Liquid and encapsulated duckweed (Lemna minor L.) extracts differentially shape metabolomic fingerprints of packaged beef burgers during shelf-life

Oxidative deterioration and color loss are critical factors limiting the shelf-life and consumer acceptance of fresh beef burgers under modified atmosphere packaging (MAP). This study evaluated Lemna minor (duckweed) extracts, applied in liquid form (LLE) and encapsulated with gum Arabic (AGL) or maltodextrin (ML), as natural antioxidants in beef burgers stored at 4 °C for 14 days. Extracts were tested at 0.1 %, 0.5 %, and 1 % (w/w), and their effects were assessed through physicochemical, microbiological, and untargeted metabolomics analyses. Encapsulation yields were high (∼80 %) for both carriers, with gum Arabic retaining higher antioxidant capacity. The liquid extract at 1 % and the encapsulated extracts at 0.1 % were the most effective treatments, preserving redness, reducing lipid oxidation below the sensory off-flavour threshold, and limiting oxygen consumption by day 7. Conversely, higher doses of encapsulated extracts (0.5-1 %) were less effective and in some cases induced pro-oxidant effects. Untargeted metabolomics revealed modulation of oxidative biomarkers, including glutathione, hemin, and tryptamine, supporting the antioxidant role of duckweed extracts in stabilising lipid and protein oxidation pathways. No antimicrobial effect was observed. These findings indicate that duckweed extracts can serve as sustainable, plant-based antioxidants for fresh beef burgers, with recommended application levels of 0.1 % (w/w) for encapsulated forms and 1 % (w/w) for liquid extracts. This represents the first demonstration of duckweed-based antioxidants in meat systems, offering a promising alternative to synthetic preservatives and supporting the transition toward clean-label strategies in the meat industry.