## 1 Introduction  
For environmental, health, social, and ethical reasons, plant proteins are of great interest in the food industry as suitable candidates for replacing proteins of animal origin (e.g., whey proteins, casein, and gelatin) in new product formulations [1, 2]. They are particularly appreciated by consumers because they are natural, \"green\", \"vegan-friendly\", and sustainable for the environment and agriculture [3]. Among all alternative protein sources, the use of legume proteins in the food sector is rapidly expanding. Legumes are being considered as more environmentally friendly alternatives to meat, poultry, and dairy products as they have low greenhouse gas and water footprints but also enrich the soil through nitrogen fixation. They are nutrients with an exceptionally high protein content compared to other plant-based protein sources. Furthermore, legumes are abundant, low-cost, sustainable, not highly allergenic, and widely acceptable by consumers [2, 4]. Chickpea (_Cicer arietinum_ L.) is a nutrient-rich food and the second most consumed pulse worldwide [5, 6], but the use of its protein preparations in the food industry is still limited. This is mainly due to the fact that their properties and how they interact within food matrices were scarcely studied, especially compared to other legume proteins such as soybean or pea proteins [7]. Both the emerging interest in chickpea proteins as a matrix in functional foods [8, 9] and the fact that chickpeas are not only a sustainable protein source but also contribute to soil health and climate resilience [5, 10] prompted us to use these proteins in the present study. Chickpea is a valuable source of high-quality protein rich in a number of essential amino acids (e.g., lysine, leucine, and arginine), including branched-chain ones [2]. The methionine content in chickpea proteins is relatively low compared to animal-based proteins, making it the limiting amino acid. However, chickpea protein can still play a crucial role in a well-balanced plant-based diet [11]. The main chickpea proteins are salt-soluble globulins (53-60%), in which the ratio of legumin (16S) and victim (7S) fractions is six to one. The legumin fraction has higher sulfur-containing amino acids (e.g., cysteine and methionine) than victims, while victims do not contain cysteine residues and therefore cannot form disulfide bonds [12; 13; 14; 15]. Chickpea and aquafaba (the viscous liquid that can be drained from canned or cooked chickpea) proteins have been reported to be nutrients with a wide range of useful technological properties, such as foaming, emulsification, and gelling [6; 16; 17; 18; 19]. These properties are affected by the solubility of proteins and their molecular state in an aqueous media (native, partially denatured, denatured, aggregated) [20; 21; 22]. It is known that external conditions such as pH, ionic strength, and temperature can control protein solubility by influencing protein-water and protein-protein interactions. There is a strong pH dependence for chickpea protein solubility. They have minimal solubility in the pH range of 4.0-5.0; above pH 6.5, all proteins have a solubility greater than 70% [23], while the maximum solubility of chickpea proteins was reported at acidic (<3.0) and alkaline (>8.0) pH [19]. Protein solubility is also affected by the presence of salt ions. Typically, at a low salt concentration regime, protein solubility increases along with salt concentration (\"salting-in\") because the charged biomolecules are surrounded by the salt's counterions, and this screening results in a decrease in the electrostatic free energy of the protein and an increase in solvent activity. However, at a high salt concentration regime, solubility decreases with increasing salt concentration (\"salting-out\") as protein and salt ions compete to interact with the solvent molecules [20; 24].