## 3 Results and Discussion
### Texture Properties and Sensory Evaluation  
The textural properties of cooked noodles depend on many factors, including flour quality, water absorption, ingredients processing parameters, etc. The texture analysis results of cooked SPI noodles are shown in Table 4. As SPI content increased, hardness, co-hesiveness, tensile strength, adhesiveness, springiness, gumminess and chewiness showed a significant downward trend. [PERSON] et al. reported a negative correlation between the hardness of noodles and their water absorption capacity [PERSON] et al. (2017). As shown in Table 1, the addition of SPI to noodles led to higher moisture content. This suggests that incorporating more SPI enhances water absorption capacity while also causing a decrease in the hardness of noodles. A whole-grain flat rice noodle containing SPI has been reported to have reduced hardness and chewiness due to SPI's high water-holding capacity [PERSON] et al. (2018). Tensile strength measures the amount of force required to break a noodle of a fixed length under a specific speed and force. A higher tensile strength indicates greater gluten strength in the noodle. The findings in Table 4 demonstrate a negative correlation between tensile strength and the addition of SPI to the noodle. This result is consistent with that of [PERSON] et al. who found that a higher SPI content in gluten-free rice spaghetti led to a lower tensile strength [PERSON] et al. (2017). As the proportion of SPI increased, the gluten strength of the noodles decreased, which affected noodle texture in terms of cohesiveness, springiness, gumminess, chewiness, and adhesiveness, ultimately impacting overall taste. Moreover, the IDDSI test results showed that both control and 20% SPI noodles were easily deformed and squashed by the fork, did not fall from the fork and also did not stick to the spoon (Figure S1). The results confirmed that the samples passed all three tests, i.e., the fork pressure test, fork drip test and the spoon tilt test, and were categorized as Level 5 minced and moist food as per IDDSI. Although the IDDSI framework is an easy-to-use and efficient testing technique to identify texture-modified foods, due to the subjective judgment with visual inspection, this method has some drawbacks. To evaluate the sensory qualities of the noodles, different proportions of SPI were used. The result presented in Table 5 showed that the control noodles (0% SPI) obtained the highest flavor, taste, and overall acceptability scores of 6.30, 7.01 and 6.97, respectively. However, the sensory evaluation scores showed that the flavor, texture, and overall preference of noodles with a 5% SPI were very similar to those of the control group, with no statistically significant differences observed. These results suggest that noodles fortified with 5% SPI are acceptable to consumers. In contrast, the scores for noodles with a 10%, 15%, and 20% SPI were lower, likely due to the increasing softness of the texture and the stronger soy flavor, which might result in an unpleasant taste. In practical application, protein-enriched noodles are essential for maintaining good health. The texture analysis and evaluation results indicate that noodles fortified with SPI have a softer texture and therefore might be more suitable for elderly individuals with poor oral and dental function.