Structural and functional characterization of duckweed protein-maltodextrin conjugates and their application in oleogels for low-fat mimetic food materials

This study explores the functional and structural characteristics of duckweed protein-maltodextrin conjugates (DPM) as potential fat substitutes through oleogel application. Conjugates were prepared at protein-to-maltodextrin ratios of 1:1, 1:2, and 1:3, labeled DPM1, DPM2, and DPM3. Among these, DPM3 exhibited the highest degree of grafting (59.48%), solubility (61.42%), and antioxidant activity (22.70%), suggesting a more extensive Maillard reaction and superior functional properties. Circular dichroism spectroscopy revealed that conjugation disrupted α-helix structures while promoting β-sheet formation, indicating enhanced intermolecular interactions and protein unfolding. Structural analyses using Fourier transform infrared spectroscopy (FT-IR) and fluorescence spectroscopy showed that conjugation altered protein secondary and tertiary structures, further supporting the improved functional performance. As maltodextrin content increased, foaming capacity decreased, with DPM3 exhibiting the lowest at 17.82%. Nevertheless, DPM3 demonstrated improved emulsion stability, likely due to thicker, viscoelastic interfacial layers. DPM-based oleogels outperformed CON counterparts in texture and oxidative stability. DPM2 formulations (O-DPM2) exhibited superior textural properties, including elasticity, chewiness, and hardness. By day 14, lipid oxidation levels were lowest in O-DPM2 (1.212 mg MDA/kg) and O-DPM3 (1.319 mg MDA/kg), with no significant difference between them. PCA analysis revealed that most of the texture attributes of oleogels were positively correlated with the degree of lipid oxidation. The findings highlight the potential of Maillard reaction-mediated conjugation to enhance functional attributes of duckweed protein, supporting its broader application in food systems.