INTRODUCTION
Insect proteins have emerged as sustainable functional ingredients, yet native mealworm proteins often exhibit low solubility and limited interfacial activity due to their compact structures. Enzymatic hydrolysis can improve dispersion while modifying structural features relevant to emulsion formation. This study examined how varying degrees of hydrolysis (DH) influence the physicochemical and interfacial properties of mealworm protein hydrolysates (MPHs) and evaluated their effectiveness as natural emulsifiers.

MATERIALS AND METHODS
Mealworm protein solution (1% w/v) were hydrolyzed using Alcalase at 50 °C with 0.5% and 1% (w/w) for 15, 30, and 60 min. The reaction was terminated by heating at 80 °C for 20 min, followed by freeze-drying. SDS-PAGE, FT-IR, circular dichroism (CD), and ANS fluorescence were used to assess peptide fragmentation, secondary structure changes, and surface hydrophobicity. O/W emulsions were prepared with soybean oil, and droplet size, microstructure, and stability were evaluated using DLS, optical microscopy, and Turbiscan analysis. Oxidative stability was assessed by TBARS.

RESULTS
Moderate hydrolysis resulted in clear improvements in colloidal and interfacial behavior. Particle size decreased from ~360 nm in native MP to ~250–260 nm in hydrolyzed samples, while PDI values remained low (~0.2–0.4). The absolute zeta potential increased (−42 mV → −46 to −49 mV), indicating stronger electrostatic repulsion and reduced aggregation.
Secondary structure analysis showed a clear shift, with α-helix content falling from 26.1% to about 10–12% and both β-sheet and random coil components increasing. These modifications enabled MPHs at moderate DH to form smaller and more uniform emulsion droplets and improved their resistance to thermal and freeze–thaw stress. Emulsions prepared with these MPHs also showed reduced creaming and lower lipid oxidation than those made with native or extensively hydrolyzed proteins.

DISCUSSION
Overall, the functional performance of MPHs reflected a balance between peptide size, solubility, and interfacial activity. Moderate hydrolysis generated peptides that readily adsorbed to the oil–water interface and formed cohesive interfacial layers, whereas excessive hydrolysis produced fragments too small to stabilize droplets or contribute to network formation, resulting in reduced stability.

KEYWORDS
mealworm protein, enzymatic hydrolysis, interfacial behavior, emulsion stability, insect protein.