Application of pulsed electric field technology for extraction of bioactives from green tea

Abstract:

Non-thermal extraction methods hold genuine promise for recovering heat-sensitive bioactives from plant matrices without the pigment and flavour damage caused by conventional solvent heating. This research evaluated Pulsed Electric Field (PEF) technology as an extraction aid for polyphenols, catechins, and antioxidant compounds from dried green tea leaves. Five PEF intensity levels (1.0, 2.0, 3.0, 4.0, and 5.0 kV/cm) were applied to aqueous green tea suspensions at a fixed pulse number of 100 and a pulse width of 20 microseconds. Total polyphenol content, epigallocatechin gallate (EGCG) concentration, and DPPH radical-scavenging activity were measured in the resulting extracts. Polyphenol yield increased steadily from 12.4 mg GAE/g at 1.0 kV/cm to a peak of 37.8 mg GAE/g at 4.0 kV/cm, beyond which no further gain was observed. EGCG followed a similar plateau pattern, reaching 9.6 mg/g at 4.0 kV/cm compared with 4.1 mg/g in the untreated control. Antioxidant activity rose in parallel, with the 4.0 kV/cm treatment showing 81.3% DPPH inhibition versus 48.7% for the control. PEF at 3.0-4.0 kV/cm therefore appears to be an effective, low-temperature route for maximising bioactive recovery from green tea.