Effect of Air Classification-Based Dry Fractionation on Structural, Thermal, and Functional Properties of Chickpea Protein Concentrate for Nanoemulsion Applications

Chickpea protein concentrate (CPC) was obtained via a dry extraction approach and systematically characterized in terms of its compositional, functional, and structural properties to evaluate its suitability for nanoemulsion (NE) applications. The dry-extracted CPC possessed a protein content of 44.8% and demonstrated superior functional performance, including a foaming capacity of 61.1% and a high foam stability of 94.7%, reflecting efficient interfacial adsorption and cohesive film formation. NE formulation prepared using 3.0% w/v CPC as the emulsifying agent achieved a significant reduction in droplet size, yielding a Z-average droplet diameter of 152.7 nm and a low polydispersity index (0.30), indicating a fine, relatively uniform droplet size distribution and kinetically stable colloidal stability. Comparative differential scanning calorimetry (DSC) analysis of chickpea flour (CF) and CPC revealed two main endothermic transitions. While both samples exhibited a similar low-temperature transition at 68.4 °C associated with the release of bound water, CPC showed a substantially lower enthalpy change, indicating partial disruption of native molecular order following dry extraction. The X-ray diffraction (XRD) profile of the CPC utilized in the NE systems exhibited a broad amorphous halo within the 2θ range of 10°-30°, interspersed with limited low-intensity sharp reflections. These findings confirm an amorphous-dominant structure with partial crystalline regions, with the overall crystallinity of the concentrate estimated at approximately 15%. This study describes a reproducible and solvent-free protocol for the production of oil-in-water NEs using dry air-classified CPC, suitable for instructional use and potential industrial scale-up.