High albumin-globulin ratio impairs gel network formation in mung bean protein isolates

Mung bean protein isolates (MBPI) are an emerging protein source with promising applications in plant-based food matrices due to their strong gel-forming ability. However, variability in gelation behavior has been attributed to differences in protein composition. This study investigated the effect of the albumin-to-globulin ratio on the gelling properties of MBPI. Purified albumin and globulin fractions were obtained from mung bean flour and recombined to produce three isolates with distinct albumin-to-globulin ratios (4/96, 8/92, and 14/86). Gel properties (least gelation concentration, water-holding capacity and rheological properties) and structural characteristics (microstructure, secondary structure, and intermolecular interactions) were investigated. Increasing albumin content decreased the LGC of MBPI from 8.5% to 7.5% and accelerated gelation kinetics. However, the final elastic moduli (G′) remained comparable at 10% protein and water-holding capacity decreased significantly as the albumin-to-globulin ratio increased, accompanied by reduced mechanical stability, higher frequency dependence, and increased gel brittleness. Globulin-rich gels (R4/96) exhibited denser and more homogeneous microstructures, higher proportions of intermolecular β-sheets, and stronger network connectivity, whereas the albumin-rich gels (R14/86) formed more heterogeneous and porous networks with higher proportions of intramolecular β-sheets and α-helices, a greater fraction of unbound proteins, and limited network integration. These findings highlight the importance of the albumin-to-globulin ratio in governing the structure and functionality of MBPI gels and emphasize the need to control protein composition to optimize the performance of mung bean protein ingredients in plant-based food systems.