Rheological behavior and release dynamics of pregelatinized pink potato starch modified by stearic acid.

The effects of stearic acid (5 %, 10 %, and 15 % w/w) and pregelatinized pink potato starch (20, 25, and 30 min) on complex formation, physicochemical properties, rheology, and release characteristics were investigated. Moisture content decreased from 14.26 % in pregelatinized starch to 13.25 %, 12.85 %, and 11.45 % in complexes with 5 %, 10 %, and 15 % stearic acid, respectively. Water-holding capacity dropped from 268.68 % to 128.26 %, 95.05 %, and 50.63 %, with increasing stearic acid concentrations. Swelling and solubility power also decreased, with swelling power reducing from 5.57 % to 3.45 % and solubility from 12.75 % to 10.34 %. Micromeritic evaluations showed improved flowability in starch-stearic acid complexes. X-ray diffraction revealed a V-type crystalline complex with characteristic peaks at 7°, 21°, 22°, and 24°, and additional peaks at 7° and 41°. FTIR spectra indicated complex formation with bands around 2917 and 1700 cm^-1. FESEM imaging showed intact granules with irregular shapes and protruding amylose fragments. Rheological assessments indicated reduced viscosity and altered viscoelastic properties in the complexes. In-vitro release studies demonstrated controlled drug release, suggesting potential applications for targeted pharmaceutical delivery. This study emphasizes the functional modifications induced by stearic acid in pregelatinized starch, enhancing material properties for industrial and biomedical applications.