## 3 Results and Discussion
### The Influence of SPI Addition on the Thermo-Mechanical Properties of the Gluten-Free Mixtures
The dough consistency continued to increase until the end of Ph IV, but also over the entire Ph V (Figure 3). The strength of the gel was higher in the case of dough with sSPI-T, followed by sSPI-B and sSPI-N. It should be noted that trypsin ensured the lowest hydrolysis degree among all enzymes used for soy protein hydrolysis [10]. Moreover, as indicated by the SDS-PAGE analysis, sSPI-T included higher-molecular-weight peptides compared to sSPI-B and sSPI-N (Figure 1). [PERSON] [39] mentioned the importance of the size of the peptide molecules within protein hydrolysates and appreciated that lowering the molecular weight can affect the strength of the gels in which they are incorporated. Anyway, the degree of hydrolysis and the nature of the enzyme used for hydrolysis are critically important. In this respect, [PERSON] and [PERSON] [40] observed that soy protein hydrolysates have better gel-forming properties than the original protein isolate but also the fact that gel properties depend on the enzyme used for hydrolysis and the degree of hydrolysis. The authors reported that the protein hydrolysate obtained with Neutrase allowed for gels with higher strength compared to those obtained with trypsin. In addition, it is mentioned that at lower degrees of hydrolysis, the strength of the gel is higher. [PERSON] et al. [41] observed that the peptide fraction with low molecular weight (0.5-10 kDa), separated from the hydrolysate obtained from soy protein isolate, allowed for obtaining gels at temperatures above 65 \({}^{\circ}\)C, and the obtained gel had high strength compared to the control. The Influence of the Insoluble Soy-Derived Peptides' Addition on the Thermo-Mechanical Properties of the Gluten-Free Mixtures  
The addition of rSPI considerably increased the consistency of the dough in Ph I and Ph II, compared to the control and dough sample supplemented with SPI (Figure 3). The abrupt drop in the dough consistency in the first 8 minutes while kneaded at 30 \({}^{\circ}\)C can be attributed to the slower formation of the dough network. The consistency at the end of Ph I (C-I) was 0.99, 0.75 and 0.59 Nm, while the minimum C2 consistency reached in Ph II was 0.42, 0.30 and 0.27 Nm for the dough samples supplemented with rSPI-T, rSPI-B and sSPI-N, respectively (Table 3). The dough sample prepared with the residue of the hydrolysate obtained with trypsin, which also had the lowest degree of hydrolysis, exhibited the highest consistency after 480 s of kneading at 30 \({}^{\circ}\)C (C-I), the steepest consistency drop (C1-C2 of \(-\)1.75 Nm) and the highest consistency value (C2) measured at 55 \({}^{\circ}\)C (Table 3). The dough samples supplemented with rSPI-B and rSPI-N recorded consistency decreases of \(-\)1.66 Nm and \(-\)1.29 Nm, respectively. All dough samples supplemented with rSPI had higher C2 values compared to the control and the sample with SPI. The peptide profile of the three hydrolysates used to supplement the gluten-free dough and their water related properties can explain the different consistency variations in the dough [36]. We can assume that the peptides from rSPI have a higher water binding capacity [39], compared to the sample with and without the addition of SPI, but the development of the dough network is more difficult and the stability lower. However, the higher C2 values registered for the samples with rSPI may indicate a greater stability of the protein network upon heating, as a result of molecular interactions through hydrogen bonding and hydrophobic contacts, involving the proteins of rice and quinoa and soy peptides, which improved the resistance of the dough to kneading and heating. The addition of rSPI to the gluten-free composite flour did not delay starch gelatinization, as observed in case of the addition of soluble soy peptides, but increased the consistency of the gel compared to the control and the sample with SPI.