Direct Formulation of a Solid Foodstuff with Phenolic-Rich Multicomponent Solutions from Grape Seed: Effects on Composition and Antioxidant Properties

Abstract

The aim of our work was to supplement a solid foodstuff with grape phenolics by osmotic treatment with an aqueous solution made of osmo-active agents (NaCl and sucrose) and a commercial grape seed extract. To investigate how the composition of the osmotic solution affected phenolic infusion, experimental conditions were set by a central composite design with two factors (the molality of NaCl and sucrose in the osmotic solution). In all experiments, the total phenolic content in the osmotic solution was kept constant (6300 +/- 45 mg gallic acid equivalents/kg), and the model food (an agar-agar gel) was processed for 8 h. Throughout the response surface, the osmo-treated model food was significantly supplemented with flavan-3-ols. At the central point of the experimental design, flavan-3-ol monomers and dimers were found in concentrations of 1334 +/- 126 and 486 +/- 55 mg/kg, respectively. Their penetration into the model food was limited by sucrose to a different extent. The Trolox equivalent antioxidant capacity of the osmo-treated gel was higher than that of fruits with a very high free radical scavenging activity.