Effect of different gluten additions on the structure and in vitro starch digestibility of extruded quinoa noodles.

Quinoa is regarded as a high-quality food because of its rich nutrients and balanced amino acid. However, its natural gluten-free property limits the processing of quinoa noodles. Gluten forms a viscoelastic network, providing noodles with essential adhesion and structural stability. Thus, it is crucial to noodle quality. To resolve this issue, the study explored the effects of adding gluten at different levels (0 %, 10 %, 20 %, 30 %, and 40 %) on the structure and in vitro starch digestibility of extruded quinoa noodles. The results showed that as the proportion of gluten added increased, both the cooking and texture properties improved. This finding was further corroborated through low-field nuclear magnetic resonance and pasting properties. Fourier transform infrared spectroscopy revealed that the 1050/1022 cm^-1 ratio decreased as gluten proportion increased from 0 % to 30 % but then increased at 40 %. X-ray diffraction showed a significant decrease in relative crystallinity, from 31.05 (with 0 % gluten) to 20.34 (with 40 % gluten). This indicated that the hydrogen bonds between gluten and starch molecules interfered with the short-range ordered structure of starch, and acted as a physical barrier to reduce water diffusion and starch dissolution, which confirmed the phenomenon of reduced cooking loss. In vitro starch digestibility demonstrated that with increasing proportion of gluten, the content of rapidly digestible starch decreased while the content of resistant starch increased. The addition of gluten enhanced the structure of extruded quinoa noodles, improving their hardness, elasticity, and resistant starch content, while reducing cooking loss, thereby elevating the overall product quality.