This study was carried out to determine the effect of biji addition on the quality of extruded isolated soy protein (ISP). ISP-based biji addition (0, 20, 40 and 60%) was extruded at die temperatures 140oC and 150oC and a screw speed of 250 rpm. The moisture contents were adjusted to 35% and 45%. As the content of biji increased from 0% to 60%, springiness, cohesiveness, and cutting strength of the extruded ISP were significantly decreased. When the die temperature increased from 140oC to 150oC and the water content increased from 35% to 45%, the nitrogen solubility index, cutting strength and integrity index decreased. When the biji addition was increased at a barrel temperature of 140oC and a moisture content of 45%, the integrity index of the ISP texture decreased. With an increase in the addition of biji to ISP, rough surface and irregular fiber structure were observed, but regular microfiber structure was not observed.

This study aims to investigate the physicochemical properties of extruded Biji. As the extrusion process variables, the barrel temperature and the moisture content were adjusted at barrel temperatures of 120, 140, and 160°C and 35, 45% respectively. L-value (lightness) increased as the moisture content and barrel temperature increased from 35% to 45% and 120°C to 160°C. In contrast, decreasing a-value and b-value resulted in increasing moisture content and barrel temperature. Total sugar, DPPH (1,1-diphenyl-2-picrylhydrazyl) radical-scavenging activity, ABTS (2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid)) radical scavenging activity, and total phenolic compound were increased by the extrusion process. The water solubility index (WSI) and dietary fiber of the extruded biji decreased to 3.9% and 592.6 mg/g compared to the non-extruded biji of 12.3% and 592.6 mg/g. According to the result of this study, the extruded biji could be used in various kinds of food processing, and future study is needed to find the optimum condition of the extrusion.