Stability and Antioxidant Activity of Black Currant Anthocyanins in Solution and Encapsulated in Glucan Gel

Abstract

The effects of ferric and ferrous ions, pH, and temperature on the stability and antioxidant activity of black currant anthocyanins (BCA) were studied, and the recovery of BCA from glucan gel [mixed linked (1→3,1→4)-β-d-glucan] after using different encapsulating procedures was determined. The degradation of individual anthocyanins follows first-order kinetics and shows Arrhenius temperature dependence. The activation energies of individual anthocyanins, evaluated over the temperature range 60−100 °C, decrease with an increase in pH. While the antioxidant activity of BCA, measured by the ferric reducing antioxidant power assay, decreased with the degradation of anthocyanins, the completely degraded products still exhibited ∼30% of the initial antioxidant activity. Ferric ions have a detrimental effect on the stability of BCA, especially for delphinidins. Freeze drying of encapsulated BCA gives ∼20% higher recovery of individual anthocyanins than infrared drying. Keywords: Anthocyanins; black currant; antioxidant activity; FRAP assay; HPLC; degradation kinetics; thermal stability; ferric-anthocyanin complexes; (1→3,1→4)-β-d-glucan; encapsulation