Fast screening method for assessment of antimicrobial activity of essential oils in vapor phase

Among promising alternative methods to control food spoilage much attention is being paid to the use of essential oils (EOs), and lately also to their activity in vapor phase. Until now, no standard assay exists, and there are many methods used by different authors, but any of them is suitably adapted for fast screening of large quantities of samples. We have modified most commonly used disc volatilization method by using four-section Petri dish (PD, 90 mm diameter), large filter paper disc (85 mm diameter) evenly impregnated with EO and medium containing lid. In comparison to normal disc volatilization method, labor and material needed are several times reduced, while the composition of headspace is more uniform than in case of 6 mm disc, where different volatility of particular compounds could influence the results. Sixty nine EOs were tested for its antimicrobial activity against three bacteria (Staphylococcus aureus, Salmonella enteritidis, Pseudomonas aeruginosa) and three fungi (Alternaria alternata, Aspergillus niger, Penicillium digitatum). Thirty nine EOs inhibited at least one microorganism, Armoracia rusticana and Cinnamomum zeylanicum being the most active, followed by EOs of Eugenia caryophyllata, Origanum compactum, Origanum vulgare, Pimenta racemosa, Thymus serpyllum and Thymus vulgaris inhibiting all six or five microorganisms, respectively. According to our opinion, this method is suitable for screening of large quantities of samples for antimicrobial activity in vapor phase.

Research highlights► New method allow fast and precise screening of volatiles for antimicrobial activity. ► Among 69 essential oils, 39 EOs inhibit at least one out of six microorganism. ► The most active genera are Armoracia, Allium, Cinnamomum. ► Allyl isothiocyanate, diallyl disulfide, cinnamaldehyde in most active essential oils.