Antioxidant Properties and Rutin Content of High Pressure-Treated Raw and Roasted Buckwheat Groats

Abstract

The effect of high hydrostatic pressure treatment (200 MPa for 2, 4, and 9 min) on the total antioxidant capacity (TAC), reducing capacity (TRC), and rutin content of raw and roasted buckwheat groats was studied by an updated analytical strategy. TAC and TRC were calculated as the overall capacity of hydrophilic and lipophilic antioxidants. Antioxidant capacity was measured against the 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonate) radical cation (ABTS•+) and the 2,2-diphenyl-1-picrylhydrazyl radical (DPPH•), and by the photo-induced chemiluminescence assay against the superoxide anion radical (O2−•), whereas the reducing capacity was evaluated with the Folin-Ciocalteu reagent (FCR) and directly by the cyclic voltammetry method. Rutin content was determined by HPLC analysis. The TAC of pressure-treated raw and roasted groats was 16–20% and 12.5–17% lower in comparison with untreated groats, respectively. Hydrophilic antioxidants were the main contributor to the TAC of pressure-treated raw and roasted groats. High pressure treatment of raw groats lowered the FCR reducing capacity of hydrophilic antioxidants by an average of 12.6% and 12%, respectively. In contrast, the pressurization of roasted groats increased radical scavenging capacity by 18% on average due to the presence of hydrophilic compounds in roasted groats. The variations in the antioxidant properties of pressure-treated raw groats were accompanied by an average 47% drop in rutin content, whereas irregular changes were noted in HP-treated and roasted material.