分離ダイズタンパク質の物性変化と消化酵素作用に及ぼすエクストルージョン加熱の効果

Extrusion heating was applied to SPI in order to investigate the interrelationship between the physicochemical properties and the enzymatic digestibility of SPI containing 70% water. Extrudates were prepared at the dough temperature of 60, 89, 126, 139, 154℃ corresponding to the die temperature of 80, 100, 125, 148, and 160℃ respectively. Conventionally heated samples were prepared by heating at 100℃ for 2hr. Melting point of SPI was measured by using a laboratory scale twin-screw extruder (Laboruder TEX-L Japan Steel Works, Ltd.). The measured melting point was about 135℃. Properties of extrudates were investigated by protein determination, SDS-PAGE, amino acid analysis and enzymatic hydrolysis. Over melting point, the solubility of extrudates increased and the digestibility was extremely enhanced. From the result of SDS-PAGE of water soluble fraction, major bands of all water soluble fraction were acid subunit of glynicin and Gly m Bd 34 K. In amino acid analysis, the amount of hydrophiric amino acids gradually increased, with rising die temperature.
Key words: Soy protein; extrusiom heating; trypsin digestion.