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

• ms and μs treatments resulted in a similar relationship between specific energy and Zp.
• PEF in both the ms and the μs range increased the BEY 6.7 and 7.2 times respectively.
• PEF in the μs range required lower specific energy to obtain similar BEY.

The efficacy of PEF treatments—in the range of milliseconds at moderate electric field strengths (0.2–0.6 kV/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 μs 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 ms and μs ranges under the conditions in which the maximum extraction was observed revealed that the improvement in the betanine extraction was similar. The more intense treatment conditions applied in the ms range (0.6 kV/cm; 40 ms) and the μs range (6 kV/cm; 150 μs) increased the BEYmax 6.6 and 7.2 times, respectively, compared with the control. However, the comparison of the BEYmax in the ms and μs ranges under the same total specific energy revealed that the improvement in the betanine extraction was higher for the treatment applied in the μs range. For example, to obtain a BEYmax of 775 μg/g, a total specific energy of 6 kJ/kg was required when the treatment was applied in the μs range (75 μs; 4 kV/cm) and around 20 kJ/kg if the treatment was applied in the ms range (40 ms, 0.4 kV/cm).