【作者】 张宏康；

【导师】 李里特；

【作者基本信息】 中国农业大学 ， 食品科学与工程， 2001， 博士

【摘要】 近年来，超高压处理技术被认为是新的食品加工与保藏技术中最有潜力和发展前途的一种，是食品工业的重点开发技术之一。超高压作用会影响生物大分子的结构，改变分子间和分子内的非共价作用力，从而使其功能特性发生变化。因此，开展超高压处理对食品中生物大分子等成分的结构和特性的研究具有重要意义，该领域也是当今世界上超高压处理技术研究的前沿。 本论文选择东方传统食品豆浆作为研究对象，运用多种分析检测手段，研究超高压处理对豆浆的物理、化学特性的影响，分析超高压处理对豆浆中大豆蛋白等生物大分子组分结构的影响，并寻找两者之间的内在联系；研究分析超高压生成新型豆腐凝胶的物理特性、微观结构；运用分形理论分析其分形维数，寻找分形维数与其宏观物性之间的内在联系；探讨超高压生成豆腐凝胶的形成机理；研究超高压处理对大豆分离蛋白凝胶物性的影响，比较超高压处理所得凝胶与热处理所得凝胶的不同特点；探讨超高压诱导大豆分离蛋白凝胶的形成机理；获得新型的大豆分离蛋白凝胶食品。研究超高压处理对大豆豆球蛋白和β-伴球蛋白分子结构特性的影响，了解超高压促使蛋白质变性的机理；模拟食品真实体系，研究超高压对蛋白质及多糖相互作用的影响；分析在多糖存在的条件下，超高压处理对蛋白质分子结构变化及功能特性的影响。 试验结果表明，豆浆的黏度随处理压力的升高而升高，但其pH值和密度没有明显变化，在低于400MPa的压力处理下，豆浆保持液体状态，而当处理压力升高至500MPa以上时，豆浆从液体状态转变为溶胶状；随着处理压力的升高豆浆中大豆蛋白的乳化活性及乳化稳定性均有所提高，而乳化容量则呈现出稍微下降的趋势。豆浆中大豆蛋白巯基含量随处理压力的升高而升高；荧光分析表明，豆浆中大豆蛋白的表面疏水区域随处理压力的升高和处理时间的延长而增加；超高压处理后豆浆乳化特性、相态的变化与超高压处理后大豆蛋白分子表面疏水性和巯基含量的变化密切相关。 研究首次发现了β-伴球蛋白和大豆豆球蛋白的变性压力，在一定条件下，经300MPa压力处理可使β-伴球蛋白完全变性，而经400MPa压力处理则可使大豆豆球蛋白完全变性；Native-PAGE电泳分析表明，经超高压处理后豆浆中的大豆蛋白发生了解离和聚合；豆浆经400MPa压力处理10min后可以杀灭其中的大部分微生物；经高压处理后豆浆中的蛋白质由于表面疏水性的增强，对豆浆中皂甙的亲合力提高，因此超高压处理将影响豆浆的部分风味。 超高压生成豆腐凝胶的破断强度与凝固剂种类、压力水平和处理时间密切相关；超高压生成豆腐凝胶，其外表光滑细腻，具有良好的外观品质；扫描电镜分析和凝胶物性分析表明，超高压生成豆腐凝胶的破断强度与其微观结构具有密切的关系，当超高压生成豆腐凝胶的网络结构致密，孔洞分布均匀时，其破断强度较高；当超高压生成豆腐凝胶的微观结构较为松散，组织呈团状聚集，孔洞大且分布不均时，其破断强度较低；超高压生成豆腐凝胶的机理可能是在超高压作用下豆浆中的蛋白质分子发生了变性，在所加凝固剂的协同架桥作用下，豆浆中的蛋白质分子互相凝聚或互相穿插缠结在一起，结合水分子而形成凝胶。 研究首次创造性地应用分形理论对凝胶物性进行分析；研究发现超高压生成豆腐凝胶的盒维数在一定程度上可以定量表征其微观结构的特征，即当凝胶微观结构较为均匀致密时，盒维数为较大值，反之，盒维数为较低值。超高压生成豆腐凝胶的盒维数与其破断强度具有正相关的关系。 中口农业大学博土学位论文 加压和加热都能使一定质量分数的大豆分离蛋白溶液形成篮胶；大豆分离蛋白高压诱 导凝胶的强度随其质量分数的增高而增高，而且与处理压力和温度密切相关；超高压诱导 大豆分离蛋白凝胶的形成，可能是由于压力使大豆蛋白变性，一定质量分数的大豆分离蛋 白分于之间相互作用，形成网络结构，从而形成凝胶；大豆分离蛋白高压诱导凝胶的强度 比加热处理形成的凝胶强度要高；而且高压处理凝胶的外观比加热处理更加光滑、细致。 因此高压处理获得的大豆分离蛋白凝胶较加热处理得到的凝胶具有更优的品质。 处理压力的升高和时间的延长都将使大豆豆球蛋白和卜伴大豆球蛋白的半眺氨酸残基 暴露，疏基含量增加。荧光分析表明，经压力处理后大豆豆球蛋白表面疏水区域增多；而 对于B－伴球蛋白，在低压作用下，其疏水区域减少，在高压作用下，其疏水区域增加，但 在过高的压力下，卜伴球蛋白中的疏水区域又呈现减少的趋势。紫外差示光谱分析表明， 经压力处理后，大豆豆球蛋白的构象发生了变化，在压力作用下发生去折叠，蛋白质分子 表面具有紫外吸收的芳香氨基酸残基暴露增多。中等处理压力可使卜伴球蛋白分子表面具更多还原

