Abstract:

Anthocyanin stability of tree penoy was evaluated under different pH and temperature conditions during heating. Analysis of kinetic data suggested a first-order reaction for the degradation of tree penoy anthocyanin with the half-lives of 27.0 to 7.9, 32.1 to 8.5, 27.9 to 8.9, 35.9 to 9.4 and 27.3 to 10.7 h for samples at pH 2.6, 3.0, 3.6, 4.0 and 4.6 between 70 and 90 ℃, respectively. Increasing temperature from 70 to 90 ℃, it enhanced the degradation of anthocyanins during heating. The temperature-dependent degradation was adequately modeled on the Arrhenius equation. The activation energy values for the degradation of tree penoy anthocyanin at different pH values(2.6~4.6) ranged from 48.4 to 69.4 kJ/mol. The first order kinetic constants showed the following decreased order for individual anthocyanin: cyanidin 3-O-glucoside > peonidin 3-O-glucoside > cyanidin 3, 5-di-O-glucoside > peonidin 3, 5-di-O-glucoside. Tree penoy anthocyanin degradation involvesin brown pigment formation. The browning index increased with increasing heating time, temperature and pH.

Key words: tree penoy, anthocyanin, thermal stability, browning, degradation kinetics