Abstract

Volatile components were isolated from the matrix of fresh and roasted samples of wild ginger (Siphonochilus aethiopicus (Schweinf) B.L Burtt) by solvent extraction and vacuum distilled. Quantitative determination of the volatiles in the distillate was done by GC-FID and organoleptic examination by GC-olfactometry. The sesquiterpenes were the major components of fresh wild ginger having a weight percent of 70 as against the monoterpene percentage of 3.5 and diterpene percentage of 25. The distillates obtained contained no ditepenes, while the monoterpene percentage increased to 72 in the fresh sample and 49 in the roasted sample. The sesquiterpene weight percent of the distillates decreased to 16 in the fresh sample and 27 in the roasted sample. Methyl-2-/-3-methyl butanoates, propyl-2-methylbutanoate, β-phellandrene, 2-isopropyl-3-methoxypyrazine, 2-isobutyl-3-methoxypyrazine, methional, furanodiene and curzerenone were odorants important for the flavour of the fresh sample having the higher FD-factors. Curzerenone and furanodiene were characterised by NMR and GCMS after isolation from the crude solvent extract. 2-Acetylthiophene together with these eight odorants was strongly involved in the characteristic pleasant flavour of the roasted spice. The lowest odour threshold value of curzerenone detected was 0.8 to 1.69 µg/L_air.

Key words: Siphonochilus aethiopicus, flavour, terpenes, curzerenone.