Essential Oils of Citrus Fruit Peels Antioxidant, Antibacterial and Additive Value as Food Preservative

Essential oils are major source of antibacterial natural compounds that could be used in storing fish. The essential oils were extracted from the fruit peels of Citrus aurantifolia (Christm.) Swingle (Key lime), C. limon (L.) Burm.f. (Lemon) and C. paradisi Macfad (Grapefruit) during January 2017 and analyzed using gas chromatography coupled with mass spectrometry (GC/MS). The essential oils antioxidant activities were determined using 2,2′-diphenypicrylhydrazyl (DPPH) and the β-carotenelinoleic acid assays. The in vitroanimicrobal activities of the essential oils were determined using the microdilution methods against Gram positive and Gram negative bacteria. The food additive value of the essential oils was examined in sardine preserving for 2, 4 and 6 days against Staphylococcus aureus. Essential oil yields were 0.5, 0.53, and 0.6% for C. aurantifolia, C. limon and C. paradisi, respectively. Essential main constitutes were limonene (40.16%), β-Pinene (19.55%) andα-Citral (8.13%) for Citrus aurantifolia; limonene (57.20%), β-Pinene (8.91%) and γ-Terpinene (6.52%) for Citrus limon; limonene (73.5%), linalool (4.71%) and linalool oxide (4.16%) in Citrus paradisi. The highest antioxidant activities were found in the essential oil of C. paradisi with a percentage of 84.92 ± 0.5 and 92.45 ± 0.6 in the DPPH and β-Carotene-linoleic acid assays, respectively. The highest antibacterial activities were found in C. paradisi showing the lowest Minimum inhibitory concentrations (MIC) values against B. cereus (0.14 mg/mL), L. monocytogenes (0.21 mg/mL), M. flavus (0.12 mg/mL), P. aeruginosa (0.14 mg/mL), and S. aureus (0.16 mg/mL). Essential oils of C. paradisi showed the highest inhibitory activities against S. aureus in sardine during 2, 4 and 6day storage at 4±1°C. The essential oil of C. paradisi showed the most promising results as antioxidant, antimicrobial and might be used for sardine cold storage for short periods compared to other species.