Kinetics of Color Loss of Djulis (Chenopodium formosanum Koidz.) Extracts during Storage in Different Concentrations of Alcohol and Temperature

The aim of this study was to investigate the effect of storage temperature on color loss (betacyanin degradation) of Djulis (Chenopodium formosanum Koidz.) extracts in various alcohol (10-60% EtOH) model systems. All samples were thermally processed and stored at 20-50 °C for 21 days after pigment regeneration. Results showed that betacyanin degradation index (DI) was accelerated by ethanol and temperature. The rate of color loss during storage followed the first-order reaction kinetics. The higher ethanol concentration and temperature corresponded to the higher rate of color loss, which was in accordance with the trend of activation energy (Ea) of color degradation. For example, the Ea values of 0%, 10%, 20%, 40% and 60% EtOH samples were 81.04, 77.89, 71.75, 71.30 and 70.16 kJ mol-1, respectively. Apparently, significant color loss of Djulis extracts occurred when ethanol concentration reached 20%.