The elderly population in developed countries has increased rapidly in recent years; the elderly may be at greater risk of protein deficiency due to dietary, socio-economic, dental, and physical restrictions. Therefore, to address the issue of protein deficiency in elderly people, the present study aimed to enhance the protein content of high-gluten flour noodles, an Asian staple food, by supplementing them with soybean protein isolate (SPI) powder. The effect of SPI addition (5-20%, w/w) on composition, quality, texture, physical and sensory properties, and glycemic index (GI) of high-gluten flour noodles was investigated. The noodles made only from high-gluten flour served as control. In comparison to control noodles, 20% SPI noodles showed a rise in protein and moisture content from 16.17% to 30.64% and 36.06 to 44.84%, respectively. The cooking yield and cooking loss increased with an increase in SPI concentration compared to control noodles. Color characteristics analysis revealed the decreasing trend in brightness and yellowness of SPI noodles with minimal L* and b* values at a 20% SPI concentration. The addition of SPI also resulted in a decrease in the hardness and tensile strength of the noodles. The sensory analysis showed that 5% SPI noodles were more similar to control noodles in terms of flavor, taste, and overall acceptability. Moreover, the addition of SPI to the noodles significantly decreased the GI of the noodles reaching the standard of low-GI food. The findings of the current study indicate that soy protein noodles, besides supplementing the desired nutrients, may also prevent the risk of diabetes in elderly people.
