Improved Functionality and Emulsifying Stability of Chickpea Protein Microgel–Mung Bean Hull Fiber Conjugates via Combined Physicochemical Pretreatment

Abstract

Native chickpea protein isolate (CPI) exhibits unsatisfactory solubility and dispersibility, restricting its interfacial performance and emulsion-stabilizing capacity. Herein, CPI gels were subjected to combined high-pressure homogenization and ultrasonication pretreatment to fabricate CPI microgel particles (CPIMPs), followed by a Maillard conjugation with mung bean hull soluble dietary fiber (MSDF). Then the effects of glycosylated CPIMP–MSDF conjugates on structural properties, functional properties, and emulsion stability were evaluated. The results demonstrated that the grafting degree of the CPIMP–MSDF conjugate reached a peak of 35.54% at a 4:1 protein-to-polysaccharide mass ratio, indicating efficient grafting. FTIR, intrinsic fluorescence spectroscopy, and free sulfhydryl content analysis confirmed the structural changes. Glycosylation was found to significantly enhance the antioxidant activity, foaming properties, and emulsifying capacity of conjugates. The emulsifying activity index (EAI) and emulsion stability index (ESI) of the CPIMP–MSDF conjugates were 2.52- and 2.91- fold higher than those of CPI, respectively. The Pickering emulsion stabilized by the CPIMP–MSDF conjugate exhibited the smallest droplet size (4.72 μm) and the lowest zeta potential (−30.71 mV). Furthermore, glycosylation significantly enhanced the storage stability and thermal stability of the Pickering emulsions. This combined physical pretreatment and Maillard conjugation provides a feasible strategy to upgrade the functional attributes of legume protein.