰能显著提高7S蛋白和7S无定型聚集体的起泡性和泡沫稳定性,对于纤维化聚集体,过度水解会导致蛋白质分子之间的相互作用力减弱,泡沫稳定性反而降低。(5)研究了7S扩展区肽对大豆蛋白组分聚集行为的影响。采用胃蛋白酶定向水解大豆7S蛋白,得到核心区和扩展区肽,并通过超滤的方法分离得到扩展区肽,扩展区肽能诱发11S聚集并有效操控11S的热聚集行为。在热处理过程中,蛋白结构逐渐展开,11S和肽分子发生疏水相互作用,部分疏水基团被重置于聚集体内部,而亲水基团侧重新排列在聚集体的表面,当11S和水解肽的比例达到1:2时,聚集体表面有足够的亲水基团,热聚集反而受到抑制。
[Abstract]:Soy protein rich source, high nutritional value, widely used in food industry. After appropriate modification application? Function properties of recombinant or modified soy protein can give better to develop soybean protein. By controlling protein heat aggregation behavior can be obtained for different types of protein aggregates, used for transport of nutrients and flavor substances at present. Protein aggregation, behavior control and its application has been extensively studied, but the differences in the effects of different types of protein aggregates on the structure of food has not been reported. In this paper, the soybean 7S protein as raw material, two different types of aggregates were prepared: amorphous aggregates and fibrosis aggregates, a systematic comparison of the structural characteristics and digestive characteristics different types of protein aggregates, focusing on the differences in different types of aggregation preparation gel and foam properties, for the development of soybean protein Provide information and theoretical basis of applications in the field of food. The main conclusions of this paper are as follows: (1) (P H 7) in neutral and acidic conditions (P H 2) were prepared by heating soybean 7S protein amorphous aggregates and fibrosis aggregates were characterized by SDS-PAGE. Aggregates (SDS-PAGE). Natural electrophoresis (Native-PAGE), Thioflavin -T fluorescence (Th T), size exclusion chromatography (SEC) and atomic force microscopy (AFM) system compared to the natural soybean 7S protein, 7S and 7S changes of amorphous aggregates composed of aggregates fibrosis in simulated gastric digestion process and structure. The results show that the natural soybean protein 7S the alpha and alpha subunit can be hydrolyzed, the final product concentration is alpha, alpha 'core subunits, the molecular weight is about 47 K Da, beta subunit cannot be pepsin digestion of.7S amorphous aggregates after heat treatment, protein structure, a large number of Exposure restriction sites in the 5 min was quickly enzymolysis.7S fibrosis aggregates in pepsin, firstly hydrolyzed into small peptides or aggregates, part of aggregates / peptide through hydrophobic and electrostatic interactions to generate short fiber aggregation aggregates like. In the protein molecular dissociation and reunion in the process, the viscosity of the solution increased significantly. (2) a systematic comparison of the aggregation behavior of soybean 7S protein and 11S protein in P H 2 of the heat, the results showed that protein concentration is higher, the greater the degree of fibrosis aggregation, 7S is easier to form aggregates than 11S. The fibrosis fibrosis aggregates as raw material, soy protein gel fibrosis the two step method. In acidic conditions, due to fibrosis surface aggregates with a large number of charge, between the molecules repel each other, although the process in the gel formation of added salt ions part of static shielding Electricity, but the rheology and texture analysis showed that the gel strength of soy protein aggregates by weaker fibrosis was prepared. In the pretreatment of the same concentration, gel hardness is 7S 11S fibrosis fibrosis gel, but 7S 11S has better viscosity and elasticity. (3) natural soybean 7S the protein was prepared and 7S amorphous aggregates (7SA), 7S (7SF) and pectin aggregates fibrosis low ester (LMP) composite gel system, comparison of three kinds of composite gel rheological properties, texture properties and morphology characteristics. Composite gel and 7S-LMP and 7SA-LMP phase ratio, elastic modulus of 7SF-LMP composite gel high (G ') and viscous modulus (G'), and it has high hardness, brittleness and viscous.7S-LMP composite gel is a protein gel network structure for continuous phase, LMP as continuous phase distribution in the gel pores; 7SA-LMP composite gel with protein And the polysaccharide with two-phase distribution, constitute the basic structure of composite gel; 7SF-LMP composite gel is LMP as continuous phase, 7SF with filler form attached to the LMP gel network. (4) a systematic comparison of the natural soybean 7S protein, 7S amorphous aggregates and 7S fibrosis aggregates of air-water interface and foam properties properties of amorphous aggregates. Compared with natural 7S protein and 7S 7S fibrosis aggregates has higher foaming ability and foam stability. The interface characteristics of protein affected by protein molecular structure. Small molecule peptide aggregation in the fibrosis formation in rapid adsorption to the gas water interface and spreading, has a strong ability to reduce the surface tension of the interface pressure (PI). With the increase of 7S fibrosis aggregates dynamic expansion viscoelastic modulus (E) increased rapidly, that protein molecules can form stable protein membrane tightly at the interface, reveals the fiber The reason of aggregates has good foam properties. Pepsin modification can significantly improve the 7S protein and 7S foaming and foam stability of aggregates for shaping, fibrosis aggregates, excessive hydrolysis can weaken the interaction between protein molecules, the foam stability decreased. (5) studied the 7S extension effect on the aggregation behavior of peptides the soy protein group. By pepsin hydrolysis of soybean protein 7S orientation, core and extension area of peptides and extended area, peptide by ultrafiltration separation method, extension peptide can induce 11S accumulation and effective manipulation of the 11S thermal aggregation behavior. In the process of heat treatment, the protein structure gradually expanded, and the peptide 11S hydrophobic interaction, hydrophobic part is reset on the aggregates, and the hydrophilic group side rearranged on the surface of the aggregates, while 11S and hydrolyzed peptide when the ratio reached 1:2, There is enough hydrophilic group on the surface of the aggregate, and the heat accumulation is restrained.

【学位授予单位】：华南理工大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TS201.21

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