<p>This study investigated the effects of selected additives on olive oil quality and olive paste properties during malaxation. Using response surface methodology, oxalic acid (OA), L-cysteine (L-cys), ascorbic acid (AA), and magnesium chloride (MgCl₂) were incorporated into olive paste at different concentrations. Additive-treated samples generally showed increased oil yield and improved oxidative stability, reflected by lower peroxide, K₂₃₂, and K₂₇₀ values, except for 2% MgCl₂, which negatively affected these parameters. The additives reduced paste pH and modified moisture content, indirectly influencing oil quality. Antioxidant capacity, evaluated by total phenolic content and DPPH radical scavenging activity, improved in most treatments, particularly with AA. However, β-carotene bleaching results decreased, possibly due to analytical interference from additive residues. Key phenolic compounds, including hydroxytyrosol, tyrosol, and oleuropein, were significantly enhanced. Controlled additive application during malaxation can improve extraction efficiency and modify the biochemical profile of olive oil, though antioxidant results should be interpreted cautiously.</p> Graphical abstract <p></p>