Essential oils of Kenyan Citrus fruits: volatile components of two varieties of mandarins (Citrus reticulata) and a tangelo (C-paradisi x C-tangerina)

The volatile flavour components of essential oils in peel of kara and sabine mandarins (Citrus reticulata) and minneola tangelo, a hybrid between Duncan grapefruit (C. paradisi Macfadyen) and Dancy tangerine (C. tangerina Tanaka) grown in Kenya were extracted by cold-pressing and analyzed by GC and GC-MS. A total of 48, 72 and 56 components amounting to 99.4, 99.8 and 99.8% were identified in each oil, respectively. Monoterpene hydrocarbons constituted 98.1, 96.9 and 96.7% in the respective oils. The major compounds were limonene (87.1-90.7%), gamma-terpinene (1.5-2.9%), terpinolene (1.4-2.2%) and myrcene (1.5-1.8%). alpha-Terpinene was prominent in sabine oil (3.4%) but absent from kara and minneola oils. beta-Caryophyllene, alpha-cubebene and (E, E)-alpha-farnesene amounting to minor percentages (0.2-0.3%) were the notable sesquiterpenes in each oil. Oxygenated compounds constituted 1.1, 2.6 and 2.8% of the kara, sabine and minneola oils, respectively. Carbonyl compounds (0.6-1.3%) and alcohols (0.3-1.3%) were the major groups, whereas linalool (0.2-0.6%), decanal (0.2-0.3%) and octanal (0.2-0.3%) were the prominent compounds. beta-Sinensal was present in each oil at trace quantities. alpha-Sinensal and nootkatone were found only in sabine oil. The oils exhibited complex and variable compositions of alcohols, aldehydes and ketones. (E)-p-Mentha-2,8-dienol, p-mentha-1(7), 8(10)-dien-9-ol, p-menth-8-en-1-ol and (E)-pinocarvyl acetate found among the oils have not been previously reported in mandarin peel oils. Copyright (C) 2004 John Wiley Sons, Ltd.