Development and creation of food materials having novel characteristics by thermal treatment of food proteins

乳清蛋白是由β-乳球蛋白（β-lactoglobulin，βLG）、α-乳清蛋白（α-lactalbumin，α-lactalbumin）和血清白蛋白（serum albumin，serum albumin）等球状蛋白质组成的。βLG分子由162个氨基酸残基组成，并且在Cys^ -Cys^和Cys^ -Cys^处具有两个二硫键（S S）<66><160><106><119>，并且在Cys^处具有游离巯基<121>。在生理条件下，这种球状蛋白以二聚体形式存在，由9条β链形成的反向平行β折叠组成。βLG有7种变异体，以变异体A和B为主。β LGA分子在受热时发生聚集，分子间二硫键对这种聚集起重要作用。β LGA的聚集依赖于pH、盐浓度和加热温度。虽然游离巯基对βLG分子在加热时的聚集起着重要作用， 关于我们 通过分子间二硫键的形成而发生的热变性和聚集事件尚未详细报道。为了揭示βLG分子热诱导聚集的机理，必须明确巯基的参与。乳清蛋白由于其高凝胶化和乳化能力而被广泛用作食品配料。蛋白质在分子水平上的构象变化强烈影响食品蛋白质的功能特性。凝胶的形成通常是由蛋白质分子在食物系统中加热时形成网络结构引起的。加热引起蛋白质分子的构象变化。变性蛋白质分子间的相互作用是构建三维网络结构所必需的。本文研究了β LGA在加热条件下的构象变化，特别是其可逆性和pH依赖性。此外，还分析了分子间通过二硫键等非共价力的相互作用，揭示了分子聚合和凝胶化的机理。少

Milk whey protein consists of globular proteins such as β-lactoglobulin (βLG), α-lactalbumin, and serum albumin βLG, the major protein component, is largely responsible for the aggregation and gelation of whey protein on heating. A βLG molecule consists of 162 amino acid residues and has two disulfide (S S) bonds, at Cys^<66>-Cys^<160> and Cys^<106>-Cys^<119>, and a free sulfhydryl group at Cys^<121>. Under physiological conditions, this globular protein exists as a dimer consisting of antiparallel β-sheets formed by nine β-strands. βLG has seven variants and most of them are variant A and B.βLG variant A (βLG A) was used throughout this study. βLG A molecules aggregate when they are heated, and intermolecular disulfide bonds seem to play an important role for such molecular aggregation. Aggregation of βLG A depends on pH, salt concentration, and heating temperature. Although the importance of free sulfhydryl residue is accepted for molecular aggregation of βLG on heating, the molecula … More r events occurring on the thermal denaturation and aggregation via intermolecular disulfide formation have not been revenaled in detail. To reveal the mechanism of heat-induced molecular aggregation of βLG, it is important to clarify the participation of sulfhydryl residue. Milk whey protein is widely used as a food ingredient due to its high gelation and emulsification ability. Change in the conformation of the protein at molecular level strongly influences the functional properties of the food protein. The gel formation is usually induced by formation of network structure with protein molecules when heated in the food system. Heating induces the conformational change in a protein molecule. The molecular interaction among the denatured protein molecules is necessary for the construction of the three-dimensional network structure. In the present study the conformational change of βLG A by heating was examined, particularly its reversibility and pH dependency. In addition, the molecular interactions through disulfide bridge and other non-covalent forces have been analyzed to reveal the mechanism of molecular polymerization and gelation. Less