Evaluation of the pH and thermal stabilities of rosella anthocyanin extracts under solar light

Anthocyanin is considered as an unstable pigment, undergoes gradual degradation processes throughout the storage or use. The degradation of Rosella anthocyanin extract (RAE) in different pH solutions was studied under solar light and compared with solutions kept in the dark. It appears that RAE solutions under solar light were suffering rapid degradation than those kept in the dark. Moreover, RAE samples at higher pH values showed faster rates of degradation than those with lower pH values. A mechanism for degradation was suggested through the formation of hydroxyl radical which is responsible for demineralization process. It is also appears that as the initial concentration of the dye increases, the requirement needed for degradation increased as well. The thermal degradation behavior of RAE at temperature range 25–60 °C under solar light showed first order kinetics with low activation energies