Acetic acid-assisted controlled drying improves the room-temperature solubility of gelatin by suppressing chain...

Achieving room-temperature solubility of gelatin remains challenging because chain crystallization and intermolecular aggregation readily occur during conventional drying. Here, acetic acid-assisted controlled drying at 45 °C was developed to improve the room-temperature solubility of type A gelatin while preserving molecular integrity. Controlled drying suppressed triple-helix crystallization, whereas acetic acid further inhibited chain aggregation, enabling aggregate formation and room-temperature solubility to be modulated by adjusting the acetic acid concentration before drying. Raising the acetic acid concentration from 0% to 15% (v/v) increased the room-temperature solubility from 5.40 ± 0.50% to 81.02 ± 2.08%, with structural contribution (excluding solution acidification effects) reaching 56.09 ± 2.66%. At low acetic acid concentrations (1-2.5%, v/v), protonation of carboxyl groups increased the zeta potential from 7.37 ± 1.02 to 23.01 ± 0.90 mV, enhancing electrostatic repulsion and, together with ion-pair-mediated steric effects, restricting chain aggregation. At higher concentrations (5-15%, v/v), undissociated acetic acid interacted with side-chain hydroxyl groups and formed hydrogen-bonded dimers that acted as molecular spacers, thereby disrupting interchain hydrogen bonding and reducing aggregate stability. These structural changes supported by increased interchain spacing, reduced apparent short-range ordered domain size, and decreased total endothermic enthalpy of dry-state matrix. Although excessive acetic acid (≥5%, v/v) reduced Bloom strength and introduced residual acidity, intermediate concentrations (2.5-5%, v/v) balanced improved solubility with acceptable quality attributes. This study provides a scalable strategy for producing gelatin with enhanced room-temperature solubility. Future work should extend this strategy to different gelatin sources, optimize continuous industrial drying, and evaluate the applicability of the resulting gelatin in cold- to mild-processed or heat-sensitive food formulations.