## 3 Results and Discussion
### Functional Properties of Protein Fractions  
#### 3.3.1 Hydrosolubility  
Protein hydrosolubility is crucial for their functional role in food systems, such as emulsification, foaming, and gelation. It refers to the amount of protein in the water phase compared with the total protein content [28]. The hydrosolubility of the protein fractions exhibited pH-dependent behaviour, except for flour globulin (12.4-14.3%) (Figure 2). Under acidic pH conditions (near the isoelectric point), the hydrosolubility of the protein was minimal or non-existent due to the reduction in protein-water interactions. Low hydrosolubility is a result of the low electrostatic repulsion of proteins by hydrophobic interactions. These interactions increase the hydrophobicity of the surface and lead to protein aggregation and precipitation [29]. However, a significant increase in hydrosolubility (\(p<0.05\)) was observed as a function of pH when the pH increased from 4.0 to 10.0. This enhancement occurs because protein molecules have a greater net negative charge, decreasing protein-protein interactions [10].  
The glutenin fraction of LPC exhibited the highest hydrosolubility, ranging from 27.7 to 88.6%, while the glutenin fraction of flour presented a hydrosolubility ranging from 19.1 to 59.2%. This was followed by the albumin fraction of flour (32.0 to 52.1%) and the prolamin fractions of flour and LPC (0.4 to 43.6%). The globulin fractions of flour and LPC displayed the lowest hydrosolubility values (0.0 to 25.9%). The high hydrosolubility of the flour and LPC glutelin fractions may be attributed to the abundance of amino acid residues such as aspartic and glutamic acids (Table 2). These amino acids are recognised for their ability to increase the hydrosolubility of proteins under alkaline conditions [10]. Consequently, the remaining fractions, those low in or lacking these amino acids, would  
Figure 2: Hydrosolubility of protein fractions of jackfruit flour and LPC (Leaf protein concentrate) at different pH values. (**A**) Albumin, (**B**) Globulin, (**C**) Prolamin, and (**D**) Glutelin. Different letters indicate significant (\(p<0.05\)) differences between the flour and LPC fractions at the same pH.  
exhibit diminished hydrosolubility values. The _Azolla pinnata_ fern protein concentrate exhibited hydrosolubility values ranging from 24.3 to 55.3% at pH values between 4.0 and 12.0 [10]. Additionally, the alfalfa protein concentrate showed a hydrosolubility of 50% within the pH range of 5.5 to 10.0 [15]. The presence of aspartic and glutamic acids was also ascertained for these green biomass proteins.  
On the other hand, in previous investigations [11], the hydrosolubility of jackfruit LCP ranged from 3.6 to 61.9% (pH 6.0 to 10.0), and in the protein hydrolysates of pepsin and pancreatin, the hydrosolubility was found to be in the range of 19-41% and 60-98%, respectively (pH values of 4.0 to 10.0). The hydrosolubility values of these protein concentrates and pepsin hydrolysates were similar to the hydrosolubility values of the albumin fractions in flour. Notably, the hydrosolubility of the protein hydrolysates of pancreatin was relatively comparable to that of the gluten fraction of LPC, which shows that the fractionation of plant proteins could be an alternative to protein modification via enzymatic methods.