Anthocyanin degradation kinetics and thermodynamic analysis of Hibiscus rosa-sinensis L. Clitoria ternatea L. and Hibiscus sabdariffa L.

Anthocyanins are natural occurrence red pigments existed in most flowers with high health benefited values. These anthocyanins rich flowers have a short shelf life and fast degradation when in fresh stage. These anthocyanins rich flowers have a short shelf life and fast degradation when in fresh stage. Therefore, drying is a conventional way to preserve them from rotten in order to be reachable for urban consumers who have busy life style and limited space for planting. The present study was conducted to evaluate the anthocyanin degradation kinetics of Hibiscus rosa-sinensis L., Clitoria ternatea L. and Hibiscus sabdariffa L. at drying temperatures of 50, 60, 70 and 80 °C for durations of 10, 20, 30 and 40 min. Anthocyanin degradation kinetic order of Hibiscus rosa-sinensis L., Clitoria ternatea L. and Hibiscus sabdariffa L. were determined by constructing natural logarithm Arrhenius equation plots from k values obtained from zero-, first-, and second-order integrated rate law plots at each temperature levels of 50 °C, 60 °C, 70 °C and 80 °C, based on the highest coefficient of determination (R2). Fresh flower of Clitoria ternatea L. has been revealed possessed the highest amount of TMA followed by Hibiscus sabdariffa L. and the Hibiscus rosa-sinensis L. Results revealed that anthocyanins degradation for Hibiscus rosa-sinensis L. and Clitoria ternatea L. followed first-order kinetic behaviour, while Hibiscus Sabdariffa L. followed the second-order. Anthocyanins of Hibiscus Sabdariffa L. has been discovered having high k values which led to shorter half-life values. However, anthocyanins of Hibiscus Sabdariffa L. is more stable during heat drying treatment as evidenced by higher activation energy and activation enthalpy, but lower free Gibbs energy and absolute value of entropy in comparison to Hibiscus rosa-sinensis L. and Clitoria ternatea L. Therefore, Hibiscus sabdariffa L. is highly recommended to be used as food colorant in food processing industries which involve heating.