Degradation kinetics and colour of anthocyanins in aqueous extracts of purple- and red-flesh potatoes (Solanum tuberosum L.)

The effect of pH and temperature on the stability and visual colour of aqueous anthocyanin (ACY) extracts from purpleand red-flesh potatoes was evaluated and compared to commercial ACY extracts from grape and purple carrot. Extracts from purple carrot and redflesh potatoes showed higher stability than grape and purple-flesh potato extracts. Stability to pH (63) and thermal degradation of extracts (pH 3) followed first-order kinetics. Changes in lightness and hue followed zero-order kinetics, while changes in chroma followed first-order kinetics. Degradation parameters such as t1/2, k-, D-, zand Q10-values were determined. Extracts from redand purple-flesh potatoes at pH 3 showed similar hues to FD&C Red #40 and red cabbage extracts, respectively. The visual colour of both potato ACY extracts was also affected by tinctorial strength. The use of purpleand red-flesh potatoes as a source of natural colorants shows potential use in the pH region around 3. 2005 Elsevier Ltd. All rights reserved.