【Abstract】 In recent years high pressure technology has received considerable attention as a method of td processing and preservation. High pressure influences the conformation of biomacromolecules, alters the non-covalent interaction among macromolecules, changes their physiochemical and functional properties. Research on this area is state- of- the- art of high pressure technology.The traditional oriental food soybean milk has been studied by multiple analysis ways. The effects of high pressure on the physiochemical properties of soybean milk and conformation change of soybean protein in soybean milk have been analyzed, the relationship between them has been clarified; Physical properties and microstructures of high pressure induced Tofu gel are studied; Fractal analysis is applied to find the relationship between box dimension and the physical properties of Tofu gel; The mechanism of high pressure induced Tofu gel is discussed; High pressure effects on physical properties of isolated soybean protein{ISP} has been elucidated, the different characteristics of high pressure induced gel are compared with heat induced gel ; and also the mechanism of high pressure induced ISP gel is discussed. The high pressure effects on the structure properties of glycinin and P -conglycinin are analyzed and the mechanism of high pressure denaturation protein is clarified; By simulating the real food systems, high pressure effects on the interaction of protein and polysaccharide are studied; The relationship between the change of protein structure and function are studied in the presence of polysaccharide.High pressure is applied to soybean milk and the physiochemical properties of soybean milk and conformation change of soybean protein are examined. Its viscosity increases when the pressure increases, but its pH value and density have no apparent change. When the pressure is lower than 400Mpa, the soybean milk keeps liquid; However, the soybean milk changes from a liquid to a sd after treatment at 500MPa for 30mm.The liquid soybean milk shows improved emulsifying activity and stability but reduced emulsifying capacity after processed by high pressure; Sulfhydryl content of the soybean milk saturated with N2 is increased slightly after high pressure processing; Fluorescence analysis reveals that soybean protein are modified by high pressure to have larger hydrophobic regions. The change of physical properties of soybean milk is related to the conformation change of soybean protein in soybean milk.The denaturation pressure of glycinin and P -conglycinin are first reported by differential scanning calorimetry analysis; P -conglycinin can be denatured completely by 300MPa,l0min and 400MPa,5min for glycinin at room temperature; Native-PAGE electrophoresis revealed that soybean proteins are dissociated and some of them coagulated by high pressure.; The effective sterilization of soybean milk is observed after processed by 400MPa for 10mm; After pressure treatment soybean milk shows a higher affinity for saponins which will lead to change the flavour of soybean milk.The strength of high pressure induced Tofu gel is related with coagulant, pressure and time; High pressure induced Tofu gel has smooth appearance; Scanning electron microscopic examinations as well as gel strength measurements reveal that when the network structure of Tofu gel is homogeneous, the strength is higher; The mechanism of high pressure induced Tofu gel may be caused by the denaturation of protein; and with the synergistic reaction of coagulant, the gel6network is formed although the protein concentration is low.Fractal theory is applied to physical properties analysis of Tofu gel in a creative way; It isfound that the box dimension of Tofu gel can represent its microstructure characteristic. The boxdimension of Tofu gel is positive correlation with its gel strength.Both pressure and heat induce the gel formation of ISP The geI strength of lSP is increasedwitIl its concentration, and tightly connected with pressure and. Temperature更多还原