Studying the Effects of pH and Storage Time on Antioxidant and Antimicrobial Activities of Essential Oil and Extracts of Lemon Verbena (Lippia citriodora) in Model Food System

Lippia Citriodoraplantis is a rich source of flavonoids that can reduce the microbial and oxidative deteriorations of food in general and therefore can extend the shelf-life of the food systems. For evaluation of the antimicrobial activity of essential oil and extract, the treated food emulsions by 1% and 2% essential oil and aqueous-alcoholic extract at the pH of 5, 7 and 9 were employed. Peroxide value, anisidine value, conjugated dienes, as oxidative parameters, and also total counts of microflora were measured during eight days of storage. Essential oil and aqueous-alcoholic extract showed good antimicrobial activities under the experimental conditions. There were not significant differences (p ≤ 0.05) in the results concerned with DPPH and FRAP between essential oil and aqueous-alcoholic extract. The results of antimicrobial and antioxidant activities of essential oil and aqueous-alcoholic extract in model food system showed that both essential oil and extract decreased the total counts of microorganisms and the amounts of oxidative rancidity as compared to the control during 8 days of storage. Antimicrobial and antioxidant activities of essential oil and extract showed a direct correlation with the pH, therefore the mentioned activities were higher at lower pH values. The results of this study showed that the essential oil and extract of Lippia Citriodora can be used as antioxidant and antimicrobial agents in food products