Anthocyanins degradation during storage of Hibiscus sabdariffa extract and evolution of its degradation products

Degradation parameters of two main anthocyanins from roselle extract (Hibiscus sabdariffa L.) stored at different temperatures (4-37 °C) over 60 days were determined. Anthocyanins and some of their degradation products were monitored and quantified using HPLC-MS and DAD. Degradation of anthocyanins followed first-order kinetics and reaction rate constants (k values), which were obtained by non-linear regression, showed that the degradation rate of delphinidin 3-O-sambubioside was higher than that of cyanidin 3-O-sambubioside with k values of 9.2·10−7 s−1 and 8.4·10−7 s−1 at 37 °C respectively. The temperature dependence of the rate of anthocyanin degradation was modeled by the Arrhenius equation. Degradation of delphinidin 3-O-sambubioside (Ea = 90 kJ mol−1) tended to be significantly more sensitive to an increase in temperature than cyanidin 3-O-sambubioside (Ea = 80 kJ mol−1). Degradation of these anthocyanins formed scission products (gallic and protocatechuic acids respectively) and was accompanied by an increase in polymeric color index.