Abstract

Citrus sinensis seed and peel oils were extracted by solvent extraction using n-hexane, after air drying and grinding. Soaps were formed by saponification methods. Fatty acid composition of the oil samples were analyzed using Gas Chromatograph-Flame Ionization Detector (GC-FID). Physicochemical properties of the oils and soaps were determined following standard methods. Antimicrobial activities were assessed by the agar disc and hole-in plate methods. The seed and peel oil yield were 38 and 30%, respectively and the colors were golden yellow and brownish-yellow, respectively. Physicochemical properties of the oil samples determined were: refractive index (RI): 1.46 and 1.47, smoke point: 140 and 149, flash point: 150 and 160, pH: 5.2 and 4.2, acid value (AV): 23.6 and 25.1 mgKOH/g, free fatty acid (FFA): 11.86% as oleic acid and 12.61% as oleic acid, iodine value (IV): 78.83I₂ g/100 g and 120.10I₂ g/100 g, peroxide value (PV): 18.00 mgKOH/g and 5.40 mgKOH/g, saponification value (SV): 222.58 and 41.25 mgKOH/g, ester value (EV): 178.24 and 28.96 mgKOH/g for the seed and the peel oil respectively. Inhibitory antimicrobial activities were assessed for the two oils and the soap produced at concentrations of 40 mg/ml and below, against most of the gram positive and gram negative bacteria as well as the two candida strains, screened as compared with streptomycin (1 mg/L) and acriflavin (6.3 mg/ml) standard controls. Seed oil demonstrated better activities than the peel oil with growth inhibitions obtained against Staphylococcus aureus and Candida albicans at a concentration as low as 2.5 mg/ml. This study has shown that the results obtained for the physicochemical and antimicrobial properties of the oils provide a synergy for the oil samples as suitable raw materials for the cosmetic and pharmaceutical industries.

Key words: Physicochemical properties, antimicrobial activity, soap, seed oil, peel oil.