Evaluation of anthocyanin stability during storage of a coloured drink made from extracts of the Andean blacberry (Rubus glaucus Benth.), açai (Euterpe oleracea Mart.) and black carrot (Daucus carota L.)

Abstract

The effect of temperature on the stability of three purified anthocyanin sources in a soft drink (pH 3, 10 °Brix) stored at (4, 20, 30 and 50) °C for 60 days was investigated. Materials and methods. Anthocyanins from Andean blackberries ( Rubus glaucus Benth.), açai (Euterpe oleracea Mart.) and black carrot ( Daucus carota L.) were purified and concentrated on a laboratory scale by adsorption to a styrene divinylbenzene copolymer. Two classical empirical approaches (Arrhenius and Ball models) were used to describe the thermal degradation kinetic of these three anthocyanins. Results. No degradation was detected during the refrigerated storage (4 °C). At all temperatures, the degradation rate constant ( k ) for black carrot anthocyanins was less than those in açai and blackberry (0.42 × 10 –2 , 0.77 × 10 –2 and 1.08 × 10 –2 )·d –1 , respectively, at 30 °C). Anthocyanins in black carrot degraded less rapidly than those in açai and Andean blackberry. The activation energy ( E a ) for degradation of black carrot anthocyanins was (63.2 ± 4.3) kJ·mol –1 , and (66.3 ± 2.7) kJ·mol –1 and (91.2 ± 0.4) kJ·mol –1 for açai and blackberry anthocyanins, respectively, at 20–50 °C. These higher E a of blackberry anthocyanins as compared with those of black carrot and açai imply that a small temperature increase is sufficient to degrade them more rapidly. Conclusion. Our results clearly showed that anthocyanins from black carrot have a good stability during thermal storage (4 °C to 50 °C) with regard to blackberry and açai anthocyanins. Acylation of black carrot anthocyanins probably explains their greater stability. Acylated anthocyanins have shown to be promising alternatives to the use of synthetic dyes in drink systems. (Résumé d'auteur