COLOR STABILITY OF BEET POWDERS

Color thermal stability kinetics tests of the major beet pigments, betanine and vulgaxanthin (I), were conducted in beet powder during storage (25, 31, 35, 40 and 45°C) and in its reconstituted solution (40 and 86°C heat treatment at pH 4.0, 5.7 and 6.8). The powders evaluated were produced by two different drying methods — drum drying and the conventional cube dehydration. Pigment degradation rates generally followed a first order reaction with an energy of activation of 7.0 and 8.0 Kcal/mole for betanine and 6.2 and 6.4 Kcal/mole for vulgaxanthin for drum and air dehydrated powders, respectively. Optimal pigment stability in the reconstituted juice was obtained at pH 5.7 for both the high and low tested temperatures (40 and 86°C). Freeze dried powder (used as a control), although having a higher initial pigment concentration, showed a markedly higher degradation rate in its reconstituted juice at the 40°C temperature, thus suggesting an enzymatic pigment degradation activity in the native beet.