| Budget Amount *help |
¥4,700,000 (Direct Cost: ¥4,700,000)
Fiscal Year 2000: ¥2,000,000 (Direct Cost: ¥2,000,000)
Fiscal Year 1999: ¥2,700,000 (Direct Cost: ¥2,700,000)
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| Research Abstract |
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
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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
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