Functional bread produced with olive mill wastewater lowers postprandial oxidative stress after red meat consumption

This study investigated the valorisation of olive oil mill wastewater (OOMW) from certified organic farms as a sustainable functional ingredient in bread production. OOMW samples were characterized for microbiological safety and pesticide residues, which confirmed low microbial loads (2.24-3.44 log CFU/mL), absence of spoilage/pathogenic organisms, and no detectable agrochemical contaminants. Fermentation trials replaced tap water with OOMW at 50 % and 100 % levels. Dough analysis revealed increased acidification and titratable acidity with OOMW inclusion, while microbial monitoring and metataxonomics confirmed lactic acid bacteria (LAB) dominance and fermentation stability. Baking performance showed reduced weight loss and improved moisture retention but decreased specific volume and increased crumb firmness at higher OOMW levels. Colorimetric and alveolation analyses indicated structural and color changes linked to polyphenolic content. Metabolomic profiling demonstrated a marked enrichment of bioactive compounds in OOMW breads, highlighting their enhanced functional potential. Sensory evaluation highlighted enhanced aroma and flavour complexity, with EXP-50 achieving the highest overall acceptance. Functional assays demonstrated that OOMW-enriched breads markedly reduced lipid peroxidation during simulated gastric digestion of red meat, achieving up to 60 % inhibition of malondialdehyde and lipid hydroperoxides formation and effectively suppressing perferryl-myoglobin radical formation. These findings confirm that OOMW fortification improves antioxidant properties while ensuring safety and sensory quality, supporting its integration into bakery products as part of circular economy strategies. • OOMW used as a safe, sustainable functional ingredient in breadmaking • OOMW fermentation stable with LAB dominance and enhanced dough acidity • Bread enriched with OOMW shows higher moisture and polyphenol-linked color • Metabolomics reveals major bioactive enrichment with 419 unique metabolites • OOMW breads reduce red-meat oxidative markers by up to 60% in digestion