The influence of acid hydrolysis on physicochemical properties of starch-oleic acid mixtures and generation of radicals

Abstract The aim of this paper was to evaluate the effect of acid hydrolysis on formation of the starch-oleic acid mixtures, their structure and functional properties. The potato starch was hydrolyzed with hydrochloric acid for 0.5 - 4.0 h, then obtained acid-hydrolyzed starches were mixed with oleic acid to prepare the starch-oleic acid mixtures. Measurements of molecular size distribution, lipids content, fatty acid composition, and complexing index of gelatinized mixtures revealed that performed modifications were effective. The water binding capacity at 80 oC of tested starch-fatty acid mixtures ranged from 14.51 (g/g) for untreated potato starch to 11.24 (g/g) for starch hydrolyzed for 4 h. The addition of oleic acid reduced the solubility in water at 80 oC of modified starches by 70-61 % compared to their counterparts. The highest DPPH radical scavenging activity (15.1 %) was found for the starch hydrolyzed for 0.5 h and mixed with oleic acid. Hot paste and final viscosities of the starch-fatty acid mixtures gradually decreased with the increasing of acid treatment time. The lowest values of these parameters were determined in mixture of starch hydrolyzed for 4 h (364 mPa·s and 536 mPa·s, respectively). Incorporation of oleic acid into starch hydrolyzed for 4 h increased by approximately 90 % content of the resistant starch fraction compared to the non-mixed counterpart. Electron paramagnetic resonance studies showed that acid hydrolysis promoted the generation of stable carbon centered radicals in starch, whereas the introduction of oleic acid strongly inhibited this process.