## 3 Results and Discussion
### The Techno-Functional Properties of Proteins
#### 3.2.2 Foaming Properties  
The foaming capacity (FC) refers to the ability of a substance, such as a protein, to form and stabilize foam. It measures the amount of interfacial area that can be created by whipping the substance. It is determined by the ability of the protein to adsorb quickly to air-water interfaces and lower the interfacial tension, trapping more air and increasing the foam volume [9]. With the application of HIU, it was possible to obtain a modified protein with a modified FC, which was not observed in the untreated LPC (control, Figure 1). The FC average at 10 min increased according to the increase of power. However, owing to the dispersion of the data, it was not possible to identify significant differences under the  
\begin{tabular}{c} NA: not apply (i.e., they are non-essential amino acids); HAAs: hydrophobic amino acids; AAAs: aromatic amino acids; EAAs: essential amino acids; NCAAs: negatively charged amino acids; TAAC: total amino acid content; ND: not detected. Different lower-case letters in the same column are significantly different, according to [PERSON]’s LSD test at \(p\leq 0.05\). \end{table}
Table 2: Cont. different conditions. Nevertheless, it is important to consider that at 15 min, the mean of the FC under all the assessed powers decreased in comparison to the modified protein that was obtained after 10 and 20 min (Figure 1). Our results are like those obtained from modified proteins of the same source using UAE (35 \(\pm\) 1.67% FC, at 42 kHz for 20 min) [6]. Studies have shown that HIU treatment can improve the foaming properties of various proteins, including soy protein isolate (SPI), whey protein microgel, pea protein isolate (PPI), and chickpea cooking water (aquafaba) [11; 13]. The treatment can increase the foaming ability and stability of proteins, enhancing foam expansion, foam stability, and the emulsifying activity index [27]. In the case of PPI, the FC increased from 145.6% to 200.0% as the intensity increased from 50 to 90% (20 kHz for 30 min) [11]. The FC of a hydrolyzed protein is strongly linked to the obtention method and the conditions used in the structural modification. The method affects the exposition of HAAs, the hydrolysis degree, and the presence of carbohydrates like sugars, which are factors that affect the FC [9]. It has been reported that as the size of the modified proteins decreases the FC does also. As the protein structure decreases in size, the number of smaller molecules also decreases, which may result in the protein not being able to stabilize air bubbles as effectively, leading to a decrease in the FC [2]. US pretreatments, in terms of power and exposure time, can reduce the size of modified rapeseed protein [28] and milk protein concentrates compared to samples that were not treated with sonication [29]. The FC of protein hydrolyses treated with HIU can vary significantly, depending on the duration of the treatment. During the initial stages of treatment (for example, at 10 min), proteins undergo partial unfolding, which increases their exposed hydrophobic regions. This unfolding is crucial for enhancing the FC, as it reduces the surface tension at the air-water interface, allowing for better foam formation [11]. However, at 15 min, the extent of unfolding may reach a point where excessive cavitation and mechanical stress lead to protein aggregation or denaturation, which can negatively impact the FC. After 15 min of treatment, the particle size becomes small (Figure 2), leading to a loss of structural integrity and a reduced FC [13]. By 20 min, the system may adapt or stabilize in a way that improves foaming again. Therefore, this phenomenon could suggest that there is an optimal treatment time at which the balance between particle size and protein structure is maintained for the maximum FC [15]. On the other hand, the FS refers to the ability of a foam to maintain its structure over time. In this research, the FS of the ultrasonicated proteins was higher than that of untreated jackfruit proteins (\(p\leq 0.05\)).