THERMOSTABILITY OF RED BEET PIGMENTS (BETANINE AND VULGAXANTHIN–I): INFLUENCE OF pH AND TEMPERATURE

The thermostability of red beet pigments (betanine and vulgaxanthin–I) was investigated in beet juice under atmospheric conditions at 61.5, 75.5 and 85.5°C and at pH range 4.8–6.2. The degradation of both pigments followed first‐order reaction kinetics. The energies of activation were 19.2 ± 0.5 and 16.3 ± 0.6 Kcal/mole for betanine and vulgaxanthin–I respectively, and were independent of pH. Maximum thermostability was observed at pH 5.8 for both pigments. In beet juice under atmospheric conditions vulgaxanthin–I was more sensitive than betanine.