## 3 Results and Discussion
### Urease Activity (UA) and Functional Properties  
Urease and trypsin inhibitor are the main unwanted components in soybean because they can cause hyperammonemia and pancreatitis, and low UA values have been correlated to lower values of trypsin inhibitor [56; 57]. As trypsin inhibitor and urease are inactivated with high temperature or radiation, UA is a measure of the heat treatment that the sample has undergone; it is known that a UA value around 0.3 indicates that the product has had enough heat treatment to inactivate trypsin inhibitor and urease [39]. Table 8 shows the UA value of the obtained SPI of 0.06, comparable to [PERSON] et al. (2020), who found a 0.04 UA value, and was better than the one obtained from the commercial SPI (0.12 UA value) [43]. Therefore, it can be said that the obtained SPI has marginal antinutritional factor activity and has a better value than a commercially available product, thus proving the need for treatment with temperatures of above 60\({}^{\circ}\)C [53]. The functional characteristics determine the application a product has in the food industry, the main functional properties of SPI at pH 4.5, SPI at pH 7, and previously reported SPI can be seen in Table 8. Water solubility is the most important functional property because it will determine foam activity and emulsion capacity [39]. The WSI in SPI at pH 7 was 1196% and 146% higher than the WSI in SPI at pH 4.5 and reported SPI, respectively. Solubility at pH 4.5 is the lowest because it is near the isoelectric pH (IPH) of soybean proteins [58]. The obtained SPI was more soluble than the reported SPI due to the heat and basic treatment that hydrolyzed the protein, making it easily soluble in water. [PERSON] et al. (2015) reported values ranging from 20% to 95% of WSL, which indicates that the obtained value is between the expected range [39]. The WAI of SPI at pH 4.5 was less than half of the reported value because of the poor solubility of the SPI at IPH. A two-phase interaction property is foam activity (FA), which is the ability of proteins to form a stable foam where a liquid layer stabilizes air droplets, and foam stability (FS), which is the capacity of a protein sample to maintain the air droplets stable for a certain amount of time. These properties are important to determine if the SPI is applicable in cakes, soutfiles, or whipped toppings [58]. FA of SPI at pH 4.5 was slightly higher than SPI at pH 7, and reported SPI had a significantly higher FA; these results are congruent to the \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Sample** & \(\boldsymbol{\beta}\)**-Conformations (\%)** & \(\boldsymbol{\alpha}\)**-Helix (\%)** &
\begin{tabular}{c} **Random** \\ **Coil (\%)** \\ \end{tabular} & \(\boldsymbol{\beta}\)**:\(\boldsymbol{\alpha}\) Ratio** \\ \hline Soybean flour & 69.23 & 15.38 & 15.38 & 4.50 \\ Soybean flour [54] & 69.20 & 12.16 & 12.34 & 5.69 \\ Commercial SPI & 77.77 & 11.11 & 11.11 & 7.00 \\ SPI & 81.81 & 9.09 & 9.09 & 9.00 \\ SPI [51] & 72.00 & 12.00 & - * & 6.00 \\ \hline \hline \end{tabular}  
* Not reported.  
\end{table} 
Table 7: Secondary structures determined by deconvolution of amide I, using ATR-FTIR.