Physicochemical Modification and Rearrangement of Structure in Potato Starch-based Film-forming Solutions Treated with Plasma-activated Water

Abstract

Cold plasma is an eco-friendly approach for tailoring starch-based film-forming solutions (FFS) through reactive oxygen and nitrogen species (RONS). This study compared (i) plasma-activated water (PAW) blended with distilled water at 10:90, 20:80, and 30:70 (PAW:DW) and (ii) direct plasma treatment of potato starch FFS for 5, 10, and 15 min, evaluating rheological, textural, optical, and structural responses. PAW exhibited strong activation (pH 2.56; ORP 434.7 mV) with elevated conductivity and dissolved solids, indicating ionic enrichment. Apparent viscosity increased in all treated samples relative to the control, with the highest viscosity observed for PAW-blended FFS. Dynamic oscillatory measurements indicated that direct plasma exposure reduced viscoelastic moduli in a time-dependent manner, consistent with disruption of the starch network at higher treatment intensities, whereas PAW blends partially preserved elasticity. Color analysis showed increased lightness and whiteness index in PAW-treated samples, indicating improved optical uniformity. FTIR spectra showed changes in O–H stretching intensity and emergence/ intensification of oxidation-related bands, which is consistent with chemical modification of the starch matrix. Overall, direct plasma and PAW blending induced distinct molecular rearrangements in hydrated starch systems, offering tunable pathways for tailoring starch-based film-forming systems for potential biodegradable packaging applications, as a precursor to future film-level investigations.