PEF-Assisted Extraction of Proteins and Bioactive Compounds from Duckweed (Lemna ssp.): An Exploratory Proof-of-Concept Study

Duckweeds (Lemna minor, LM and Lemna gibba, LG) represent promising protein-rich biomass for sustainable food ingredients, yet efficient physical aqueous extraction from fresh material remains largely unexplored. This proof-of-concept study presents the first application of pulsed electric fields (PEF) pre-treatment to enhance protein and bioactive compound release from homogenized Lemna ssp. suspensions. PEF parameters (1–8 kV cm−1, unipolar) and homogenization intensity (10 s vs. 5 min Ultra Turrax) were screened by quantifying protein yields, cell disintegration index (Zd), energy input and chlorophylls, carotenoids and polyphenols. Homogenization proved essential, with 5 min treatment alone yielding 22.0–34.6% protein extraction; subsequent 5 kV cm−1 PEF increased this by 11.0–16.8% (33% LG; 51% LM). Among the tested conditions, 5 kV cm−1 following 5 min homogenization maximized yields; however, it required the highest energy input (~239 kJ/kg), while 8 kV cm−1 after 10 s offered a promising efficiency trade-off (~54 kJ/kg). Zd values ≥ 0.9 confirmed electroporation as the mechanism, with PEF and homogenization ~5–25× more energy efficient than the freeze–thaw process. Bioactive compounds nearly doubled under optimal conditions, with trends mirroring protein release. These findings validate PEF as a green pre-treatment strategy for the protein recovery of Lemna spp., while also offering mechanistic understanding that can support its future implementation in extraction processes.