Characterisation of supercritical carbon dioxide extracts from olive leaves: antimicrobial activity, volatile composition and mineral oil contamination

This study investigated the antimicrobial efficacy of olive leaf extract (OLE) obtained via supercritical carbon dioxide (SC-CO 2 ) extraction, with additional attention to volatile composition and contamination by mineral oil hydrocarbons (MOH). The water-soluble fraction of OLE inhibited the growth of pathogenic ( Listeria monocytogenes , Escherichia coli , Staphylococcus aureus , Salmonella enterica ) and spoilage ( Pseudomonas fluorescens , Leuconostoc mesenteroides ) bacteria, while OLE vapor phase was also able to inhibit fungi such as Penicillium roqueforti . These effects were attributed to the combined presence of water soluble polyphenols (139.95 ± 2.50 mg GAE/g DW ) and bioactive volatiles with antimicrobial properties ( e.g. , 1-pentanol, nonanal), which may have differentially impacted the tested microorganisms. However, OLE was found to be contaminated with MOH, likely deriving from harvesting or processing operations. Although these findings highlight the strong antimicrobial potential of OLE obtained by SC-CO 2 extraction, they also emphasize the need to address contamination risks for its safe use in food and pharmaceutical applications. • Supercritical CO 2 extracts from olive leaves (OLE) showed antimicrobial properties • OLE water-soluble fraction strongly inhibited the growth of foodborne pathogens • OLE vapor phase exhibited antifungal action • OLE effects were attributed to antimicrobial polyphenols and volatile compounds • OLE was found to be contaminated with mineral oil hydrocarbons