Résumé
A 3D model of a reactor was developed, combining heat transfer and chemical reaction, to identify kinetic parameters under non-isothermal conditions for intermediate-moisture foodstuffs. In particular, the model was used to assess the impact of high-temperature heat treatments (100–140 °C) on anthocyanin degradation in blackberry juice. A quartz-sand system was used at 25 °C, with three different water activities (aw = 0.34, 0.76 and 0.95). Heat transfer resistance and kinetic parameters were identified, using a nonlinear regression method. Estimates of kinetic parameters showed that the constant for the anthocyanin-degradation reaction rate (k120 °C) increased from 0.9 to 4.1 X 10 -3 s -1 with decreasing water activity, with a maximum rate at aw ¼ 0.76. No significant difference (p < 0.05) was found between the corresponding activation energies (Ea = 94 + 7 kJ mol -1). Reduced water activity therefore negatively affects anthocyanin stability at high temperatures.