Effect of ohmic heating parameters on peroxidase inactivation, phenolic compounds degradation and color changes of sugarcane juice

The non-thermal effects of electricity on enzymatic inactivation kinetics of peroxidase (POD) and on phenolic compounds degradation during ohmic heating (OH) of sugarcane juice were investigated. Experiments with different frequencies (10-105 Hz), waveforms (sine, square, triangle and pulsed waves) and voltage gradients (3.9 and 20.5 V/cm) were conducted at 75 °C for 25 min and compared with the conventional treatment, performed with similar temperature histories. Overall, the results indicated that the non-thermal effects of OH (voltage gradient up to 20.5 V/cm, with different frequencies and waveforms) did not influence the biochemical reactions that occur during POD inactivation in sugarcane juice. Moreover, there was no effect of electric field frequency or voltage gradient on phenolic compounds stability; on the other hand, some waveforms promoted higher degradation of these compounds. Some color changes were observed when 10 Hz/25 V and 60 Hz/130 V were applied, with higher magnitude at the higher electric field strength.