Physicochemical, antioxidant and antimicrobial properties of citrus peel essential oils

Abstract

Essential oils are produced as secondary metabolites of aromatic plants and can be extracted from leaves, seeds or fruit peel of the plants. Citrus peel is a rich source of limonene which is antimicrobial in nature. The present study aimed to deal with the physicochemical, antioxidant and antimicrobial properties of citrus peel essential oil from Citrus reticulate (mandarin orange), Citrus limetta (mosambi) and Citrus limon (lemon).  The lemon peel oil had lower peroxide value (1.6 meq/kg of sample), saponification value (112.2 mg KOH/g of oil) and higher iodine value (116 gI₂/100g oil) when compared with orange and mosambi peel essential oil. DPPH (2,2-diphenyl-1-picrylhydrazyl) free radical scavenging activity of citrus peel essential oil was measured  and the result indicated that the total antioxidant activity of lemon peel oil was 89.2 % Radical Scavenging activity (RSA). The antifungal activity was assessed by agar dilution method, whereas the antibacterial property was assessed by the agar diffusion method. Lemon peel oil recorded better antimicrobial properties with minimum inhibitory concentration of 0.3% against Aspergillus flavus MTCC 277, 0.2% for Penicillium  MTCC 1995 and Fusarium oxysporum MTCC 284. Likewise, the minimum inhibitory concentration of lemon peel oil against Staphylococcus aureus MTCC 96 was 0.3%; Salmonella enterica MTCC 733 and Erwinia sp MTCC 2760 was 0.5%; Pseudomonas aeruginosa MTCC 1688 and Escherichia coli MTCC 443 was 0.7%. This comparative study showed that lemon peel oil had better physicochemical and antioxidant property. Lemon peel oil can be used as a preservative in the food system as it exhibited antibacterial and antifungal activity.