Effects of millisecond and microsecond pulsed electric fields on red beet cell disintegration and extraction of betanines

The efficacy of PEF treatments in the range of milliseconds at moderate electric field strengths (0.2-0.6kV/cm) and in the range of microseconds at high electric field strengths (2-6 kV/cm) has been compared in terms of red beet cell disintegration degree (Zp), extraction of betanines and total specific energy requirements. In the range of treatment conditions investigated, the highest Zp value was larger for the treatments applied in the millisecond range than for the treatments applied in the microsecond range. While in the treatment applied at 0.6 kV achieved a Zp value higher than 0.95 after 60 ms of treatment, the highest Zp value obtained at 6 kV/cm in the microsecond range was 0.78 after 75 mu s of treatment. In the range of 0-20 kJ/kg and Zp values among 0-0.75, the disintegration index mainly depended on the total specific energy applied, independently of the electric field strength or the duration of the treatment. The comparison of the maximum betanine extraction yield (BEYmax) in the mu s and ps ranges under the conditions in which the maximum extraction was observed revealed that the improvement in the beta nine extraction was similar. The more intense treatment conditions applied in the ms range (0.6 kV/cm; 40 ms) and the mu s range (6 kV/cm; 150 mu s) increased the BEYmax 6:6 and 7.2 times, respectively, compared with the control. However, the comparison of the BEYmax in the ms and ps ranges under the same total specific energy revealed that the improvement in the betanine extraction was higher for the treatment applied in the p,s range. For example, to obtain a BEYmax of 775 mu g/g, a total specific energy of 6 kJ/kg was required when the treatment was applied in the mu s range (75 mu s; 4kV/cm) and around 2014/kg if the treatment was applied in the ms range (40 ms, 0.4 kV/cm). (C) 2016 Elsevier B.V. All rights reserved.