Kinetics of anthocyanin degradation and polymeric colour formation in black carrot juice concentrates during storage

The changes in anthocyanins (ACNs) and polymeric colour of black carrot juice concentrate (BCJC) samples were monitored during storage at -23, 5 and 20 degrees C for 319 days and at 30 degrees C for 53 days. While ACN degradation was fitted to a first-order reaction model, polymeric colour formation was fitted to a zero-order reaction model during the storage. Half-life periods for ACN degradation in BCJCs were 603, 137 and 29 days at 5, 20 and 30 degrees C, respectively. The reaction rate constants for polymeric colour formation were 0.0207, 0.1435 and 0.5581%/days at 5, 20 and 30 degrees C, respectively. HPLC-MS analyses of BCJC showed that cyanidin-3-galactoside-xyloside-glucoside-ferulic acid (56%) was the major ACN, followed by cyanidin-3-galactoside-xyloside (19%) and cyanidin-3-galactoside-xyloside-glucoside-sinapic acid (10%). Cyanidin-3-galactoside-xyloside-glucoside-ferulic acid was the most stable ACN in BCJC at storage temperatures. BCJCs should be kept at sub-freezing temperatures to minimise ACN degradation.