DECOMPOSITION OF BETACYANINS AND BETAXANTHINS BY HEAT AND PH CHANGES

Authors investigated the decomposition of the main beetroot colourings betanin and vulgaxanthin I as a function of temperature and pH value in acetate and citrate buffer solutions, in a temperature-range betwee n 60 degrees C and 80 degrees C and pH range of 3.3-6.2. The temperatu re dependence of betain decomposition is characterized by a Q(10) valu e of 2.23 +/- 0.45, and the reaction rate was doubled by reducing the pH value from 6.2 to 3.3 independent from the type of acid used. Also the interaction between temperature and pH value on colour decompositi on was verified, Investigations were carried out at low oxygen content , and under this conditions the reaction was exactly described - consi dering the time interval of 20 min - by a linear function at 60 degree s C, pH value 3.3-6.2 and by an exponential function at 70 degrees C a nd 80 degrees C and pH 3.3-4.65. Activation energy for betain degradat ion is 77.5 +/- 6.76 kJ/mol.