## 3 Results
### Functional Analysis of Vegetable Proteins  
Table 2 shows the functional characterization of isolates and hydrolyses of soybean proteins and the soybean-maize mixture. Solubility is the property of significant importance as it influences other functional parameters measured by the gravimetric method (water solubility: WS) and spectrophotometric or Kjeldahl methods (nitrogen solubility index: NSI). The WS determines the amount of protein and non-protein solids soluble in water and is rarely used for functionality-specific studies but is widely used in the food industry for its accessibility. SMI was 10% more hydrosoluble than the commercial soybean counterpart. Interestingly, the SMI was 52% more soluble than soybean because it had a higher degree of hydrolysis or FAN value. The SH has less FAN than the isolate, despite being a hydrolyzed sample, resulting in a protein with lower solubility. Another property-related to solubility is the nitrogen solubility index (NSI). This parameter determines the percentage of total nitrogen dispersible in a 0.1 M sodium chloride (NaCl) solution corresponding to globulins and small peptides. The solubility of SMI and SMI proteins was 25% and 41% higher than soybean, respectively (Table 2). However, the soybean isolate and hydrolysate solubility did not show significant differences (\(p>0.05\)). The water absorption index (WAI) is the amount of water absorbed per gram of sample. The structural configuration and environmental factors determine if the interaction of the protein with the water is retention by entrapment or absorption, respectively. As analysis conditions were standard for all samples, the WAI depends on the conformation of each protein. The soybean isolate and hydrolysate did not present significant differences in the WAI (\(p>0.05\)). The soybean-maize samples had significantly lower (\(p<0.05\)) water absorption indexes than the soybean counterparts. The functional properties associated with the hydrophobicity of the protein are the fat absorption index (FAI), emulsifying activity index (EAI), and emulsion stability (ES). The FAI of a protein depends on intrinsic factors such as amino acid composition, protein conformation, and polarity or hydrophobicity of the surface. The FAI can be achieved by physical entrapment of the oil with the protein by non-covalent interactions (hydrophobic, electrostatic, hydrogen bonding). The isolate  
\begin{table}
\begin{tabular}{c c c c c} \hline \multirow{2}{*}{**Parameter**} & \multicolumn{4}{c}{**Vegetable Proteins**} \\  & **Soybean Isolate (S)** & **Soybean-Maize** & **Soybean** & **Soybean-Maize** \\  & & **Isolate (SMI)** & **Hydrolysate (SH)** & **Hydrolysate (SMH)** \\ \hline WAI & \(7.97\pm 0.16\)1  & \(5.56\pm 0.18\)2 [FOOTNOTE:2]Footnote 2:  
and hydrolysate of soybean and soybean-maize proteins had the same FAI (\(p>0.05\)); therefore, fat absorption was independent of protein content and degree of hydrolysis. EAI refers to the ability of a protein to establish interactions at the interface water-protein-oil, while the ES determines the resistance of the protein to maintain the emulsion for a specific time [16]. Table 2 shows that SMI and SMH proteins had the highest emulsifying activity and were not significantly different (\(p>0.05\)). Concerning the ES, the SH was more stable at 24 h of storage followed by the soybean-maize hydrolysate, soybean-maize isolate, and finally, soybean isolates with 43.4% stability. However, at 48 h of storage, all soybean and soybean-maize samples showed a slight stability increase, and statistical analysis indicated no significant differences among proteins (\(p>0.05\)). The foaming activity (FA) of a protein, related to the EAI, is mainly due to the air-protein-water interactions. FA is related to the ability of a protein to form a two-phase system where the air molecules are separated by a continuous layer of liquid [2]. The FA of both the soybean isolate and hydrolysate were higher than the soybean-maize.