THERMAL DEGRADATION KINETICS OF BIOACTIVE COMPOUNDS AND VISUAL COLOR IN RASPBERRY PULP

The effect of heating on degradation of some bioactive compounds (total monomeric anthocyanins, L-ascorbic acid and total phenolics) and color loss in raspberry pulp were investigated at 60, 70, 80 and 90C for 7 h. Total monomeric anthocyanins and L-ascorbic acid followed first-order kinetics, while a zero-order kinetic model was determined for the degradation of total phenolics. The first-order reaction was also described for the color loss in terms of Hunter a, b and C values. The activation energies for the degradation of raspberry anthocyanins, L-ascorbic acid and total phenolics were 49.3, 15.7 and 32.2 kJ/mol, respectively. Higher activation energies (49.0-75.5 kJ/mol) found for color loss indicates, this reaction is more sensitive to the temperature elevations than the other reactions.