The effect of modification with phenolic extracts from grape pomace (GPE) and sorghum bran (SBE) under alkaline conditions for 6 and 12 h, with and without washing with aqueous ethanol (post modification) on the enzymatic hydrolysis as measured by viscosity decrease and antioxidant activity of maize starch was studied. Phenolic-modified starches showed lower rate of starch hydrolysis. The DSC of residues after enzyme hydrolysis showed the conversion of type I inclusion complexes in the unwashed to type II inclusion complexes in the washed phenolic-modified starches. FTIR suggests the presence of covalent bonds in the residues of the phenolic-modified starches due to the retention of starch-bound phenolics. Phenolic-modified starches showed ABTS radical scavenging activity. Ultra-fast liquid chromatography showed polymerisation of monomeric and dimeric procyanidins to oligomeric procyanidins in GPE and SBE-modified starches. It can be concluded that phenolic-modified starches with relatively low hydrolysis and antioxidant activity can be produced under alkaline conditions.
Keywords: FTIR; Proanthocyanidins; Radical scavenging activity; Thermal properties; Viscosity.
Copyright © 2020 Elsevier Ltd. All rights reserved.