## 3 Results and Discussion
### Functional Properties of Protein Fractions
#### 3.3.2 Foaming and Emulsifying Properties  
The capacity of proteins to generate enduring foams is essential in producing a diverse range of food products. The foaming capacity (FC) and foaming stability (FS) are commonly used as critical metrics for evaluating the foaming properties of proteins. Although the gluten fractions presented greater amino acid contents and enhanced hydrosolubility compared to the other protein fractions, the findings indicated that the prolamin fraction of the LPC presented the most notable (\(p\) < 0.05) FC (Figure 3A) and FS (Figure 3B), followed by the albumin and prolamin fractions. In contrast, globulin demonstrated the lowest FC without FS, which is consistent with the hydrosolubility results obtained for this particular protein fraction. Figure 3: Emulsifying and foaming properties of protein fractions of jackfruit flour and LPC (leaf protein concentrate) at pH 7.0. **(A)** Foaming capacity, **(B)** foaming stability, **(C)** emulsifying activity index, and **(D)** emulsion stability index. Different letters indicate significant (\(p\) < 0.05) differences between the flour and LPC fractions. Although the foaming properties of proteins have been widely studied, their foaming behaviour cannot be attributed only to factors such as hydrosolubility and amino acid composition [30]. Indeed, the FC is influenced by the adsorption rate, flexibility, and hydrophobicity, and the FS is determined by the rheological properties of the films, including hydration, thickness, protein concentration, and favourable intermolecular interactions [31]. These variables present a potential explanation for the observed foaming characteristics of the prolamin fraction and permit further exploration in future research. The FC and FS of the prolamin fraction were greater than those reported for the foam (pH 7.0) formed with the alfalfa concentrate [15], _A. pimata_ fern protein concentrate [10], and broccoli leaf protein [21]. This was observed even with lower protein concentrations than those reported by the respective authors. Also, the results demonstrated superior FC (70-100%) and FS (42-70%) compared to the findings for jackfruit LPC and its hydrolyses, as documented in previous studies [11]. The emulsifying properties of proteins are also significant in emulsion-based food systems. These properties are evaluated through the emulsifying activity index (EAI) and emulsifying stability index (ESI). The fractions containing gluten (flour and LPC) exhibited the highest EAI (Figure 3C) and ESI (Figure 3D), followed by albumin (flour), prolamin (LPC), and globulin (flour and LPC). This pattern was related to the hydrosolubility profiles of the protein fractions (Figure 2). Specifically, a higher concentration of soluble proteins facilitates rapid migration to the oil-water interface, consequently enhancing the formation and stability of emulsions [32]. Then, the high EAI and ESI exhibited by the glutenlin and albumin fractions can be attributed to this observation. In the same way, the glutenlin and albumin fractions contained significantly more hydrophobic amino acids than the other fractions. As discussed earlier, this finding positively impacts their ability to create emulsions and their capacity to absorb oil. Furthermore, the high concentration of ionisable amino acids in the glutenlin fraction, such as aspartic acid, glutamic acid, and tyrosine, enhances its emulsifying ability. The amino acids aspartic acid and glutamic acid can also react with calcium ions, leading to the formation of aggregates that strengthen gelation. Consequently, the substantial presence of these specific amino acids within the protein structure can promote the interactions with calcium ions and facilitate the encapsulation of substances. This observation highlights the potential of plant-based sources as viable coating materials for the encapsulation technique in question. It suggests potential practical uses in food science for the glutenlin fraction [33].