Comprehensive Evaluation of OS Starch–Oleic Acid Mixtures: From Functional Properties to Their Application in Films with Improved Water Resistance

This study investigated the effects of octenyl succinate (OS) starches mixed with oleic acid on functional properties and potential use in edible films. Potato starches esterified with 1%, 3%, 5%, or 7% of octenyl succinic anhydride (OSA) were mixed with oleic acid. Degree of substitution (DS), hydrodynamic volume, and lipid content were measured to evaluate effectiveness of modification. Blank sample and modified starches were analyzed for water binding capacity, solubility, characteristic of gelatinization, pasting properties, and surface/interfacial tensions. Edible films were prepared from the obtained starches and tested for water vapor permeability, water binding capacity, and solubility. The complexation index increased linearly with DS. Oleic acid reduced water binding capacity and solubility, particularly at 80 °C, altered thermodynamic characteristic of gelatinization, decreased viscosities of OS starch pastes, and increased pasting temperatures by up to 20%. It also enhanced the surface tension lowering effect of OS starch and reduced water vapor permeability in films, especially at higher DS. Films from starch–oleic acid mixtures exhibited lower water binding capacity and solubility, notably in 5% and 7% OSA modified starch. Results show that oleic acid addition to OS starch markedly affect functional properties of starch, highlighting its potential for use in edible film applications.