Influence of lipids and proteins amounts and pH values on the inhibitory effects of Origanum vulgare L. essential oil against Escherichia coli and Salmonella Typhimurium

ABSTRACT

Origanum vulgare L. (OVEO) essential oil has been considered a candidate antimicrobial for use in food conservation systems. However, studies on the influence of concomitant variations of different food components or physicochemical parameters on the antibacterial properties of OVEO are scarce. This study assessed the influence of concomitant variations in amounts of proteins - PTN (4.0, 6.0 or 8.0 g/100 mL) and lipids - LIP (3.75, 5.0 or 6.25 g/100 mL) and pH values (5.0, 5.5 or 6.0) in cultivation medium on the inhibitory effects of OVEO against Escherichia coli (EC) and Salmonella Typhimurium (ST). Lowest minimum inhibitory concentration values of OVEO against EC and ST were observed in media with the highest LIP amounts regardless the PTN amount and pH value. In absorbance based microtiter plate assay (MPA), for both EC and ST, OVEO caused the lowest Grmax values in medium containing the highest LIP and PTN amounts and lowest pH value. Highest Grmax values for EC and ST were observed in medium containing the lowest LIP and PTN amount and highest pH value. Grmax values estimated from viable counts of EC and ST in tested media with OVEO confirmed bacterial growth behavior similar to that observed in MPA. Overall, the LIP amount in media was as the most influential factor to enhance the antibacterial effects of OVEO. These results indicate that the concomitant influence of LIP and PTN amounts and pH values on the antibacterial effects of OVEO should be considered for optimizing its antimicrobial efficacy in foods.