Degradation kinetics of monomeric anthocyanins in acerola pulp during thermal treatment by ohmic and conventional heating was evaluated at different temperatures (75-90°C). Anthocyanin degradation fitted a first-order reaction model and the rate constants ranged from 5.9 to 19.7 × 10(-3)min(-1). There were no significant differences between the rate constants of the ohmic and the conventional heating processes at all evaluated temperatures. D-Values ranged from 116.7 to 374.5 for ohmic heating and from 134.9 to 390.4 for conventional heating. Values of the free energy of inactivation were within the range of 100.19 and 101.35 kJ mol(-1). The enthalpy of activation presented values between 71.79 and 71.94 kJ mol(-1) and the entropy of activation ranged from -80.15 to -82.63 J mol(-1)K(-1). Both heating technologies showed activation energy of 74.8 kJ mol(-1) and close values for all thermodynamic parameters, indicating similar mechanisms of degradation.

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a b s t r a c tThe present work evaluates the anthocyanin degradation in blueberry pulp after thermal treatment using ohmic and conventional heating. The ohmic heating technology was studied using a rotatable central composite design, and the variables studied were voltage and solids content. The anthocyanin content of the samples was determined using HPLC. The results show that degradation increased with both increasing voltage and increasing solids content. The comparison between ohmic and conventional heating showed that when lower voltage levels were used, the percentage of degradation was lower or similar to those obtained during conventional heating. However, for high electric fields, the pulp processed using ohmic heating exhibited higher anthocyanin degradation.

a b s t r a c tVitamin C degradation in acerola pulp during thermal treatment by ohmic and conventional heating was evaluated. The ohmic heating technology was studied using a Central Composite Rotatable Design, and two variables were evaluated: the solids content of the pulp (2e8 g/100 g) and the heating voltage (120 e200 V). The results indicate that ascorbic acid degradation was significantly influenced by both of the aforementioned variables. The total vitamin C degradation was influenced by the linear and the quadratic effects of the voltage. A comparative evaluation of the conventional and the ohmic heating processes showed that ohmic heating, when performed with low voltage gradients, promoted degradation of both the ascorbic acid and the total vitamin C in a manner similar to conventional heating. However, high voltage gradients induced greater ascorbic acid degradation because of electrochemical reactions. These reactions increased when high electric fields were applied, producing compounds that catalyzed the degradation pathways of ascorbic acid in the presence of oxygen.

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