Effects of ultrasound-assisted Maillard reaction on the emulsifying and flavor properties of brewer’s spent grain protein–gum arabic conjugates

This study explores the effects of ultrasound-assisted heating compared to conventional wet heating on the Maillard reaction (MR) between brewer's spent grain (BSG) protein and gum arabic (GA), focusing on various factors like reaction kinetics, structural changes, emulsifying performance, and volatile formation. Ultrasound process markedly accelerated glycation, with a 45 min sonicated sample glycation to a similar degree to that induced by traditional 3 h treatment, such that cavitation facilitates early MR pathways. Both approaches enhanced solubility and remodeled secondary structures, although in different manners: conventional heating promoted a gradual increase in β-sheet content and a decrease in α-helix content, while ultrasound induced rapid unfolding and structural reorganization. All MRPs enhanced the emulsifying properties, but the conventional sample after 3 h obtained the highest emulsifying activity index (EAI) and emulsion stability index (ESI) values. Samples treated with ultrasound showed moderate improvement, however, at considerably reduced reaction times. Dynamic light scattering (DLS) and fluorescence microscopy have also confirmed that conventionally heated MRPs form smaller and more uniform droplets. Volatile profiling indicated that conventional heating produced a broader spectrum of aldehydes, ketones, and furans associated with off-flavors, whereas ultrasound greatly reduced compounds such as (E,E)-2,4-decadienal and 2-pentylfuran, indicating a flavor-protective potential. In general, the reaction efficiencies and flavor quality of ultrasound-assisted heating are higher, and emulsifying performance is optimized by the conventional heating technology. This work shows that BSG protein-GA conjugates are versatile enough to achieve clean-label, plant-based emulsifier applications and its desired functional/sensory properties.