• Korean Journal of Food Science and Technology
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• v.27 no.6
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• pp.1013-1016
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• 1995

The color stability of betacyanins and effects of antioxidants from Opuntia dillenii Haw were determined in the fruit juice at temperature up to $90^{\circ}C$. The absorption maxima of betacyanins occurred between 536 nm and 538 nm. When fruit juice was heated at $90^{\circ}C$ for various times, the red color gradually diminished and the absorption maxima slightly shifted toward uv region. The kinetic analysis of the data obtained indicated that the discoloration for betacyanins obeyed first order reaction pattern, when the thermal stability test was performed at $50{\sim}90^{\circ}C$. And the rate constant increased from $1.56{\times}10^{-3}/min\;to\;71.91{\times}10^{-3}/min$ with the half-life decreasing from 444.23 min to 9.64 min. The results also indicated that the thermal stability of pigment decreased with increasing temperature. The energy of activation was 10.94 kcal/mole for the pigment. N-propyl gallate, L-cysteine, and ascorbic acid were added to cactus fruit juice at concentrations of $0.01{\sim}0.3%$ at different temperatures. Npropyl gallate and L-cysteine had a little antioxidant effect on betacyanins stability at $50^{\circ}C\;and\;70^{\circ}C$, whereas ascorbic acid had a great antioxidant effect with the half-life value of 2 to 10 times to that of the control.