Extractability of phenolics from spearmint treated with pulsed electric field

• A system for PEF treatment of leaves with impedance monitoring was suggested.
• Conductivity changes showed a complete permeabilization at micropulses of 3 kV/cm.
• Extractability of the phenolics using PEF was comparable with the full level.
• DPPH method indicated decreases in the tissue post non-thermal treatments.

The effects of pulsed electric fields (PEF) on the extractability of phenolics from fresh spearmint leaves were studied. The circular tissue slices treated with PEF were subjected to a solid–liquid extraction process and the extracted phenolics were evaluated by measuring total phenolic content (TPC), antioxidant capacity (AC) and antioxidant activity (AA). The results obtained were compared with those of the extractions repeated with freezing/thawing, heat, microwave and solvent treatment.As measured from a conductivity-based tissue disintegration index, the highest disintegration (0.86 ± 0.02) was obtained at a PEF intensity corresponding to 99 pulses of 3 kV/cm with a specific energy input of 4102 ± 239 J/kg. The extraction with the PEF pre-treatment produced comparable TPC, AC and AA values with the heat and microwave pre-treatments, and a markedly higher AA value than the freezing/thawing. Furthermore, the combined effects of the PEF and other pre-treatments resulted in significant synergism in TPC and AC while showing antagonism in AA properties.