Wettability and Functionality of Extruded Potato Starch Films Enriched with Edible Oil

Potato starch extrudates, chemically modified by a K₂CO₃ catalyst and enriched with two types of edible oils (rapeseed or sunflower) at varying concentrations (3%, 6%, 9%), were used as film substrates. This study was carried out as a continuation of previous research on analogous extrudates in the form of dry powders and liquid solutions. The main objective was to determine surface properties of polysaccharide films as a function of oil type and concentration to monitor their wettability, biocompatibility, and functional characteristics (e.g., transparency, colour, thickness, flexibility, solubility). Advancing and receding contact angles for polar liquids (water and formamide) and non-polar diiodomethane were measured on the base and oil-modified extruded starch films. Based on these measurements, the surface free energy of the films was determined using the contact angle hysteresis (CAH) model. Optical profilometry confirmed the wettability results through surface morphology and roughness evaluation. Additionally, FTIR analysis of the films was compared to the FTIR spectra of extruded starch powders. Combining these methods provided an in-depth characterization of the films, thereby improving control over their stability and wettability, which is essential for applications in the pharmaceutical and food industries to extend product freshness and enhance resistance to oxidation and spoilage.